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  • 1.
    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.
    Bragg-Gray Dosimetry: Theory of Burch2001Report (Other academic)
    Abstract [en]

    The theoretical approach to Bragg-Gray dosimetry is: a Bragg-Gray cavity is a cavity (detector) so small that, when inserted into a medium, it does not disturb the fluence of charged particles existing in the medium.

    This means that the ideal Bragg-Gray cavity (detector) is one of infinitesimal dimensions, a "point" detector. In practice, such detectors do not exist but many real detectors may, in a first approximation, be treated as Bragg-Gray detectors to a high degree of accuracy. Corrections needed (so called perturbation corrections) to account for the deviation of the signal from a practical detector from that of an ideal one has been treated by, e.g., ICRU 1984, Alm Carlsson, 1985, Svensson and Brahme 1986, Alm Carlsson 1987.

    Derivation of "perturbation corrections" needs careful consideration and under-standing of the ideal case, i.e., that from which deviations are to be corrected for. The ideal case of a Bragg-Gray detector has been treated by Bragg 1912, Gray 1936, Laurence 1937, Spencer and Attix 1955 and Burch 1955.

    The formulation of Bragg-Gray theory by Spencer and Attix has found wide practical application and has been treated in detail elsewhere. The theory of Burch treats the same problem as did Spencer and Attix, viz., the significance of generation and slowing down of delta-particles in both medium and detector. Burch treated the problem in considerable detail but didn't find a solution for practical calculations. From a physical point of view, however, there is much to learn from Burch's approach. Also, his treatment of so called track ends, evaluated in some detail by Burch 1957, has been adapted in later versions of the Spencer-Attix formulation of Bragg-Gray theory.

  • 2.
    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.
    Spencer-Attix kavitetsteori2001Report (Other academic)
    Abstract [en]

    Spencer-Attix kavitetsteori behandlar energideponeringen i en Bragg-Gray kavitet (detektor) inuti ett medium bestrålat med fotoner och med elektronjämvikt i mediet på kavitetens plats. Med en Bragg-Gray kavitet menas en kavitet så liten att

    • energideponeringen i kaviteten från elektroner frigjorda av fotoner i kaviteten är försumbar jämfört med energideponeringen från elektroner frigjorda av fotoner i omgivande mediet och som passerar in kaviteten
    • kaviteten skall inte nämnvärt störa fluensen av elektronerna i mediet, dvs kaviteten antas i varje punkt genomkorsad av samma fluens av elektroner, som finns i mediet i frånvaro av kaviteten
  • 3.
    Alm Carlsson, Gudrun
    et al.
    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.
    Carlsson, Carl A.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Pettersson, Håkan
    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.
    Riskuppskattningar och strålskydds-rekommendationer: Vår strålningsmiljö1991Report (Other academic)
    Abstract [sv]

    Människan har i alla tider varit utsatt för joniserande strålning. Kosmiskstrålning och naturligt radioaktiva nuklider i vår omgivning och i vår kropp ger ett årligtbidrag till den absorberade dosen i hela kroppen, som i genomsnitt för människorna påjorden uppgår till 1 mGy/år (1Gy = 1 J/kg). Det finns områden på jorden där stråldosenfrån naturlig strålning är 10-100 ggr större, jfr avsnittet "Vår strålningsmiljö".

    I slutet av 1800-talet upptäckte Röntgen röntgenstrålningen och Becquerel den naturligaradioaktiviteten. Människan fick därmed för första gången tillgång till starka källor avjoniserande strålning. Dessa togs snabbt i bruk framförallt inom medicinsk röntgendiagnostikoch radioterapi. Man gjorde snart bittra erfarenheter av den joniserandestrålningens skadliga biologiska verkningar efter höga stråldoser. Fram till år 1922 hadec:a 100 radiologer dött av strålskador. Man insåg att något måste göras för att förbättraläget för personalen och år 1928 bildades ICRP (International Commission on RadiationProtection). ICRP ger ut rekommendationer för strålskydd, som ligger till grund förnationella lagar och förordningar över hela världen.

    Den förhållandevis långa erfarenhet människan har av joniserande strålning och denlätthet med vilken även små stråldoser kan mätas har gett oss stränga normer vad gällerhanteringen av producerade strålkällor. Många har därför uppfattningen att joniserandestrålning är en exklusiv miljökomponent. Så är knappast fallet. Förutom att vi alltid varitnaturligt bestrålade finns det idag anledning att förmoda att den kemiska nedsmutsningenav miljön är ett långt allvarligare hot mot vårt välbefinnande än den nuvarandeanvändningen av producerade strålkällor. En rättvis bedömning av olika miljökomponenterkan endast göras den gång alla mäts med samma mått. Arbete med dennainriktning pågår med strålskydds-verksamheten som förebild.

  • 4.
    Alm Carlsson, Gudrun
    et al.
    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.
    Ekberg, Stefan
    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.
    Helmrot, Ebba
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Lindström, Jan
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Lund, Eva
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Matscheko, Georg
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Nilsson, Håkan
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Persliden, Jan
    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.
    Sandborg, Michael
    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.
    Stenström, Mats
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Monte Carlo metoden: ett verktyg inom strålningsfysiken1995Report (Other academic)
    Abstract [sv]

    Detta kompendium är tänkt att användas som ett propedeutiskt kursmaterial för kursdeltagare i kursen "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter".

    Först följer en kort repetition av den grundläggande statistik som utnyt1jas i beräkningarna. Därefter följer en beskrivning av slumptal. det fundament som metoden bygger på. Vidare beskrivs val ur olika frekvensfunktioner. Valet kan även göras ur så kallade falska fördelningar för att reducera variansen i den skattade storheten. Metoderna belyses i ett avsnitt om problemlösningsmetodik. först i allmänna termer för att sen gå in på ett specifikt problem (Buffons nålproblem) där en analys och strukturering av problemet görs varefter flödesschema och kodning exemplifieras. Så följer två moment där en beskrivning görs av färderna av fotoner respektive elektroner genom materia. För elektronfärderna gör man en indelning i klass 1- och klass II-färder. Vad detta innebär och hur deltapartiklar tas om hand beskrivs i ett kapitel. Till sist kommer en kort introduktion till de tre laborationerna med laborationshandledningar. Speciell vikt har lagts vid att initiera laboranten att fundera på fysiken i de simulerade experimenten.

    Detta kompendium har tillkommit som examinationsarbete vid en kurs i "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter", med andra ord den kurs du själv nu ämnar studera. Författarna önskar dig lycka till med kursen och hoppas att du kommer att få glädje av den. Speciellt hoppas vi att denna skrift ska underlätta för dig att tillgodogöra dig informationen vid föreläsningarna och under laborationerna.

  • 5.
    Carlsson, Carl A.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Differences in reported backscatter factors,BSF, for low energy X-rays: A literature study1991Report (Other academic)
    Abstract [en]

    This work was ini tia ted by the large discrepancy in published values of the backscatter factor (BSF) as function of the half value layer (HVL) that exists in a new code of practice (IAEA, 1987) compared to the earlier, general ly used code (BJR, 1983). Change to the IAEA-code changes reported values of absorbed dose with up to 10%. These deviations apply for X-rays with HVL < 8 mm Al.

  • 6.
    Carlsson, Sten
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Liquid Scintillation Counting1993Report (Other academic)
    Abstract [en]

    In liquid scintillation counting (LSC) we use the process of luminescense to detect ionising radiation emit$ed from a radionuclide. Luminescense is emission of visible light of nonthermal origin. 1t was early found that certain organic molecules have luminescent properties and such molecules are used in LSC. Today LSC is the mostwidespread method to detect pure beta-ernitters like tritium and carbon-14. 1t has unique properties in its efficient counting geometry, deteetability and the lack of any window which the betaparticles have to penetrate. These properties are achieved by solving the sample to measure in a scintillation cocktail composed of an organic solvent and a solute (scintillator).

    Even if LSC is a weil established measurement technique, the user can run into problems and abasic knowledge of the deteetor and its different components is of fundamental importance in a correct use of the technique. The alm of this presentation is to provide the user with some of this fundamental knowledge.

  • 7.
    Edholm, Paul R.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    The Linogram Algorithm and Direct Fourier Method with Linograms1991Report (Other academic)
    Abstract [en]

    The conventionai map of projection data will here be called the sinogram map. Among the algorithms used with this map of data there are two of main interest for this paper: the Filtered Back Projection (FBP) and the Direct Fourier Method (DFM). FBP is the most popular algorithm used in commercial eT machines although it is computationally expensive compared to the DFM. The reason for its popularity is that FBP gives better pictures than the DFM uniess the lat ter is used with very careful interpolations.

    In this paper another map of projection data will be presented, here called the linogram map. The FBP may be implemented with this map in a particularly simple way, here called the Linogram Algorithm (LA). In this the back projection, which is so computationally expensive with the sinogram map, can be reduced to a computationally inexpensive series of FFT's.

  • 8.
    Edholm, Paul R.
    et al.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Olander, Birger
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Rekonstruktion av saknade projektioneri datortomografi1991Report (Other academic)
    Abstract [sv]

    Vid datortomografi besväras de rekonstruerade bilderna ofta av störande artefakter, dvs strukturer i bilden som inte motsvarar strukturer i patienten. Det finns många olika orsaker till artefakter och en viktig orsak är att vissa projektioner saknas helt eller delvis eller är av otillräcklig kvalitet. Delar av projektioner kan exempelvis saknas när implantat av metallproteser eller plomber i tänderna skymmer anatomin för de projicerande strålarna. Saknade projektioner av ena eller andra slaget ger upphov till artefakter i form av raka linjer som störande breder ut sig över hela bilden, ofta på ett sådant sätt att bilden blir otjänlig för sitt ändamål.

    I detta projekt har vi valt att studera en möjlighet att rekonstruera så mycket av de projektioner som saknas i ett visst vinkelavsnitt, att de inte längre ger upphov till störande artefakter.

    Arbetet har utförts med simulerade modellförsök. Vi har antagit en skiva i anatomin som avbildats med datortomografi med användande av parallellprojektioner. Försök har gjorts där enstaka projektioner saknas, och där projektioner saknas inom ett större vinkelavsnitt. Vid beskrivningen av vår metod skall vi först ge en verbal beskrivning och därpå en matematisk.

  • 9.
    Lamm, Inger-Lena
    et al.
    Institutionen för radiofysik, Lunds Universitet.
    Persliden, Jan
    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.
    Modulationsöverföringsfunktionen (MTF): De matematiska grunderna med exempel1993Report (Other academic)
    Abstract [sv]

    Vid överföring av information kan man karakterisera ett överföringssystem på olika sätt. Man kan t.ex. ange hur en signal förstärks, hur den förvr~ngs (distorderas), hur mycket brus systemet innehåller etc.

    Ett bildgivande system kan i princip karakteriseras av ett objekt som ger en insignal till en detektor vars utsignal antagligen innehåller signal + brus. För att beskriva hur utsignalen ser ut i jämförelse med insignalen används flera begrepp som:

    • Punktspridningsfunktionen (PSF)
    • Linjespridningsfunktionen (LSF)
    • Halvvärdesbredden (FWHM)

    Inom bildöverförande system använder man sig av begreppet MTF (MTF= Modulation Transfer Eunction) .

    Vi skall i det följande gå igenom grunderna för MTF och även ge exempel på hur man beräknar MTF. Genom att införa Fourier-transformen kan man lättare beräkna MTF och vi kommer därför att beskriva denna. För mätning av MTF för olika system inom röntgendiagnostiken hänvisas-till litteraturen.

  • 10.
    Larsson, Peter
    et al.
    Linköping University, Department of Medicine and Health Sciences, 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. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Evaluation of the uncertainties in KAP-meter calibrations1996Report (Other academic)
    Abstract [en]

    This report was prepared in order to give more details to the uncertainty evaluation of the Kerma area product meter calibration procedure described in the paper:

    Larsson J P Persliden J Sandborg S and Alm Carlsson G 1996 Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration. Phys. Med. Biol. 41 2381-2398.

    Figures and equations referred to in this report will be found in the paperabove.

    For convenience, however, the equations in the paper that are used in the uncertainty analysis are retyped on the next two sides, see text in section 2.7. in the paper for further details. The numbering of the equations are kept as in the paper.

  • 11.
    Lund, Eva
    et al.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Pernicka, Frantisek
    Institute of Radiation Dosimetry, Czeckoslovak Academy of Sciences, Prague, Czeck Republic.
    Carlsson, Carl A
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Experimental determination of the angular dependence of the directional dose equivalent, H’(d), for ISO “narrow” X ray fields and 137Cs γ-rays measured in a PMMA sphere and a PMMA slab phantom1993Report (Other academic)
    Abstract [en]

    For the purpose of calibrating individual dosimeters in X-ray fields conversion factors from air kerma free in air to dose equivalent at a specified depth in a phantom have been calculated among others by Grosswendt (1991, 1992). By means of Monte Carlo calculations the angular dependence factor for photon beams of oblique incidence is also studied for different phantom shapes and compositions as well as for different X-ray qualities. However, till now there has been a lack of experimental verification of the angular dependence factors.

    In this investigation the conversion factor from air kerma to Hp(10) has been determined for the following X-ray qualities: 40 kV, 80 kV, and 295 kV, ISO "narrow" spectra and for 137Cs γ-rays using thermoluminescent (TL) dosimeters. The angular dependence factor H'(10,α)/H'(10,0o) has also been experimentally determined for the same X-ray and γ -ray qualities and for different angles between 0o and 180o.

    The conversion factors are found to be in good agreement with the calculated ones for the PMMA sphere phantom, while some minor discrepancies are found between the experimental and calculated angular dependence factors for the 30x30x15cm3 PMMA slab phantom.

    The difference in angular dependence obtained for the slab and the sphere is discussed as well as the possibility to underestimate the personal dose equivalent, Hp(10), compared to effective dose, E.

  • 12.
    Olander, Birger
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Centre of Rotation Determination Using Projection Data in X-ray Micro Computed Tomography1994Report (Other academic)
    Abstract [en]

    There are several methods available to determine the Centre Of Rotation, COR, and align detectors and X-ray focus to COR in X-ray computed tomography. Some methods use narrow rods/needles or specially made alignment objects or phantoms. In X-ray Micro Computed Tomography (or Computerized Micro Tomography), μCT (CMT), methods using sample projection data for COR measurements are preferred since the replacement of alignment objects with samples often displace translation stages and make the alignment obsolete. To achieve an optimal image quality, precise positioning of COR to the detector and X-ray focus is essential. In μCT this can be accomplished in an alignment procedure using sample projection data prior to scanning. This alignment procedure will add examination time and increase the dose to the sample. Therefore the alignment procedure should incorporate as few projections as possible and be insensitive to noise. Some scanning equipment cannot be modified to implement such alignment procedure but actual COR can be determined from projection data and used in reconstruction. This report introduces a new Translated Opposite Projection, TOP, technique using a pair of opposite parallel projections (180° apart). Two TOP methods are developed: TOPlin using linear interpolation in the spatial domain and TOPfft in the frequency domain. The two TOP methods are compared to two Centre Of Gravity, COG, methods. The two COG methods are: COGsin, an enhancement of a method presented by Hogan et al [Hogan93] and COGopp, a simplification of this method possible with a fixed COR.

    In this report all projections in one scan are assumed to have a fixed, COR, as in third (or higher) generation tomography or first (and second generation) tomography if the translation stage errors is negligible. This also means that the rotation stage errors must be negligible. The COGsin is the only method presented here capable of determine a COR for each projection angle, thus allowing for a COR moving as a function of projection angle. The TOP methods normally give better precision with non-ideal projection data compared to the COG methods. Tests using both simulated and scanned projection data indicate that the TOP methods give higher precision in presence of stochastic errors (noise) and system errors like calibration errors. A μCT scan often takes a long time and detector calibration and X-ray intensity profiles might vary with time giving non-stationary system errors during a single scan. If the system errors can be approximated with simple polynomial functions, a new Baseline Restoration, BR, technique can be used together with the TOP methods to reduce COR errors.

  • 13.
    Persliden, Jan
    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.
    Analys av filmkassation: Ett SSI-projekt1996Report (Other academic)
    Abstract [en]

    Reject analysis in a radiology department can play an important role in the quality assurance process. Reject analysis was performed in the Department of Radiology, University Hospital in Linköping, Sweden, during 22 weeks 1992 and 5 weeks 1994. Between the two occasions, an education and training program was carried through. The rejected films were classified acording to 6 criteria. The reject frequency was 9.9% before and 8.5% after. Faulty exposure and faulty positioning of the patient contributing with 53 % of all rejected films.

    It was shown that reject analysis can easily be carried through. Compared to reports from the literature, the level found here was neither high nor low. The decrease in reject frequency after the training program was low and probably not significant. Reducing the rejections results in reduced patient doses and lower costs for the films. However, too low frequencies may be an indication of accepting bad image quality and reduced diagnostic accuracy. In the future when digital equipment is more frequently introduced the rejection of films will decrease, but not necessarily the retakes. Here, measurements of mean absorbed doses to the patients may provide a better toal for quality assurance of the radiology department.

  • 14.
    Sandborg, Michael
    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.
    Computed Tomography: Physical principles and biohazards1995Report (Other academic)
    Abstract [en]

    In planar projected images of the patient, important details may be hidden by over-laying tissues. By using slice-imaging techniques (tomography), selective demonstration of morphologic properties, layer by layer, may be performed.

    Computerised tomography, CT, is an ideal form of tomography yielding sequence images of thin consecutive slices of the patient and providing the opportunity to localise in three dimensions. Unlike conventional, classical tomography, computerised tomography does not suffer from interference from structures in the patient outside the slice being imaged. This is achieved by irradiating only thin slices of the patient with a fan-shaped beam. Transaxial images (tomograms) of the patient’s anatomy can give more selective information than conventional planar projection radiographs. Compared to planar radiography, CT images have superior contrast resolution, i.e., they are capable of distinguishing very small differences in tissue-attenuation (contrasts), but have inferior spatial resolution. An attenuation difference of 0.4% can be visualised but the smallest details in the image that can be resolved must be separated at least 0.5 mm. In conventional planar radiography, the lowest detectable contrast is larger but details of smaller size can be separated.

  • 15.
    Sandborg, Michael
    et al.
    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.
    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.
    Jämförelse mellan ett niobfilter (NIOBI-X) och konventionell filtrering vid skärmfilm radiografi: Inverkan på primärspektrum, kontrast, rörbelastning och strålrisk1990Report (Other academic)
    Abstract [sv]

    Optimering av information till strålrisk inom diagnostisk radiologi innebär att finna den.metod att framställa en bild, innehållande den nödvändiga informationen (bildkvaliteten), som ger lägsta strålrisk för patienten. Valet av fotonenergispektrum är en betydelsefull parameter vid optimeringen. Olika energispektrum kan erhållas då man varierar rörspänningen, tilläggsfiltermaterial och filtertjocklek. Av de fundamentala bildkvalitetsparamerarna kontrast, skärpa och brus är, vid konventionell skärm-film radiografi, kontrast och skärpa de viktigaste. De påverkas båda, men framförallt kontrasten, av energispektrum, dvs. rörspänningen och tilläggsfiltrets material och tjocklek.

  • 16.
    Sandborg, Michael
    et al.
    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.
    Dance, David R.
    Department of Medical Physics, The Royal Marsden Hospital, Fulham Road, SW3 6JJ London, United Kingdom.
    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.
    Persliden, Jan
    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.
    The choice of anti-scatter grids in diagnostic radiology: the optimization of image quality and absorbed dose1993Report (Other academic)
    Abstract [sv]

    A Monte Carlo model is developed to study and optimise the design of antiscatter grids in diagnostic radiology. The imaging chain including X-ray energy spectra, phantom (representing the patient), grid and image receptor is simulated. Image quality is quantified in terms of contrast (conventionai screen-film imaging) and signal-to-noise ratio, SNR (digital imaging) and the radiation detriment to the patient (risk) by the mean absorbed dose in the phantom. The advantages of using fibre instead of aluminium for grid interspaces and covers are quantified. Compared to aluminium grids, the absorbed dose is reduced by 10-50%, contrast is improved by 0-10% and SNR by 10-40% (digital radiography). The advantages are larger at low tube potentials and for grids with high ratio and low strip density. Commercial grids, with different interspace materials, strip density, strip width and grid ratio, are compared in paediatric, lumbar spine and chest examinations. The differences in dose increase and contrast improvement factors obtained with these grids are mainly due to the use of different materials in the grid interspaces, but the strip design is also important. In a global optimisation of grid design and tube potential at fixed contrast, it is found that grids of different strip density and ratio all can have good performances provided that they are used with appropriate strip width and tube potential. In the paediatric examination, low ratio grids need thinner strips than used today to be optimal. A small air gap could alternatively be used. In examinations with more scatter (adult AP), present commercial grids are optimal (r=12-16, d=30-50µm). In the lateral view (even more scatter), grids with ratios larger than 16 are optimal provided the grid can be accurately aligned in the beam. The optimization is performed with grids with fibre interspaces and covers since low atomic number materials should preferably be used for materials between the patient and the receptor. Optimal grids with aluminium for these components have lower grid ratio and higher strip densities than optimal fibre grids.

  • 17.
    Sandborg, Michael
    et al.
    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.
    McVey, Graham
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    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.
    Persliden, Jan
    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.
    Collection and analysis of patient and image data for calibration of a voxelphantombased Monte Carlo code and for the modelling of important structures1997Report (Other academic)
    Abstract [en]

    The contribution of the Medical Physics Departments at Linköping University (LKP) and The Royal Marsden NHS Trust (RMH) to the joint project ‘Predictivity and Optimisation in Medical Radiation Protection’ is in modelling of the chest and lumbar spine radiographic examinations. This involves:

    1. the development of quantitative imaging requirements;
    2. an investigation of the effect of imaging technique on image quality and patientdose, and
    3. an optimisation of system design.

    One of the objectives for this first reporting period (0-12 months) was to collect a set of chest and lumbar spine radiographs of patients for subsequent analysis in order to establish patient doses and important features in the images. The set of radiographs and the outcome of the image feature analysis will during this project’s second year be used to calibrate our Monte Carlo computational model of the conventional chest and lumbar spine screen-film X-ray imaging systems.

  • 18.
    Sandborg, Mickael
    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.
    Radiography and Flouroscopy: Physical principles and biohazards1995Report (Other academic)
    Abstract [en]

    Diagnostic radiology has come a long way since the discovery of ‘A New Kind of Rays’ in Würzburg by Professor Wilhelm Conrad Röntgen in November 1895. Professor Röntgen called the unknown rays ‘X rays’, but they are also, most appropriately and less mysteriously, referred to as Röntgen rays after their discoverer. In the last decades, imaging techniques using X rays has developed rapidly and play an important role in modern health care.

    The benefit of an X-ray examination for a patient could be assessed as how the patient’s risk situation is affected. The medical condition or illness leading to the examination may imply an increased risk of deteriorating health. Correct diagnosis and proper treatment, based on the information in the X-ray image, could lower the patient’s risk. For the individual the risks associated with the X-ray examination itself are small as is the radiation risk (patient absorbed dose) for well-designed imaging systems. Since the number of individuals undergoing X-ray examinations is very large, the collective absorbed dose to the whole population will be significant. Medical X-ray examinations are the manmade source giving the single largest radiation burden to the population, e.g., consisting 87% of the total radiation burden in the United Kingdom. Failure to diagnose is probably the largest single risk for the patient, but for some patients adverse effects of injected contrast media may be potentially hazardous.

1 - 18 of 18
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