ファントムを用いたPET/CT による腫瘍標的体積の自動輪郭抽出に関する検討

Objective : The aim of this study was to determine an appropriate threshold value for delineation of the target volume in PET/CT and to investigate whether we could delineate a target volume by phantom studies. Methods : A phantom consisted of six spheres (φ10~37 mm) filled with 18F solution. Data acquisition was performed PET/CT in non-motion and motion status with high 18F solution and in non-motion status with low 18F solution. In non-motion phantom experiments, we determined two types of threshold value, an absolute SUV (TSUV) and a percentage of the maximum SUV (T%). Delineation using threshold values was applied for all spheres and for selected large spheres (a diameter of 22 mm or larger). In motion phantom xperiments, data acquisition was performed in a static mode (sPET) and a gated mode (gPET). CT scanning was performed with helical CT (HCT) and 4-dimentional CT (4DCT). Results : The appropriate threshold values were aT% = 27% and aTSUV = 2.4 for all spheres, and sT% = 30% and sTSUV = 4.3 for selected spheres. For all spheres in sPET/HCT in motion, the delineated volumes were 84%~129% by the aT% and 34%~127% by the aTSUV. In gPET/4DCT in motion, the delineated volumes were 94~103% by the aT% and 51~131% by the aTSUV. For low radioactivity spheres, the delineated volumes were all underestimated. Conclusion : A threshold value of T%= 27% was proposed for auto-contouring of lung tumors. Our results also suggested that the respiratory gated data acquisition should be performed in both PET and CT for target volume delineation

Phantom Study on Three-Dimensional Target Volume Delineation by PET/CT-Based Auto-Contouring

Objective : The aim of this study was to determine an appropriate threshold value for delineation of the target volume in PET/CT and to investigate whether we could delineate a target volume by phantom studies. Methods : A phantom consisted of six spheres (φ10~37 mm) filled with 18F solution. Data acquisition was performed PET/CT in non-motion and motion status with high 18F solution and in non-motion status with low 18F solution. In non-motion phantom experiments, we determined two types of threshold value, an absolute SUV (TSUV) and a percentage of the maximum SUV (T%). Delineation using threshold values was applied for all spheres and for selected large spheres (a diameter of 22 mm or larger). In motion phantom xperiments, data acquisition was performed in a static mode (sPET) and a gated mode (gPET). CT scanning was performed with helical CT (HCT) and 4-dimentional CT (4DCT). Results : The appropriate threshold values were aT% = 27% and aTSUV = 2.4 for all spheres, and sT% = 30% and sTSUV = 4.3 for selected spheres. For all spheres in sPET/HCT in motion, the delineated volumes were 84%~129% by the aT% and 34%~127% by the aTSUV. In gPET/4DCT in motion, the delineated volumes were 94~103% by the aT% and 51~131% by the aTSUV. For low radioactivity spheres, the delineated volumes were all underestimated. Conclusion : A threshold value of T%= 27% was proposed for auto-contouring of lung tumors. Our results also suggested that the respiratory gated data acquisition should be performed in both PET and CT for target volume delineation

High-Contrast In Vivo Imaging of Tau Pathologies in Alzheimer’s and Non-Alzheimer’s Disease Tauopathies

A panel of radiochemicals has enabled in vivo positron emission tomography (PET) of tau pathologies in Alzheimer’s disease (AD), although sensitive detection of frontotemporal lobar degeneration (FTLD) tau inclusions has been unsuccessful. Here, we generated an imaging probe, PM-PBB3, for capturing diverse tau deposits. In vitro assays demonstrated the reactivity of this compound with tau pathologies in AD and FTLD. We could also utilize PM-PBB3 for optical/PET imaging of a living murine tauopathy model. A subsequent clinical PET study revealed increased binding of 18F-PM-PBB3 in diseased patients, reflecting cortical-dominant AD and subcortical-dominant progressive supranuclear palsy (PSP) tau topologies. Notably, the in vivo reactivity of 18F-PM-PBB3 with FTLD tau inclusion was strongly supported by neuropathological examinations of brains derived from Pick’s disease, PSP, and corticobasal degeneration patients who underwent PET scans. Finally, visual inspection of 18F-PM-PBB3-PET images was indicated to facilitate individually based identification of diverse clinical phenotypes of FTLD on a neuropathological basis