Room: AAPM ePoster Library
Purpose: dosimetrically compare the graphical optimization plan with the inverse planning simulated annealing (IPSA) method in Oncentra brachytherapy treatment planning system on gynecological interstitial cases using MUPIT applicator.
Methods: gynecological tumor plans previously treated on a Nucleotron remote afterloader Martinez Universal Perineal Interstitial Template (MUPIT) applicator was selected in this study. IPSA-optimized treatment plans were created using three values of the dwell time deviation constraint (DTDC) (0, 0.5, and 1.0). Comparison plans were created using a manual graphical optimization technique (GRO). Both planning methods intended to achieve brachytherapy equivalent dose in 2-Gy fraction (EQD2) to 90% target volume (D90%) of atleast 48 Gy for prescription dose (Rx) of 5 Gy over 5 fractions. Dose objectives include a maximum tolerable dose to 2 cc volume (D2cc) of OARs (including rectum, bladder, sigmoid). Additionally, several other plan evaluation metrics including percent volume coverage by 100%, 150%, and 200% of Rx, percent dose irradiating 50%, 90%, and 100% of target volume, dose conformity index, total dwell timings, and time for plan generation. Wilcoxon signed-rank test was used to ascertain significant differences at p-value<0.05.
Results: gynecological tumor cases using a MUPIT interstitial applicator were analyzed. Clinical target volume (CTV) ranged from 33 cc to 189 cc (mean±SD=78±49 cc) were re-planned. The volume of hotspots (V200%), the mean dwell times and the planning times were significantly lower in any IPSA computation compared to the GRO plans (p-value<0.05).
Conclusion: GRO and IPSA computed plans using a MUPIT interstitial brachytherapy applicator produced plans which met the dose objectives. Although the plans were equivalent on many counts, IPSA-optimized plans had significantly smaller volume of hotspots, used lower dwell times, and took less time to plan.
Not Applicable / None Entered.