A task-based evaluation of PEM detector element size

Positron Emission Mammography (PEM) is a planar imaging method that utilizes arrays of discrete detector elements for the detection of radiotracer-avid breast cancer. In this investigation we have systematically studied, through computer simulations, the effect of detector element size (width and length) on breast lesion detection and localization tasks. The contrast-to-noise ratios of the spheres simulating breast lesions were calculated as a function of detector element dimension to gauge detectability. System resolution (fwhm) across the field-of-view was used as the metric for the localization task. For both tasks, individual detector elements of lyso with cross sectional dimensions of 2x2 mm (96x72 element arrays, step 2.1mm) and 3x3mm (65x49 element arrays, step 3.1 mm), and lengths of 10,15 and 20 mm were simulated. The results revealed that narrower pixel dimensions reduced the partial volume effect, while the thicker pixels increased pixel sensitivity, thus reducing noise per pixel and increasing the contrast-to-noise ratio.