Effect of Collimator Selection on Tumor Detection for Dedicated Nuclear Breast Imaging Systems

The effect of collimation on the detection of small (<1 cm) breast tumors with dedicated nuclear breast imaging systems was determined. A breast phantom modeling tumors 4-9 mm in diameter was imaged with three dedicated systems (GE Medical Prototype CZT, Gamma Medica LumaGEM 3200 s, and Digirad 2020 tc), and a conventional gamma camera (Elscint Helix) using a variety of system-specific and generic collimators ranging from LEUHS to LEUHR. Acquisitions were performed using clinically relevant count densities determined from analysis of patient exams. Tumors were placed at depths of 1, 3, and 5 cm from the collimator in a 6-cm-thick breast, and tumor-to-background ratio was varied from 3:1 to 35:1. Tumor signal-to-noise ratio (SNR) was measured in each image. SNR measurements showed that an all-purpose or high sensitivity collimator is optimal for the detection of small tumors close to the collimator face. The three pixilated systems gave similar results and performed significantly better than the conventional gamma camera