An Assessment of the Accuracy of 3 Dimensional Acquisition in F-18 fluorodeoxyglucose Brain PET Imaging / 대한핵의학회잡지

PURPOSE: To assess the quantitative accuracy and the clinical utility of 3D volumetric PET imaging with FDG in brain studies, 24 patients with various neurological disorders were studied. MATERIALS AND METHODS: Each patient was injected with 370 MBq of 2-[18F]fluoro-2-deoxy-D-glucose. After a 30 min uptake period, the patients were imaged for 30 min in 2 dimensional acquisition (2D) and subsequently for 10 min in 3 dimensional acquisition imaging (3D) using a GE AdvanceTM PET system. The scatter corrected 3D (3D SC) and non scatter-corrected 3D images were compared with 2D images by applying ROIs on gray and white matter, lesion and contralateral normal areas. Measured and calculated attenuation correction methods for emission images were compared to get the maximum advantage of high sensitivity of 3D acquisition. RESULTS: When normalized to the contrast of 2D images, the contrasts of gray to white matter were 0.75+/-0.13 (3D) and 0.95+/-0.12 (3D SC). The contrasts of normal area to lesion were 0.83+/-0.05 (3D) and 0.96+/-0.05 (3D SC). Three nuclear medicine physicians judged 3D SC images to be superior to the 2D with regards to resolution and noise. Regional counts of calculated attenuation correction was not significantly different to that of measured attenuation correction. CONCLUSION:: 3D PET images with the scatter correction in FDG brain studies provide quantitatively and qualitatively similar images to 2D and can be utilized in a routine clinical setting to reduce scanning time and patient motion artifacts.

Improved Activity Estimation using Combined Scatter and Attenuation Correction in SPECT / 대한핵의학회잡지

PURPOSE: The pvrpose of this study was to evaluate the accuracy of radioactivity quantitation in Tc-99m SPECT by using combined scatter and attenuation correction. MATERIALS AND METHODS: A cylindrical phantom which simulates tumors (T) and normal tissue (B) was filled with varying activity ratios of Tc-99m. We acquired emission scans of the phantom using a three-headed SPECT system (Trionix, Inc.) witb two energy windows (photopeak window: 126 154 keV and scatter window: 101 123 keV). We performed the scatter correction with dual-energy window subtraction method (k=0.4) and Chang attenuation correction. Three sets of SPECT images were reconstructed using combined scatter and attenuation correction (SC+AC', attenuation correction (AC) and without any correction (NONE). We compared T/B ratio, irnage contrast [(T-B)/(T+B)) and absolute radioactivity with true values. RESULTS: SC+AC images had the highest mean values of T/B ratios. Image contrast was 0.92 in SC+AC, which was close to the true value of 1, and higher than AC (0.77) or NONE (0.80). Errors of true activity by SPECT images ranged from 1 to 11% for SC+AC, 22-47% for AC, and 2 16% for NONE in a phantom which was located 2.4cm from the phantom surface. In a phantom located 10,0cm from the surface, SC+AC underestimated by ?4%, NON.E 40%. However, AC overestimated by 10%. CONCLUSION: We conclude that accurate SPECT activity quantitation of Tc-99m distribution can be achieved by dual window scatter correc.tion combined with attenuation correction.