Physical performance evaluation of the Toshiba GCA-9300A triple-headed system

The physical performance of the Toshiba GCA-9300A triple-headed SPECT system has been assessed. Using a water-filled cylinder containing 99mTc, the tomographic volume sensitivity was 33.8 and 34.8 kcps/(MBq/ml)/cm for the high-resolution, parallel-hole (HR-PH) collimator and the super high-resolution, lead fanbeam (SHR-FB) collimator, respectively, excluding the rotation time(s) during scanning when data are not acquired. The tomographic spatial resolution at the center, in air, with 132 mm radius of rotation was 10.2 and 7.8 mm FWHM with the HR-PH and SHR-FB collimators, respectively; in water it was 11.0 and 7.8 mm. Reconstructed relative activity concentrations were accurate for both collimator sets if attenuation correction was used. With the SHR-FB collimators, the average peak-to-valley ratio of five-line sources in water improved significantly when an asymmetric energy window was used. Using the three-dimensional Hoffman brain phantom which simulates a 4:1 grey matter-to-white matter ratio and the usual choice of acquisition and processing parameters for brain studies, the reconstructed grey matter-to-white matter ratio was only about 1.7 for total counts typically acquired in a 99mTc-HMPAO study (4.0 M counts) and only 2.3 for 40 M counts. There was a qualitative improvement with an asymmetric energy window.