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Optimal Virtual Monoenergetic Image in TwinBeam Dual-Energy CT for Head-And-Neck Radiotherapy

T Wang*, J Ghavidel , J Beitler , X Tang , W Curran , T Liu , X Yang , Emory University, Atlanta, GA


(Wednesday, 8/1/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 2

Purpose: Monoenergetic images synthesized from dual-energy CT (DECT) data could reduce beam-hardening artifacts and provide quantitative attenuation measurements. The “twinbeam� DECT simultaneously captures two CT images with different energy spectra, which can eliminate patient motion between two CT images. This study’s purpose is to investigate the “twinbeam� scan scheme in head and neck radiotherapy workflow and choose optimal monoenergetic image for organ-at-risk (OARs) delineation for treatment planning.

Methods: We synthesized monochromatic images at various energies from “twin-beam� DECT images. Specifically, we generated monochromatic images 40 keV to 190 keV at 5keV increment, and totally obtained 30 monochromatic images for each DECT image. We collected the Hounsfield unit (HU) numbers of OARs (brain stem, mandible, spinal cord and parotid glands), the HU numbers of marginal regions outside OARs and the noise levels for each monochromatic image. We then calculated the contrast-to-noise ratio (CNR) for the different OARs at each energy level to generate a serial of spectral curves for each OAR. Based on these spectral curves of CNR, the mono-energy corresponding to the max CNR was identified for each OAR of each patient.

Results: CT scans of 8 patients scanned with the “twin-beam� protocol were used to test the optimal monoenergetic image for the delineation of OAR. Based on the maximized CNR, the optimal energy values were 81.92.6 keV for brain stem, 75.65.0 keV for mandible, 85.04.6 keV for spinal cord, and 83.12.6 keV for parotid glands. Overall, the optimal energy for the delineation of these OARs for head-and-neck cancer patients is 80 keV.

Conclusion: We have proposed an approach to select the optimal energy level for OAR delineation in the head-and-neck radiotherapy planning using “twin-beam� DECT and demonstrated its clinical feasibility. This can be used to develop a “twin-beam� RT simulation protocol, and has the potential to improve head-and-neck radiotherapy.


Not Applicable / None Entered.


IM- CT: Dual Energy and Spectral

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