Feasibility study for SPECT mammography based on compact imagers rotating around breast vertical axis

The detection limit of invasive carcinoma by standard prone scintimammography appears to be >=1 cm diameter. Since it is desirable to detect lesions at very earliest stages of growth (0.8 cm or less), the development of prototype scintimammographic systems with improved imaging performances is a primary goal. Here, the authors propose a dedicated high resolution breast imaging scanner for SPECT around the Vertical Axis of Rotation (VAOR) with the breast in prone position. The rotating detector module consists of a compact position sensitive photomultiplier tube (PS-PMTHamamatsu R7600-00-C8 coupled to a CsI(Tl) scintillating array. The compactness is the peculiarity of this detector module to allow the lodging in the breast interspace to work close to the chest wall and to minimize the tumor to collimator front distance. A preliminary study was performed by a breast phantom and 5" small FOV gamma camera with an actual rotation radius of 6.5 cm. Images were reconstructured using a filtered back projection implementation. Tumor SNR from planar images shown very low values: on the contrary reconstructed images strongly enhanced the contrast of a tumor 1 cm sized. A further enhancement was obtained by the compact detector module that was able to achieve higher SNR values for tumor less 1 cm sized)