Improving Structure Delineation for Radiation Therapy Planning Using Dual-Energy CT

George Noid; Justin Zhu; An Tai; Nilesh Mistry; Diane Schott; Douglas Prah; Eric Paulson; Christopher Schultz; X Allen Li

doi:10.3389/fonc.2020.01694

Improving Structure Delineation for Radiation Therapy Planning Using Dual-Energy CT

Front Oncol. 2020 Aug 28:10:1694. doi: 10.3389/fonc.2020.01694. eCollection 2020.

Authors

George Noid¹, Justin Zhu¹, An Tai¹, Nilesh Mistry², Diane Schott¹, Douglas Prah¹, Eric Paulson¹, Christopher Schultz¹, X Allen Li¹

Affiliations

¹ Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States.
² Siemens Medical Solutions USA, Inc., Malvern, PA, United States.

Abstract

Purpose: We present the advantages of using dual-energy CT (DECT) for radiation therapy (RT) planning based on our clinical experience.

Methods: DECT 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.

Results: When 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.

Conclusion: The use of DECT for RT simulation offers clinically meaningful advantages through improved simulation workflow and enhanced structure delineation for RT planning.

Keywords: dual-energy CT; image contrast; metal artifacts; mono-energetic image; motion artifacts; photon starvation; radiation oncology; radiation therapy.