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- Giussani, Augusto, et al.
(författare)
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A Compartmental Model for Biokinetics and Dosimetry of 18F-Choline in Prostate Cancer Patients
- 2012
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 53:6, s. 985-993
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Tidskriftsartikel (refereegranskat)abstract
- PET with F-18-choline (F-18-FCH) is used in the diagnosis of prostate cancer and its recurrences. In this work, biodistribution data from a recent study conducted at Skane University Hospital Malmo were used for the development of a biokinetic and dosimetric model. Methods: The biodistribution of F-18-FCH was followed for 10 patients using PET up to 4 h after administration. Activity concentrations in blood and urine samples were also determined. A compartmental model structure was developed, and values of the model parameters were obtained for each single patient and for a reference patient using a population kinetic approach. Radiation doses to the organs were determined using computational (voxel) phantoms for the determination of the S factors. Results: The model structure consists of a central exchange compartment (blood), 2 compartments each for the liver and kidneys, 1 for spleen, 1 for urinary bladder, and 1 generic compartment accounting for the remaining material. The model can successfully describe the individual patients' data. The parameters showing the greatest interindividual variations are the blood volume (the clearance process is rapid, and early blood data are not available for several patients) and the transfer out from liver (the physical half-life of F-18 is too short to follow this long-term process with the necessary accuracy). The organs receiving the highest doses are the kidneys (reference patient, 0.079 mGy/MBq; individual values, 0.033-0.105 mGy/MBq) and the liver (reference patient, 0.062 mGy/MBq; individual values, 0.036-0.082 mGy/MBq). The dose to the urinary bladder wall of the reference patient varies between 0.017 and 0.030 mGy/MBq, depending on the assumptions on bladder voiding. Conclusion: The model gives a satisfactory description of the biodistribution of F-18-FCH and realistic estimates of the radiation dose received by the patients.
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- Lehti, Leena, et al.
(författare)
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Reliability of virtual non-contrast computed tomography angiography: comparing it with the real deal
- 2018
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Ingår i: Acta Radiologica Open. - : SAGE Publications. - 2058-4601. ; 7, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Background:Computed tomographic angiography (CTA) may require a non-contrast enhanced dataset for the diagnostic workup. By using dual-energy acquisition, it is possible to obtain a virtual non-contrast-enhanced (VNC) dataset, thereby possibly eliminating the non-contrast acquisition and reducing the radiation dose.Purpose:To compare image quality of VNC images reconstructed from arterial phase dual-energy CTA to true non-contrast (TNC) images, and to assess whether VNC images were of sufficient quality to replace TNC images.Material and methods:Thirty consecutive patients with suspected abdominal aortic aneurysm, aortic dissection, or subacute control after EVAR/TEVAR were examined with dual-energy CT (DECT). The examination protocol included a single-energy TNC, DECT arterial phase (80 kV/Sn140 kV), and single-energy in venous phase of the aorta. A VNC dataset was obtained from the DE acquisition from arterial phase scans. Mean attenuation and image noise were measured within regions of interest at three levels in the aorta in TNC and VNC images. Comparison of the TNC and VNC images for artefacts was made side-by-side. Subjective evaluation included overall image quality on a 4-grade scale, and quantitative analysis of algorithm-induced artefacts by two experienced readers.Results:For all cases, the aortic attenuation was significantly higher at VNC than at TNC. Image noise measured quantitatively was also significantly higher at VNC than at TNC. Subjective image quality was lower for VNC (mean = 3.1 for VNC, 3.7 = for TNC) but there were no cases rated non-diagnostic.Conclusion:VNC images based on arterial phase CTA have significantly higher mean attenuation and higher noise levels compared to TNC.
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- Holmquist, Fredrik, et al.
(författare)
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Can iterative reconstruction algorithms replace tube loading compensation in low kVp hepatic CT? Subjective versus objective image quality
- 2020
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Ingår i: Acta Radiologica Open. - : SAGE Publications. - 2058-4601 .- 2058-4601. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Background: Hepatic computed tomography (CT) with decreased peak kilovoltage (kVp) may be used to reduce contrast medium doses in patients at risk of contrast-induced acute kidney injury (CI-AKI); however, it increases image noise. To preserve image quality, noise has been controlled by X-ray tube loading (mAs) compensation (TLC), i.e. increased mAs. Another option to control image noise would be to use iterative reconstructions (IR) algorithms without TLC (No-TLC). It is unclear whether this may preserve image quality or only reduce image noise. Purpose: To evaluate image quality of 80 kVp hepatic CT with TLC and filtered back projection (FBP) compared with 80 kVp with No-TLC and IR algorithms (SAFIRE 3 and 5) in patients with eGFR <45 mL/min. Material and Methods: Forty patients (BMI 18-32 kg/m(2)) were examined with both protocols following injection of 300 mg I/kg. Hepatic attenuation, image noise, enhancement, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were evaluated for each patient. Results: Comparing TLC/FBP with No-TLC/IR-S5, there were no significant differences regarding hepatic attenuation, image noise, enhancement, SNR and CNR: 114 vs. 115 HU, 14 vs. 14 HU, 55 vs. 57 HU, 8.0 vs. 8.4, and 3.8 vs. 4.0 in median, respectively. No-TLC/IR-S3 resulted in higher image noise and lower SNR and CNR than TLC/FBP. Subjective image quality scoring with visual grading showed statistically significantly inferior scores for IR-S5 images. Conclusion: CT of 80 kVp to reduce contrast medium dose in patients at risk of CI-AKI combined with IR algorithms with unchanged tube loading to control image noise does not provide sufficient diagnostic quality.
