Emulation of gynecological brachytherapy doses with external beam

Erich Schnell, Spencer Thompson, Terence Herman, Salahuddin Ahmad, Tania de la Fuente Herman

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Purpose: To evaluate the viability of external beam methods in substitution or replacement of brachytherapy techniques, while maintaining similar dosimetric performance. Methods: Three original tandem and ring brachytherapy plans were re-planned using external beam techniques. A physician recreated the target volumes on CT scans without instruments present, and volumetric photon and intensity modulated proton plans were generated to deliver either a uniform dose or to emulate the brachytherapy distribution with the escalated dose core. Proton plans were additionally generated using several different planning parameters. Resultant plans were compared dosimetrically by evaluating the dose to 2 cm3 for critical organs, the dose coverage to 90% of the target volume, the low-dose normal tissue exposure at 20% and 50% of the prescription, and the target volume receiving 200% and 300% of the prescription for the escalated-dose plans. Results: External beam plans performed well, achieving comparable D90 coverage and critical structure dose to 2 cm3. Higher robustness distance settings increased the D100 for proton plans, along with increases to critical structure doses. Photon plans achieved good escalated dose patterns when emulating the brachytherapy distribution, with better result for the 200% volume than the 300% volume. Photon plans did not meet the 300% coverage in any plans. Escalated proton plans did not meet the brachytherapy dose volumes in any plan, and doses along the entry paths rose to over 150% of the prescription. Conclusion: Brachytherapy is still the preferred method for delivery of the local boost for cervical cancer, despite continued advancement of external beam technologies. Brachytherapy is able to achieve the highest target dose heterogeneity while still protecting organs at risk. External beam photon plans are superior to proton plans when attempting to emulate the brachytherapy dose heterogeneity.

Original languageEnglish (US)
Title of host publicationProceedings of the XVI Mexican Symposium on Medical Physics
EditorsIvan Miguel Rosado-Mendez, Mariana Hernandez-Bojorquez, Jose Hector Morales-Barcenas, Paulina Esther Galavis, Mariela Adelaida Porras-Chaverri
PublisherAmerican Institute of Physics Inc.
ISBN (Electronic)9780735440944
StatePublished - Apr 30 2021
Externally publishedYes
Event16th Mexican Symposium on Medical Physics, MSOMP 2020 - Merida, Mexico
Duration: Oct 26 2020Oct 30 2020

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference16th Mexican Symposium on Medical Physics, MSOMP 2020


  • Brachytherapy
  • Dosimetry
  • External Beam
  • Gynecological Cancer
  • High Dose Rate
  • Proton
  • SBRT

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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