Low-energy X-ray imaging of secondary electron bremsstrahlung X-rays emitted during carbon-ion irradiation is a promising method for range estimation and could be used for imaging with almost clinical dose levels of carbon ion. However, the number of counts in images with clinical dose levels is relatively small, making it difficult to obtain precise range estimations. Since improving the sensitivity of the X-ray camera may solve this issue, we developed two new types of X-ray cameras. One uses a 1-mm thick, 40 mm × 40-mm cerium-doped yttrium aluminum perovskite (YA1O3: YAP(Ce)) scintillator plate combined with a 2-inch square flat panel photomultiplier tube (FP-PMT) contained in a 2-cm thick tungsten shield with a pinhole collimator positioned 50 mm from the scintillator; the other uses a 0.5-mm thick, 20 mm × 20-mm YAP(Ce) scintillator plate combined with a 1-inch square position sensitive photomultiplier tube (PS-PMT) contained in the same tungsten shield with a pinhole collimator, but with the scintillator positioned closer (30 mm) to the pinhole collimator to obtain a similar field-of-view (FOV). For both cameras, we used a wider angle (~55 degrees) pinhole collimator to measure the phantom closer to improve sensitivity. Although the 40 mm × 40-mm YAP(Ce) camera had high system spatial resolution, the background count fractions were high and produced a high count area at the center of the images due to the pulse pileup of the signals. With the 20 mm × 20-mm YAP(Ce) camera, we obtained X-ray images with low background counts without a high count area at the image center. By smoothing the measured images, we were able to estimate the ranges even for clinical dose levels. We therefore confirmed that one of our newly developed YAP(Ce) cameras had high sensitivity and is promising for the imaging of secondary electron bremsstrahlung X-rays during irradiation of carbon ions in clinical conditions.

中文翻译：

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YAP（Ce）相机在碳离子辐照期间发出的二次电子致X射线成像的感光度改进：问题和解决方案。

碳离子辐照过程中发射的二次电子stra致辐射X射线的低能X射线成像是一种有希望的范围估计方法，可用于几乎临床剂量水平的碳离子成像。但是，具有临床剂量水平的图像中的计数数量相对较小，因此难以获得精确的范围估计。由于提高X射线摄影机的灵敏度可以解决此问题，因此我们开发了两种新型的X射线摄影机。一种使用1毫米厚，40毫米×40毫米掺铈的钇铝钛矿（YA1O3：YAP（Ce））闪烁体板与2英寸方形平板光电倍增管（FP-PMT）相结合-cm厚的钨丝屏蔽层，针状准直仪距离闪烁体50mm；另一个使用0.5毫米厚 20毫米×20毫米YAP（Ce）闪烁体板与1英寸正方形位置敏感光电倍增管（PS-PMT）结合在一起，该管体与带针孔准直器的同一钨屏蔽罩相同，但闪烁体的位置更靠近（30 mm）针孔准直仪以获得类似的视野（FOV）。对于这两种相机，我们都使用了更宽的角度（约55度）的针孔准直器来测量幻像，以提高灵敏度。尽管40 mm×40 mm YAP（Ce）相机具有较高的系统空间分辨率，但由于信号的脉冲堆积，背景计数分数很高，并且在图像中心产生了较高的计数区域。使用20毫米×20毫米的YAP（Ce）相机，我们获得了背景计数低，图像中心没有高计数区域的X射线图像。通过平滑测量的图像，我们甚至可以估算出临床剂量水平的范围。因此，我们确认了我们新开发的YAP（Ce）相机之一具有很高的灵敏度，并且有望在临床条件下对碳离子辐照过程中的二次电子stra致X射线成像。