An elongated position sensitive block detector design using the PMT quadrant-sharing configuration and asymmetric light partition

Although the photomultiplier tube (PMT) quadrant-sharing design introduced by our group for position-sensitive detector blocks is very effective for reducing the cost of a high-resolution PET camera, a section of the PMT´s sensitive windows at the edge of the block array remains unused. An elongated, asymmetrically offset position-sensitive detector block has been developed to utilize this unused area of the PMT´s window. The block design employed asymmetric light partitions to achieve an evenly distributed 2D position-decoding map. The block was divided into 7×8 elements. For this study, the dimensions of each detector element were 2.66×3.05 mm, with a depth of 18 mm. This detector design is applicable to any camera using the PMT quadrant-sharing detector design, such as the variable-field prototype PET camera developed at the authors´ institution and the Siemens/CTI LSO cameras. A second improvement incorporated into the detector design was the replacement of the saw-cut grooves in the detector blocks by painted masks. The application of the present block design to a clinical high-resolution camera expands the axial field-of-view, which, when combined with the gapless block design used in this study, increases the coincidence detection efficiency of the camera by factor of about 2.9 in 3D data acquisition