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An Efficient Optimization Method for Prostate LDR Planning by Including Prior Knowledge

G Szalkowski1*, R Chen2, T Royce1, A Wang1, J Lian1, (1) University of North Carolina at Chapel Hill, Chapel Hill, NC, (2) University Of Kansas

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: decrease the time needed to conduct prostate LDR planning, and to reduce the number of needles and/or sources used for treatment while meeting dosimetric objectives.


Methods: the LDR planning software Variseed (version 9.0, Varian Medical Systems, Palo Alto, CA), we created new dose optimization tuning structures and dosimetric constraints. Tuning structures consider the preferred location from prior clinical knowledge. These optimization protocols were then used retrospectively to develop initial plans for ten previously treated patients that were further manually adjusted to meet the dosimetric requirements. We recorded the number of modifications needed during the planning process to make the plan clinically acceptable, (V100% > 95% for the prostate, V100% < 1 cc for the rectum, and max point dose of the urethra less than 150% of the prescription dose). These metrics, as well as the total number of needles and sources used, were then compared to the values obtained from running a similar analysis on plans generated using our current workflow.


Results: the retrospectively analyzed plans, the newly developed workflow resulted in a significant reduction in the number of modifications necessary to make a plan clinically acceptable compared to the current clinical practice. The new workflow required, on average, the modification of 5.7 needle and 0.7 source positions compared to 18.4 and 12.1, respectively, for the current procedure (p< 0.001 for both). Additionally, the plans created using the new workflow use an average of 0.9 fewer needles and 6.5 fewer sources than the clinically delivered plans (p<0.01 for both).


Conclusion: results show that the newly developed workflow is, on average, more efficient than the current, default workflow both in terms of time required for planning as well as the number of sources and needles required to produce a clinical plan.

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Keywords

Interstitial Brachytherapy, Optimization, Prostate Therapy

Taxonomy

TH- Brachytherapy: Dose optimization and planning

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