Pitch, roll, and yaw variations in patient positioning
- Department of Radiation Oncology, University of California Irvine, Orange, CA (United States)
- Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA (United States) and Department of Radiation Physics, City of Hope National Medical Center, Duarte, CA (United States)
- Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA (United States)
- Division of Information Sciences, City of Hope National Medical Center, Duarte, CA (United States)
Purpose: To use pretreatment megavoltage-computed tomography (MVCT) scans to evaluate positioning variations in pitch, roll, and yaw for patients treated with helical tomotherapy. Methods and Materials: Twenty prostate and 15 head-and-neck cancer patients were selected. Pretreatment MVCT scans were performed before every treatment fraction and automatically registered to planning kilovoltage CT (KVCT) scans by bony landmarks. Image registration data were used to adjust patient setups before treatment. Corrections for pitch, roll, and yaw were recorded after bone registration, and data from fractions 1-5 and 16-20 were used to analyze mean rotational corrections. Results: For prostate patients, the means and standard deviations (in degrees) for pitch, roll, and yaw corrections were -0.60 {+-} 1.42, 0.66 {+-} 1.22, and -0.33 {+-} 0.83. In head-and-neck patients, the means and standard deviations (in degrees) were -0.24 {+-} 1.19, -0.12 {+-} 1.53, and 0.25 {+-} 1.42 for pitch, roll, and yaw, respectively. No significant difference in rotational variations was observed between Weeks 1 and 4 of treatment. Head-and-neck patients had significantly smaller pitch variation, but significantly larger yaw variation, than prostate patients. No difference was found in roll corrections between the two groups. Overall, 96.6% of the rotational corrections were less than 4 deg. Conclusions: The initial rotational setup errors for prostate and head-and-neck patients were all small in magnitude, statistically significant, but did not vary considerably during the course of radiotherapy. The data are relevant to couch hardware design for correcting rotational setup variations. There should be no theoretical difference between these data and data collected using cone beam KVCT on conventional linacs.
- OSTI ID:
- 20850184
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 66, Issue 3; Conference: 48. annual meeting of the American Society for Therapeutic Radiology and Oncology, Pennsylvania, PA (United States), 5-9 Nov 2006; Other Information: DOI: 10.1016/j.ijrobp.2006.05.055; PII: S0360-3016(06)00973-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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