Purpose: Investigate the feasibility of achieving a simultaneous high-resolution and high-sensitivity PET detector with a unique design that adds a high-resolution but low-stopping power detector (with small-size and short-length scintillators) to a low-resolution but high-stopping power detector (with large-size and long-length scintillators), for providing the development and economic advantage of enabling high-resolution/high-sensitivity imaging without developing an expensive and technically-challenging detector with scintillators of the same size and length.
Methods: DETECTOR: the high-resolution detector consists of a 32x32 array of 1x1x3 mmÂ³ LYSO scintillators; the low-resolution detector consists of an 8x8 aray of 4x4x17 mmÂ³ LYSO scintillators. They were aligned together to provide a combined 20 mm scintillator depth, with each 4x4 high-resoluiton scintillators atop of one 1 low-resolution scintillator. The key to this novel hybrid-detection method is to accurately convert the coincidence line-of-response (LOR) detected by a pair of low-reslution scintilaltors (L-L LOR) to an LOR that can be equivalently detected by a pair of high-resolution scintillators (H-H LOR), thus both high-sensitivity and high-resoluiton can be achieved by this hybrid detector. DATA PROCESSING: based on the mutual information between H-H LORs and L-L LORs constrained by the hybrid detector, each L-L LOR can be converted to a H-H LOR under certain probability. We used standard MLEM algorithm to solve this inverse problem. TEST: GATE-based simulated phantom imaging studies were conducted.
Results: Very initial study: Accuracy of L-L LORs to H-H LORs conversion is 12%. Acquired from a 1mm-diameter point-source, images reconstructed with the detected and converted H-H LORs show spatial resolutions (FWHM) of 0.72 and 0.74 mm. Images with a hot-rod (0.75 to 2.0 mm diameter) phantom show simultaneous high-resolution/high-sensitivity images were achieved by the hybrid-detector PET.
Conclusion: We demonstrated the feasibility of simultaneous high-resolution/high-sensitivity imaging based on the proposed hybrid detector and low-resolution LOR to high-resolution LOR conversion.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by 1R01EB019438, 1R01CA218402, R21CA187717.