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Intrafraction prostate motion during IMRT for prostate cancer
Eugene Huang1, Lei Dong, Anurag Chandra
1Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
Summary
Intrafraction prostate motion during intensity-modulated radiotherapy (IMRT) is predominantly anterior and superior but clinically insignificant. This intrafraction motion is much smaller than interfraction motion and does not correlate with it.
Area of Science:
- Radiation oncology
- Medical imaging
- Prostate cancer treatment
Background:
- Interfraction prostate motion is well-studied, but intrafraction motion is less documented.
- Accurate prostate positioning is crucial for effective intensity-modulated radiotherapy (IMRT).
Purpose of the Study:
- To measure intrafraction prostate motion during IMRT using the B-mode, Acquisition, and Targeting (BAT) ultrasound system.
- To compare intrafraction motion with previously documented interfraction motion.
Main Methods:
- Twenty men with localized prostate cancer undergoing IMRT were studied.
- The BAT ultrasound system collected alignment images before and after IMRT over 10 days (400 procedures).
- Prostate shifts were recorded in right-left (RL), anteroposterior (AP), and superior-inferior (SI) dimensions.
Main Results:
- BAT ultrasound images were of acceptable quality and alignment.
- Dominant intrafraction motion directions were anterior and superior.
- Mean shifts were minimal (e.g., 0.2 ± 1.3 mm anteriorly), with most motion <5 mm. Intrafraction motion was significantly smaller than interfraction motion and showed no correlation.
Conclusions:
- Intrafraction prostate motion during IMRT is primarily anterior and superior but clinically insignificant.
- The measured intrafraction motion is substantially less than interfraction motion.
- There is no significant correlation between intrafraction and interfraction prostate motion.