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SU‐E‐J‐229: Quantitative Assessment for Timely Adaptive Re‐Planning Using Weekly Dose Monitoring for Head and Neck Cancer
Author(s) -
Shang Q,
Li Z,
Liu H,
Greskovich J,
Koyfman S,
Xia P
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4888282
Subject(s) - medicine , head and neck cancer , radiation treatment planning , radiation therapy , nuclear medicine , radiology
Purpose: For patients with head and neck (HN) cancer, mid‐course adaptive radiation therapy (ART) is a common practice in our institution to accommodate anatomic changes. The aim of the study is to evaluate whether dose re‐calculation on weekly verification images can provide quantitative assessment for timely adaptive re‐planning with daily image‐guided intensity modulated radiotherapy (IMRT). Methods: We retrospectively selected sixty daily verification images acquired on CT‐on‐rail/CBCT from ten HN patients. These image sets were typically a week apart. Among these patients, six patients received a mid‐course ART. Contours of the tumors and organ‐at‐risks (OARs) were manually delineated by a physician on each verification CT. After placing the treatment iso‐center on the verification CTs according to the recorded clinical shifts, daily dose was re‐calculated with the same beam configuration as the original plan. For the purpose of this study, electron densities for both verification CTs and planning CTs were set to 1.0 g/cm3. Results: Two patients had D99 of the CTV < 97% of the planned dose for more than three fractions due to remarkable tumor volume shrinkages. D_max of the spinal cord exceeded a tolerance of 45 Gy for four fractions in additional two patients. D_mean of the parotid increased within 25% of the planned value. D_max of the brainstem and D_mean of the oral cavity did not show significant variation. If the re‐planning criteria included D99 of the CTV < 97% of the planned dose and D_max of the spinal cord > 45 Gy, two out ten patients required ART at week 2 and two patients required ART at week 3, respectively. Conclusion: Weekly dose monitoring with re‐calculation on verification images can provide quantitative dose guidance for timely adaptive re‐planning. Future work will include accumulative dose analysis for the decision of adaptive re‐planning. The study is supported in part by Siemens Medical Solutions.