Improved Performance of a Dual-Headed Molecular Breast Imaging system by Detector Angulation

We are developing a stationary tomographic molecular breast imaging system consisting of two planar CZT detectors and multi-pinhole collimators. One downside is that the limited angular sampling results in a limited spatial resolution perpendicular to the detectors. Here we investigate the potential to improve both resolution and sensitivity over a reduced field-of-view (FOV) by introducing some flexibility in the detector orientation. By tilting the external parts of the detector arrays towards the centre, the angular sampling and sensitivity could be improved in the central FOV. The system would still be stationary during acquisition. We performed computer simulations, assuming 198 mm wide detector arrays, divided into 3 sections, such that the first and last one could be tilted by different angles. The activity distribution consisted of an elliptical cylinder containing three line-sources on the mid-plane between the detectors at different horizontal distances from the centre (0, 25 and 50 mm). On average for the three sources, the resolution was improved (reduced FWHM) by factors of 0.92, 0.81, and 0.76 in the x-direction and 0.88, 0.72 and 0.64 in the y-direction for detector tilt angles of 10°, 20° and 30°, respectively. The sensitivity was increased by factors of 1.19, 1.45 and 1.72, respectively, for the same angles. The improvements are due to both increased angular sampling and reduced detector distance. Our simulations show that, by introducing some flexibility in the detector configuration, it is possible to improve both spatial resolution and sensitivity by sacrificing part of the FOV. However, as the standard configuration of two opposing parallel planar detectors could be easier to integrate in a clinical system, we will explore different pinhole configurations as an alternative.