Photon counting computed tomography: Concept and initial results
Photon counting computed tomography: Concept and initial results
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DOI：
10.1118/1.1854779
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发表时间：
2005-02-01
期刊：
影响因子：
3.8
通讯作者：
Molloi, S
中科院分区：
文献类型：
--
作者：
Shikhaliev, PM;Xu, T;Molloi, S
提出了一种光子计数锥束CT的概念。该系统采用了一种新的多缝多切片(MSMS)锥束采集几何结构，采用了线性阵列光子计数探测器。MSMS锥束采集器是投影X射线成像中使用的扫描多缝采集器的直接类比。这种几何结构提供了具有剂量效率的散射抑制的CT成像，并允许使用可用的光子计数探测器。提出了一种用于MSMS锥束CT系统的线阵光子计数探测器--微通道板探测器。对用于CT应用的MCP探测器进行了初步测试。MCP探测器样机的视场为60 mm。使用了延迟线位置编码电子器件。该电子器件具有单通道输入，用于评估来自整个探测器视野的事件。这将系统的计数速率限制在2×10(5)次/S，该探测器的空间分辨率在40kVp时为80um半高宽，在90kVp管电压下为200um半高宽。对于80微米像素大小，CT投影中的探测器噪声小于1计数/像素。CT投影包含量子受限和无散射信号。在50kVp和80kvp管电压下采集对比体模和小动物的图像。计算了不同对比剂对给定X射线能谱的CT数，并与实验值进行了比较。电流探测器在90kVp时的量子效率为56%，这是由于这些MCP的大通道直径(25am)而不是最优的。具有更小通道和更高效率的MCP正在进行测试。对一种沟道直径为5微米的新型MCP的量子效率进行了测量，结果为70%。对临床可用于乳腺成像的光子计数MSMS锥束CT的设计参数进行了评估。系统采用基于5微米通道MCP的20 cm视场MCP探测器和高计数率ASIC电子器件。结论：带光子计数MCP探测器的MSMS锥束CT用于乳腺体积成像是可行的。(C)2005年美国医学物理学家协会。
A concept of a photon counting cone beam CT is proposed. The system uses a new Multi Slit Multi Slice (MSMS) cone beam acquisition geometry utilizing a linear array photon counting detectors. The MSMS cone beam acquisition is a direct analogy of the scanning multislit acquisition used in projection x-ray imaging. This geometry provides a CT imaging with dose efficient scatter rejection and allows for using available photon counting detectors. The microchannel plate (MCP) detector is proposed as a linear array photon counting detector for MSMS cone beam CT system. Initial testing of the MCP detector for CT application was performed. The field of view of the prototype MCP detector is 60 mm. A delay line position encoding electronics was used. The electronics has a single channel input for evaluation of events from the entire detector field of view. This limits the system count rate at 2 x 10(5) count/s. The spatial resolution of this detector is 80 mum FWHM at 40 kVp and 200 mum FWHM at 90 kVp tube voltages. The detector noise in CT projections is less than 1 count/pixel for the 80 mum pixel size. The CT projections contain quantum-limited and scatter free signal. Images of a contrast phantom and a small animal were acquired at 50 kVp and 80 kVp tube voltages. The CT numbers for different contrast elements were calculated for a given x-ray spectrum and compared with experimental values. The quantum efficiency of the current detector is 56% at 90 kVp, which is suboptimal because of the large channel diameter (25 Am) of these MCPs. The MCPs with smaller channels and higher efficiencies are being tested. The quantum efficiency was measured to be 70% for a new MCP with 5 mum channel diameter. Design parameters of a clinically applicable photon counting MSMS cone beam CT for breast imaging was evaluated. System uses 20 cm field of view MCP detectors based on 5 mum channel MCPs and high count rate ASIC electronics. It was concluded that the MSMS cone beam CT with a photon counting MCP detector is feasible for volume breast imaging. (C) 2005 American Association of Physicists in Medicine.