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| 3. |
- Chen, Hanwei, et al.
(författare)
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Tumor Volumes Measured From Static and Dynamic F-18-fluoro-2-deoxy-D-glucose Positron Emission Tomography-Computed Tomography Scan : Comparison of Different Methods Using Magnetic Resonance Imaging as the Criterion Standard
- 2014
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Ingår i: Journal of computer assisted tomography. - 0363-8715 .- 1532-3145. ; 38:2, s. 209-215
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective of this study was to compare the accuracy of calculating the primary tumor volumes using a gradient-based method and fixed threshold methods on the standardized uptake value (SUV) maps and the net influx of FDG (Ki) maps from positron emission tomography-computed tomography (PET-CT) images. Materials and Methods: Newly diagnosed patients with head and neck cancer were recruited, and dynamic PET-CT scan and T2-weighted magnetic resonance imaging were performed. The maps of Ki and SUV were calculated from PET-CT images. The tumor volumes were calculated using a gradient-based method and a fixed threshold method at 40% of maximal SUV or maximal Ki. Four kinds of volumes, VOLKi-Gra (from the Ki maps using the gradient-based method), VOLKi-40% (from the Ki maps using the threshold of 40% maximal Ki), VOLSUV-Gra (from the SUV maps using the gradient-based method), and VOLSUV-40% (from the SUV maps using the threshold of 40% maximal SUV), were acquired and compared with VOLMRI (the volumes acquired on T2-weighted images) using the Pearson correlation, paired t test, and similarity analysis. Results: Eighteen patients were studied, of which 4 had poorly defined tumors (PDT). The positron emission tomography-derived volumes were as follows: VOLSUV-40%, 2.1 to 41.2 cm(3) (mean [SD], 12.3 [10.6]); VOLSUV-Gra, 2.2 to 28.1 cm(3) (mean [SD], 13.2 [8.4]); VOLKi-Gra, 2.4 to 17.0 cm(3) (mean [SD], 9.5 [4.6]); and VOLKi-40%, 2.7 to 20.3 cm(3) (mean [SD], 12.0 [6.0]). The VOLMRI ranged from 2.9 to 18.1 cm(3) (mean [SD], 9.1 [3.9]). The VOLKi-Gra significantly correlated with VOLMRI with the highest correlation coefficient (PDT included, R = 0.673, P = 0.002; PDT excluded, R = 0.841, P < 0.001) and presented no difference from VOLMRI (P = 0.672 or 0.561, respectively, PDT included and excluded). The difference between VOLKi-Gra and VOLMRI was also the smallest. Conclusions: The tumor volumes delineated on the Ki maps using the gradient-based method are more accurate than those on the SUV maps and using the fixed threshold methods.
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| 4. |
- Gal, Yaniv, et al.
(författare)
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New Spatiotemporal Features for Improved Discrimination of Benign and Malignant Lesions in Dynamic Contrast-Enhanced-Magnetic Resonance Imaging of the Breast
- 2011
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Ingår i: Journal of Computer Assisted Tomography. - 1532-3145 .- 0363-8715. ; 35:5, s. 645-652
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The objective of this study was to measure the efficacy of 7 new spatiotemporal features for discriminating between benign and malignant lesions in dynamic contrast-enhanced-magnetic resonance imaging (MRI) of the breast.Methods: A total of 48 breast lesions from 39 patients were used: 25 malignant and 23 benign. Lesions were acquired using 1.5-T MRI machines in 3 different protocols. Two experiments were performed: (i) selection of the most discriminatory subset of features drawn from the new features and features from the literature and (ii) validation of classification performance of the selected subset of features.Results: Results of the feature selection experiment show that the subset comprising 2 of the new features is the most useful for automatic classification of suspicious lesions in the breast: (i) gradient correlation of maximum intensity and (ii) mean wash-in rate. Results of the validation experiment show that using these 2 features, unseen data can be classified with an area under the receiver operating characteristic curve of 0.91 ± 0.06.Conclusions: Results of the experiments suggest that suspicious lesions in dynamic contrast-enhanced-MRI of the breast can be classified, with high accuracy, using only 2 of the proposed spatiotemporal features. The selected features indicate heterogeneity of enhancement and speed of enhancement in a tissue. High values of these indicators are likely to be correlated with malignancy.
