Conventional SPECT reconstruction assumes that the volume of response for each collimator hole is a cylinder, but due to the finite depth of the holes, the volume of response is actually cone shaped. This leads to a loss of resolution as the distance from the collimator face is increased. If distance-dependent resolution compensation (DRC) is incorporated into an iterative reconstruction algorithm, then some of the lost resolution can be recovered (T Yokoi, H Shinohara and H Onishi, 2002, Ann Nuc Med, 16, 11-18). DRC has recently been included in some commercial reconstruction software, and the aim of this study was to assess whether the significantly increased reconstruction processing time can be justified for clinical or for research purposes.
HMPAO brain scans from 104 healthy subjects were reconstructed using iterative OSEM, with and without DRC. A voxel based iterative sensitivity (VBIS) technique was used for gain correction in the scans. A Statistical Parametric Mapping (SPM) analysis found the statistical strength of the SPECT aging effect increased when the non-DRC image set was compared to the images with DRC, probably due to improvement in the imaging of partial volume effects when the inter-hemispheric fissure and sulci enlarge with age (L Barnden, S Behin-Ain, R Kwiatek, R Casse and L Yelland. 2005, Nuc Med Comm, 26, 497-503). It was concluded that the use of DRC is justified for research purposes, but may not be for routine clinical use.