Multipinhole collimation for super-high resolution, small field-of-view SPECT
- Duke Univ. Medical Center, Durham, NC (United States); and others
Three super-high resolution, small field-of-view SPECT systems with multipinhole (MPH) collimation were investigated using Monte Carlo simulations. The purpose of using MPH collimation was to more efficiently use the detector surface, and hence increase the system sensitivity, when imaging small objects and animals with certain radius of rotation. These MPH collimators were designed based on our triple-camera system (40 cm by 20 cm Nal(Tl) crystal). The pinholes in each collimator were positioned so that no overlap of projections from each pinhole was allowed. An in-plane three-pinhole (3PH) collimator was designed to image a rat-brain-size object diameter of region-or-interest (DROI) < (2.6 cm). For larger objects (DROI<3.8 cm), an in-plane two-pinhole (2PH) collimator was used. A four-pinhole (4PH) collimator was introduced to reduce the axial blurring artifacts in pinhole filtered backprojection (FBP) reconstruction. In this case, two of the pinholes were placed in-plane, while the other two pinholes were placed off-plane. These off-plane pinholes were used to provide better axial sampling. Sensitivities of MPH collimators were compared to that of single pinhole (SPH) collimator with similar resolution characteristics. System sensitivities for the on-axis point source at 4 cm from the collimator were increased by factors ranged from 1.6 (2PH) to 2.9 (4PH), compared with SPH collimator. A three-dimensional FBP algorithm has been derived for MPH SPECT. The algorithm has been evaluated using Monte Carlo simulations. Two kinds of phantom were simulated. One phantom was a four-rod phantom, and the other was a non-zero, multi-activity-level disk phantom. The results demonstrated that while both MPH FBP and SPH FBP reconstructions provided good transaxial images for the midplane, the 4PH EBP reconstruction greatly reduced the axial blurring artifacts.
- OSTI ID:
- 197903
- Report Number(s):
- CONF-940605--
- Journal Information:
- Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 35; ISSN JNMEAQ; ISSN 0161-5505
- Country of Publication:
- United States
- Language:
- English
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