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  • 1.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Mats
    Center for Medical Imaging and Physiology, Skåne University Hospital, Lund, Sweden; Lund University, Lund, Sweden.
    Norrman, Eva
    Örebro University Hospital.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Low-dose computed tomography of the lumbar spine: a phantom study on imaging parameters and image quality2014In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 55, no 7, p. 824-832Article in journal (Refereed)
    Abstract [en]

    Background: Lumbar spine radiography has limited diagnostic value but low radiation dose compared with computed tomography (CT). The average effective radiation dose from lumbar spine radiography is about 1.1 mSv. Low-dose lumbar spine CT may be an alternative to increase the diagnostic value at low radiation dose, around 1 mSv.

    Purpose: To determine the optimal settings for low-dose lumbar spine CT simultaneously aiming for the highest diagnostic image quality possible.

    Material and Methods: An ovine lower thoracic and lumbar spine phantom, with all soft tissues around the vertebrae preserved except the skin, was placed in a 20 L plastic container filled with water. The phantom was scanned repeatedly with various technical settings; different tube potential, reference mAs, and with different convolution filters. Five radiologists evaluated the image quality according to a modification of the European guidelines for multislice computed tomography (MSCT) quality criteria for lumbar spine CT 2004. In a visual comparison the different scans were also ranked subjectively according to perceived image quality. Image noise and contrast were measured.

    Results: A tube potential of 120 kV with reference mAs 30 and medium or medium smooth convolution filter gave the best image quality at a sub-millisievert dose level, i.e. with an effective dose comparable to that from lumbar spine radiography.

    Conclusion: Low-dose lumbar spine CT thus opens a possibility to substitute lumbar spine radiography with CT without obvious increase in radiation dose.

  • 2.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden; Department of Medical Imaging and Physiology, Skåne University Hospital, Lund University, Lund, Sweden.
    Norrman, Eva
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Krauss, Wolfgang
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Jendeberg, Johan
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Magnuson, Anders
    Örebro University Hospital.
    Geijer, Håkan
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spine2017In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 58, no 6, p. 702-709Article in journal (Refereed)
    Abstract [en]

    Background: Iterative reconstruction (IR) is a recent reconstruction algorithm for computed tomography (CT) that can be used instead of the standard algorithm, filtered back projection (FBP), to reduce radiation dose and/or improve image quality.

    Purpose: To evaluate and compare the image quality of low-dose CT of the lumbar spine reconstructed with IR to conventional FBP, without further reduction of radiation dose.

    Material and Methods: Low-dose CT on 55 patients was performed on a Siemens scanner using 120 kV tube voltage, 30 reference mAs, and automatic dose modulation. From raw CT data, lumbar spine CT images were reconstructed with a medium filter (B41f) using FBP and four levels of IR (levels 2-5). Five reviewers scored all images on seven image quality criteria according to the European guidelines on quality criteria for CT, using a five-grade scale. A side-by-side comparison was also performed.

    Results: There was significant improvement in image quality for IR (levels 2-4) compared to FBP. According to visual grading regression, odds ratios of all criteria with 95% confidence intervals for IR2, IR3, IR4, and IR5 were: 1.59 (1.39-1.83), 1.74 (1.51-1.99), 1.68 (1.46-1.93), and 1.08 (0.94-1.23), respectively. In the side-by-side comparison of all reconstructions, images with IR (levels 2-4) received the highest scores. The mean overall CTDIvol was 1.70 mGy (SD 0.46; range, 1.01-3.83 mGy). Image noise decreased in a linear fashion with increased strength of IR.

    Conclusion: Iterative reconstruction at levels 2, 3, and 4 improves image quality of low-dose CT of the lumbar spine compared to FPB.

  • 3.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Geijer, Mats
    Department of Medical Imaging and Physiology, Skåne University Hospital, Lund University, Lund, Sweden.
    Norrman, Eva
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Medical Physics,, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Krauss, Wolfgang
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Wilamowski, Franciszek
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Low dose CT of the lumbar spine compared with radiography: a study on image quality with implications for clinical practice2016In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 5, p. 602-611Article in journal (Refereed)
    Abstract [en]

    Background: Lumbar spine radiography is often performed instead of CT for radiation dose concerns.

    Purpose: To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography.

    Material and Methods: Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes.

    Results: Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3-2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1-5.9), intervertebral joints (OR, 139; 95% CI, 59-326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3-11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2-5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1-4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66-539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2-0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194-214 s.), radiography 152 s (95% CI, 146-158 s.). The effective dose for low dose CT was 1.0-1.1 mSv, for radiography 0.7 mSv.

    Conclusion: Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.

