2214 - Dual-Energy Spectral CT Quantitative Parameters as Potential Indicator of Response Assessment in Head-Neck Cancer Treatment: A Preliminary Study
Presenter(s)
S. Samanta1, R. J. Megahed2, M. Patel1, and W. C. Hsi3; 1Department of Radiation Oncology, UAMS Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR, 2Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, 3Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL
Purpose/Objective(s): Outcomes of head-neck cancer are typically assessed by PET CT images after the completion of definitive treatments. However, response assessment during the course of radiation treatments or immediately at the end is challenging due to lack of appropriate imaging. In this study we propose that quantitative parameters from dual- energy spectral CT (DECT) , acquired before and during the treatment course , could be a potential indicator for response assessment in head neck cancer treated with chemo radiation approach.
Materials/Methods: In this study 5 patients treated with Pencil beam proton therapy and 8 patients with VMAT/IMRT were selected. Patients received standard chemo radiation treatments. Post treatment PET CT images were acquired and were used to determine response. These responses were scored as complete response, partial response, and progressive disease. Then we retrospectively investigated the quantitaive parameters such as spectral Hounsfield unit curve (SHUC) and iodine concentration (IC) to correlate with scored response. We observed a large variation on the slope of SHUC between planning and consequent DECTs; referred as DECTp and DECTQA respectively. Instead of the slope variation of SHUC, the ratios of HU values for 70, 140 kev with respect t0 55 kev was obtained from acquired DECT for locations with target irradiated with high or/and middle dose, and a referent location of normal tissue without irradiations.
Results: Because all DECT were acquired without contrast, the value of IC for locations with target and normal tissue are within the background of 0.2 mg/ml. No significant variation between all locations and DECT images for each of 5 patients. For two patients of complete response, the ratio of HU for 70 and 140 kev with respect to 50 kev for locations with the target was decreased at DECT acquired later fraction of treatment while the ratio of HU for normal tissue are similar in all acquired DECT. For two patients with progression of disease, the ratio of HU for location with target and normal tissue are similar in all acquired DECT.
Conclusion: The HU ratio or SHUC could possibly be used as good quantitative parameters to correlate with the outcome response in head neck cancer treatments. However, the characteristics of these parameters over various tissues within target or normal tissue need to be further investigated and quantified.