Adaptive Replanning Strategies Accounting for Shrinkage in Head and Neck IMRT

Journal Article · Sun Nov 01 04:00:00 EST 2009 · International Journal of Radiation Oncology, Biology and Physics

OSTI ID:21367483

Yuwei, Chi; Chen, Peter Y; Krauss, Daniel J; Di, Yan; Martinez, Alvaro ^[1]

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1. Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI (United States)

Purpose: Significant anatomic and volumetric changes occur in head and neck cancer patients during fractionated radiotherapy, and the actual dose can be considerably different from the original plan. The purposes of this study were (1) to evaluate the differences between planned and delivered dose, (2) to investigate margins required for anatomic changes, and (3) to find optimal replanning strategies. Methods and Materials: Eleven patients, each with one planning and six weekly helical CTs, were included. Intensity-modulated radiotherapy plans were generated using the simultaneous integrated boost technique. Weekly CTs were rigidly registered to planning CT before deformable registration was performed. The following replanning strategies were investigated with different margins (0, 3, 5 mm): midcourse (one replan), every other week (two replans), and every week (six replans). Doses were accumulated on the planning CT for comparison of various dose indices for target and critical structures. Results: The cumulative doses to targets were preserved even at the 0-mm margin. Doses to cord, brainstem, and mandible were unchanged. Significant increases in parotid doses were observed. Margin reduction from 5 to 0 mm led to a 22% improvement in parotid mean dose. Parotid sparing could be preserved with replanning. More frequent replanning led to better preservation; replanning more than once a week is unnecessary. Conclusion: Shrinkage does not result in significant dosimetric difference in targets and critical structures, except for the parotid gland, for which the mean dose increases by approx10%. The benefit of replanning is improved sparing of the parotid. The combination of replanning and reduced margins can provide up to a 30% difference in parotid dose.

• OSTI ID: 21367483
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 75; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BODY
DISEASES
DOSES
HEAD
MEDICINE
NECK
NEOPLASMS
NUCLEAR MEDICINE
PLANNING
RADIATION DOSES
RADIOLOGY
RADIOTHERAPY
SHRINKAGE
THERAPY