liu.seSearch for publications in DiVA
Change search
Refine search result
1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ainsbury, Elizabeth A.
    et al.
    Publ Hlth England, England.
    Samaga, Daniel
    Bundesamt Strahlenschutz, Germany.
    Della Monaca, Sara
    Ist Super Sanita, Italy.
    Marrale, Maurizio
    Univ Palermo, Italy; Univ Palermo, Italy.
    Bassinet, Celine
    Inst Radioprotect and Surete Nucl, France.
    Burbidge, Christopher I.
    Environm Protect Agcy, Ireland.
    Correcher, Virgilio
    Ctr Moncloa, Spain.
    Discher, Michael
    Univ Salzburg, Austria.
    Eakins, Jon
    Publ Hlth England, England.
    Fattibene, Paola
    Ist Super Sanita, Italy.
    Guclu, Inci
    Turkish Atom Energy Commiss, Turkey.
    Higueras, Manuel
    Basque Ctr Appl Math, Spain.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Maltar-Strmecki, Nadica
    Rudjer Boskovic Inst, Croatia.
    McKeever, Stephen
    Oklahoma State Univ, OK 74078 USA.
    Raaf, Christopher L.
    Lund Univ, Sweden.
    Sholom, Sergey
    Oklahoma State Univ, OK 74078 USA.
    Veronese, Ivan
    Univ Milan, Italy; Natl Inst Nucl Phys, Italy.
    Wieser, Albrecht
    Helmholtz Zentrum Munchen, Germany.
    Woda, Clemens
    Helmholtz Zentrum Munchen, Germany.
    Trompier, Francois
    Inst Radioprotect and Surete Nucl, France.
    UNCERTAINTY ON RADIATION DOSES ESTIMATED BY BIOLOGICAL AND RETROSPECTIVE PHYSICAL METHODS2018In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 178, no 4, p. 382-404Article in journal (Refereed)
    Abstract [en]

    Biological and physical retrospective dosimetry are recognised as key techniques to provide individual estimates of dose following unplanned exposures to ionising radiation. Whilst there has been a relatively large amount of recent development in the biological and physical procedures, development of statistical analysis techniques has failed to keep pace. The aim of this paper is to review the current state of the art in uncertainty analysis techniques across the EURADOS Working Group 10-Retrospective dosimetry members, to give concrete examples of implementation of the techniques recommended in the international standards, and to further promote the use of Monte Carlo techniques to support characterisation of uncertainties. It is concluded that sufficient techniques are available and in use by most laboratories for acute, whole body exposures to highly penetrating radiation, but further work will be required to ensure that statistical analysis is always wholly sufficient for the more complex exposure scenarios.

  • 2.
    Ardenfors, Oscar
    et al.
    Stockholm University, Sweden.
    Gudowska, Irena
    Stockholm University, Sweden.
    Flejmer, Anna M.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Oncology.
    Dasu, Alexandru
    The Skandion Clinic, Sweden.
    Impact of irradiation setup in proton spot scanning brain therapy on organ doses from secondary radiation2018In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 180, no 1-4, p. 261-266Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo model of a proton spot scanning pencil beam was used to simulate organ doses from secondary radiation produced from brain tumour treatments delivered with either a lateral field or a vertex field to one adult and one paediatric patient. Absorbed doses from secondary neutrons, photons and protons and neutron equivalent doses were higher for the vertex field in both patients, but the differences were low in absolute terms. Absorbed doses ranged between 0.1 and 43 μGy.Gy−1 in both patients with the paediatric patient receiving higher doses. The neutron equivalent doses to the organs ranged between 0.5 and 141 μSv.Gy−1 for the paediatric patient and between 0.2 and 134 μSv.Gy−1 for the adult. The highest neutron equivalent dose from the entire treatment was 7 mSv regardless of field setup and patient size. The results indicate that different field setups do not introduce large absolute variations in out-of-field doses produced in patients undergoing proton pencil beam scanning of centrally located brain tumours.

  • 3.
    Bahar Gogani, Jalil
    et al.
    Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Surgery in Östergötland. Linköping University, Faculty of Health Sciences.
    Hägglund, P
    Wickman, G
    Assessment of correlated dose and sensitivity profiles on a multi-slice CT scanner2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 332-336Article in journal (Refereed)
    Abstract [en]

    In the case of computed tomography (CT) scanners as well as other imaging techniques utilising ionising radiation, it is imperative that radiation is confined to the sensitive part of the image detector. Assuring this for a CT scanner requires detailed information about the scanner dose and sensitivity profiles and their spatial correlation. The profiles should ideally be co-centric and tightly fit to each other. Ensuring this inherent performance of the scanner can be seen as one of the fundamental steps in optimising diagnostic examinations with CT. A measurement device using a dedicated liquid ionisation chamber is employed to investigate the performance of a Toshiba Aquilion 16 scanner in this aspect. Dose profile and sensitivity profile pairs for four collimations are presented where each pair of profiles are spatially correlated to each other. The measurement device can be applied to any scanner for fast and accurate assessment of dose and sensitivity profiles and their spatial correlation. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 4.
    Carlsson, C.A.
    et al.
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Lund, Eva
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Pettersson, Håkan
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Matscheko, G.
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    An instrument for measuring ambient dose equivalent, H*(10)1996In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 67, no 1, p. 33-39Article in journal (Refereed)
    Abstract [en]

    The design and calibration of a small and simple instrument for measuring the ambient dose equivalent, H*(10), in photon fields is described. Comprising a thermoluminescence LiF dosemeter inside a 20 mm diameter PMMA sphere, it is capable of measuring the ambient dose equivalent with a nearly isotropic response. In the interval 0.1-100 mSv and for the energy range 30 keV to 1.25 MeV the energy response is within -31% and +15% relative to that of 137Cs gamma radiation (662 keV). In practical use, it is therefore sufficient to calibrate the instrument in a 137Cs gamma field using the corresponding conversion coefficient H*(10)/Kair taken from tabulations. The possibility of using the instrument to monitor the ambient dose equivalent for energies above 1.25 MeV is discussed and indicates that the range of applicability can be extended to 4.4 MeV with an energy response within -10% relative to 662 keV.

