From the Institute of Radiation Physics, University Hospital Lausanne (CHUV), University of Lausanne, Lausanne, Switzerland (D.R., A.V., V.V.); Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland (V.M., T.F., H.A., A.E.); and Department of Radiology, Kantonsspital Baden, Baden, Switzerland (A.E.).
Invest Radiol. 2024 Aug 1;59(8):554-560. doi: 10.1097/RLI.0000000000001060. Epub 2024 Jan 3.
The aim of this study was to evaluate the optimal energy level of virtual monoenergetic images (VMIs) from photon-counting detector computed tomography (CT) for the detection of liver lesions as a function of phantom size and radiation dose.
An anthropomorphic abdominal phantom with liver parenchyma and lesions was imaged on a dual-source photon-counting detector CT at 120 kVp. Five hypoattenuating lesions with a lesion-to-background contrast difference of -30 HU and -45 HU and 3 hyperattenuating lesions with +30 HU and +90 HU were used. The lesion diameter was 5-10 mm. Rings of fat-equivalent material were added to emulate medium- or large-sized patients. The medium size was imaged at a volume CT dose index of 5, 2.5, and 1.25 mGy and the large size at 5 and 2.5 mGy, respectively. Each setup was imaged 10 times. For each setup, VMIs from 40 to 80 keV at 5 keV increments were reconstructed with quantum iterative reconstruction at a strength level of 4 (QIR-4). Lesion detectability was measured as area under the receiver operating curve (AUC) using a channelized Hotelling model observer with 10 dense differences of Gaussian channels.
Overall, highest detectability was found at 65 and 70 keV for both hypoattenuating and hyperattenuating lesions in the medium and large phantom independent of radiation dose (AUC range, 0.91-1.0 for the medium and 0.94-0.99 for the large phantom, respectively). The lowest detectability was found at 40 keV irrespective of the radiation dose and phantom size (AUC range, 0.78-0.99). A more pronounced reduction in detectability was apparent at 40-50 keV as compared with 65-75 keV when radiation dose was decreased. At equal radiation dose, detection as a function of VMI energy differed stronger for the large size as compared with the medium-sized phantom (12% vs 6%).
Detectability of hypoattenuating and hyperattenuating liver lesions differed between VMI energies for different phantom sizes and radiation doses. Virtual monoenergetic images at 65 and 70 keV yielded highest detectability independent of phantom size and radiation dose.
本研究旨在评估光子计数探测器 CT 的虚拟单能量图像（VMIs）的最佳能量水平，以检测肝脏病变，该能量水平与体模大小和辐射剂量有关。
使用双源光子计数探测器 CT 在 120 kVp 下对具有肝实质和病变的人体腹部体模进行成像。使用 5 个低衰减病变，病变与背景对比度差异为-30 HU 和-45 HU，以及 3 个高衰减病变，+30 HU 和+90 HU。病变直径为 5-10 mm。添加环形脂肪等效材料以模拟中等或大型患者。中等大小的体模在体积 CT 剂量指数为 5、2.5 和 1.25 mGy 时进行成像，而大型体模在 5 和 2.5 mGy 时进行成像。每个设置均进行 10 次成像。对于每个设置，以 5 keV 为增量，从 40 到 80 keV 重建 40 个 VMIs，使用具有 10 个高斯通道密集差异的通道化 Hotelling 模型观察者测量病变检测性能。
总体而言，在中大型体模中，对于两种低衰减和高衰减病变，在中等和大型体模中，65 和 70 keV 时的检测性能最高，独立于辐射剂量（AUC 范围，0.91-1.0 中等大小，0.94-0.99 大型）。无论辐射剂量和体模大小如何，最低检测性能均为 40 keV（AUC 范围，0.78-0.99）。当辐射剂量降低时，与 65-75 keV 相比，40-50 keV 时的检测性能降低更为明显。在相等的辐射剂量下，大尺寸体模与中等尺寸体模的 VMI 能量检测功能差异更大（12%对 6%）。
不同体模大小和辐射剂量的 VMIs 对肝内低衰减和高衰减病变的检测性能不同。VMIs 在 65 和 70 keV 时可获得最高的检测性能，而与体模大小和辐射剂量无关。
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