RSNA November 2000

Lesion Detectability for Hot Spot Imaging of Positron Emitters with Dedicated PET and Coincidence Gamma Camera

H.Zhang, T.Inoue, S.Alyafei, N.Oriuchi, A.Ichikawa, K.Endo

Department of Nuclear Medicine, Gunma University School of Medicine, Maebashi, Japan.

To investigate the correlation of detectability and the semi-quantification for hot spot lesion of positron emitters of positron emission tomography (PET) and positron coincidence gamma camera (PCG). Phantom studies for measurements of T/N ratio from 2.0 to 30.3, and detectability for hot spot lesion of PET and PCD were performed corresponding to clinical conditions. The detectability and T/N ratios of hot spot from 4.4mm to 36.9mm in diameter were derived from the 2D PET and PCG images. The patient FDG studies were also performed to verify the accuracy and reproducibility of detectability and semi-quantification from phantom studies. There was strong correlation between the T/N ratios derived from PET and PCG and actual T/N ratios, however the T/N ratio derived from PET was higher than that derived from PCG with a 30% to 48.4% difference. The detectability of hot spot lesion with PCG was lower than that of PET (64.8% Vs 75.9%). If an actual T/N ratio was 8.0, hot spots more than 10.6mm could be clearly identified with PCG imaging. The same identification could be achieved with PET imaging even if an actual T/N ratio was 4.0. In this study, PCG has similar detectability of hot spot lesion comparing to PET; however, semi-quantification using T/N ratio in PCG was inferior to that in PET.