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- Abul-Kasim, Kasim, et al.
(författare)
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Optimization of Radiation Exposure and Image Quality of the Cone-beam O-arm Intraoperative Imaging System in Spinal Surgery.
- 2012
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Ingår i: Journal of Spinal Disorders and Techniques. - 1539-2465. ; 25:1, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: Retrospective study. OBJECTIVES: To optimize the radiation doses and image quality for the cone-beam O-arm surgical imaging system in spinal surgery. SUMMARY OF BACKGROUND: Neurovascular compromise has been reported after screw misplacement during thoracic pedicle screw insertion. The use of O-arm with or without navigation system during spinal surgery has been shown to lower the rate of screw misplacement. The main drawback of such imaging surgical systems is the high radiation exposure. METHODS: Chest phantom and cadaveric pig spine were examined on the O-arm with different scan settings: 2 were recommended by the O-arm manufacturer (120 kV/320 mAs, and 120 kV/128 mAs), and 3 low-dose settings (80 kV/80 mAs, 80 kV/40 mAs, and 60 kV/40 mAs). The radiation doses were estimated by Monte Carlo calculations. Objective evaluation of image quality included interobserver agreement in the measurement of pedicular width in chest phantom and assessment of screw placement in cadaveric pig spine. RESULTS: The effective dose/cm for 120 kV/320 mAs scan was 13, 26, and 69 times higher than those delivered with 80 kV/80 mAs, 80 kV/40 mAs, and 60 kV/40 mAs scans, respectively. Images with 60 kV/40 mAs were unreliable. Images with 80 kV/80 mAs were considered reliable with good interobserver agreement when measuring the pedicular width (random error 0.38 mm and intraclass correlation coefficient 0.979) and almost perfect agreement when evaluating the screw placement (κ value 0.86). CONCLUSIONS: The radiation doses of the O-arm system can be reduced 5 to 13 times without negative impact on image quality with regard to information required for spinal surgery.
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| 7. |
- Aho Fält, Tobias, et al.
(författare)
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Simulated Dose Reduction for Abdominal CT With Filtered Back Projection Technique: Effect on Liver Lesion Detection and Characterization
- 2019
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Ingår i: American Journal of Roentgenology: diagnostic imaging and related sciences. - 0361-803X. ; 212:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE. Previous studies have shown the possibility to reduce radiation dose in abdominal CT by 25–50% without negatively affecting detection of liver lesions. How radiation dose reduction affects characterization of liver metastases is not as well known. The objective of this study was to investigate how different levels of simulated dose reduction affect the detection and characterization of liver lesions, primarily hypovascular metastases. A secondary objective was to analyze the relationship between the lesion size and contrast-to-noise ratio (CNR) and the detection rate.MATERIALS AND METHODS. Thirty-nine patients (19 with metastases and 20 without) were retrospectively selected. The following radiation dose levels (DLs) were simulated: 100% (reference level), 75%, 50%, and 25%. Five readers were asked to mark liver lesions and rate the probability of malignancy on a 5-grade Likert scale. Noninferiority analysis using the jackknife free-response ROC (JAFROC) method was performed as well as direct comparison of detection rates and grades.RESULTS. JAFROC analysis showed noninferior detection and characterization of metastases at DL75 as compared with DL100. However, the number of benign lesions and false-positive localizations rated as “suspected malignancy” was significantly higher at DL75.CONCLUSION. Radiation dose can be reduced by 25% without negatively affecting diagnosis of hypovascular liver metastases. Characterization of benign lesions, however, is impaired at DL75, which may lead to unnecessary follow-up examinations. Finally, increased image noise seems to affect the detection of small lesions to a degree that cannot be explained solely by the reduction in CNR.
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| 10. |
- Aurumskjöld, Marie-Louise, et al.
(författare)
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Evaluation of an iterative model-based reconstruction of pediatric abdominal CT with regard to image quality and radiation dose
- 2018
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 59:6, s. 740-747
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundIn pediatric patients, computed tomography (CT) is important in the medical chain of diagnosing and monitoring various diseases. Because children are more radiosensitive than adults, they require minimal radiation exposure. One way to achieve this goal is to implement new technical solutions, like iterative reconstruction.PurposeTo evaluate the potential of a new, iterative, model-based method for reconstructing (IMR) pediatric abdominal CT at a low radiation dose and determine whether it maintains or improves image quality, compared to the current reconstruction method.Material and MethodsForty pediatric patients underwent abdominal CT. Twenty patients were examined with the standard dose settings and 20 patients were examined with a 32% lower radiation dose. Images from the standard examination were reconstructed with a hybrid iterative reconstruction method (iDose4), and images from the low-dose examinations were reconstructed with both iDose4 and IMR. Image quality was evaluated subjectively by three observers, according to modified EU image quality criteria, and evaluated objectively based on the noise observed in liver images.ResultsVisual grading characteristics analyses showed no difference in image quality between the standard dose examination reconstructed with iDose4 and the low dose examination reconstructed with IMR. IMR showed lower image noise in the liver compared to iDose4 images. Inter- and intra-observer variance was low: the intraclass coefficient was 0.66 (95% confidence interval = 0.60–0.71) for the three observers.ConclusionIMR provided image quality equivalent or superior to the standard iDose4 method for evaluating pediatric abdominal CT, even with a 32% dose reduction.
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