  • 5. Dance, D
    et al.
    Hunt, R
    Bakic, P
    Maidment, A
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ullman, Gustaf
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Breast dosimetry using high-resolution voxel phantoms2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 359-363Article in journal (Refereed)
    Abstract [en]

    A computer model of X-ray mammography has been developed, which uses quasi-realistic high-resolution voxel phantoms to simulate the breast. The phantoms have 400 μm voxels and simulate the three-dimensional distributions of adipose and fibroglandular tissues, Cooper's ligaments, ducts and skin and allow the estimation of dose to individual tissues. Calculations of the incident air kerma to mean glandular dose conversion factor, g, were made using a Mo/Mo spectrum at 28 kV for eight phantoms in the thickness range 40-80 mm and of varying glandularity. The values differed from standard tabulations used for breast dosimetry by up to 43%, because of the different spatial distribution of glandular tissue within the breast. To study this further, additional voxel phantoms were constructed, which gave variations of between 9 and 59% compared with standard values. For accurate breast dosimetry, it is therefore very important to take the distribution of glandular tissues into account. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 6. Dance, David
    et al.
    McVey, Graham
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Verdun, Francis
    The optimisation of lumbar spine AP radiography using realistic computer model.2000In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, p. 207-210Article in journal (Refereed)
  • 7.
    Dance, David
    et al.
    n/a.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Persliden, Jan
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Optimisation of the design of antiscatter grids by computer modelling1995In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 57, no 1, p. 207-210Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo computer program has been developed to model diagnostic radiological examinations, and has been used to study and optimise the design of antiscatter grids. This is important because the use of an inappropriate or poorly designed grid can lead to increased patient dose. Optimal grid parameters may be different for large and small scattering volumes. The program treats the patient as a rectangular block of tissue and takes account of the grid and image receptor. Image quality is measured in terms of contrast and signal-to-noise ratio and patient risk in terms of mean absorbed dose. Test objects of appropriate size and composition are used in the calculation of these image quality parameters. A new performance comparison and optimisation procedure has been developed, and the program has been used to study grid design in screen-film and digital radiology for small, medium and large scattering volumes.

  • 8. Geijer, H
    et al.
    Persliden, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Varied tube potential with constant effective dose at lumbar spine radiography using a flat-panel digital detector2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 240-245Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to evaluate the image quality at different tube potential (kV) settings using anteroposterior lumbar spine radiography as a model. An Alderson phantom was used with a flat-panel detector. The tube potential varied between 48 and 125 kV while the tube charge (mAs) was adjusted to keep an effective dose of 0.11 mSv. Image quality was assessed with a visual grading analysis and with a CDRAD contrast-detail phantom together with a computer program. The VGA showed inferior image quality for the higher kV settings, ≥ 96 kV with similar results for the contrast-detail phantom. When keeping the effective dose fixed, it seems beneficial to reduce kV to get the best image quality despite the fact that the mAs is not as high as with automatic exposure. However, this cannot be done with automatic exposure, which is set for a constant detector dose.

  • 9.
    Grindborg, J.-E.
    et al.
    Swedish Radiation Protection Authority, Stockholm, Sweden.
    Lillhok, J.E.
    Lillhök, J.E., Swedish Radiation Protection Authority, Stockholm, Sweden.
    Lindborg, L.
    Swedish Radiation Protection Authority, Stockholm, Sweden.
    Gudowska, I.
    Medical Radiation Physics, Karolinska Institutet, Stockholm University, Stockholm, Sweden.
    Söderberg, Jonas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics .
    Carlsson, Görel
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Thematic Studies.
    Nikjoo, H.
    NASA Johnson Space Center, Houston, TX, United States.
    Nanodosimetric measurements and calculations in a neutron therapy beam2007In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 126, no 1-4, p. 463-466Article in journal (Refereed)
    Abstract [en]

    A comparison of calculated and measured values of the dose mean lineal energy (yD) for the former neutron therapy beam at Louvain-la-Neuve is reported. The measurements were made with wall-less tissue-equivalent proportional counters using the variance-covariance method and simulating spheres with diameters between 10 nm and 15 µm. The calculated yD-values were obtained from simulated energy distributions of neutrons and charged particles inside an A-150 phantom and from published yD-values for mono-energetic ions. The energy distributions of charged particles up to oxygen were determined with the SHIELD-HIT code using an MCNPX simulated neutron spectrum as an input. The mono-energetic ion yD-values in the range 3-100 nm were taken from track-structure simulations in water vapour done with PITS/KURBUC. The large influence on the dose mean lineal energy from the light ion (A > 4) absorbed dose fraction, may explain an observed difference between experiment and calculation. The latter being larger than earlier reported result. Below 50 nm, the experimental values increase while the calculated decrease. © The Author 2007. Published by Oxford University Press. All rights reserved.

  • 10.
    Gudowska, Irena
    et al.
    Stockholm University, Sweden.
    Ardenfors, Oscar
    Stockholm University, Sweden.
    Toma-Dasu, Iuliana
    Stockholm University, Sweden.
    Dasu, Alexandru
    Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Radiation burden from secondary doses to patients undergoing radiation therapy with photons and light ions and radiation doses from imaging modalities2014In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 161, no 1-4, p. 357-362Article in journal (Refereed)
    Abstract [en]

    Ionising radiation is increasingly used for the treatment of cancer, being the source of a considerable fraction of the medical irradiation to patients. With the increasing success rate of cancer treatments and longer life expectancy of the treated patients, the issue of secondary cancer incidence is of growing concern, especially for paediatric patients who may live long after the treatment and be more susceptible to carcinogenesis. Also, additional imaging procedures like CT, kV and MV imaging and PET, alone or in conjunction with radiation therapy, may add to the radiation burden associated with the risk of occurrence of secondary cancers. This work has been based on literature studies and is focussed on the assessment of secondary doses to healthy tissues that are delivered by the use of modern radiation therapy and diagnostic imaging modalities in the clinical environment.

  • 11.
    Helmrot, Ebba
    et al.
    Linköping University, Department of Medicine and Care, Radio Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Measurement of radiation dose in dental radiology.2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, p. 168-171Article in journal (Refereed)
    Abstract [en]

    Patient dose audit is an important tool for quality control and it is important to have a well-defined and easy to use method for dose measurements. In dental radiology, the most commonly used dose parameters for the setting of diagnostic reference levels (DRLs) are the entrance surface air kerma (ESAK) for intraoral examinations and dose width product (DWP) for panoramic examinations. DWP is the air kerma at the front side of the secondary collimator integrated over the collimator width and an exposure cycle. ESAK or DWP is usually measured in the absence of the patient but with the same settings of tube voltage (kV), tube current (mA) and exposure time as with the patient present. Neither of these methods is easy to use, and, in addition, DWP is not a risk related quantity. A better method of monitoring patient dose would be to use a dose area product (DAP) meter for all types of dental examinations. In this study, measurements with a DAP meter are reported for intraoral and panoramic examinations. The DWP is also measured with a pencil ionisation chamber and the product of DWP and the height that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs. H (DWP H) of the secondary collimator (measured using film) was compared to DAP. The results show that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs.

