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Title: SU-E-J-154: Deformable Image Registration Based Delivered Dose Estimation for Head and Neck Radiotherapy

Purpose: To estimate the accumulated dose to targets and organs at risk (OAR) for head and neck (H'N) radiotherapy using 3 deformable image registration (DIR) algorithms. Methods: Five H'N patients, who had daily CBCTs taken during the course of treatment, were retrospectively studied. All plans had 5 mm CTV-to-PTV expansions. To overcome the small field of view (FOV) limitations and HU uncertainties of CBCTs, CT images were deformably registered using a parameter-optimized B-spline DIR algorithm (Elastix, elastix.isi.uu.nl) and resampled onto each CBCT with a 4 cm uniform FOV expansion. The dose of the day was calculated on these resampled CT images. Calculated daily dose matrices were warped and accumulated to the planning CT using 3 DIR algorithms; SmartAdapt (Eclipse/Varian), Velocity (Velocity Medical Solutions), and Elastix. Dosimetric indices for targets and OARs were determined from the DVHs and compared with corresponding planned quantities. Results: The cumulative dose deviation was less than 2%, on average, for PTVs from the corresponding plan dose, for all algorithms/patients. However, the parotids show as much as a 37% deviation from the intended dose, possibly due to significant patient weight loss during the first 3 weeks of treatment (15.3 lbs in this case). The mean(±SD) cumulative dosemore » deviations of the 5 patients estimated using the 3 algorithms (SmartAdapt, Velocity, and Elastix) were (0.8±0.9%, 0.5±0.9%, 0.6±1.3%) for PTVs, (1.6±1.9%, 1.4±2.0%, 1.7±1.9%) for GTVs, (10.4±12.1%, 10.7±10.6%, 6.5±10.1%) for parotid glands, and (4.5±4.6%, 3.4±5.7%, 3.9±5.7%) for mucosa, respectively. The differences among the three DIR algorithms in the estimated cumulative mean doses (1SD (in Gy)) were: 0.1 for PTVs, 0.1 for GTVs, 1.9 for parotid glands, and 0.4 for mucosa. Conclusion: Results of this study are suggestive that more frequent plan adaptation for organs, such as the parotid glands, might be beneficial during the course of H'N RT. This study was supported in part by a research grant from Varian Medical Systems, Palo Alto, CA.« less
Authors:
; ; ; ; ; ;  [1]
  1. Henry Ford Health System, Detroit, MI (United States)
Publication Date:
OSTI Identifier:
22334046
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; 60 APPLIED LIFE SCIENCES; ALGORITHMS; CAT SCANNING; DOSES; GLANDS; HEAD; IMAGES; MUCOUS MEMBRANES; NECK; PATIENTS; RADIOTHERAPY; WEIGHT