Practical evaluation of several cone beam orbits for SPECT

Several alternative orbits have been suggested for cone beam single photon emission computed tomography (SPECT), since the standard circular orbit provides incomplete sampling. The authors´ computer simulation evaluates the practicality of several orbits, using the following criteria: spatial resolution, sensitivity, elimination of truncation, and theoretical completeness of the acquired data. All orbits are evaluated for brain imaging with a realistic human model. The results indicate that the simple transverse circular orbit has high sensitivity and resolution. The acquired data are incomplete. Modest improvement in resolution is obtained with a contoured transverse plane orbit. A single straight line orbit was inadequate. Three orbits, each composed of two noncoplanar curves, satisfy the completeness condition, and thus should produce more accurate reconstructions. Their resolution is similar to the circle, but the sensitivity is reduced by 15-30%. None of the orbits studied are as good in both resolution and sensitivity as the transverse plane orbits (circle and contoured), which do not satisfy the completeness condition