  • 12. Helmrot, Ebba
    et al.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Eckerdal, Olof
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics .
    Use of an ivory wedge as a test phantom in analysing the influence of scattered radiation and tube potential on radiolographic contrast in intraoral dental radiography1993In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 49, no 1, p. 125-127Article in journal (Refereed)
    Abstract [en]

    Contrast, noise and spatial resolution are fundamental physical concepts used to describe image quality. Contrast is one of the most important parameters in conventional film radiography. To facilitate the analysis of the radiographic contrast over a wide range of optical densities, an ivory wedge representative of objects with marked tissue discontinuities has been constructed. It can be used either separately or included within a PMMA phantom representing the middle face to simulate realistic scatter conditions. It is thus possible to investigate how radiographic contrast may be influenced by kV setting, beam filtration, type of generator (constant potential or single pulse) and type of film. The phantom has been used in optimising image quality relative to radiation risk, with the radiographic contrast being determined both theoretically and experimentally in terms of type of film (D and E speed), radiation and object contrast. The importance of controlling physical parameters when investigating image quality and how to achieve this using a well defined phantom is clearly demonstrated.

  • 13.
    Helmrot, Ebba
    et al.
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Sandborg, Michael
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Eckerdal, Olle
    n/a.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences.
    Scientific  instrument for a controlled choice of optimal photon energy in intra-oral radiography1998In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 80, no 1, p. 321-325Article in journal (Refereed)
    Abstract [en]

    Basic performance parameters are defined and analysed in order to optimise physical image quality in relation to the energy imparted to the patient in dental radiology. Air cavities were embedded in well-defined multimaterial, hard tissue phantoms to represent various objects in dento-maxillo-facial examinations. Basic performance parameters were: object contrast (C), energy imparted (_) to the patient, signal-to-noise ration (SNR), C2/_ (film) and (SNR)2/_ (digital imaging system) as functions of HVL (half-value layer), used to describe the photon energy spectrum. For the film receptor, the performance index C2/_ is maximum (optimal) at HVL values of 1.5-1.7 mm Al in the simulated Incisive, Premolar and Molar examinations. Other imaging tasks (examinations), not simulated here, may require other optimal HVL. For the digital imaging system (Digora) the performance index (SNR)2/_, theoretically calculated, indicates that a lower value of HVL is optimal than with film as receptor. However, due to the limited number of bits (8 bits) in the analogue to digital converter (ADC) contrast resolution is degraded and calls for use of higher photon energies (HVL). Customised optimisations with proper concern for patient category, type of examination, diagnostic task is the ultimate goal of this work. The conclusions stated above give some general advice on the appropriate choice of photon energy spectrum (HVL). In particular situations, it may be necessary to use more dose demanding kV settings (lower HVL) in order to get sufficient image quality for the diagnostic task.

  • 14.
    Helmrot, Ebba
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Thilander Klang, Anne
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, SE-413 45.
    METHODS FOR MONITORING PATIENT DOSEIN DENTAL RADIOLOGY2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 303-305Article in journal (Refereed)
    Abstract [en]

    Different types of X-ray equipment are used in dental radiology, such as intra-oral, panoramic, cephalometric, cone-beam computed tomography (CBCT) and multi-slice computed tomography (MSCT) units. Digital receptors have replaced film and screen-film systems and other technical developments have been made.

    The radiation doses arising from different types of examination are sparsely documented and often expressed in different radiation quantities. In order to allow the comparison of radiation doses using conventional techniques, i.e. intra-oral, panoramic and cephalometric units, with those obtained using, CBCT or MSCT techniques, the same units of dose must be used. Dose determination should be straightforward and reproducible, and data should be stored for each image and clinical examination.

    It is suggested here that air kerma-area product (PKA) values be used to monitor the radiation doses used in all types of dental examinations including CBCT and MSCT. However, for the CBCT and MSCT techniques, the estimation of dose must be more thoroughly investigated. The values recorded can be used to determine diagnostic standard doses and to set diagnostic reference levels for each type of clinical examination and equipment used. It should also be possible to use these values for the estimation and documentation of organ or effective doses. 

  • 15. Hunt, R
    et al.
    Dance, D
    Bakic, P
    Maidment, A
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ullman, Gustaf
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Calculation of the properties of digital mammograms using a computer simulation2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 395-398Article in journal (Refereed)
    Abstract [en]

    A Mote Carlo computer model of mammography has been developed to study and optimise the performance of digital mammographic systems. The program uses high-resolution voxel phantoms to model the breast, which simulate the adipose and fibroglandular tissues, Cooper's ligaments, ducts and skin in three dimensions. The model calculates the dose to each tissue, and also the quantities such as energy imparted to image pixels, noise per image pixel and scatter-to-primary (S/P) ratios. It allows studies of the dependence of image properties on breast structure and on position within the image. The program has been calibrated by calculating and measuring the pixel values and noise for a digital mammographic system. The thicknesses of two components of this system were unknown, and were adjusted to obtain a good agreement between measurement and calculation. The utility of the program is demonstrated with the calculations of the variation of the S/P ratio with and without a grid, and of the image contrast across the image of a 50-mm-thick breast phantom. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 16. Hunt, R
    et al.
    Dance, D
    Pachoud, M
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ullman, Gustaf
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Verdun, F
    Monte Carlo simulation of a mammographic test phantom2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 432-435Article in journal (Refereed)
    Abstract [en]

    A test phantom, including a wide range of mammographic tissue equivalent materials and test details, was imaged on a digital mammographic system. In order to quantify the effect of scatter on the contrast obtained for the test details, calculations of the scatter-to-primary ratio (S/P) have been made using a Monte Carlo simulation of the digital mammographic imaging chain, grid and test phantom. The results show that the S/P values corresponding to the imaging conditions used were in the range 0.084-0.126. Calculated and measured pixel values in different regions of the image were compared as a validation of the model and showed excellent agreement. The results indicate the potential of Monte Carlo methods in the image quality-patient dose process optimisation, especially in the assessment of imaging conditions not available on standard mammographic units. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 17. Håkansson, M
    et al.
    Båth, M
    Börjesson, S
    Kheddache, S
    Flinck, A
    Ullman, Gustaf
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Månsson, LG
    Nodule detection in digital chest radiography: Effect of nodule location2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 92-96Article in journal (Refereed)
    Abstract [en]

