Detector design issues for compact nuclear emission cameras dedicated to breast imaging

Certain gamma ray and positron emitting radiotracers have shown great promise for use in the detection, diagnosis and staging of breast cancer. Unfortunately, standard nuclear emission cameras (SPECT, PET) found in the clinic are not practical for breast imaging of these emissions due to inadequate spatial and energy resolutions and sensitivity, large and awkward size, and relatively high cost per study. High spatial and energy resolutions and sensitivity are needed for good lesion detectability. Due to these limitations of standard cameras, there has been recent research into the development of small, compact nuclear emission imagers dedicated for close-proximity breast imaging. The small detector head size means a variety of exotic detectors or collimators may be implemented to improve spatial and energy resolution and sensitivity performances at a reasonable cost. In this paper, we will present some of the compact gamma ray and annihilation photon imaging detector designs that have been proposed and/or developed for dedicated breast imaging. We will review the physics and discuss the advantages and disadvantages of various detector configurations. Finally we will estimate the fundamental spatial resolution potential available with close-proximity nuclear emission imaging and discuss how one may approach those limits through proper detector design.