Department of Physics & Astronomy, University of Manitoba, Winnipeg, Canada.
Phys Med Biol. 2012 Dec 21;57(24):N501-12. doi: 10.1088/0031-9155/57/24/N501. Epub 2012 Nov 23.
In this work we explored the effects of using systematic band patterns of surface roughing to modulate the light transport in a dual-ended readout detector for PET imaging that uses 100 mm long LYSO crystals oriented in the axial direction. The long surfaces of 3 × 2 × 100 mm³ LYSO crystals, initially polished on all sides, were systematically roughed in a band pattern with 0.8 mm bands of roughed surface spaced at 5 mm increments over the central 8 cm of the crystal length. Cases of one to four surfaces of the crystal roughed with this pattern were explored. Two configurations of bands were examined for the opposite surfaces of the crystals: (i) bands created in the same axial location (coinciding bands) and (ii) band locations interleaved (interleaving bands). Each crystal was then wrapped in Teflon and read out at both ends using position sensitive photomultiplier tubes (PSPMTs). An electronically collimated 511 keV photon beam was oriented perpendicular to the long direction of the crystal and data acquired at discrete locations along the crystal length. The ratio of the two PMT signals was used to find the axial position of interaction and axial-positioning resolution in the light sharing direction of the dual-ended readout detector while their sum was used to determine the light output and energy resolution. The axial-positioning resolution corrected for the beam width improved from an average of 8.7 mm FWHM with no surface treatment to 5.9, 3.9 or 3.4 mm FWHM for coinciding band patterns on one, two or four surfaces, respectively. The banding patterns resulted in degraded energy resolution, with a decrease from 11.1% FWHM for the untreated crystal to 12.0%, 13.5% and 13.6% for the patterns on one, two and four surfaces, respectively. When the axial-positioning resolution is corrected for the beam width, we estimated the best resolution for the case of four banded surfaces to be 3.4 mm FWHM in this study. The same axial-positioning resolution was obtained when interleaving bands were created on only two opposite surfaces with a better energy resolution of 12.2%.
在这项工作中，我们探索了使用表面粗糙的系统带图案来调制 PET 成像的双端读出探测器中的光传输的效果，该探测器使用沿轴向定向的 100mm 长 LYSO 晶体。最初对 3×2×100mm³LYSO 晶体的所有侧面进行抛光，然后在晶体长度的中心 8cm 范围内以 5mm 的增量以 0.8mm 的粗糙表面带的间隔对其进行系统地粗糙化。探索了对晶体的一个到四个表面进行这种图案粗糙化的情况。检查了晶体相对表面的两种带图案：(i)在同一轴向位置创建的带（重合带）和 (ii)带位置交错（交错带）。然后，用特氟隆包裹每个晶体，并使用位置灵敏光电倍增管（PSPMT）从两端读取。电子准直的 511keV 光子束垂直于晶体的长方向定向，并且在晶体长度的离散位置处获取数据。使用两个 PMT 信号的比率找到双端读出探测器的光共享方向的轴向位置和轴向位置分辨率，而使用它们的总和来确定光输出和能量分辨率。对于光束宽度进行校正的轴向位置分辨率从无表面处理时的平均 8.7mm FWHM 提高到分别为 5.9、3.9 或 3.4mm FWHM 的情况下，对应的是一个、两个或四个表面的重合带图案。带图案导致能量分辨率下降，从未处理晶体的 11.1%FWHM 下降到分别为 12.0%、13.5%和 13.6%的图案的情况。当对于光束宽度校正轴向位置分辨率时，我们估计在本研究中四个带图案的情况下最佳分辨率为 3.4mm FWHM。当仅在两个相对表面上创建交错带时，可以获得相同的轴向位置分辨率，同时具有更好的能量分辨率 12.2%。
