Design and simulation of a stationary SPECT imaging system based on axially varying tilted parallel-hole collimation

Stationary SPECT systems present many advantages compared to non-stationary systems: more stability (less calibration necessary), no need for large and expensive rotation / positioning mechanisms... They are normally based on multi-pinhole collimation, which gives complete angular sampling but only for a small portion of the transaxial field-of-view, thereby limiting them to imaging small objects relative to the bore. We propose a new type of collimator for stationary SPECT imaging that uses tilted parallel-holes whose viewing direction changes according to their axial position. This collimator allows complete angular sampling of a larger percentage of the bore, using only longitudinal bed movement. We have simulated a small animal system with a hexagonal detector configuration that fits inside a cube of 100mm side. The collimator fits inside this detector system, and is designed such that we can image a 65mm diameter rat with a target resolution at the center of 2mm. Our results show that we are indeed able to reconstruct objects of 65mm diameter without sampling artifacts with the simulated system, using only longitudinal bed translations. The (mean) volume sensitivity and resolution obtained were 170 cps/MBq and 1.4mm, respectively, for a field-of-view of 65 mm diameter and 46 mm length (75% of the bore's volume). We envision this novel collimator concept as having many applications, from small-animal to human imaging. It is particularly useful for systems with spatial restrictions, such as SPECT/MR inserts, due to its very efficient use of space and no need for a rotation mechanism. It could also be used to perform a full-body scout scan, prior to a targeted region-of-interest scan with a pinhole collimator. Furthermore, such a collimator can be inserted and used in existing scanners, since it only requires axial bed movement.

Jaar van publicatie:2014