Jensen Nikolaj K G, Stewart Errol, Lock Michael, Fisher Barbara, Kozak Roman, Chen Jeff, Lee Ting-Yim, Wong Eugene
Physics and Engineering, London Regional Cancer Program, London, Ontario N6A3K7, Canada.
Radiology, St. Joseph's Health Care, London, Ontario N6A 4V2, Canada; Imaging Research Lab, Robarts Research Institute, London, Ontario N6A 5B7, Canada; and Imaging Program, Lawson Health Research Institute, London, Ontario N6C 2R5, Canada.
Med Phys. 2014 May;41(5):051905. doi: 10.1118/1.4870385.
Contrast enhancement and respiration management are widely used during image acquisition for radiotherapy treatment planning of liver tumors along with respiration management at the treatment unit. However, neither respiration management nor intravenous contrast is commonly used during cone-beam CT (CBCT) image acquisition for alignment prior to radiotherapy. In this study, the authors investigate the potential gains of injecting an iodinated contrast agent in combination with respiration management during CBCT acquisition for liver tumor radiotherapy.
Five rabbits with implanted liver tumors were subjected to CBCT with and without motion management and contrast injection. The acquired CBCT images were registered to the planning CT to determine alignment accuracy and dosimetric impact. The authors developed a simulation tool for simulating contrast-enhanced CBCT images from dynamic contrast enhanced CT imaging (DCE-CT) to determine optimal contrast injection protocols. The tool was validated against contrast-enhanced CBCT of the rabbit subjects and was used for five human patients diagnosed with hepatocellular carcinoma.
In the rabbit experiment, when neither motion management nor contrast was used, tumor centroid misalignment between planning image and CBCT was 9.2 mm. This was reduced to 2.8 mm when both techniques were employed. Tumors were not visualized in clinical CBCT images of human subjects. Simulated contrast-enhanced CBCT was found to improve tumor contrast in all subjects. Different patients were found to require different contrast injections to maximize tumor contrast.
Based on the authors' animal study, respiration managed contrast enhanced CBCT improves IGRT significantly. Contrast enhanced CBCT benefits from patient specific tracer kinetics determined from DCE-CT.
在肝脏肿瘤放射治疗计划的图像采集过程中，对比增强和呼吸管理被广泛应用，同时在治疗单元也进行呼吸管理。然而，在放疗前用于校准的锥形束CT（CBCT）图像采集过程中，呼吸管理和静脉注射对比剂都不常用。在本研究中，作者调查了在肝脏肿瘤放疗的CBCT采集过程中，注射碘化对比剂并结合呼吸管理的潜在益处。
对五只植入肝脏肿瘤的兔子进行了有无运动管理和对比剂注射的CBCT检查。将采集到的CBCT图像与计划CT进行配准，以确定校准精度和剂量学影响。作者开发了一种模拟工具，用于从动态对比增强CT成像（DCE-CT）模拟对比增强CBCT图像，以确定最佳对比剂注射方案。该工具针对兔子受试者的对比增强CBCT进行了验证，并用于五名诊断为肝细胞癌的人类患者。
在兔子实验中，当既不采用运动管理也不使用对比剂时，计划图像与CBCT之间的肿瘤质心错位为9.2毫米。当两种技术都采用时，这一错位减少到了2.8毫米。在人类受试者的临床CBCT图像中未观察到肿瘤。发现模拟的对比增强CBCT可改善所有受试者的肿瘤对比度。发现不同患者需要不同的对比剂注射量以最大化肿瘤对比度。
基于作者的动物研究，呼吸管理的对比增强CBCT显著改善了图像引导放射治疗（IGRT）。对比增强CBCT受益于根据DCE-CT确定的患者特异性示踪剂动力学。
