Abstract
Endorectal balloons (ERBs) are routinely used in prostate proton radiation therapy to immobilize the prostate and spare the rectal wall. Rectal gas can distend the rectum and displace the prostate even in the presence of ERBs. The purpose of this work was to quantify the effects an ERB with a passive gas release conduit had on the incidence of rectal gas. Fifteen patients who were treated with a standard ERB and 15 with a gas‐release ERB were selected for this retrospective study. Location and cross‐sectional area of gas pockets and the fraction of time they occurred on 1133 lateral kilovoltage (kV) images were analyzed. Gas locations were classified as trapped between the ERB and anterior rectal wall, between the ERB and posterior rectal wall, or superior to the ERB. For patients using the standard ERB, gas was found in at least one region in 45.8% of fractions. Gas was trapped in the anterior region in 37.1% of fractions, in the posterior region in 5.0% of fractions, and in the sigmoid region in 9.6% of fractions. For patients using the ERB with the gas‐release conduit, gas was found in at least one region in 19.7% of fractions. Gas was trapped in the anterior region in 5.6% of fractions, in the posterior region in 8.3% of fractions, and in the sigmoid region in 7.4% of fractions. Both the number of fractions with gas in the anterior region and the number of fractions with gas in at least one region were significantly higher in the former group than in the latter. The cross‐sectional area of trapped gas did not differ between the two groups. Thus gas‐release balloon can effectively release gas, and may be able to improve clinical workflow by reducing the need for catheterization.PACS number: 87.56.Da
Highlights
As radiation therapy technology has matured, the delivery of increasingly conformal radiation fields with commensurately smaller margins at higher doses has become commonplace
The presence of gas is neither predictable nor reproducible, leading to unpredictable prostate movement between treatments and during the delivery of treatment.[14]. This effect is especially influential in proton therapy, for which the presence of rectal gas can significantly alter the dose distribution; protons are highly sensitive to the medium they travel through, and when tissue is displaced by gas, protons penetrate further than planned
Our analysis indicates that the gas-release Endorectal balloons (ERBs) significantly decreased the number of fractions in which gas was present, primarily by decreasing the incidence of gas trapped between the rectal balloon and the anterior rectal wall
Summary
As radiation therapy technology has matured, the delivery of increasingly conformal radiation fields with commensurately smaller margins at higher doses has become commonplace. The presence of gas is neither predictable nor reproducible, leading to unpredictable prostate movement between treatments and during the delivery of treatment.[14] This effect is especially influential in proton therapy, for which the presence of rectal gas can significantly alter the dose distribution; protons are highly sensitive to the medium they travel through, and when tissue is displaced by gas, protons penetrate further than planned. This increased proton penetration results in unnecessary irradiation of normal tissue
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