    Most detection studies in chest radiography treat the entire chest image as a single background or divided into the two regions parenchyma and mediastinum. However, the different parts of the lung show great variations in attenuation and structure, leading to different amounts of quantum noise and scattered radiation as well as different complexity. Detailed data on the difference in detectability in the different regions are of importance. The purpose of this study was to quantify the difference in detectability between different regions of a chest image. The chest X ray was divided into six different regions, where each region was considered to be uniform in terms of detectability. Thirty clinical chest images were collected and divided into the different regions. Simulated designer nodules with a full-width-at-fifth-maximum of 10 mm but with varying contrast were added to the images. An equal number of images lacking pathology were included and a receiver operating characteristic (ROC) study was conducted with five observers. Results show that the image contrast needed to obtain a constant value of Az (area under an ROC curve) differs by more than a factor of four between different regions. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 18.
    Israelsson, Axel
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dose response of xylitol and sorbitol for EPR retrospective dosimetry with applications to chewing gum2013In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 154, no 2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    The purpose of this investigation was to study the radiation-induced electron paramagnetic resonance signal in sweeteners xylitol and sorbitol for use in retrospective dosimetry. For both sweeteners and chewing gum, the signal changed at an interval of 1–84 d after irradiation with minimal changes after 4–8 d. A dependence on storage conditions was noticed and the exposure of the samples to light and humidity was therefore minimised. Both the xylitol and sorbitol signals showed linearity with dose in the measured dose interval, 0–20 Gy. The dose-response measurements for the chewing gum resulted in a decision threshold of 0.38 Gy and a detection limit of 0.78 Gy. A blind test illustrated the possibility of using chewing gums as a retrospective dosemeter with an uncertainty in the dose determination of 0.17 Gy (1 SD).

  • 19.
    Kardell, Martin
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Faculty of Science & Engineering.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Jeuthe, Julius
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Malusek, Alexandr
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    AUTOMATIC SEGMENTATION OF PELVIS FOR BRACHYTHERAPYOF PROSTATE2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 398-404Article in journal (Refereed)
    Abstract [en]

    Advanced model-based iterative reconstruction algorithms in quantitative computed tomography (CT) perform automatic segmentation of tissues to estimate material properties of the imaged object. Compared with conventional methods, these algorithms may improve quality of reconstructed images and accuracy of radiation treatment planning. Automatic segmentation of tissues is, however, a difficult task. The aim of this work was to develop and evaluate an algorithm that automatically segments tissues in CT images of the male pelvis. The newly developed algorithm (MK2014) combines histogram matching, thresholding, region growing, deformable model and atlas-based registration techniques for the segmentation of bones, adipose tissue, prostate and muscles in CT images. Visual inspection of segmented images showed that the algorithm performed well for the five analysed images. The tissues were identified and outlined with accuracy sufficient for the dual-energy iterative reconstruction algorithm whose aim is to improve the accuracy of radiation treatment planning in brachytherapy of the prostate.

  • 20.
    Kataria, Bharti
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Nilsson Althen, Jonas
    Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    IMPLICATIONS OF PATIENT CENTRING ON ORGAN DOSE IN COMPUTED TOMOGRAPHY2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 130-135Article in journal (Refereed)
    Abstract [en]

    Automatic exposure control (AEC) in computed tomography (CT) facilitates optimisation of dose absorbed by the patient. The use of AEC requires appropriate ‘patient centring’ within the gantry, since positioning the patient off-centre may affect both image quality and absorbed dose. The aim of this experimental study was to measure the variation in organ and abdominal surface dose during CTexaminations of the head, neck/thorax and abdomen. The dose was compared at the isocenter with two off-centre positions—ventral and dorsal to the isocenter. Measurements were made with an anthropomorphic adult phantom and thermoluminescent dosemeters. Organs and surfaces for ventral regions received lesser dose (5.6–39.0 %) than the isocenter when the phantom was positioned 13 cm off-centre. Similarly, organ and surface doses for dorsal regions were reduced by 5.0–21.0 % at 25 cm off-centre. Therefore, correct vertical positioning of the patient at the gantry isocenter is important to maintain optimal imaging conditions.

  • 21.
    Kolbun, Natallia
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Adolfsson, Emelie
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Gustafsson, Håkan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    High-resolution mapping of 1D and 2D dose distributions using X-band electron paramagnetic resonance imaging2014In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 159, no 1-4, p. 182-187Article in journal (Refereed)
    Abstract [en]

    Electron paramagnetic resonance imaging (EPRI) was performed to visualise 2D dose distributions of homogenously irradiated potassium dithionate tablets and to demonstrate determination of 1D dose profiles along the height of the tablets. Mathematical correction was applied for each relative dose profile in order to take into account the inhomogeneous response of the resonator using X-band EPRI. The dose profiles are presented with the spatial resolution of 0.6 mm from the acquired 2D images; this value is limited by pixel size, and 1D dose profiles from 1D imaging with spatial resolution of 0.3 mm limited by the intrinsic line-width of potassium dithionate. In this paper, dose profiles from 2D reconstructed electron paramagnetic resonance (EPR) images using the Xepr software package by Bruker are focussed. The conclusion is that using potassium dithionate, the resolution 0.3 mm is sufficient for mapping steep dose gradients if the dosemeters are covering only +/- 2 mm around the centre of the resonator.

  • 22.
    Lillhök, Jan
    et al.
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Persson, Linda
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Andersen, Claus E.
    Center for Nuclear Technologies, Technical University of Denmark, Roskilde, Denmark.
    Dasu, Alexandru
    The Skandion Clinic, Uppsala, Sweden.
    Ardenfors, Oscar
    Medical Radiation Physics, Department of Physics, Stockholm University, Stockholm, Sweden.
    Radiation protection measurements with the variance-covariance method in the stray radiation fields from photon and proton therapy facilities2018In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 180, no 1-4, p. 338-341Article in journal (Refereed)
    Abstract [en]

    The microdosimetric variance–covariance method was used to study the stray radiation fields from the photon therapy facility at the Technical University of Denmark and the scanned proton therapy beam at the Skandion Clinic in Uppsala, Sweden. Two TEPCs were used to determine the absorbed dose, the dose-average lineal energy, the dose-average quality factor and the dose equivalent. The neutron component measured by the detectors at the proton beam was studied through Monte Carlo simulations using the code MCNP6. In the photon beam the stray absorbed dose ranged between 0.3 and 2.4 μGy per monitor unit, and the dose equivalent between 0.4 and 9 μSv per monitor unit, depending on beam energy and measurement position. In the proton beam the stray absorbed dose ranged between 3 and 135 μGy per prescribed Gy, depending on detector position and primary proton energy.

