Study of a high-resolution PET system using a Silicon detector probe

Abstract

A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm 3 pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PETprobe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to Institute of Physics and Engineering in Medicine

Evaluation of a high resolution silicon PET insert module

“…Thus, close to 1% relative efficiency per 1 mm of active silicon thickness for regions close to the insert could be expected in a clinical situation where high-resolution detectors would be positioned within the standard PET ring. Similar efficiencies have also been reported by [29]. Based on those results, reconstructed image quality such as shown in Fig.…”

“…If a single module is used that remains stationary during data acquisition, improvement in resolution can only be observed in the direction parallel to the sensor surface [29]. Rather than rotating a single module around the region of interest, a more convenient solution may be to use multiple modules placed at variable angles with respect to each other, depending on the clinical application.…”

A compact high resolution flat panel PET detector based on the new 4-side buttable MPPC for biomedical applications

“…For organ-specific clinical applications, instead of building a dedicated PET scanner, higher resolution imaging applications with improved sensitivity are possible using a flat panel insert device (shown in Figure 1), potential uses include clinical imaging of head and neck, breast, internal mammary nodes, prostate, etc. The simulation study in a Siemens Biograph 64 PET/CT scanner of a silicon detector insert with detection area similar to our flat panel detector shows significant improvement in resolution with hot rods phantom study[6]. Silicon detectors have much lower density than lutetium yttrium oxyorthosilicate (LYSO) based detectors, thus the proposed silicon probe detector was composed of 10 layers to achieve reasonable detection efficiency.…”

Impact of Point-Spread Function Modeling on PET Image Quality in Integrated PET/MR Hybrid Imaging

“…The intrinsic resolution of modern clinical PET scanners is typically in the range of 4-6 mm (3,7). Spatial resolution in PET is generally restricted by several physical factors including positron range; noncollinearity of the annihilation photons; detection processes, such as scatter inside the scintillation crystals; finite dimensions of the crystals; and depth of interaction (8). Theoretically, each of these effects could be estimated by experimental or simulation studies and integrated into the PET image reconstruction process.…”