scholarly journals Evaluation of Scatter Fraction (SF) of a 16-Ring Positron Emission Tomography (PET) System

2013 ◽  
Vol 4 (1) ◽  
pp. 81-86
Author(s):  
M Monjur Ahasan
Keyword(s):  
Time Window ◽  
Medical Physics ◽  
Mean Value ◽  
Filtered Backprojection ◽  
Scatter Fraction ◽  
Positron Emission ◽  
Acquisition Mode ◽  
Pet System ◽  
Slight Discrepancy ◽  
Coincidence Time

Scatter fraction (SF) characteristic of a newly constructed 16-ring PET system with a FOV of 20 cm was experimentally evaluated in 2D acquisition mode (ring difference ? 3) but without septa, using a 10 cm diameter phantom. The scatter fraction measured from the backprojected images and the sinogram data aiming to find the discrepancy between the two approaches and to test the camera performance operating without septa. The images were reconstructed by the filtered backprojection (FBP) technique using some different filter functions. SF measured from the reconstructed images agreed within uncertainties and had a mean value of 26.1±0.8% at 250-850 keV energy and 12 ns coincidence time window. Scatter fraction also measured from analysis of the PET sinogram was slightly lower, at 23.6 ±0.7%. In each case, the procedure used for estimating the background under the peak is only approximate, and this may account for the slight discrepancy between the two approaches. The results so far indicate that the system can be operated in 2D mode without septa. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14691 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 81-86

scholarly journals NEMA NU4-2008 Performance Evaluation of Albira: A Two-Ring Small-Animal PET System Using Continuous LYSO Crystals

2016 ◽  
Vol 3 (1) ◽  
pp. 12-26 ◽  
Author(s):  
Malgorzata Z. Pajak ◽  
David Volgyes ◽  
Sally L. Pimlott ◽  
Carlos C. Salvador ◽  
Antonio S. Asensi ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Small Animal Imaging ◽  
Small Animal ◽  
Axial Direction ◽  
Small Animal Pet ◽  
Performance Review ◽  
Good Spatial Resolution ◽  
Positron Emission ◽  
Animal Images ◽  
Pet System

Goals:This paper presents the performance review based on a dual-ring Positron Emission Tomography (PET) scanner being a part of Bruker Albira: a multi-modal small-animal imaging platform. Each ring of Albira PET contains eight detectors arranged as octagon, and each detector is built using a single continuous lutetium-yttrium oxyorthosilicate crystal and multi-anode photo multiplier tube. In two-ring configuration, the scanner covers 94.4 mm in axial- and 80´80 mm in trans-axial direction, which is sufficient to acquire images of small animals (e.g.mice) without the need of moving the animal bed during the scan.Methods:All measurements and majority of data processing were performed according to the NEMA NU4-2008 standard with one exception. Due to the scanner geometry, the spatial resolution test was reconstructed using iterative algorithm instead of the analytical one. The main performance characteristics were compared with those of the other PET sub-systems of tri-modal small-animal scanners.Results:The measured spatial resolution at the centre of the axial field of view in radial, tangential and axial directions was 1.72, 1.70 and 2.45 mm, respectively. The scatter fraction for the mouse-like phantom was 9.8% and for the rat-like phantom, 21.8%. The maximum absolute sensitivity was 5.30%. Finally, the recovery co-efficients for 5, 4, 3, 2, 1 mm diameter rods in image quality phantom were: 0.90, 0.77, 0.66, 0.30 and 0.05, respectively.Conclusion:The Bruker Albira is a versatile small-animal multi-modal device that can be used for variety of studies. Overall the PET sub-system provides a good spatial resolution coupled with better-than average sensitivity and the ability to produce good quality animal images when administering low activities.

scholarly journals [18F]FDG Positron Emission Tomography for Initial Staging and Healing Assessment at the End of Therapy in Lymph Nodes and Bone Tuberculosis

2021 ◽  
Vol 8 ◽  
Author(s):  
Laure Sarda-Mantel ◽  
Jidar Kaoutar ◽  
Toni Alfaiate ◽  
Amanda Lopes ◽  
Frédéric Paycha ◽  
...  
Keyword(s):  
Fdg Pet ◽  
Roc Curves ◽  
Mean Value ◽  
Extra Pulmonary Tuberculosis ◽  
Positron Emission ◽  
End Of Treatment ◽  
Pet Ct ◽  
Bone Tuberculosis ◽  
Fdg Pet Ct ◽  
Healing Assessment

