Abstract
Purpose  The aim of this study was to improve the uniformity of the axial spatial resolution and sensitivity in pinhole single-photon emission computed tomography (SPECT) and to extend the axial field of view, by using a dedicated three-pinhole collimator.
Methods  A rectangular tungsten plate with three pinhole apertures of 1.5 mm diameter was designed to image a cylindrical field of view of 55 mm diameter and 160 mm axial length using a clinical gamma camera. To evaluate the non-uniformity of spatial resolution and noise, a multiple-disk phantom was built. The phantom was filled with Tc-99m, and data were acquired using a circular orbit and reconstructed with a dedicated iterative reconstruction algorithm. The axial spatial resolution together with the noise was measured in each disk. These measurements were compared to a single-pinhole system using an identical acquisition geometry and reconstruction.
Results  At the central slice, a spatial resolution of 2.7 mm was observed for both the three-pinhole and single-pinhole geometries. At 17.5 mm from the central slice, the axial spatial resolution deteriorated to 10.3 mm when using a single pinhole, while the spatial resolution remained 2.7 mm for the three-pinhole system. In the central slice, 19% noise was observed for both geometries. At 31.5 mm from this central slice, the noise remained 19% for the three-pinhole geometry, while it increased to 32% using a single pinhole.
Conclusion  The presented three-pinhole collimator improves the uniformity of the axial spatial resolution and sensitivity in pinhole SPECT and consequently extends the axial field of view, a requirement for whole-body small-animal imaging.

URL : http://www.springerlink.com/content/x3j6565q17728w62/