Researchers Determine Main Cause of the Bladder Motion That Occurs During Intrafraction Radiation Therapy
October 19, 2009
British researchers believe they have narrowed down the possible causes of motion during intrafraction radiation therapy of the bladder to a major one: filling.
By employing cine-magnetic resonance imaging, Catherine A. McBain, et al, set out to determine how to increase accuracy in applying radiation to bladder cancers. The researchers applied a 28-minute cine-MRI sequence during testing of 10 research and five control participants after bladder emptying and abstinence from drinking for an hour prior to the imaging.
The bladder was contoured “in imaging volume sets at 0, 14, and 28 minutes to measure changes to bladder volumes, wall displacements, and center of gravity (COG) over time,” the researchers wrote in the “Assessment of Bladder Motion for Clinical Radiotherapy Practice Using Cine-Magnetic Resonance Imaging.”
They found that bladder filling, up to a 101% volume increase, was the dominant source of motion and similar for all participants. However, wall displacements were up to 58 mm larger, less symmetrical and more variable for patients with bladder cancer compared to the control participants. Rectal and small bowel movements were transient.
“Significant and individualized intrafraction bladder wall displacements may occur during bladder radiation therapy delivery. This important source of inaccuracy should be incorporated into treatment planning and verification,” the researchers concluded.
The article was published online in the Nov. 1, 2009, International Journal of Radiation Oncology Biology — Physics at www.redjournal.org.
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