Gaulin L-D, Nadig V, Herweg K, Lemaire G, Gagnon F, Bouchard J, Rossignol J, Schulz V, Fontaine R, Gundacker S
Interdisciplinary Institute for Technological Innovation (3iT), Université de Sherbrooke, Sherbrooke, Québec, Canada.
Department of Electrical Engineering and Computer Engineering, Université de Sherbrooke, Sherbrooke, Québec, Canada.
Phys Med Biol. 2025 Feb 6;70(4). doi: 10.1088/1361-6560/adac9f.
Integrating time-of-flight (ToF) measurements in radiography and computed tomography (CT) enables an approach for scatter rejection in imaging systems that eliminates the need for anti-scatter grids, potentially increasing system sensitivity and image quality. However, present hardware dedicated to the time-correlated measurement of x-rays is limited to a single pixel physically too large for the desired spatial resolution. A switch to highly integrated electronics and detectors is needed to progress towards detector arrays capable of acquiring images, while offering a timing resolution below 300 ps FWHM to achieve scatter rejection comparable to current anti-scatter grids.Using off-the-shelf scintillators, photodetectors and readouts designed for ToF positron emission tomography (PET) provides a preliminary evaluation of available highly integrated readout systems supporting detector arrays for ToF scatter rejection. The TOFPET2c ASIC from PETSys offers an established development platform necessary for fast and reliable results, with no known limitation regarding time-correlated detection of medical imaging x-rays (20-140 keV).Reliable photon detection down to 31 keV was achieved, reaching energy resolutions from 23% to 92% FWHM throughout the desired energy range. Optimal detector timing resolution (DTR) from 250 ps FWHM at 130 keV to 678 ps FWHM at 30 keV was reached. Strong time walk effects were observed, showing a time shift of 642 ps up to 1740 ps between events spanning the energies used in x-ray medical imaging.The TOFPET2c ASIC has shown its potential for ToF scatter rejection, but meets the time resolution requirement of 300 ps FWHM only for limited energies (110-140 keV). This significant timing degradation observed at lower energies limits the use of the TOFPET2c ASIC for ToF scatter rejection, but offers significant advancements regarding the understanding of the phenomenon arising from the time-correlated detection of medical imaging x-rays.
在射线照相和计算机断层扫描（CT）中整合飞行时间（ToF）测量，可为成像系统中的散射抑制提供一种方法，该方法无需使用反散射格栅，从而有可能提高系统灵敏度和图像质量。然而，目前专门用于X射线时间相关测量的硬件仅限于单个像素，从物理尺寸上来说，对于所需的空间分辨率而言太大了。要朝着能够采集图像的探测器阵列迈进，同时提供低于300 ps半高宽（FWHM）的定时分辨率以实现与当前反散射格栅相当的散射抑制，就需要转向高度集成的电子设备和探测器。使用为ToF正电子发射断层扫描（PET）设计的现成闪烁体、光电探测器和读出电路，可对支持用于ToF散射抑制的探测器阵列的现有高度集成读出系统进行初步评估。来自PETSys的TOFPET2c专用集成电路（ASIC）提供了一个实现快速可靠结果所需的成熟开发平台，在医学成像X射线（20 - 140 keV）的时间相关检测方面没有已知限制。实现了低至31 keV的可靠光子检测，在整个所需能量范围内达到了23%至92% FWHM的能量分辨率。达到了从130 keV时250 ps FWHM到30 keV时678 ps FWHM的最佳探测器定时分辨率（DTR）。观察到了强烈的时间游动效应，在跨越X射线医学成像所用能量的事件之间，时间偏移高达642 ps至1740 ps。TOFPET2c ASIC已显示出其在ToF散射抑制方面的潜力，但仅在有限能量（110 - 140 keV）下满足300 ps FWHM的时间分辨率要求。在较低能量下观察到的这种显著定时退化限制了TOFPET2c ASIC用于ToF散射抑制，但在理解医学成像X射线时间相关检测所产生的现象方面取得了重大进展。
