3D printed phantom with 12 000 submillimeter lesions to improve efficiency in CT detectability assessment.
3D printed phantom with 12 000 submillimeter lesions to improve efficiency in CT detectability assessment.
复制标题
具有 12000 个亚毫米病变的 3D 打印模型，可提高 CT 可检测性评估的效率。
DOI：
10.1002/mp.17064
复制
发表时间：
2024
期刊：
影响因子：
3.8
通讯作者：
Hsieh,ScottS
中科院分区：
文献类型：
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作者：
Shunhavanich,Picha;Mei,Kai;Shapira,Nadav;Stayman,JosephWebster;McCollough,CynthiaH;Gang,Grace;Leng,Shuai;Geagan,Michael;Yu,Lifeng;Noël,PeterB;Hsieh,ScottS
背景当重建过程中存在非线性时，CT扫描仪的检测性能很难精确量化。需要一种对剂量和扫描仪设置的小影响敏感的有效的可检测性评估方法。我们之前提出了一种使用搜索挑战工具的方法：将一个模体嵌入数百个随机位置的病变，并使用模型观察器来检测病变。在这项工作中，我们制作了一个全尺寸的搜索挑战体模，包括改变病变大小、对比度和数量，并通过比较非预白化模型观察者在不同曝光水平下的不同重建图像之间的病变可探测性，以及通过估计仪器灵敏度来检测剂量的变化来研究我们的实现。方法为适应QRM拟人化体模的设计，我们的搜索挑战体模是一个圆柱形插入件，宽10 cm，厚4 cm，嵌入12000个病变(标称宽度0.6 mm，高度0.8 mm，对比度为−350Hu)，它是使用3D打印技术PixelPrint制作的。单独以高剂量扫描插入物以评估打印准确性。为了评估病变的可探测性，将插入物放置在QRM胸模中，扫描范围为50-625毫安，增量为25毫安，每次照射水平一次，所有暴露水平的平均值作为高剂量参考。扫描采用三种不同的设置：滤波式反投影(FBP)，采用Br40和Br59；Singraph Affirmed迭代重建(Safire)，强度等级为5，核为Br59。使用NPW模型观测器搜索病变，并使用自由反应ROC曲线(AUC)的指数变换下的面积来比较不同设置的检测性能。利用不确定度传播，通过在100、200、300和400 mAs的5次重复扫描中测量的AUC的一个标准偏差引起的曝光百分比变化来评估对剂量变化的敏感性。结果与打印参考相比，打印插入物病变的平均位置误差为0.20 mm。当照射水平从50 mA增加到625 mAs时，FBP Br40、FBP Br59和Safire Br59的病变可探测性AUC分别从0.38增加到0.92、0.42增加到0.98和0.41增加到0.97，且在高暴露水平下增加的速度较小。FBP Br59表现最好，AUC值平均比Safire Br59高0.01%，比FBP Br40高0.07%(均P<；0.001)。对于FBPBr59，AUC值的标准偏差小于0.006，检测mAs变化的灵敏度在2%以内。结论我们的3D打印搜索挑战体模具有12000个亚毫米病变，结合NPW模型观察者，提供了一种有效的CT可检测性评估方法，该方法对重建中的细微影响敏感，对剂量的微小变化敏感。
BackgroundThe detectability performance of a CT scanner is difficult to precisely quantify when nonlinearities are present in reconstruction. An efficient detectability assessment method that is sensitive to small effects of dose and scanner settings is desirable. We previously proposed a method using a search challenge instrument: a phantom is embedded with hundreds of lesions at random locations, and a model observer is used to detect lesions. Preliminary tests in simulation and a prototype showed promising results.PurposeIn this work, we fabricated a full‐size search challenge phantom with design updates, including changes to lesion size, contrast, and number, and studied our implementation by comparing the lesion detectability from a nonprewhitening (NPW) model observer between different reconstructions at different exposure levels, and by estimating the instrument sensitivity to detect changes in dose.MethodsDesigned to fit into QRM anthropomorphic phantoms, our search challenge phantom is a cylindrical insert 10 cm wide and 4 cm thick, embedded with 12 000 lesions (nominal width of 0.6 mm, height of 0.8 mm, and contrast of −350 HU), and was fabricated using PixelPrint, a 3D printing technique. The insert was scanned alone at a high dose to assess printing accuracy. To evaluate lesion detectability, the insert was placed in a QRM thorax phantom and scanned from 50 to 625 mAs with increments of 25 mAs, once per exposure level, and the average of all exposure levels was used as high‐dose reference. Scans were reconstructed with three different settings: filtered‐backprojection (FBP) with Br40 and Br59, and Sinogram Affirmed Iterative Reconstruction (SAFIRE) with strength level 5 and Br59 kernel. An NPW model observer was used to search for lesions, and detection performance of different settings were compared using area under the exponential transform of free response ROC curve (AUC). Using propagation of uncertainty, the sensitivity to changes in dose was estimated by the percent change in exposure due to one standard deviation of AUC, measured from 5 repeat scans at 100, 200, 300, and 400 mAs.ResultsThe printed insert lesions had an average position error of 0.20 mm compared to printing reference. As the exposure level increases from 50 mAs to 625 mAs, the lesion detectability AUCs increase from 0.38 to 0.92, 0.42 to 0.98, and 0.41 to 0.97 for FBP Br40, FBP Br59, and SAFIRE Br59, respectively, with a lower rate of increase at higher exposure level. FBP Br59 performed best with AUC 0.01 higher than SAFIRE Br59 on average and 0.07 higher than FBP Br40 (allP< 0.001). The standard deviation of AUC was less than 0.006, and the sensitivity to detect changes in mAs was within 2% for FBP Br59.ConclusionsOur 3D‐printed search challenge phantom with 12 000 submillimeter lesions, together with an NPW model observer, provide an efficient CT detectability assessment method that is sensitive to subtle effects in reconstruction and is sensitive to small changes in dose.