IMPACT OF POST-IMPLANT EDEMA ON DOSE COVERAGE
IN PROSTATE BRACHYTHERAPY: CAN IMPLANT QUALITY BE ASSESSED ON DAY 0?
Frank M. Waterman and Adam P. Dicker
Supported in part by P30 CA 56036-03 (NCI)
Department of Radiation Oncology,
Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University Hospital,
Philadelphia, PA 19107
Results:
The mean DVHs for days 0 and 46 are similar in shape, but displaced such that D90, D80,
D50, and D25 were higher by 15 +17 %, 17 + 14 %, 20 + 12%, and 25 +
13 %, respectively, on day 46. This increase in dose is due to a mean decrease of 37 +
17 % in the prostate volume between days 0 and 46. More notably, the shapes of the
post-implant DVHs were different from the pre-plan DVH. The slope of the post-implant DVHs
are not as steep and the curves have a broader shoulder. This difference is attributed to
effect of source placement errors which increase dose heterogeneity, a factor which is not
reflected in the pre-plan DVH. The reduction in the slope of the DVH curve effectively
reduces the sensitivity of dose coverage to edema. The results show that the percentage
increase in coverage depends upon the coverage on day 0 and is greatest when the coverage
is poor: 70%, 80 %, 85%, and 90% coverage on day 0 increased to 80 + 8 %, 87 +
7 %, 90 + 6 %, and 94 + 4 %, respectively. Based on these findings, it is
possible to express equivalent standards for implant quality on day 0 and day 30. Our
results indicate that D85 > 140 Gy on day 0 is equivalent to D90 > 140
Gy on day 30.
Purpose
| Materials and Methods | Results | Conclusions
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