Advanced applications of dual-energy computed tomography in radiation oncology

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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.********