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| 5. |
- Pourjabbar, Sarvenaz, et al.
(författare)
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Preliminary Results : prospective clinical study to assess image-based iterative reconstruction for abdominal computed tomography acquired at 2 radiation dose levels
- 2014
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Ingår i: Journal of computer assisted tomography. - : Lippincott Williams & Wilkins. - 0363-8715 .- 1532-3145. ; 38:1, s. 117-122
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:The objective of this study was to compare image quality for abdominal computed tomographic (CT) images acquired at 200 and 50 mA s and reconstructed with image-based iterative reconstruction.MATERIALS AND METHODS:In this institutional review board-approved prospective study, 22 patients (mean [SD] age, 64.3 [14.4] years; male-female ratio, 12:10) gave informed consent for acquisition of additional abdominal CT images on 64-slice multi-detector CT (MDCT) (Siemens Definition Flash). Standard-dose images were acquired at 200 quality reference mA s, whereas low-dose images were acquired at 50 mA s (all series: 120 kV; 5-mm section thickness; pitch, 0.9:1). The low-dose images were reconstructed with a nonlinear 3-dimensional iterative image reconstruction (3D-IIR) (SafeCT; MedicVision, Tirat Carmel, Israel) (4 settings, namely, A1, A2, A3, and A4) and were assessed by 3 abdominal radiologists for lesion detection, image noise, and visibility of small structures. CATPHAN 500 was scanned at the respective doses to obtain noise spectral density and modulation transfer function.RESULTS:Subjective image noise was unacceptable at 50-mA s filtered back projection and improved to average in 50-mA s A1 and minimal or no noise in 50-mA s A4. However, the visibility of small structures was similar to standard-dose filtered back projection images on 50-mA s A2. Objective image noise was reduced to 66% for the 50-mA s 3D-IIR images (9.08 [2.3]/26.75 [6.8]). The modulation transfer function curve demonstrated resolution improvement in the low-dose images with the 3D-IIR technique, whereas the noise spectral density curve confirmed noise suppression in the 50-mA s 3D-IIR images.CONCLUSIONS:Three-dimensional iterative image reconstruction helps to lower image noise without affecting the visibility of small structures at "moderate" settings. Diagnostically acceptable abdominal CT examinations can be acquired at 75% lower-radiation dose with the help of the image-based iterative reconstruction technique.
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| 9. |
- Ekberg, Olle, et al.
(författare)
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Neck pain and dysphagia: MRI of retropharyngitis
- 1995
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Ingår i: Journal of Computer Assisted Tomography. - 1532-3145. ; 19:4, s. 555-558
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Acute neck pain developing over hours or a few days is often an alarming symptom that may be due to an inflammatory process or another process affecting the spine or the spinal canal, nerve roots, or peripheral nerves. MATERIALS AND METHODS: Four patients with acute onset of neck pain and dysphagia are presented. They were examined with MRI and CT, barium swallow, and plain radiography of the neck. RESULTS: In all patients T2-weighted MRI demonstrated a slitlike area with high signal intensity in the retropharyngeal space at the level C2-C7 suggestive of inflammation in the retropharyngeal space. The patients were treated with antibiotics and antiinflammatory drugs and became asymptomatic rapidly. CONCLUSION: We suggest the name retropharyngitis for this characteristic disease entity. Patients with acute onset of neck pain and dysphagia should undergo MRI to reach the correct diagnosis rapidly.
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| 10. |
- Fransson, Veronica, et al.
