PET/CT検査におけるµ-mapのトランケーシヨンエラーが体幹部のStandardized Uptake Valueに与える影響

摘要

陽十成出断層撮影(positron emission tomography: PET)装置が臨床に用いられはじめた当初は，外部線源を装着したPET単体の装置であったが，現在臨床にて使用されているほとんどのPET装置力が，多列型computed tomography(CT)とPETとの複合装置であるPET/CT装置となっている.またPET画像再構成法は，コンピュータの高性能化，およびソフトウェアの開発によって著しく進歩し，正確なPET画像を再構成するにあたって，CT画像で得られた情報を利用，また精度の高いシミュレーシヨンを駆使して減弱補正(X-CT attenuation correction: CTAC)や散乱線補正(scatter correction: SC)などが行われている1〜3).%Purpose: The aim of this study was evaluate to impact of standardized uptake value (SUV) on the body trunk with truncation error of µ-map for CT attenuation correction (CTAC) in whole-body 2-deoxy-2-[~（18）F] fluoro-D-glucose (~（18)F-FDG)-positron emission tomography (PET)/CT with use of anthropomorphic phantom. Methods: We used body phantom (2.5 MBq/l) including simulated tumor targets (11.25 MBq/l) and arm phantom. The CT scan was used with a field of view (FOV) of 50 cm. The µ-maps were created by assuming a state of the arm protruding from the FOV (Pmap). A 3D-PET scan with an emission time of 20 min was performed. The PET images were then reconstructed with CTAC, and with and without scatter correction. We evaluated the relationship to Pmap size and the count of simulated tumors and background (B.G.) in PET images which reconstructed the use of each Pmap, respectively. Results: The count of simulated tumor (large) with scatter correction was decreased to 1.3% (Pmap:15 mm) and 8.8% (Pmap: 35 mm). Then, the count severe reduction was 86.9% in Pmap of 65 mm. The same trend was shown by simulated tumor (middle, small) and B.G. The count of the simulated tumor (large) without scatter correction decreased to 1.3% (Pmap:15 mm), 6.4% (Pmap: 35 mm) and 13.1% (Pmap: 65 mm). Conclusion: Truncation error by µ-map for CTAC in whole-body ~(18)F-PET/CT caused a decrease of the SUV on the body trunk used for attenuation and scatter correction in the PET images.