A positron emission computed tomograph HEADTOME-III(SET-130W)

A positron emission computed tomograph, HEADTOME-III (SET-130W), was developed. It is provided with three detector rings, each of which has 160 BGO detectors arranged in a circle of 750 mm in diameter. The three detector rings are mounted with an interval of 30 mm, and can take 5 slices simultaneously. Slice shields are accommodated on a cart behind the gantry and can be used selectively with an easy operation. Spatial resolution was improved from 8.2 mm FWHM to 6.5 mm FWHM by the use of shadow masks at the center of the field of view (F.O.V.) at the possible expense of sensitivity loss, from which effectiveness of shadow masks on a central region of the F.O.V. was confirmed. Sensitivity without shadow masks was 34.5 kcps/(μCi/ml) for intra-ring slice, and 56.7 kcps/(μCi/ml) for inter-ring slice respectively. Maximum count rate was 110 kcps. Count rate linearity was improved to within +-1% at the count rate of 50 kcps by the software dead time correction. In order to realize a highly quantitative measurement normalization and transmission data acquisition programs were installed besides emission data acquisition. Furthermore, dynamic data acquisition, gated heart imaging, linear scan programs were also provided. For clinical applications, rCBF, rCMRO2, rOEF measurement by 15O labelled gas-steady-state model and rCMRG 1 measurement by 18FDG were developed and evaluated. (author)