Yang Yongfeng, Wu Yibao, Cherry Simon R
Department of Biomedical Engineering, University of California-Davis, CA 95616 USA.
IEEE Trans Nucl Sci. 2009 Oct 7;56(5):2594-2599. doi: 10.1109/TNS.2009.2016094.
A new approach to depth of interaction (DOI) encoding for a pixelated LSO array using a single multi-channel PMT was investigated. In this method the DOI information was estimated by taking advantage of optical crosstalk between LSO elements and examining the standard deviation (spread) of signals on all channels of the PMT. Unpolished and polished 6×6 LSO arrays with a crystal size of 1.3×1.3×20 mm(3) were evaluated on a Hamamatsu H7546 64-channel PMT. The arrays were placed on the center of the PMT and the central 16 channels of the PMT were individually read out and digitized. For the unpolished array, all crystals were resolved in the flood histogram. An average DOI resolution of 8 mm was obtained. The energy resolution was ∼25% after the signal amplitude was corrected using the measured DOI information. For the polished array, the flood histogram was superior to the unpolished array, however no DOI information could be measured. Using unpolished crystals, this method could be a practical way to achieve limited DOI information in PET detectors. The standard deviation of all PMT channels can be readily obtained using a resistor network. Only five signals (four signals to determine the x-y position and one signal measuring the standard deviation) need to be digitized, and this method only requires a single photon detector to read out the array. Unlike phoswich detectors, the method does not require segmenting the scintillator array into layers. The measured DOI resolution was much worse than that obtained with the dual-ended readout method, however, it was similar to that obtained with a two-layer phoswich detector.
研究了一种使用单个多通道光电倍增管（PMT）对像素化LSO阵列进行相互作用深度（DOI）编码的新方法。在该方法中，通过利用LSO元件之间的光学串扰并检查PMT所有通道上信号的标准偏差（展宽）来估计DOI信息。在滨松H7546 64通道PMT上评估了晶体尺寸为1.3×1.3×20 mm³的未抛光和抛光的6×6 LSO阵列。将阵列放置在PMT的中心，并分别读出和数字化PMT的中央16个通道。对于未抛光的阵列，在泛光直方图中所有晶体都能分辨出来。获得的平均DOI分辨率为8 mm。在使用测量的DOI信息校正信号幅度后，能量分辨率约为25%。对于抛光阵列，泛光直方图优于未抛光阵列，但是无法测量DOI信息。使用未抛光的晶体，该方法可能是在PET探测器中实现有限DOI信息的一种实用方法。使用电阻网络可以很容易地获得所有PMT通道的标准偏差。只需要数字化五个信号（四个信号用于确定x-y位置，一个信号用于测量标准偏差），并且该方法只需要一个单光子探测器来读出阵列。与磷光体探测器不同，该方法不需要将闪烁体阵列分割成层。然而，测量得到的DOI分辨率比双端读出方法获得的分辨率差得多，但与双层磷光体探测器获得的分辨率相似。
