Daily Bone Alignment With Limited Repeat CT Correction Rivals Daily Ultrasound Alignment for Prostate Radiotherapy
- Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)
- Department of Biostatistics and Applied Mathematics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)
- Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)
Purpose: To compare the effectiveness of daily ultrasound (US)- and computed tomography (CT)-guided alignments with an off-line correction protocol using daily bone alignment plus a correction factor for systematic internal prostate displacement (CF{sub ID}). Methods and Materials: Ten prostate cancer patients underwent CT scans three times weekly using an integrated CT-linear accelerator system, followed by alignment using US for daily radiotherapy. Intensity-modulated radiotherapy plans were designed with our current clinical margins. The treatment plan was copied onto the repeat CT images and aligned using several methods: (1) bone alignment plus CF{sub ID} after three off-line CT scans (bone+3CT), (2) bone alignment plus CF{sub ID} after six off-line CT scans (bone+6CT), (3) US alignment, and (4) CT alignment. The accuracy of the repeated US and CT measurements to determine the CF{sub ID} was compared. The target dosimetric effect was quantified. Results: The CF{sub ID} for internal systematic prostate displacements was more accurately measured with limited repeat CT scans than with US (residual error, 0.0 {+-} 0.7 mm vs. 2.0 {+-} 3.2 mm). Bone+3CT, bone+6CT, and US provided equivalent prostate and seminal vesicle dose coverage, but bone+3CT and bone+6CT produced more precise daily alignments. Daily CT alignment provided the greatest target dose coverage. Conclusion: Daily bone alignment plus CF{sub ID} for internal systematic prostate displacement provided better daily alignment precision and equivalent dose coverage compared with daily US alignment. The CF{sub ID} should be based on at least three repeat CT scans, which could be collected before the start of treatment or during the first 3 treatment days. Daily bone alignment plus CF{sub ID} provides another option for accurate prostate cancer patient positioning.
- OSTI ID:
- 21124210
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 71, Issue 1; Conference: 2007 interorganizational symposium on quality assurance of radiation therapy: Challenges of advanced technology, Dallas, TX (United States), 20-22 Feb 2007; Other Information: DOI: 10.1016/j.ijrobp.2008.01.026; PII: S0360-3016(08)00144-2; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The 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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