Abstract
PurposeWe present the advantages of using dual-energy CT (DECT) for radiation therapy (RT) planning based on our clinical experience.MethodsDECT data acquired for 20 representative patients of different tumor sites and/or clinical situations with dual-source simultaneous scanning (Drive, Siemens) and single-source sequential scanning (Definition, Siemens) using 80 and 140-kVp X-ray beams were analyzed. The data were used to derive iodine maps, fat maps, and mono-energetic images (MEIs) from 40 to 190 keV to exploit the energy dependence of X-ray attenuation. The advantages of using these DECT-derived images for RT planning were investigated.ResultsWhen comparing 40 keV MEIs to conventional 120-kVp CT, soft tissue contrast between the duodenum and pancreatic head was enhanced by a factor of 2.8. For a cholangiocarcinoma patient, contrast between tumor and surrounding tissue was increased by 96 HU and contrast-to-noise ratio was increased by up to 60% for 40 keV MEIs compared to conventional CT. Simultaneous dual-source DECT also preserved spatial resolution in comparison to sequential DECT as evidenced by the identification of vasculature in a pancreas patient. Volume of artifacts for five patients with titanium implants was reduced by over 95% for 190 keV MEIs compared to 120-kVp CT images. A 367-cm3 region of photon starvation was identified by low CT numbers in the soft tissue of a mantle patient in a conventional CT scan but was eliminated in a 190 keV MEI. Fat maps enhanced image contrast as demonstrated by a meningioma patient.ConclusionThe use of DECT for RT simulation offers clinically meaningful advantages through improved simulation workflow and enhanced structure delineation for RT planning.
Highlights
Conventional poly-energetic CT is the most widely used imaging modality for radiation therapy (RT) planning
Results are presented for the evaluation of simultaneous Dual-energy CT (DECT) vs. sequential DECT (SE-DECT), as well as for the study on DECT-derived fat maps in the context of DECT-derived mono-energetic images (MEIs) and T1 + contrast images
These 190 keV images with iMAR (Figures 1C,F) demonstrated a metal artifact reduction of over 95% compared to conventional CTs (Figures 1A,D), as calculated from the volume of low CT numbers (CTNs) voxels restored
Summary
Conventional poly-energetic CT is the most widely used imaging modality for radiation therapy (RT) planning. Improving Radiation Therapy via DECT effectiveness relative to the prescription, with the goal of adequately covering the targets while maximally sparing OARs. RT planning depends on the quality of the planning images, which may lack in image contrast and functional information due to the limitations of poly-energetic CT [1]. A typical solution to the problem of poor image contrast is to register the CT with other imaging modalities (MRI and PET) to offer enhanced image contrast and information about functional or metabolic activity [2]. Such registration inherently introduces registration uncertainty, which may be substantial in some cases due to differences in patient setup [3]. Information from other imaging modalities may not be available for some patients
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