  • 23.
    Lindborg, Lennart
    et al.
    Karolinska Institute, Sweden.
    Hultqvist, Martha
    RaySearch Labs, Sweden.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Swedish Radiat Safety Author, Sweden.
    Nikjoo, Hooshang
    Karolinska Institute, Sweden.
    Nanodosimetry and RBE values in radiotherapy2015In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 166, no 1-4, p. 339-342Article in journal (Refereed)
    Abstract [en]

    In a recent paper, the authors reported that the dose mean lineal energy, (y) over bar (D) in a volume of about 10-15 nm is approximately proportional to the alpha-parameter in the linear-quadratic relation used in fractionated radiotherapy in both low- and high-LET beams. This was concluded after analyses of reported radiation weighting factors, W-isoE (clinical RBE values), and (y) over bar (D) values in a large range of volumes. Usually, microdosimetry measurements in the nanometer range are difficult; therefore, model calculations become necessary. In this paper, the authors discuss the calculation method. A combination of condensed history Monte Carlo and track structure techniques for calculation of mean lineal energy values turned out to be quite useful. Briefly, the method consists in weighting the relative dose fractions of the primary and secondary charged particles with their respective energy-dependent dose mean lineal energies. The latter were obtained using a large database of Monte Carlo track structure calculations.

  • 24.
    Lund, Eva
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Adolfsson, Emelie
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Kolbun, Natallia
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Gustafsson, Håkan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    EPR imaging of dose distributions aiming at applications in radiation therapy2014In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 159, no 1-4, p. 130-136Article in journal (Refereed)
    Abstract [en]

    A one-dimensional electron paramagnetic resonance (EPR) imaging method for visualisation of dose distributions in photon fields has been developed. Pressed pellets of potassium dithionate were homogeneously irradiated in a Co-60 radiation field to 600 Gy. The EPR analysis was performed with an X-Band (9.6 GHz) Bruker E540 EPR and EPR imaging spectrometer equipped with an E540 GC2X two-axis X-band gradient coil set with gradients along the y axis (along the sample tube) and z axis (along B-0) and an ER 4108TMHS resonator. Image reconstruction, including deconvolution, baseline corrections and corrections for the resonator sensitivity, was performed using an in-house-developed Matlab code for the purpose to have a transparent and complete algorithm for image reconstruction. With this method, it is possible to visualise a dose distribution with an accuracy of similar to 5 % within +/- 5 mm from the centre of the resonator.

  • 25.
    Lund, Eva
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Kyllönen, JE
    Grindborg, JE
    Lindborg, L
    Performance testing of personal dosemeters from eleven dosimetry services in Sweden2001In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 96, no 1-3, p. 99-103Article in journal (Refereed)
    Abstract [en]

    The Swedish regulation, SSI FS 98:5, requires that radiological workers of category A use dosemeters from an approved personal dosimetry service. The 11 services operating in Sweden at the moment use five different types of dosemeter. All have been tested for their ability to determine Hp(10) and some of them to determine Hp(0.07) according to the European Commission report Radiation Protection 73, EUR 14852, of 1994. The five unique systems have been tested regarding the angular and energy dependence of the response of the dosemeters. The test points for the determination of Hp(10) are all, except one, within the trumpet curve and for the unique systems it is shown that the uncertainty related to angular response at three different energies is within the required ▒40% except for the lowest X ray quality 40 kV. The energy dependence dominates over the directional dependence and the choice of radiation quality for calibration is of great importance for the system performance.

  • 26.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Medicine and Health Sciences.
    ACCURATE KAP METER CALIBRATION AS A PREREQUISITE FOR OPTIMISATION IN PROJECTION RADIOGRAPHY2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 353-359Article in journal (Refereed)
    Abstract [en]

    Modern X-ray units register the air kerma–area product, PKA, with a built-in KAP meter. Some KAP meters show an energydependent bias comparable with the maximum uncertainty articulated by the IEC (25 %), adversely affecting dose-optimisation processes. To correct for the bias, a reference KAP meter calibrated at a standards laboratory and two calibration methods described here can be used to achieve an uncertainty of <7 % as recommended by IAEA. A computational model of the reference KAP meter is used to calculate beam quality correction factors for transfer of the calibration coefficient at the standards laboratory, Q0, to any beam quality, Q, in the clinic. Alternatively, beam quality corrections are measured with an energy-independent dosemeter via a reference beam quality in the clinic, Q1, to beam quality, Q. Biases up to 35 % of built-in KAP meter readings were noted. Energy-dependent calibration factors are needed for unbiased PKA. Accurate KAP meter calibration as a prerequisite for optimisation in projection radiography.

  • 27. Moores, B
    et al.
    Mattsson, S
    Månsson, LG
    Panzer, W
    Regulla, D
    Dance, D
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Verdun, F
    Buhr, E
    Hoeschen, C
    RADIUS - Closing the circle on the assessment of imaging performance2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 450-457Article in journal (Refereed)
    Abstract [en]

    The RADIUS (Radiological Imaging Unification Strategy) project addresses the assessment of image quality in terms of both physical and clinically relevant measures. The aim is to unify our understanding of both types of measure as well as the numerous underlying factors that play a key role in the assessments of imaging performance. In this way it is expected to provide a solid basis for the improvement in radiological safety management, where not only radiation risks are considered but also diagnostic risks of incorrect clinical outcomes (i.e. false positive/false negative). The project has applied a variety of relevant experimental and theoretical methods to this problem, which is generic to medical imaging as a whole. Digital radiography of the chest and the breast has been employed as the clinical imaging domain vehicles for the study. The project addressed the problem from the following directions: role and relevance of pathology, human observer studies including receiver operating characteristics, image quality criteria analysis, structural noise analysis, physical measurements on clinical images, physical measurements on imaging system, modelling of imaging system, modelling of visual processes, modelling of doses delivered and IT-based scientific support strategies. This paper presents an overview of the main outcomes from this project and highlights how the research outcomes actually apply to the real world. In particular, attention will be focused on new and original findings and methods and techniques that have been developed within the framework of the project. The relevance of the project's outcomes to future European research will also be presented. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 28.
    Nilsson Althén, Jonas
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Medicine and Health Sciences.
    Sandborg, Michael
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    VERIFICATION OF INDICATED SKIN ENTRANCE AIR KERMA FORCARDIAC X-RAY-GUIDED INTERVENTION USING GAFCHROMIC FILM2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 245-248Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to verify the indicated maximum entrance surface air kerma (ESAK) using a GE Innova IGS 520 imaging system during cardiac interventional procedures. Gafchromic XR RV3 films were used for the patient measurements to monitor the maximum ESAK. The films were scanned and calibrated to measure maximum ESAK. Thermoluminescent dosemeters were used to measure the backscatter factor from an anthropomorphic thorax phantom. The measured backscatter factor, 1.53, was in good agreement with Monte Carlo simulations but higher than the one used by the imaging system, 1.20. The median of the ratio between indicated maximum ESAK and measured maximum ESAKwas 0.68. In this work, the indicated maximum ESAK by the imaging system’s dose map model underestimates the measured maximum ESAK by 32 %. The threshold ESAK for follow-up procedures for patient with skin dose in excess of 2 Gy will be reduced to 1.4 Gy.

