氟－18-FDG PET不同區域腦造影中List Mode影像之變異係數分析

Abstract

Purpose: Coefficient of variance (CV), a relative measure of the variation, is defined as the ratio of the standard deviation (SD) to the mean. It is often referred to as the relative standard deviation (RSD or %RSD). This retrospective study aimed to find out if different emission duration time has influence on CV by using region of interest (ROI) method to compare CV of regional radiotracer distribution at frontal lobe, temporal lobe, occipital lobe and caudate. Methods: Thirty-one healthy control subjects free of neurological diseases (age range, 40~74 years; mean±SD, 53.4±10.7 years) underwent 18F-FDG PET scans in list mode were included. The list mode image data in 4 group images (i.e., 2-min, 5-min, 10-min and 20-min) were reconstructed. All images were spatially normalized and proportional scaled using SPM2. A mean image was made from averaging all 120 images from 4 groups by the software Matlab through the image calculation interface of SPM2. ROI's were placed manually onto the mean image at bilateral caudate, frontal lobe, temporal lobe and occipital lobe, respectively, using the software MRIcro. The size of ROI of frontal, the temporal and the occipital lobe was 1,000 voxels, and ROI of caudate was 125 voxels. The SD, the mean and the CV of voxel values in each ROI were calculated. Paired t-test was applied to analyze the difference of CV for each ROI between 2, 5, 10 and 20-min images. The difference was statistically significant if P value ＜0.05. Results: For caudate and temporal lobe, the CVs of 2-min images were significantly different from those of 20-min images, respectively. For frontal lobe, the CVs of 2-min, 5-min and 10-min images were significantly different from that of 20-min image. For occipital lobe, the CVs of 2-min and 5-min images were significantly different from that of 20-min images. Conclusion: For imaging the regions of caudate and temporal lobe, the emission duration may not be less than 5 min. For imaging frontal lobe region, the suggested emission duration is as long as possible. For imaging occipital lobe region, the emission duration less than 10 min should be avoided. If variation of intra-subject regional radiotracer distribution is taken into account, we suggest that longer emission duration is more advisable.