Objective: In extra-pulmonary tuberculosis, therapeutic management is difficult in the absence of reliable tool to affirm healing at the end of treatment. In this prospective multicenter study, we evaluated [18F]FDG-PET for this purpose.Methods: Forty-two patients out of 55 included patients could be analyzed. Additionally to usual biological, histological and morphological explorations, [18F]FDG-PET was performed at diagnosis (PET1), at the end of treatment (PET2), indeed 6 months later. Then patients were followed until 12 months after end of prescribed treatment.Results: PET1 was positive in 97.6% of patients and discovered unknown injured sites in 52.7% of cases. PET2 was positive in 83.3% of uncured patients, and in 82.3% of cured patients. The sum and mean value of SUVmax measured in PET/CT lesions decreased between PET1 and PET2 in all patients. Mean value of SUVmax (MSUV) and sum value of SUVmax on PET2 showed the highest AUC on ROC curves for the diagnosis of healing at the end of prescribed treatment; MSUV 3.5 on PET2 had a sensitivity of 76.5% and a specificity of 80.0% to affirm healing at the end of prescribed treatment.Conclusions: [18F]FDG-PET/CT was useful at diagnosis, discovering unknown lesions in 52.7% of cases. MSUV on PET2 was the best criteria to affirm healing at the end of prescribed treatment.

Clinical-Radiological Parameters Improve the Prediction of the Thrombolysis Time Window by Both MRI Signal Intensities and DWI-FLAIR Mismatch

2016 ◽  
Vol 42 (1-2) ◽  
pp. 57-65 ◽  
Author(s):  
Vince Istvan Madai ◽  
Carla N. Wood ◽  
Ivana Galinovic ◽  
Ulrike Grittner ◽  
Sophie K. Piper ◽  
...  
Keyword(s):  
Acute Stroke ◽  
Prediction Models ◽  
Time Window ◽  
Area Under The Curve ◽  
Lesion Size ◽  
Mean Value ◽  
Roc Curve Analysis ◽  
Vessel Occlusion ◽  
Relative Signal Intensity ◽  
Radiological Parameters

Background: With regard to acute stroke, patients with unknown time from stroke onset are not eligible for thrombolysis. Quantitative diffusion weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR) MRI relative signal intensity (rSI) biomarkers have been introduced to predict eligibility for thrombolysis, but have shown heterogeneous results in the past. In the present work, we investigated whether the inclusion of easily obtainable clinical-radiological parameters would improve the prediction of the thrombolysis time window by rSIs and compared their performance to the visual DWI-FLAIR mismatch. Methods: In a retrospective study, patients from 2 centers with proven stroke with onset <12 h were included. The DWI lesion was segmented and overlaid on ADC and FLAIR images. rSI mean and SD, were calculated as follows: (mean ROI value/mean value of the unaffected hemisphere). Additionally, the visual DWI-FLAIR mismatch was evaluated. Prediction of the thrombolysis time window was evaluated by the area-under-the-curve (AUC) derived from receiver operating characteristic (ROC) curve analysis. Factors such as the association of age, National Institutes of Health Stroke Scale, MRI field strength, lesion size, vessel occlusion and Wahlund-Score with rSI were investigated and the models were adjusted and stratified accordingly. Results: In 82 patients, the unadjusted rSI measures DWI-mean and -SD showed the highest AUCs (AUC 0.86-0.87). Adjustment for clinical-radiological covariates significantly improved the performance of FLAIR-mean (0.91) and DWI-SD (0.91). The best prediction results based on the AUC were found for the final stratified and adjusted models of DWI-SD (0.94) and FLAIR-mean (0.96) and a multivariable DWI-FLAIR model (0.95). The adjusted visual DWI-FLAIR mismatch did not perform in a significantly worse manner (0.89). ADC-rSIs showed fair performance in all models. Conclusions: Quantitative DWI and FLAIR MRI biomarkers as well as the visual DWI-FLAIR mismatch provide excellent prediction of eligibility for thrombolysis in acute stroke, when easily obtainable clinical-radiological parameters are included in the prediction models.

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