  • 29.
    Nilsson, Jonas
    Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Surgery in Östergötland. Linköping University, The Institute of Technology.
    Automatic tube-current modulation in CT - A comparison between different solutions2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 308-312Article in journal (Refereed)
    Abstract [en]

    In this study, tube-current modulation systems on two different CT equipments have been evaluated: Care Dose from Siemens and Auto mA from GE Medical Systems. Care Dose modulates the tube current in the xy-plane during rotation whereas Auto mA modulates the tube current in the z-direction. xy-Plane modulation was investigated by using an elliptic Poly-methylmethacrylate phantom and a CTDI-ion chamber. To investigate modulation in the z-direction, an anthropomorphic dosimetry phantom (Atom) was used. Tests performed with and without tube-current modulation were compared with respect to absorbed dose and image quality. In the anthropomorphic phantom measurements, the dose savings were 15% using Care Dose and the photon starvation artefacts were negligible. Using Auto mA the absorbed dose depends on the chosen noise level. Image noise becomes more constant throughout the patient but photon starvation artefacts remain. We conclude that the two tube-current modulation techniques show different dose advantages and image quality artefacts. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 30.
    Norrman, E.
    et al.
    Department of Natural Sciences, Örebro University, S-70182 Örebro, Sweden.
    Persliden, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    A factorial experiment on image quality and radiation dose2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 246-252Article in journal (Refereed)
    Abstract [en]

    To find if factorial experiments can be used in the optimisation of diagnostic imaging, a factorial experiment was performed to investigate some of the factors that influence image quality, kerma area product (KAP) and effective dose (E). In a factorial experiment the factors are varied together instead of one at a time, making it possible to discover interactions between the factors as well as major effects. The factors studied were tube potential, tube loading, focus size and filtration. Each factor was set to two levels (low and high). The influence of the factors on the response variables (image quality, KAP and E) was studied using a direct digital detector. The major effects of each factor on the response variables were estimated as well as the interaction effects between factors. The image quality, KAP and E were mainly influenced by tube loading, tube potential and filtration. There were some active interactions, for example, between tube potential and filtration and between tube loading and filtration. The study shows that factorial experiments can be used to predict the influence of various parameters on image quality and radiation dose. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 31.
    Persliden, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Patient and staff doses in interventional X-ray procedures in Sweden2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 150-157Article in journal (Refereed)
    Abstract [en]

    Interventional procedures in radiology are of concern because of irradiation doses to the patients and also to the staff. A questionnaire sent to all radiology departments in Sweden showed that 11,350 procedures were performed annually 1996-1997. In a follow-up study, data from patient procedures were recorded. Type of procedure, dose-area product (DAP) values, fluoroscopy times, number of radiography series and patient data were recorded. For some procedures, staff doses were measured. Skin doses to the patients were also calculated where possible. Results: A total of 380 interventional procedures were described. The procedures were grouped into cranial, neck and thorax, intestine and abdominal, uro/genital and pelvis and extremities. DAP and fluoroscopy times (mean values) were 200 Gy cm2 for 57 min, 57 Gy cm2 for 16 min, 270 Gy cm2 for 35 min, 212 Gy cm2 for 37 min, 67 Gy cm2 for 21 min, respectively, for the named procedures. Maximum patient skin doses exceeded threshold values for erythema (2 Gy) in cranial, neck/thorax and intestine/abdominal procedures. Effective doses to the patients could be high, 200 mSv. Conclusion: It was found that patient doses could exceed threshold values for skin erythema (2 Gy) and temporary epilation (3 Gy). Hence, the procedures require immediate improvement. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 32.
    Persson, Anders
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Will medical visualisation tools meet medical user requirements in the future?2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 12-19Article in journal (Refereed)
    Abstract [en]

    This paper describes state-of-the-art medical visualisation and discusses the need for a research agenda that focuses on the development of the next generation of medical acquisition and visualisation tools, emphasising the fact that these tools must be based on medical user requirement and workflow studies as well as on new technical developments.

  • 33.
    Sandborg, Michael
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Persliden, Jan
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dance, David
    n/a.
    Comparison of different materials for test phantoms in diagnostic radiology1993In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 49, no 1, p. 345-347Article in journal (Refereed)
    Abstract [en]

    The use of test phantoms in diagnostic radiology is a well established practice in image quality control. Here Monte Carlo methods are used for comparing different phantom materials (water, Lucite, polystyrene, paraffin wax, Mylar, Mix-D, M3, Alderson muscle B and A-150) relative to soft tissue with regard to different physical quantities such as contrast and mean absorbed dose in the phantom. The results for each material are derived as the equivalent thicknesses resulting in the same value of the quantity of interest as a soft tissue phantom of a given thickness, this being varied between 5 and 25 cm. The phantom material yielding the smallest spread of equivalent thicknesses is regarded as the most soft tissue equivalent one. Water, Mix-D and M3 are the materials most equivalent to soft tissue of the phantom materials tested. Paraffin wax, polystyrene and Lucite show a larger spread in equivalent thicknesses.

  • 34.
    Sandborg, Michael
    et al.
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dance, David
    n/a.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Persliden, Jan
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Results from an optimisation of grid design in diagnostic radiology1995In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 57, no 1, p. 211-215Article in journal (Refereed)
    Abstract [en]

    Results of an optimisation of grid design using a Monte Carlo model of the imaging chain are presented. Patient dose is significantly reduced by changing from aluminium to fibre grid covers and interspaces while keeping contrast constant. Numerous commercial grids have been investigated to identify superior designs. For optimal use, grids with high strip density require thinner lead strips and higher ratios than grids with low strip density. In paediatric radiology, grids with very thin strips (10-20 µm), or an air gap can be considered. In an adult lumbar spine examination, the optimal grid ratios are higher (greater than 15) than in commercial grids. This is particularly accentuated for grids with high strip density, fibre interspaces and in the lateral view. For a given imaging task, it is possible to identify grids of different design that have good performance, provided an appropriate strip width and tube potential are selected.

