Practical evaluation of several cone beam orbits for SPECT

Several alternative orbits have been suggested for cone beam SPECT (single photon emission computed tomography) since the standard circular orbit provides insufficient sampling. The authors used a computer simulation to evaluate the practicality of several orbits using the following criteria: spatial resolution, sensitivity, elimination of truncation, and theoretical sufficiency of the acquired data. All orbits were evaluated for brain imaging with a realistic human model. The results indicate that the simple transverse circular orbit has high sensitivity and resolution, but of course the acquired data are insufficient. Modest improvement in resolution was obtained with a contoured transverse plane orbit. A single straight line orbit was inadequate. Three orbits, each composed of two noncoplanar curves, satisfied the sufficiency condition, and thus should produce more accurate reconstructions. Their resolution was similar to the circle, but the sensitivity was reduced by 15-30%. None of the orbits studied was as good as the transverse plane orbits (circle and contoured) in both resolution and sensitivity.<>