(författare)
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Detection of Perfusion Deficits in Multiphase Computed Tomography Angiography—A Stroke Imaging Technique Based on Iodine Mapping on Spectral Computed Tomography: Initial Findings
- 2021
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Ingår i: Journal of Computer Assisted Tomography. - 1532-3145. ; 45:4, s. 618-624
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The purpose of this study was to explore a novel method forbrain tissue differentiation using quantitative analysis of multiphase computedtomography (CT) angiography (MP-CTA) on spectral CT, to assesswhether it can distinguish underperfused fromnormal tissue, using CT perfusion(CTP) as reference.Methods: Noncontrast CT and MP-CTA images from 10 patients wereanalyzed in vascular regions through measurements of Hounsfield unit (HU)at 120 kV, HU at 40 keV, and iodine density. Regions were categorizedas normal or ischemic according to CTP. Hounsfield unit and iodinedensity were compared regarding ability to separate normal and ischemictissue, the difference in maximum time derivative of the right overleft hemisphere ratio.Results: Iodine density had the highest maximum time derivatives andgenerated the largest mean separation between normal and ischemic tissue.Conclusions: The method can be used to categorize tissue as normal orunderperfused. Using iodine quantification seems to give a more distinctdifferentiation of perfusion defects compared with conventional HU.
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| 13. |
- Jensen, Kristin, et al.
(författare)
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Evaluation of image quality for 7 iterative reconstruction algorithms in chest computed tomography imaging : A phantom study
- 2020
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Ingår i: Journal of Computer Assisted Tomography. - 0363-8715. ; 44:5, s. 673-680
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Tidskriftsartikel (refereegranskat)abstract
- Objectives This study aimed to evaluate the image quality of 7 iterative reconstruction (IR) algorithms in comparison to filtered back-projection (FBP) algorithm. Methods An anthropomorphic chest phantom was scanned on 4 computed tomography scanners and reconstructed with FBP and IR algorithms. Image quality of anatomical details - large/medium-sized pulmonary vessels, small pulmonary vessels, thoracic wall, and small and large lesions - was scored. Furthermore, general impression of noise, image contrast, and artifacts were evaluated. Visual grading regression was used to analyze the data. Standard deviations were measured, and the noise power spectrum was calculated. Results Iterative reconstruction algorithms showed significantly better results when compared with FBP for these criteria (regression coefficients/P values in parentheses): vessels (FIRST: -1.8/0.05, AIDR Enhanced: <-2.3/0.01, Veo: <-0.1/0.03, ADMIRE: <-2.1/0.04), lesions (FIRST: <-2.6/0.01, AIDR Enhanced: <-1.9/0.03, IMR1: <-2.7/0.01, Veo: <-2.4/0.02, ADMIRE: -2.3/0.02), image noise (FIRST: <-3.2/0.004, AIDR Enhanced: <-3.5/0.002, IMR1: <-6.1/0.001, iDose: <-2.3/0.02, Veo: <-3.4/0.002, ADMIRE: <-3.5/0.02), image contrast (FIRST: -2.3/0.01, AIDR Enhanced: -2.5/0.01, IMR1: -3.7/0.001, iDose: -2.1/0.02), and artifacts (FIRST: <-3.8/0.004, AIDR Enhanced: <-2.7/0.02, IMR1: <-2.6/0.02, iDose: -2.1/0.04, Veo: -2.6/0.02). The iDose algorithm was the only IR algorithm that maintained the noise frequencies. Conclusions Iterative reconstruction algorithms performed differently on all evaluated criteria, showing the importance of careful implementation of algorithms for diagnostic purposes.
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| 14. |
- Kalra, Mannudeep K., et al.