  • 4.
    Dimitriou, Praxitelis
    et al.
    Department of Radiology, Örebro University Hospital , Örebro, Sweden.
    Kähäri, Anders
    Department of Clinical Physiology, Örebro University Hospital , Örebro, Sweden.
    Emilsson, Kent
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Clinical Physiology, Örebro University Hospital , Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden .
    Cardiovascular magnetic resonance imaging and transthoracic echocardiography in the assessment of stenotic aortic valve area: a comparative study2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 9, p. 995-1003Article in journal (Refereed)
    Abstract [en]

    Background: Magnetic resonance (MR) imaging and echocardiography both allow assessment of aortic valve stenosis. In MR the aortic valve area (AvA) is measured using planimetry while in transthoracic echocardiography (TTE) AvA is usually calculated by applying the continuity equation.

    Purpose: To compare the measured stenotic aortic valve areas using five different MR-acquisition alternatives with the corresponding area values calculated by TTE.

    Material and Methods: The aortic valve was imaged in 14 patients, with diagnosed aortic valve stenosis, using balanced steady state free precession (bSSFP) gradient echo (GE) and phase contrast imaging (PC). Three adjacent slices were planned to encompass the aortic valve and the aortic valve area was measured using planimetry. The two sets of complex valued images generated by the PC sequence formed three kinds of images that could be used for aortic valve area measurements: the magnitude image (PC/Mag), the modulus (PCA/M), and phase difference (PCA/P) between the two complex images, respectively. The valve area from TTE was calculated using the continuity equation. A cut-off of <1.0 cm(2) was used as a criteria for severe stenosis.

    Results: The mean area differences between the different MR acquisitions and TTE method were -0.05 ± 0.37 cm(2) (GE), -0.18 ± 0.46 cm(2) (bSSFP), 0.27 ± 0.43 cm(2) (PC/Mag), 0.15 ± 0.32 cm(2) (PCA/P), and 0.26 ± 0.27 cm(2) (PCA/M). The valve area was significantly overestimated using PCA/M that, in turn, implied a significant underestimation of the aortic valve stenosis severity compared to the assessments using TTE.

    Conclusion: The smallest area valve difference between TTE and an MR-acquisition alternative is obtained with gradient echo images. The use of PCA/M leads to significant differences in planimetry measurements of the aortic valve orifice and the gradation of the stenosis severity compared to TTE.

  • 5.
    Geijer, Mats
    et al.
    Örebro University Hospital. Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden; Department of Clinical Sciences, Lund University, Lund, Sweden.
    Rundgren, Gustav
    Department of Clinical Sciences, Lund University, Lund, Sweden.
    Weber, Lars
    Department of Clinical Sciences, Lund University, Lund, Sweden; Department of Radiation Physics, Skåne University Hospital, Lund, Sweden.
    Flivik, Gunnar
    Department of Clinical Sciences, Lund University, Lund, Sweden; Department of Orthopedics, Skåne University Hospital, Lund, Sweden.
    Effective dose in low-dose CT compared with radiography for templating of total hip arthroplasty2017In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 58, no 10, p. 1276-1282Article in journal (Refereed)
    Abstract [en]

    Background: Recently, total hip arthroplasty (THA) has come to focus on restoration of individual anatomy including femoral neck anteversion and global offset (femoral and acetabular offset). Three-dimensional (3D) computed tomography (CT) data could provide a better basis for preoperative templating. The use of CT has been hampered by high radiation dose.

    Purpose: To evaluate the effective dose used in pelvis and hip CT for THA templating.

    Material and Methods: CT data from two clinical trials of THA were evaluated for CT scan length and volume CT dose index (CTDIvol). The effective doses from hip-knee-ankle CT and pelvis and hip radiography were compared. Conversion factors for effective dose for radiography were calculated using the PCXMC software.

    Results: A reduced dose CT protocol for pelvis imaging gave a substantial dose reduction compared with standard CT, while maintaining sufficient image quality. Between the two clinical trials there was a significant reduction in effective CT dose corresponding to changes in the CT protocol (P<0.01). The CT dose for the latter group was similar to, but nevertheless significantly higher than for, radiography (P<0.01). However, in the latter group the theoretical minimum dose for CT, using the minimum scan length required by the templating software, was equal to the dose from radiography.

    Conclusion: Although the CT dose remained higher than for radiography, potential reductions in scan length could reduce the dose further so that CTwould have a comparable level of risk to radiography with the added benefit of 3D templating.

  • 6.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
    Thunberg, Per
    Örebro University Hospital. Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. School of Health and Medical Sciences, Örebro University, Örebro, Sweden; Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Broxvall, Mathias
    Modeling and Simulation Research Center, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative study2015In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 56, no 4, p. 487-492Article in journal (Refereed)
    Abstract [en]

    Background: The standard imaging procedure for a patient presenting with renal colic is unenhanced computed tomography (CT). The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on two-dimensional (2D) reformats.

    Purpose: To develop and validate a calculus oriented three-dimensional (3D) method for measuring the length and width of urinary calculi and to compare the calculus oriented measurements of the length and width with corresponding 2D measurements obtained in axial and coronal reformats.

    Material and Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3D symmetric segmentation algorithm was validated against reader size estimations. The calculus oriented size from the segmentation was then compared to the estimated size in axial and coronal 2D reformats.

