Racine Damien, Ryckx Nick, Ba Alexandre, Ott Julien G, Bochud François O, Verdun Francis R
Institute of Radiation Physics, CHUV, Lausanne, Switzerland
Institute of Radiation Physics, CHUV, Lausanne, Switzerland.
Radiat Prot Dosimetry. 2016 Jun;169(1-4):78-83. doi: 10.1093/rpd/ncw021. Epub 2016 Mar 2.
Patient dose optimisation in computed tomography (CT) should be done using clinically relevant tasks when dealing with image quality assessments. In the present work, low-contrast detectability for an average patient morphology was assessed on 56 CT units, using a model observer applied on images acquired with two specific protocols of an anthropomorphic phantom containing spheres. Images were assessed using the channelised Hotelling observer (CHO) with dense difference of Gaussian channels. The results were computed by performing receiver operating characteristics analysis (ROC) and using the area under the ROC curve (AUC) as a figure of merit. The results showed a small disparity at a volume computed tomography dose index (CTDIvol) of 15 mGy depending on the CT units for the chosen image quality criterion. For 8-mm targets, AUCs were 0.999 ± 0.018 at 20 Hounsfield units (HU) and 0.927 ± 0.054 at 10 HU. For 5-mm targets, AUCs were 0.947 ± 0.059 and 0.702 ± 0.068 at 20 and 10 HU, respectively. The robustness of the CHO opens the way for CT protocol benchmarking and optimisation processes.
在计算机断层扫描（CT）中，进行患者剂量优化时，在处理图像质量评估时应使用临床相关任务。在本研究中，使用模型观察者对56台CT设备上平均患者形态的低对比度可探测性进行了评估，该模型观察者应用于通过包含球体的拟人化体模的两种特定协议采集的图像上。使用具有高斯通道密集差异的通道化霍特林观察者（CHO）对图像进行评估。通过进行接收器操作特性分析（ROC）并使用ROC曲线下面积（AUC）作为品质因数来计算结果。结果表明，对于所选图像质量标准，在容积计算机断层扫描剂量指数（CTDIvol）为15 mGy时，根据CT设备的不同存在微小差异。对于8毫米的目标，在20亨氏单位（HU）时AUC为0.999±0.018，在10 HU时为0.927±0.054。对于5毫米的目标，在20 HU和10 HU时AUC分别为0.947±0.059和0.702±0.068。CHO的稳健性为CT协议基准测试和优化过程开辟了道路。