(författare)
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Radiation Dose Reduction with Sinogram Affirmed Iterative Reconstruction Technique for abdominal Computer Tomography
- 2012
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Ingår i: Journal of Computer Assisted Tomography. - USA : Lippincott Williams & Wilkins. - 0363-8715. ; 36:3, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The objective of this study was to assess the effect of Sinogram Affirmed Iterative Reconstruction (SAFIRE) and filtered back-projection (FBP) techniques on abdominal computed tomography (CT) performed with 50% and 75% radiation dose reductions.Methods: Twenty-four patients (mean age, 64 ± 14 years; male-female ratio, 10:14) gave informed consent for an institutional review board–approved prospective study involving acquisition of additional research images through the abdomen on 128-slice multi–detector-row CT (SOMATOM Definition Flash) at quality reference mAs of 100 (50% lower dose) and 50 (75% lower dose) over a scan length of 10 cm using combined modulation (CARE Dose 4D). Standard-of-care abdominal CT was performed at 200 quality reference mAs, with remaining parameters held constant. The 50- and 100-mAs data sets were reconstructed with FBP and at 4 SAFIRE settings (S1, S2, S3, S4). Higher number of SAFIRE settings denotes increased strength of the algorithm resulting in lower image noise. Two abdominal radiologists independently compared the FBP and SAFIRE images for lesion number, location, size and conspicuity, and visibility of small structures, image noise, and diagnostic confidence. Objective noise and Hounsfield units (HU) were measured in the liver and the descending aorta.Results: All 43 lesions were detected on both FBP and SAFIRE images. Minor blocky, pixelated appearance of 50% and 75% reduced dose images was noted at S3 and S4 SAFIRE but not at S1 and S2 settings. Subjective noise was suboptimal in both 50% and 75% lower-dose FBP images but was deemed acceptable on all SAFIRE settings. Sinogram Affirmed Iterative Reconstruction images were deemed acceptable in all patients at 50% lower dose and in 22 of 24 patients at 75% lower dose. As compared with 75% reduced dose FBP, objective noise was lower by 22.8% (22.9/29.7), 35% (19.3/29.7), 44.3% (16.7/29.3), and 54.8% (13.4/29.7) on S1 to S4 settings, respectively (P < 0.001).Conclusions: Sinogram Affirmed Iterative Reconstruction–enabled reconstruction provides abdominal CT images without loss in diagnostic value at 50% reduced dose and in some patients also at 75% reduced dose.
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| 15. |
- Lehti, Leena, et al.
(författare)
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Comparing Arterial- and Venous-Phase Acquisition for Optimization of Virtual Noncontrast Images From Dual-Energy Computed Tomography Angiography
- 2019
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Ingår i: Journal of Computer Assisted Tomography. - 1532-3145. ; 43:5, s. 770-774
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Follow-up with computed tomographic angiography is recommended after endovascular aneurysm repair, exposing patients to significant levels of radiation and iodine contrast medium. Dual-energy computed tomography allows virtual noncontrast (VNC) images to be reconstructed from contrast-enhanced images using a software algorithm. If the VNC images are a good-enough approximation of true noncontrast (TNC) images, a reduction in radiation dose can be ensured through omitting a TNC scan. PURPOSE: To compare image quality of VNC images reconstructed from arterial phase and venous phase dual-energy computed tomographic angiography to TNC images and to assess which one is more suitable to replace TNC images. METHODS: Sixty-three consecutive patients were examined using a dual-energy computed tomography as elective follow-up after endovascular aneurysm repair. The examination protocol included 1 unenhanced and 2 contrast-enhanced scans (80 kV/Sn140 kV) of the aorta. Virtual noncontrast data sets were reconstructed from the arterial (A-VNC) and venous (V-VNC) phase scans, respectively. Mean attenuation and image noise were measured for TNC, A-VNC, and V-VNC images within regions of interest at 2 levels in the aorta, the liver, retroperitoneal fat, and psoas muscle. Subjective image quality was assessed on a 4-point scale by 2 blinded readers. RESULTS: The differences between A-VNC and TNC, and between A-VNC and V-VNC, were substantial aorta at the level of diaphragm and aorta at the level of renal arteries. The difference between V-VNC and TNC was, on the other hand, very small and not statistically significant for the renal artery aorta. For liver, fat, and muscle tissue, there were significant differences between both A-VNC and V-VNC compared with TNC, but findings were similar between A-VNC and V-VNC. CONCLUSIONS: Virtual noncontrast images based on venous-phase scans appear to be a more accurate representation of TNC scans than VNC images based on arterial-phase scans.
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| 17. |
- Sharma, Aseem, et al.
(författare)
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Interpretation of Morphological Details of Nondegenerated Lumbar Intervertebral Discs on Magnetic Resonance Imaging: Insights From a Comparison Between Computed Tomography Discograms and Magnetic Resonance Imaging.
