Pitch, roll, and yaw variations in patient positioning.

Full Abstract

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 degrees.

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.

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Author information

Author/s: Kaiser, Adeel (A); Schultheiss, Timothy E (TE); Wong, Jeffrey Y C (JY); Smith, David D (DD); Han, Chunhui (C); Vora, Nayana L (NL); Pezner, Richard D (RD); Chen, Yi-Jen (YJ); Radany, Eric H (EH);

Affiliation: Department of Radiation Oncology, University of California Irvine, Orange, CA, USA.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys), published in United States. (Language: eng)

Reference: 2006-Nov; vol 66 (issue 3) : pp 949-55

Dates: Created 2006/10/02; Completed 2006/11/06; Revised 2006/11/15;

PMID: 16949765, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Head and Neck Neoplasms - radiography; radiotherapy
Humans
Male
Prostatic Neoplasms - radiography; radiotherapy

Radiotherapy Planning, Computer-Assisted - methods
Radiotherapy, Conformal
Rotation
Tomography, X-Ray Computed - methods

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