  • 35.
    Sandborg, Michael
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    McVey, Graham
    Dance, David
    Alm Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Comparison of model predictions of image quality with results of clinical trials in chest and lumbar spine screen-film imaging2000In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, no 1-2, p. 173-176Article in journal (Refereed)
    Abstract [en]

    The ability to predict image quality from known physical and technical parameters is a prerequisite for making successful dose optimisation. In this study, imaging systems have been simulated using a Monte Carlo model of the imaging systems. The model includes a voxelised human anatomy and quantifies image quality in terms of contrast and signal-to-noise ratio for 5-6 anatomical details included in the anatomy. The imaging systems used in clinical trials were simulated and the ranking of the systems by the model and radiologists compared. The model and the results of the trial for chest PA both show that using a high maximum optical density was significantly better than using a low one. The model predicts that a good system is characterised by a large dynamic range and a high contrast of the blood vessels in the retrocardiac area. The ranking by the radiologists and the model agreed for the lumbar spine AP.

  • 36.
    Sandborg, Michael
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    McVey, Graham
    Dance, David
    Persliden, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics.
    Alm Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    A voxel phantom based Monte Carlo computer program for optimisation of chest and lumbar spine X ray imaging systems2000In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, no 1-2, p. 105-108Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo computer model of X ray imaging systems has been developed which uses a voxel phantom to simulate the patient. Image details were selected in accordance with the European quality criteria document. Contrast and signal-to-noise ratio for these details were calculated to estimate image quality. Effective dose was computed to enable optimisation. The program was validated with measurements on phantoms, patients and digitised patient images. It was demonstrated that the computational model of the imaging system provides predictions of entrance dose and contrast that lie within the range of values measured on patients. To illustrate the importance of using a realistic model of the patient, scatter-to-primary ratios, S/P, in a chest PA examination were calculated. It was found that the S/P varied by a factor of 10 in the image and that a grid was slightly more efficient than an air gap in removing the scatter behind the heart.

  • 37.
    Sandborg, Michael
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Nilsson Althen, Jonas
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Gustafsson, Agneta
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    EFFICIENT QUALITY ASSURANCE PROGRAMS IN RADIOLOGY AND NUCLEAR MEDICINE IN ÖSTERGÖTLAND, SWEDEN2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 410-417Article in journal (Refereed)
    Abstract [en]

    Owners of imaging modalities using ionising radiation should have a documented quality assurance (QA) program, as well as methods to justify new radiological procedures to ensure safe operation and adequate clinical image quality. This includes having a system for correcting divergences, written imaging protocols, assessment of patient and staff absorbed doses and a documented education and training program. In this work, how some aspects on QA have been implemented in the County of Östergötland in Sweden, and efforts to standardise and automate the process as an integrated part of the radiology and nuclear medicine QA programs were reviewed. Some key performance parameters have been identified by a Swedish task group of medical physicists to give guidance on selecting relevant QA methods. These include low-contrast resolution, image homogeneity, automatic exposure control, calibration of air kerma-area product metres and patient–dose data registration in the radiological information system, as well as the quality of reading stations and of the transfer of images to the picture archive and communication system. IT-driven methods to automatically assess patient doses and other data on all examinations are being developed and evaluated as well as routines to assess clinical image quality by use of European quality criteria. By assessing both patient absorbed doses and clinical image quality on a routine basis, the medical physicists in our region aim to be able to spend more time on imaging optimisation and less time on periodic testing of the technical performance of the equipment, particularly on aspects that show very few divergences. The role of the Medical Physics Expert is rapidly developing towards a person doing advanced data-analysis and giving scientific support rather than one performing mainly routine periodic measurements. It is concluded that both the European Council directive and the rapid development towards more complex diagnostic imaging systems and procedures support this changing role of the medical physics professional.

  • 38.
    Tapiovaara, Markku
    et al.
    n/a.
    Servomaa, Antti
    n/a.
    Sandborg, Michael
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dance, David
    n/a.
    Optimizing the imaging conditions in paediatric fluoroscopy2000In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, no 1-2, p. 211-216Article in journal (Refereed)
    Abstract [en]

    Patient dose and image quality were studied in paediatric fluoroscopy. The study consisted of two parts: theoretical calculation of optimal imaging conditions by the Monte Carlo method and clinical measurements of dose rate and SNR2rate at six hospitals. For many imaging tasks the most efficient imaging technique in fluoroscopy is obtained by using high filtration, relatively low X ray tube potential and a fibre-interspaced and -covered grid for all but the smallest patients and X ray field sizes. The clinical measurements supported our theoretical results and revealed a notable variation in image quality and dose rate among the hospitals studied. Notable patient dose rate reduction seems possible in paediatric fluoroscopy by adjusting the equipment to work with more efficient imaging factors and a low image receptor input dose rate.

  • 39.
    Tesselaar, Erik
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    CLINICAL AUDIT OF IMAGE QUALITY IN RADIOLOGY USING VISUAL GRADING CHARACTERISTICS ANALYSIS2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 340-346Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to assess whether an audit of clinical image quality could be efficiently implemented within a limited time frame using visual grading characteristics (VGC) analysis. Lumbar spine radiography, bedside chest radiography and abdominal CT were selected. For each examination, images were acquired or reconstructed in two ways. Twenty images per examination were assessed by 40 radiology residents using visual grading of image criteria. The results were analysed using VGC. Inter-observer reliability was assessed. The results of the visual grading analysis were consistent with expected outcomes. The inter-observer reliability was moderate to good and correlated with perceived image quality (r2 5 0.47). The median observation time per image or image series was within 2 min. These results suggest that the use of visual grading of image criteria to assess the quality of radiographs provides a rapid method for performing an image quality audit in a clinical environment.

  • 40.
    Tesselaar, Erik
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    ASSESSING THE USEFULNESS OF THE QUASI-IDEAL OBSERVER FORQUALITY CONTROL IN FLUOROSCOPY2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 360-364Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to evaluate the reliability of the square of the signal-to-noise ratio rate, SNR2rate, as a precise measurement for quality control test in a digital fluoroscopy system. The quasi-ideal model observer was used to measure SNR2rate. The dose rate, pulse rate and field of view were varied, and their effect on dose efficiency, defined as SNR2rate=PKA;rate, was evaluated (where PKA;rate is the air kerma-area product rate). Measurements were repeated to assess reproducibility. The relative standard deviation in SNR2rate=PKA;rate over seven consecutive measurements was 5 %. No significant variation in SNR2rate=PKA;rate was observed across different pulse rates (10–30 pulses s-1). The low-dose-rate setting had a superior dose efficiency compared with the medium- and high-dose-rate settings. A smaller field of view resulted in higher dose efficiency. The results show that SNR2rate=PKA;rate measurements offer the high precision required in quality control constancy tests.

