Richardson AK, et al. – This research develops the extent of intrafraction prostate motion as measured by Clarity and explores the potential benefits of TPUS for intrafraction monitoring. Researchers exhibited evidence that intrafraction monitoring with Clarity has the potential to enhance accuracy through application of in–treatment motion correction. This is most useful for specific patients who exhibit a higher frequency and/or duration of prostate motion. Moreover, consideration must be given to the added time implications and radiographer workload in clinical practice to correct for prostate motion. In addition, clarity could help facilitate future protocols using tighter treatment margins, although further research is required.

Methods

• Researchers examined monitoring data for 526 fractions from 20 localised prostate cancer patients.
• They evaluated intrafraction prostate displacements exceeding thresholds of 3 mm, 7 mm and 10 mm along patient axes for frequency and duration of motion.

Results

• It was demonstrated that prostate motion exceeds the above displacement thresholds during 52%, 8%, and 2% of fractions analysed.
• The evidence showed that displacement at the 3 mm threshold occurred for 100% of patients, 60% at 7 mm and 35% at 10 mm.
• For the overall population, the mean frequency and duration of displacements is low.
• In contrast specific patients exhibit much higher displacement values.
• It has been validated that posterior motion is most common, averaging at 24% of the treatment time at 3 mm, 3% at 7 mm and 1% at 10 mm, ranging up to 92%, 35% and 10% for individual patients.