Cuddy S G, Rowlands J A
Thunder Bay Regional Research Institute.
Lakehead University, ON.
Med Phys. 2012 Jul;39(7Part4):4640. doi: 10.1118/1.4740188.
With high specificity for malignant breast lesions, dedicated-breast molecular imaging systems such as positron emission mammography (PEM) have potential to improve the sensitivity of cancer in women with radio-dense breasts and to reduce the false-positive rate of breast screening when used as a diagnostic adjunct. For high signal-to-noise ratio and to minimize the patient dose, scintillation detectors in a PEM system must have high annihilation photon detection efficiency. This efficiency can be increased by accepting annihilation photons from wider incident angles and by using depth-of-interaction (DOI) measurement within a scintillation crystal to minimize parallax blurring. We have developed a dual-ended readout block (DERB) detector that uses asymmetry of signals from photodetectors on either end of a scintillation array to measure DOI and uses Anger Logic with light sharing to identify interacting crystal elements while minimizing the number of photodetectors required.
A prototype DERB detector was constructed from two arrays of silicon photomultipliers (SiPM), two glass optical diffusers, and an array of LYSO scintillation crystals. Assembled, each of the 2 × 2 SiPM arrays detect photons that are dispersed via the optical light diffusers originating from either end of 3 × 3 scintillation crystal elements. We evaluated the ability of the detector to identify the crystal index, resolve DOI, and discriminate energy.
The DERB detector was able to clearly identify interacting crystal elements, to measure DOI with ̃5mm resolution in 2mm × 2mm × 20mm crystals, and to achieve an average energy resolution of ̃20%.
The DERB detector characteristics suggest that it can be used to reduce the parallax effect in PEM systems without increasing the number of required photodetectors. Further investigation is warranted to improve performance with high optical photon detection efficiency photodetectors.
正电子发射乳腺断层成像（PEM）等专用乳腺分子成像系统对恶性乳腺病变具有高度特异性，有潜力提高乳腺致密女性癌症检测的灵敏度，并在用作诊断辅助手段时降低乳腺筛查的假阳性率。为了获得高信噪比并将患者剂量降至最低，PEM系统中的闪烁探测器必须具有高湮灭光子探测效率。通过接受更宽入射角的湮灭光子，并在闪烁晶体内使用相互作用深度（DOI）测量来最小化视差模糊，可以提高这种效率。我们开发了一种双端读出模块（DERB）探测器，该探测器利用闪烁阵列两端光电探测器信号的不对称性来测量DOI，并使用带有光共享的安杰逻辑来识别相互作用的晶体单元，同时将所需光电探测器的数量降至最低。
一个DERB探测器原型由两组硅光电倍增管（SiPM）阵列、两个玻璃光学漫射器和一组LYSO闪烁晶体构成。组装后，每组2×2的SiPM阵列检测通过光学漫射器散射的光子，这些光子源自3×3闪烁晶体单元的两端。我们评估了该探测器识别晶体索引、分辨DOI和区分能量的能力。
DERB探测器能够清晰地识别相互作用的晶体单元，在2mm×2mm×20mm的晶体中以约5mm的分辨率测量DOI，并实现约20%的平均能量分辨率。
DERB探测器的特性表明，它可用于减少PEM系统中的视差效应，而无需增加所需光电探测器的数量。有必要进一步研究以提高使用高光光子探测效率光电探测器时的性能。