  • 41.
    Thilander Klang, Anne
    et al.
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, SE-413 45.
    Helmrot, Ebba
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Faculty of Health Sciences.
    METHODS OF DETERMINING THE EFFECTIVE DOSE INDENTAL RADIOLOGY2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 306-309Article in journal (Refereed)
    Abstract [en]

    A wide variety of X-ray equipment is used today in dental radiology, including intra-oral, orthopantomographic, cephalometric, cone-beam computed tomography (CBCT) and computed tomography (CT). This raises the question of how the radiation risks resulting from different kinds of examinations should be compared. The risk to the patient is usually expressed in terms of the effective dose. However, it is difficult to determine its reliability, and it is difficult to make comparisons, especially when different modalities are used. The classification of the new CBCT units is also problematic as they are sometimes classified as CT units. This will lead to problems in choosing the best dosimetric method, especially when the examination geometry more resembles an ordinary orthopantomographic examination, as the axis of rotation is not at the centre of the patient, and small radiation field sizes are used. The purpose of this study was to present different methods for the estimation of the effective dose from the equipment currently used in dental radiology, and to discuss their limitations. The methods are compared based on common used measurable and computable dose quantities, and their reliability in the estimation of effective dose.

  • 42. Tingberg, A
    et al.
    Båth, M
    Håkansson, M
    Medin, J
    Besjakov, J
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Mattsson, S
    Månsson, LG
    Evaluation of image quality of lumbar spine images: A comparison between FFE and VGA2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 53-61Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim of the present study is to compare two different methods for evaluation of the quality of clinical X-ray images. Methods: Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists. Results: In the VGA study, images with low noise were preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study, the visibility of the lesions was independent of the sharpness and the noise level. No correlation was found between the two image quality measures. Conclusions: FFE is a precise method for evaluation of image quality, but the results are only valid for the type of lesion used in the study, whereas VGA is a more general method for clinical image quality assessment. The results of the FFE study indicate that there might be a potential to lower the dose levels in lumbar spine radiography without losing important diagnostic information. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 43. Tingberg, A
    et al.
    Eriksson, F
    Medin, J
    Besjakov, J
    Båth, M
    Håkansson, M
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Almen, A
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Mattsson, S
    Månsson, LG
    Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 62-68Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. Background: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. Methods: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point, and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. Results: The results of this study indicate that - contrary to what was supposed - the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. Conclusions: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 44.
    Ullman, Gustaf
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dance, David R.
    Royal Surrey County Hospital, Guildford.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Svalkvist, Angelica
    University of Gothenburg.
    Båth, Magnus
    University of Gothenburg.
    A Monte Carlo-based model for simulation of digital chest tomosynthesis2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 159-163Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to calculate synthetic digital chest tomosynthesis projections using a computer simulation model based on the Monte Carlo method. An anthropomorphic chest phantom was scanned in a computed tomography scanner, segmented and included in the computer model to allow for simulation of realistic high-resolution X-ray images. The input parameters to the model were adapted to correspond to the VolumeRAD chest tomosynthesis system from GE Healthcare. Sixty tomosynthesis projections were calculated with projection angles ranging from +15 to −15°. The images from primary photons were calculated using an analytical model of the anti-scatter grid and a pre-calculated detector response function. The contributions from scattered photons were calculated using an in-house Monte Carlo-based model employing a number of variance reduction techniques such as the collision density estimator. Tomographic section images were reconstructed by transferring the simulated projections into the VolumeRAD system. The reconstruction was performed for three types of images using: (i) noise-free primary projections, (ii) primary projections including contributions from scattered photons and (iii) projections as in (ii) with added correlated noise. The simulated section images were compared with corresponding section images from projections taken with the real, anthropomorphic phantom from which the digital voxel phantom was originally created. The present article describes a work in progress aiming towards developing a model intended for optimisation of chest tomosynthesis, allowing for simulation of both existing and future chest tomosynthesis systems.

  • 45.
    Ullman, Gustaf
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Sandborg, Michael
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Dance, D
    Hunt, R
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    The influence of patient thickness and imaging system on patient dose and physical image quality in digital chest imaging2005In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, no 1-3, p. 294-297Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to study the influence of patient thickness, tube voltage and image detector on patient dose, contrast and ideal observer signal-to-noise ratio (SNRI), for pathological details positioned at different regions in the image in posterior-anterior (PA) chest radiology. A Monte Carlo computational model was used to compute measures of physical image quality (contrast, SNRI) and patient effective dose, E. Two metastasis-like details positioned in the central right lung and right lung near the spine, respectively, were studied. The tube voltage was varied between 100 and 150 kV and the patient thickness between 20 and 28 cm. Both, a computed radiography (CR) system and a direct radiography (DR) system, were investigated. The DR system provides both lower doses and better image quality compared with the CR system. The SNRI2/E is ∼2.9 times higher for the DR system compared with the CR system. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 46.
    Örtenberg, Alexander
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering. Linköping University, Faculty of Medicine and Health Sciences.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Malusek, Alexandr
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    PARALLELISATION OF THE MODEL-BASED ITERATIVE RECONSTRUCTION ALGORITHM DIRA2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 405-409Article in journal (Refereed)
    Abstract [en]

    New paradigms for parallel programming have been devised to simplify software development on multi-core processors and many-core graphical processing units (GPU). Despite their obvious benefits, the parallelisation of existing computer programs is not an easy task. In this work, the use of the Open Multiprocessing (OpenMP) and Open Computing Language (OpenCL) frameworks is considered for the parallelisation of the model-based iterative reconstruction algorithm DIRA with the aim to significantly shorten the code’s execution time. Selected routines were parallelised using OpenMP and OpenCL libraries; some routines were converted from MATLAB to C and optimised. Parallelisation of the code with the OpenMP was easy and resulted in an overall speedup of 15 on a 16-core computer. Parallelisation with OpenCL was more difficult owing to differences between the central processing unit and GPU architectures. The resulting speedup was substantially lower than the theoretical peak performance of the GPU; the cause was explained.

1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf