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  • 1.
    Bagesund, M
    et al.
    Karolinska Inst, Sch Dent, Dept Pediat Dent, S-10401 Stockholm, Sweden.
    Richter, S
    Karolinska Inst, Sch Dent, Dept Pediat Dent, S-10401 Stockholm, Sweden.
    Agren, B
    Karolinska Inst, Sch Dent, Dept Pediat Dent, S-10401 Stockholm, Sweden.
    Dahllof, G
    Karolinska Inst, Sch Dent, Dept Pediat Dent, S-10401 Stockholm, Sweden.
    Correlation between quantitative salivary gland scintigraphy and salivary secretion rates in children and young adults treated for hematological, malignant and metabolic diseases2000Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 29, nr 5, s. 264-271Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: To study the correlation between whole salivary secretion rates and different variables from the radionuclide time-activity curve and to determine a reliable region for background correction in salivary gland scintigraphy. Methods: Salivary gland scintigraphy (SGS) was performed before bone marrow transplantation or more than 4 years later in 23 patients aged 13.5 (s.d. 4.9) years. Unstimulated and stimulated whole salivary secretion rates were measured before SGS. Six different methods for background correction were evaluated. Results: The unstimulated secretion rate was significantly correlated (P<0.05) with the percentage stimulated secretion (S) and reaccumulation-slope (RS) after stimulation. The stimulated secretion rate was significantly correlated with RS, S and down-slope (DS). The temporal region above the parotid glands and the area above the thyroid gland was used for subtraction of background radiation for the parotid and submandibular glands respectively showed a strong correlation between repeated measurements of the variables analysed. The mean maximum uptake was 0.73-1.34% of total dose injected. Conclusions: The salivary scintigraphic variables which correlated more strongly with salivary secretion rates were RS, S and DS. The temporal region above the parotid gland and the area above the thyroid gland can be used reliably for correction background radiation in the analysis of the time-activity curve in SGS of the parotid and submandibular glands respectively.

  • 2.
    Eckerdal, O
    et al.
    University of Umeå, Umeå.
    Ahlqvist, J
    Alehagen, Urban
    Linköpings universitet, Institutionen för medicin och hälsa, Kardiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Kardiologiska kliniken US.
    Wing, K
    Length dimensions and morphologic variations of the external bony auditory canal. A radiographic and histologic investigation.1978Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 7, nr 1, s. 43-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autopsy material comprising a total of 58 specimes of the temporal bone and the proximal part of the mandible was investigated tomographically and by microtome in comparative layers. Microradiographs and histologic sections were used as the main sources of information to determine the length dimensions of the different parts of the external auditory canal. The morphology and its developmental variations are compared and described. The diagnostic implications are discussed. In the authors' opinion, tomography is the method of choice to illustrate the morphologic properties of the external auditory canal. It is suggested that when the tomographic image reveals morphologic developmental or pathologic defects which give rise to problematic diagnosis, a control examination of the contralateral side should be performed.

  • 3.
    Helmrot Ebba,
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Carlsson, G.A.
    n/a.
    Eckerdahl, O
    n/a.
    Effects of contrast equalization on energy imparted to the patient: a comparison of two dental generators and two types of intraoral film.1994Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 23, nr 2, s. 83-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technical evolution in maxillofacial radiology has in the last decade provided faster films and the constant potential generator. The consequences of these innovations for radiographic contrast and energy imparted to the patient are analysed. On the basis of physical measurements a test model has been developed for correcting exposure parameters in order to maintain or restore image contrast. These measurements are expressed in and developed from basic radiological concepts and physical formulas presented in an earlier paper (Helmrot E. et al., Dentomaxillofac. Radiol. 1991; 20: 135-46). The test model can also be used to demonstrate the balance between contrast and energy imparted to the patient in the radiographic process. Changing to constant potential generators and faster film may each result in a degradation in contrast, which is possible to restore by a controlled adjustment of the kV-setting. Maintenance of constant image quality results in a slight reduction in the net gain in energy imparted, due to the generator and/or film shift. When, for example, a conventional single-pulse generator operated at 65kVp tube potential was replaced by a modern constant potential unit, the kV-setting had to be decreased by 5 to 8 kV to maintain the same radiographic contrast. This correction could be done without increasing energy imparted to the patient, taking into account the fact that the spectral characters of the photon energy are not identical. If, in addition, faster intraoral film with lower film contrast was introduced, together with the constant potential unit, the kV-setting had to be further decreased to maintain the radiographic contrast.

  • 4.
    Helmrot, Ebba
    et al.
    Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Influence of scattered radiation and tube potential on radiographic contrast: comparison of two different dental X-ray films1991Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 20, nr 3, s. 135-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fundamental concept in image quality of contrast has been analysed in terms of its elements; film, radiation and object contrast, and the theoretical formula to describe their interrelationship have been evaluated. Experiments were designed to investigate the dependence of radiographic contrast on the kV, the type of generator and dental film used (D and E speed). An ivory wedge was used as the object, both alone and within a polymethyl methacrylate phantom as scattering medium. Precise definition and control of the X-ray generators were achieved by means of measurements of the primary X-ray spectra using a Compton spectrometer. D speed was found to have higher film contrast than E speed when compared at the same optical density, due to its lower base and fog and lower level of saturation in these experiments. On the other hand, E speed was found to have wider latitude. The experimental object was reproduced with the highest radiographic contrast using D-speed film and, with a given type of generator, this increased when the kV was decreased. While no difference in scatter/primary ratios was observed using the two different films, a weak dependence on kV in the range from 36 to 77 kV was found and confirmed by Monte Carlo calculations. The results indicate that the D and E speed films used had equal energy absorption properties; the difference in radiographic performance is due to their different film characteristics. The importance of controlling the physical parameters (photon energy spectrum, base and fog and optical density level) when comparing image qualities is clearly demonstrated.

  • 5.
    Helmrot, Ebba
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Matscheko, G
    n/a.
    Carlsson, CA
    n/a.
    Eckerdahl, O
    n/a.
    Ericson, S
    n/a.
    Image contrast using high frequency and half-wave rectified dental x-ray generators.1988Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 17, nr 1, s. 33-40Artikel i tidskrift (Refereegranskat)
  • 6.
    Klintström, Eva
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Smedby, Örjan
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Klintström, Benjamin
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet.
    Brismar, Torkel
    Karolinska University Hospital Huddinge, Stockholm, Sweden.
    Moreno, Rodrigo
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Trabecular bone histomorphometric measurements and contrast-to-noise ratio in CBCT2014Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 43, nr 8, s. 20140196-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: The aim of this study was to evaluate how imaging parameters at clinical dental CBCT affect the accuracy in quantifying trabecular bone structures, contrast-to-noise ratio (CNR) and radiation dose.

    Methods: 15 radius samples were examined using CBCT (Accuitomo FPD; J. Morita Mfg., Kyoto, Japan). Nine imaging protocols were used, differing in current, voltage, rotation degree, voxel size, imaging area and rotation time. Radiation doses were measured using a KAP-meter. After segmentation, six bone structure parameters and CNR were quantified. Micro-CT images with an isotropic resolution of 20 microns were used as a gold standard.

    Results: Structure parameters obtained by CBCT were strongly correlated to those by micro CT, with correlation coefficients .0.90 for all studied parameters. Bone volume and trabecular thickness were not affected by changes in imaging parameters. Increased tube current from 5 to 8 mA, decreased isotropic voxel size from 125 to 80 microns and decreased rotation anglefrom 360° to 180° affected correlations for trabecular termini negatively. Decreasing rotation degree also weakened correlations for trabecular separation and trabecular number at 80 microns voxel size. Changes in the rotation degree and tube current affected CNR significantly. The radiation dose varied between 269 and 1284 mGy cm2.

    Conclusions: Trabecular bone structure can be accurately quantified by clinical dental CBCT in vitro, and the obtained structure parameters are strongly related to those obtained by micro CT. A fair CNR and strong correlations can be obtained with a low radiation dose, indicating the possibility for monitoring trabecular bone structure also in vivo.

  • 7.
    Lofthag-Hansen, S
    et al.
    Public Dental Health, Göteborg.
    Thilander-Klang, A
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Göteborg, Sweden.
    Ekestubbe, A
    Department of Oral and Maxillofacial Radiology The Sahlgrenska Academy at Göteborg University, Sweden.
    Helmrot, Ebba
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Gröndahl, K
    Department of Oral and Maxillofacial Radiology, The Sahlgrenska Academy at Göteborg University, Sweden.
    Calculating effective dose on a cone beam computed tomographydevice: 3D Accuitomo and 3D Accuitomo FPD2008Ingår i: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 37, nr 2, s. 72-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: This study evaluates two methods for calculating effective dose, CT dose index (CTDI) and dose–area product (DAP) for a cone beam CT (CBCT) device: 3D Accuitomo at field size 30x40 mm and 3D Accuitomo FPD at field sizes 40x40 mm and 60x60 mm. Furthermore, the effective dose of three commonly used examinations in dental radiology was determined.

    Methods: CTDI100 measurements were performed in a CT head dose phantom with a pencil ionization chamber connected to an electrometer. The rotation centre was placed in the centre of the phantom and also, to simulate a patient examination, in the upper left cuspid region. The DAP value was determined with a plane-parallel transmission ionization chamber connected to an electrometer. A conversion factor of 0.08 mSv per Gy cm2 was used to determine the effective dose from DAP values. Based on data from 90 patient examinations, DAP and effective dose were determined.

    Results: CTDI100 measurements showed an asymmetric dose distribution in the phantom when simulating a patient examination. Hence a correct value of CTDIw could not be calculated. The DAP value increased with higher tube current and tube voltage values. The DAP value was also proportional to the field size. The effective dose was found to be 11–77 microSv for the specific examinations.

    Conclusions: DAP measurement was found to be the best method for determining effective dose for the Accuitomo. Determination of specific conversion factors in dental radiology must, however, be further developed

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