Dual collimation acquisition for high resolution, low noise SPECT

Dual-collimation (DC) imaging for single photon emission computed tomography (SPECT) is presented as a technique to improve effective sensitivity with little loss of resolution. For some imaging tasks, DC can overcome the inherent tradeoff between resolution and sensitivity of gamma camera collimators. Simulations were used to investigate the system performance without the expense of collimator fabrication. With DC for SPECT, a single image which is consistent with two projection sets acquired in two different collimators is reconstructed, one with high resolution/low sensitivity and another with high sensitivity/low resolution. By incorporating a detailed model of the SPECT acquisition geometry (including each collimator) into the maximum-likelihood expectation maximization reconstruction algorithm, an image having a combination of moderate noise and moderate resolution is produced. Based on a preliminary evaluation of DC for SPECT, it is concluded that, for moderate-size (2-cm radius) cold lesion imaging, DC can provide significant improvement in contrast-to-noise without significantly sacrificing image contrast, although for smaller lesions this advantage is diminished. For small hot spot imaging, DC can provide significant improvement in image noise without significantly sacrificing image resolution