- 2022
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Ingår i: Journal of computer assisted tomography. - 1532-3145. ; 46:3, s. 487-491
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Tidskriftsartikel (refereegranskat)abstract
- To gain better insight into the magnetic resonance imaging (MRI) appearance of morphological intervertebral disc (IVD) details, such as annular and nucleus pulposus dimensions, by comparing contemporaneously obtained MRI and postdiscogram computed tomography (CT) scans of nondegenerated IVDs.Axial T2-weighted images and same-day postdiscography CTs, acquired after the MRI, of 26 normal-appearing lumbar IVDs (control IVDs at discography) were compared. The location and extent of central hyperintense zone on MRI and the extent of contrast distribution on CT relative to the IVD width (in anteroposterior [AP] and lateral planes) were assessed, with difference in measures between the modalities used to provide apparent inner annulus thickness and to estimate dimensions of also the outer annulus and location of nucleus pulposus.The mean (SD) extent of contrast distribution on CT discograms (53.1% [6.6%] and 58.1% [8.7%] of AP and lateral IVD width) was smaller than (P < 0.001 for both), and correlated weakly (r = 0.31 and 0.32 for AP and lateral planes) with corresponding measurements (58.4% [5.3%] and 65.7% [5.9%], respectively) for central hyperintense zone at MRI. The center of contrast opacification on CT discograms was located posterior to that of central T2 hyperintense zone on MRI in AP (P < 0.01), without any difference in lateral direction (P = 0.60).Normal-appearing lumbar IVDs are supported by outer annulus of larger relative thickness anteriorly, seen on both modalities. The shown discrepancy between the central T2 hyperintense zone and contrast distribution on CT discogram might reflect the inner annulus or structural changes within the borderzone nucleus and annulus. The exact nucleus size and inner annulus thickness could not be established due to a variable permeation of contrast across the central hyperintense zone on T2-weighted images.
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| 18. |
- Ståhlberg, Freddy, et al.
(författare)
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Quantitative study of flow dependence in NMR images at low flow velocities
- 1986
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Ingår i: Journal of Computer Assisted Tomography. - : Ovid Technologies (Wolters Kluwer Health). - 0363-8715. ; 10:6, s. 1006-1015
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Tidskriftsartikel (refereegranskat)abstract
- A basic theoretical model that describes the effects of flow in and out of the imaging plane in nuclear magnetic resonance (NMR) images, obtained with the standard pulse sequences single spin echo, multiple spin echo, and inversion recovery, is presented. Theoretically calculated signal values are compared with experimental results obtained from single-slice images of a flow phantom for variable flow velocity v as well as for variable echo time and inversion time at flow velocities <10 mm/s, corresponding to those found in cerebrospinal fluid, in capillary systems, and in smaller veins. The quantitative correspondence between theory and experiment is good in the range of velocities studied and for the imaging parameters used, but discrepancies occur when higher velocities are studied. In addition, flow in a capillary model is demonstrated qualitatively for very low linear flow velocities, <1 mm/s. It is concluded that the model describes the essentials of the inflow-outflow effect and that this effect can predict the flow dependence of the NMR signal for low flow velocities. Observed differences between model and experiment may be due to effects of flow-induced phase alterations and due to uncertainty in measurements of the relaxation times T1 and T2. The model described here can be extended to suit other types of pulse sequences and to suit multislice imaging. It can also be extended to incorporate flow-induced phase effects.
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| 19. |
- Wirestam, Ronnie, et al.
(författare)
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Regional cerebral blood flow distributions in normal volunteers: dynamic susceptibility contrast MRI compared with 99mTc-HMPAO SPECT
- 2000
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Ingår i: Journal of Computer Assisted Tomography. - 1532-3145. ; 24:4, s. 526-530
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Relative regional cerebral blood flow (rCBF) at rest was measured in 44 volunteers using both dynamic susceptibility contrast (DSC) MRI and (99m)Tc-HMPAO SPECT on the same day. METHOD: In MRI, a Gd-DTPA-BMA contrast agent bolus (0.3 mmol/kg body wt) was monitored with a simultaneous dual FLASH pulse sequence (time resolution 1.5 s). MRI-based rCBF images were calculated by singular value decomposition-based deconvolution of the measured tissue concentration-time curve with an arterial input function from a small artery within the imaging slice. In the SPECT investigation, 900 MBq of (99m)Tc-HMPAO was injected intravenously. Relative rCBF in gray matter in the thalamus and in frontal white matter was determined. RESULTS: The ratio of relative rCBF in gray matter to relative rCBF in white matter was 2.21 +/- 0.57 using MRI and 2.24 +/- 0.54 using SPECT (mean +/- SD). CONCLUSION: Relative rCBF maps from DSC MRI and (99m)Tc-HMPAO SPECT showed good agreement, and the MRI-based rCBF ratio correlated with the corresponding SPECT-based ratio (r = 0.79, p < 0.0000006).
