Advanced applications of dual-energy computed tomography in radiation oncology

在放射肿瘤学中，通过使用医学成像对每个患者进行扫描，个性化的3D治疗计划成为可能。目前的临床模式是以计算机断层扫描(CT)为基础，并辅之以其他可用和相关的成像技术。为了治疗计划的目的，这些图像提供了辐射剂量计算和器官描绘所需的患者解剖的定量表征。 治疗计划基于单能量CT(SECT)：一种带有穿过患者的多能光子束的X射线源和一个测量传输强度的检测系统。最近，一种新的CT技术--双能CT(DECT)问世了。这项技术提供了使用两种不同的X射线能量(两种不同的源和两种不同的检测系统)同时扫描患者的可能性。因此，同时获得了两个不同的图像。 在该中心，我们在2013年安装了首批致力于放射肿瘤治疗计划的DECT设备之一。我们的研究假设是，这种DECT可以在不同水平上帮助改进放射肿瘤学的治疗计划。围绕这一设备开发了一项研究计划，涉及医学物理学家、放射肿瘤学家、住院医师和研究生。目前的拨款提案涵盖了全球部门研究计划的一部分。 DECT用于近距离放射治疗：AAPM TG186报告建议使用DECT进行前列腺近距离放射治疗剂量学计算。我们将建立一个蒙特卡罗重新计算平台，研究低剂量率近距离放射治疗剂量计算精度的改进。将尝试基于西门子提出的标准分解方法和内部方法来减少伪影。将在与瓦里安合作的基础上将这些DECT数据整合到临床系统中，将DECT数据和Acuros结合起来。 DECT用于质子治疗：我们将开发一个蒙特卡罗模拟环境来研究由于DECT成像对剂量计算准确性的改善。我们还将研究将DECT图像数据整合到商业质子治疗治疗计划系统中。我们有埃莱克塔和瓦里安关于这一特定主题的研究许可证。 DECT用于对比度增强的图像：DECT成像可以提供所谓的“虚拟非对比度”(VNC)图像。基于组织分解方法，VNC技术可以将最初填充了对比剂的图像转换为没有对比剂的虚拟图像。从图像中移除对比剂还会修改给定图像的其他高Z区域。我们将评估这项技术在特定解剖中的价值。我们将研究将这些图像整合到治疗计划系统中。改进的VNC技术将在改进的分解技术的基础上在内部开发。

In radiation oncology, personalized 3D treatment planning is made possible by the scanning of every patient using medical imaging. The current clinical paradigm is based on computed tomography (CT), complemented by other imaging technologies when available and relevant. For treatment planning purposes, the images offer quantitative characterization of the patient’s anatomy needed for radiation dose calculation and for organ delineation. Treatment planning is based on single energy CT (SECT): an x-ray source with a poly-energetic photon beam that crosses the patient and a detection system that measures the transmitted intensity. Recently, a new CT technology is commercially available; the dual-energy CT (DECT). This technology offers the possibility to simultaneously scan the patient using two different x-ray energies (two distinct sources and two distinct detection systems). Two different images are thus simultaneously obtained. At the CHUM, we installed one of the first DECT devices dedicated to radiation oncology treatment planning in 2013. Our research hypothesis is that this DECT can help improving treatment planning in radiation oncology on various levels. A research program was developed around this device involving medical physicists, radiation oncologists, medical residents and graduate students. The current grant proposal covers part of the global departmental research program. DECT for brachytherapy: The usage of DECT for prostate brachytherapy dosimetry calculation has been suggested by the AAPM TG186 report. We will build a Monte Carlo re-calculation platform to study improvements in dose calculation accuracy for low-dose rate brachytherapy. Reduction in artifact will be attempted based on standard decomposition methods proposed by Siemens and by in-house methods. The integration of this DECT data into the clinical system will be performed based on collaboration with Varian combining DECT data and Acuros. DECT for protontherapy: We will develop a Monte Carlo simulation environment to study the improvement in the accuracy of dose calculation due to DECT imaging. We will also study the integration of DECT image data into commercial protontherapy treatment planning systems. We have a research licenses from elekta and Varian on this specific subject. DECT for contrast-enhanced images: DECT imaging can provide a so-called “virtual non-contrast” (VNC) image. Based on tissue-decomposition methods, the VNC technique can transform an image initially filled with injected contrast agent into a virtual image without the contrast agent. Removing contrast agent from an image will also modify other high-Z regions of a given image. We will evaluate the value of this technique for specific anatomies. We will study the integration of such images into treatment planning systems. Improved VNC techniques will be developed in-house based on improved decomposition techniques.