High-sensitivity brain SPECT system using cadmium telluride (CdTe) semiconductor detector and 4-pixel matched collimator

Abstract

For high-sensitivity brain imaging, we have developed a two-head single-photon emission computed tomography (SPECT) system using a CdTe semiconductor detector and 4-pixel matched collimator (4-PMC). The term, '4-PMC' indicates that the collimator hole size is matched to a 2 × 2 array of detector pixels. By contrast, a 1-pixel matched collimator (1-PMC) is defined as a collimator whose hole size is matched to one detector pixel. The performance of the higher-sensitivity 4-PMC was experimentally compared with that of the 1-PMC. The sensitivities of the 1-PMC and 4-PMC were 70 cps/MBq/head and 220 cps/MBq/head, respectively. The SPECT system using the 4-PMC provides superior image resolution in cold and hot rods phantom with the same activity and scan time to that of the 1-PMC. In addition, with half the usual scan time the 4-PMC provides comparable image quality to that of the 1-PMC. Furthermore, (99m)Tc-ECD brain perfusion images of healthy volunteers obtained using the 4-PMC demonstrated acceptable image quality for clinical diagnosis. In conclusion, our CdTe SPECT system equipped with the higher-sensitivity 4-PMC can provide better spatial resolution than the 1-PMC either in half the imaging time with the same administered activity, or alternatively, in the same imaging time with half the activity.

Semiconductor Detector-Based Scanners for Nuclear Medicine

“…4-PMC was designed to improve the sensitivity and spatial resolution in clinical SPECT imaging compared with 1-PMC. The sensitivities of 1-PMC and 4-PMC were 70 and 220 cps/MBq/head, respectively [7]. Therefore, 4-PMC has three times the sensitivity of 1-PMC.…”

“…The PSF of each collimator type was obtained by ray-tracing simulation [6,7]. The attenuation factor of the gamma rays in a subject was approximated by an exponential function of the line integral from an image pixel to a detector pixel in an attenuation map.…”

“…This system is described in detail in previous reports [6,7]. In brief, CdTe-SPECT includes two detector heads.…”

“…For high-sensitivity imaging, a wide aperture parallel-hole collimator (Fig. 4.1), which we call the "4-pixel matched collimator" (4-PMC), was previously developed [6,7]. The hole size of the 4-PMC is matched to four detector pixels, that is, there are four (2 Â 2) pixels per collimator hole.…”

“…These features of semiconductor detectors may lead to improved PET and SPECT images. The authors previously developed CdTe semiconductor detector-based PET (CdTe-PET) [1,2] and SPECT (CdTe-SPECT) [6,7]. The physical and clinical performances of the systems were evaluated through phantom, animal, and clinical studies.…”