    Results: The validation showed 0.1 +/- 0.7mm agreement against reference measure. There was a 0.4mm median bias for 3D estimated calculus length compared to 2D (P < 0.001), but no significant bias for 3D width compared to 2D.

    Conclusion: The length of a calculus in axial and coronal reformats becomes underestimated compared to 3D if its orientation is not aligned to the image planes. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.

  • 7.
    Lundin, Margareta
    et al.
    Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Liden, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Magnuson, Anders
    Clinical Epidemiology and Biostatistic Unit, Örebro University Hospital, Örebro, Sweden.
    Mohammed, Ahmed Abdulilah
    Department of Radiology, Linköping University Hospital, Linköping, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Andersson, Torbjörn
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Persson, Anders
    Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
    Virtual non-contrast dual-energy CT compared to single-energy CT of the urinary tract: a prospective study2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 6, p. 689-694Article in journal (Refereed)
    Abstract [en]

    Background: Dual-energy computed tomography (DECT) has been shown to be useful for subtracting bone or calcium in CT angiography and gives an opportunity to produce. a virtual non-contrast-enhanced (VNC) image from a series where contrast agents have been given intravenously. High noise levels and low resolution have previously limited the diagnostic value of the VNC images created with the first generation of DECT. With the recent introduction of a second generation of DECT, there is a possibility of obtaining VNC images with better image quality at hopefully lower radiation dose compared to the previous generation.

    Purpose: To compare the image quality of the single-energy series to a VNC series obtained with a two generations of DECT scanners. CT of the urinary tract was used as a model.

    Material and Methods: Thirty patients referred for evaluation of hematuria were examined with an older system (Somatom Definition) and another 30 patients with a new generation (Somatom Definition Flash). One single-energy series was obtained before and one dual-energy series after administration of intravenous contrast media. We created a VNC series from the contrast-enhanced images. Images were assessed concerning image quality with a visual grading scale evaluation of the VNC series with the single-energy series as gold standard.

    Results: The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, OR 11.5-67.3 for the Definition and OR 2.1-2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than Definition.

    Conclusion: Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images. However, the difference is smaller with the new compared to the older system.

  • 8. Thoumas, K.-Å.
    et al.
    Möller, Claes
    Örebro University, School of Health and Medical Sciences.
    Ödkvist, L. M.
    Flodin, U.
    Dige, N.
    MR imaging in solvent-induced chronic toxic encephalopathy1996In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 37, no 2, p. 177-179Article in journal (Refereed)
    Abstract [en]

    Purpose: To use MR to examine patients with CNS symptoms indicating chronic intoxication.

    Material and Methods: Thirty-two subjects exposed to industrial solvents for 5 to 28 years and 40 age-matched, healthy controls were examined.

    Results: All patients showed decreased signal in the basal ganglia on T2-weighted images. In 11 of the patients the white matter showed diffuse hyperintensity with loss of the grey-white matter discrimination and with distinct periventricular hyperintensities in 5 of the patients. The controls had no pathological changes in the brain.

    Conclusion: Although the relatively small number of patients may obscure the significance, findings observed on T2-weighted images were patchy periventricular hyperintensities and hypointensities in the basal ganglia. Fast spin-echo is a good technique with fast acquisition of images with true spin-echo contrast features.

  • 9.
    Thunberg, Per
    et al.
    Department of Biomedical Engineering, Örebro University Hospital, Örebro, Sweden.
    Emilsson, Kent
    Örebro University, School of Health and Medical Sciences. Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Rask, Peter
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Kähäri, Anders
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Estimation of ejection fraction and stroke volume using single- and biplane magnetic resonance imaging of the left cardiac ventricle2008In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 49, no 9, p. 1016-1023Article in journal (Other academic)
    Abstract [en]

    Background: In cardiac magnetic resonance imaging (MRI), left ventricular stroke volume (SV) and ejection fractions (EF) are occasionally calculated using single-plane and biplane ellipsoid models. In previous studies, the calculated SV and EF using single- and biplane ellipsoid models have been compared to reference values calculated from short-axis (SA) images. In these studies, however, it has been emphasized that through-plane motion of the basal SA images represents an important source of error, which may result in incorrect reference values.

    Purpose: To compare the calculated SV and EF using single-plane and biplane ellipsoid models with SV and EF calculated from SA images in which compensation was made for through-plane motion.

    Material and Methods: A group of 20 patients who underwent MRI examination were included in the study. SV and EF were calculated using the stack of SA images (which had been compensated for through-plane motion) and compared to the SV and EF calculated according to the single- and biplane ellipsoid models.

    Results: The mean difference between the single-plane model and the reference was -0.3±6.5 for EF and 7.2±17.1 ml for SV. Corresponding comparison between the biplane method and the reference resulted in a mean difference of 0.3±6.1 for EF and 11.8±14.9 ml for SV.

    Conclusion: The results from this study show that left ventricular EF can be adequately estimated using the single- and biplane ellipsoid models, while SV tends to be overestimated using both geometrical models

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