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Dosimetric Comparison of LDR Vs. HDR Tandem Ovoid Brachytherapy

W Li

W Li*, L Liu , S Tanny , SUNY Upstate Medical Univ, Syracuse, NY


SU-I-GPD-T-45 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Studies have shown that the outcomes of the treatment of cervical carcinoma using LDR and HDR are comparable. The selection of the modality is mostly based on the availability in the individual clinic. In terms of the dosimetry, HDR has the advantage of multiple dwell positions with continuous dwell time adjustment, while LDR sources normally are 2 cm long and with a collection of limited activities.Both HDR and LDR modalities are used in this hospital. This study is intended to investigate that with a limited collection of Cs-137 LDR sources, if LDR plans can be created that are dosimetrically comparable to the HDR plans.

Methods: 25 CTs from five patients that received HDR Tandem Ovoid treatments were used in this study. For each HDR plan, a LDR plan was created, matching the mean point-A doses to be within <1% difference, Volumes receiving mean point-A doses to be within <10%. Efforts were put to match DVHs of the target volumes. D2cc of the critical structures such as bladder, rectum and sigmoid were expressed as percentage of point-A dose to facilitate the comparisons.

Results: Differences in terms of biologically equivalent doses from HDR and LDR were not taken into account. After matching the point-A doses, for each HDR plan, a LDR plan can be created with comparable DVHs for treatment volume and critical structures.

Conclusion: When volume-based planning is used, LDR plans can be generated with dosimetry that is comparable to HDR plans.

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