Dynamic laser-guided contouring for dedicated emission mammotomography
The dedicated breast CZT-based SPECT imaging system in our lab implements novel 3D camera trajectories that can minimize breast-detector separation, thus improving resolution and image quality. Current trajectories are manually customized for each patient by measuring breast-detector separations at several positions and interpolating. This study seeks to transition from this manual method to an automated contouring solution for routine patient SPECT imaging, given the vast array of uncompressed breast shapes in women. In the initial effort to model "typical" SPECT camera trajectories for patients, a sub-study was conducted of 103 MRI breast data sets to categorize the shape and size of uncompressed, pendant breasts. Obtained parameters include measured nipple-to-chest wall (mean=8.4cm), superior-inferior (mean=10.8cm), medial-lateral distances (mean=14.3cm), and estimated breast volume (mean=720mL). These images will be used as digital "phantoms" when utilizing computer models for orbit optimization and system development purposes. Automated breast surface contouring is implemented using a dual-layer, low divergence, ribbon laser feedback sensor system mounted along the edge of the SPECT camera. The upper and lower sensor layers consist of two laser-detector pairs that identify the region on the camera face that has been penetrated, defining a virtual plane. In both layers, receivers sense reduced signal intensity when the beam path is interrupted by the breast surface. The ROR can then be automatically adjusted such that the breast is within -tcm of the camera face, but no closer than O.5cm, thus safely keeping the camera face as close to breast as possible. Robustness of the contouring system is assessed using flexible anthropomorphic breast phantoms to model various pendant breast shapes and sizes. Initial results indicate that dynamic contouring both improves image quality and potentially adds comfort to the patient by shortening scan setup time. © 2008 IEEE.