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| 20. |
- Ziegelitz, Doerthe, et al.
(författare)
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In Patients With Idiopathic Normal Pressure Hydrocephalus Postoperative Cerebral Perfusion Changes Measured by Dynamic Susceptibility Contrast Magnetic Resonance Imaging Correlate With Clinical Improvement
- 2015
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Ingår i: Journal of Computer Assisted Tomography. - : Ovid Technologies (Wolters Kluwer Health). - 0363-8715. ; 39:4, s. 531-540
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Tidskriftsartikel (refereegranskat)abstract
- Objective To explore relationships between clinical improvement and relative cerebral blood flow (rCBF) changes after shunt-insertion in idiopathic normal pressure hydrocephalus (iNPH) as measured by dynamic susceptibility contrast magnetic resonance imaging. In 20 idiopathic normal pressure hydrocephalus patients rCBF was measured preoperatively and 3 months postoperatively. Because of shunt-induced right-sided artefacts, evaluation was restricted to 12 left-sided cortical, subcortical, and periventricular regions of interest. Correlations between rCBF and clinical symptoms were analyzed in shunt responders. In responders, the postoperative regions of interest-based rCBF increase of 2% to 9% was significant in the parenchyma, the hippocampus, and the anterior periventricular white matter. Perfusion improvement in the cingulus, caudate head, and thalamus correlated with decreased disturbance in one or more of the domains neuropsychology, gait, balance, and total performance. Apparently, dynamic susceptibility contrast magnetic resonance imaging can measure postoperative perfusion changes in responders. Postoperatively, perfusion increase in some grey matter structures seems to determine the degree of clinical improvement.
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| 21. |
- Nilsson, Jan, et al.
(författare)
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A short version of the nurse professional competence scale for measuring nurses' self-reported competence
- 2018
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Ingår i: Nurse Education Today. - Amsterdam : Elsevier BV. - 0260-6917 .- 1532-2793. ; 71, s. 233-239
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Tidskriftsartikel (refereegranskat)abstract
- Background: The Nurse Professional Competence (NPC) Scale with 88-items has been used to measure self-reported competence among nursing students and registered nurses in many national and international nursing research projects. However, a shorter version of the scale with maintained quality has been requested to further enhance its usability.Objectives: To develop and evaluate the construct validity and internal consistency of a shorter version of the NPC Scale. Design: A developmental and methodological design. Participants and Settings: The study was based on a sample of 1810 nursing students at the point of graduation from 12 universities in Sweden.Methods: The number of items in the original NPC Scale was reduced using several established research steps and then evaluated for data quality and construct validity using principal component analysis and confirmatory factor analysis. Reliability was measured as internal consistency using Cronbach's alpha.Results: The extensive process of reducing the number of items resulted in a version with 35 items. Principal component analysis resulted in six factors explaining 53.6% of the variance: “Nursing Care” “Value-based Nursing Care” “Medical and Technical Care” “Care Pedagogics” “Documentation and Administration of Nursing Care” and “Development, Leadership, and Organization of Nursing Care”. All factors showed Cronbach's alpha values of >0.70. The confirmative factor analysis goodness-of-fit indexes were for root mean square error of approximation 0.05 and for comparative fit index 0.89.Conclusions: The NPC Scale Short Form (NPC Scale-SF) 35-items revealed promising results with a six-factor structure explaining 53.6% of the total variance. This 35-item scale can be an asset when used alone and together with other instruments it can provide the possibility of more complex analyses of self-reported competence among nursing students and registered nurses.
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