BIOMEDICAL ENGINEERING

Single photon emission computed tomography (SPECT) is undergoing a renaissance due to recent advances in collimation technology and system modeling. Though rarely used in clinical practice, pinhole collimation has advantages over conventional parallel-hole collimation in certain applications, most notably for high resolution SPECT imaging of small animals. Small animal SPECT scanners utilizing pinhole collimation are now commercially available, but at quite high cost. An interesting low cost alternative is to use standard gamma camera detectors that are widely available on clinical SPECT scanners. Although gamma cameras have intrinsic spatial resolution of about 4 mm, with sufficient pinhole magnification it is possible to achieve image resolution of 1 mm or better. Count statistics is usually the limiting factor in SPECT image quality. To improve count sensitivity, the trend is to use multiple pinholes in a non-overlapping or overlapping configuration. Multi-pinhole imaging poses new challenges in system modeling. An accurate system model is necessary to properly account for data overlap and interference from data originating outside the local region of interest. Though there are technical challenges, multi-pinhole imaging offers substantial improvement in image quality. The current state of the art of multi-pinhole SPECT is reviewed, and latest developments at Cleveland Clinic are presented.

Suggested Reading:

DiFilippo FP, Riffe MJ, Harsch KM, McCabe NP, Heston WD, "Detached multi-pinhole small animal SPECT device with real-time calibration", IEEE Trans Nucl Sci 2006; 53(5): 2605-2612.