Wei Shuoyang, Zhu Qizhen, Yu Lang, Li Wenbo, Zhou Bing, Guo Mengya, Dai Jiaqi, Liu Xiaonan, Yang Bo, Qiu Jie
Department of Radiotherapy, Peking Union Medical College Hospital, Beijing, China.
CT Imaging Research Center, GE Healthcare China, Beijing, China.
Quant Imaging Med Surg. 2024 Dec 5;14(12):8443-8455. doi: 10.21037/qims-24-885. Epub 2024 Oct 17.
In the traditional computed tomography (CT) simulation process, patients need to undergo CT scans before and after injection of iodine-based contrast agent, resulting in a cumbersome workflow and additional imaging dose. Contrast-enhanced spectral CT can synthesize true contrast-enhanced (TCE) images and virtual noncontrast (VNC) images in a single scan without geometric misalignment. To improve work efficiency and reduce patients' imaging dose, we studied the feasibility of using VNC images for radiotherapy treatment planning, with true noncontrast (TNC) images as references and explored its dosimetric advantages compared to using TCE images. Specifically, this study examined tumors near bones, including cases of bone metastasis and myeloma.
A total of 54 patients (20 patients with cervical cancer, 15 patients with esophageal cancer, and 15 patients with laryngeal cancer, and 4 patients with bone metastasis or hip replacement) who underwent non-contrast-enhanced and contrast-enhanced spectral CT simulation were retrospectively enrolled between July 2023 and March 2024. The study was approved by the institutional review board. The CT images were acquired using a second-generation fast kilovoltage peak-switching CT. Treatment plans for photon radiotherapy were optimized and calculated using TNC images and recalculated based on TCE and VNC images. To evaluate image and dosimetric equivalent, several metrics, including Hounsfield unit (HU) value differences, gamma pass rates and dose-volume histogram (DVH) parameters of planning target volume (PTV), and organs at risk (OARs), were compared.
In terms of HU value difference, for the majority of patients, the HU value differences of the PTV between TCE and TNC images (36.7±23.9 and 27.8±2.1 in esophageal and laryngeal cancer, respectively) were greater than those between VNC and TNC images (10.59±25.8 and 3.55±1.9 in esophageal and laryngeal cancer, respectively). Regarding dosimetry, the gamma pass rates between VNC and TNC were 1 in 2%/2 mm and 3%/3 mm. Most DVH parameter differences were less than 1% between the VNC and TNC plans and between TCE and TNC plans. Meanwhile, in some blood-rich OARs such as heart and small intestine, VNC shows dosimetric potential compared to TCE based on the statistically significant DVH parameters differences.
By analyzing radiotherapy treatment plans with target areas located in different locations, including tumors near bones such as bone metastasis, we preliminarily verified the feasibility of using VNC images for photon dose calculation. This approach can effectively improve clinical workflow and reduce the image dose to patients.
在传统的计算机断层扫描（CT）模拟过程中，患者需要在注射碘造影剂前后进行CT扫描，导致工作流程繁琐且增加了成像剂量。对比增强光谱CT可以在一次扫描中合成真正的对比增强（TCE）图像和虚拟平扫（VNC）图像，而不会出现几何错位。为了提高工作效率并降低患者的成像剂量，我们以真正的平扫（TNC）图像为参考，研究了使用VNC图像进行放射治疗计划的可行性，并探讨了其与使用TCE图像相比的剂量学优势。具体而言，本研究检查了靠近骨骼的肿瘤，包括骨转移和骨髓瘤病例。
回顾性纳入2023年7月至2024年3月期间接受非增强和对比增强光谱CT模拟的54例患者（20例宫颈癌患者、15例食管癌患者、15例喉癌患者以及4例骨转移或髋关节置换患者）。该研究经机构审查委员会批准。使用第二代快速千伏峰值切换CT获取CT图像。使用TNC图像优化并计算光子放射治疗的治疗计划，并基于TCE和VNC图像重新计算。为了评估图像和剂量学等效性，比较了几个指标，包括亨氏单位（HU）值差异、γ通过率以及计划靶区（PTV）和危及器官（OARs）的剂量体积直方图（DVH）参数。
在HU值差异方面，对于大多数患者，TCE与TNC图像之间PTV的HU值差异（食管癌和喉癌分别为36.7±23.9和27.8±2.1）大于VNC与TNC图像之间的差异（食管癌和喉癌分别为10.59±25.8和3.55±1.9）。在剂量学方面，VNC与TNC之间在2%/2mm和3%/3mm时的γ通过率为1。VNC与TNC计划之间以及TCE与TNC计划之间的大多数DVH参数差异小于1%。同时，在一些血供丰富的OARs中，如心脏和小肠，基于具有统计学意义的DVH参数差异，VNC与TCE相比显示出剂量学潜力。
通过分析靶区位于不同位置（包括骨转移等靠近骨骼的肿瘤）的放射治疗计划，我们初步验证了使用VNC图像进行光子剂量计算的可行性。这种方法可以有效改善临床工作流程并降低患者的图像剂量。
