3D dose reconstruction based on in vivo dosimetry for determining the dosimetric impact of geometric variations in high-dose-rate prostate brachytherapy

Erik B. Jørgensen, Simon Buus, Lise Bentzen, Steffen B. Hokland, Susanne Rylander, Gustavo Kertzscher, Sam Beddar, Kari Tanderup, Jacob G. Johansen

Research output: Contribution to journalArticlepeer-review

Abstract

Introduction: In vivo dosimetry (IVD) can be used for source tracking (ST), i.e., estimating source positions, during brachytherapy. The aim of this study was to exploit IVD-based ST to perform 3D dose reconstruction for high-dose-rate prostate brachytherapy and to evaluate the robustness of the treatments against observed geometric variations. Materials and Methods: Twenty-three fractions of high-dose-rate prostate brachytherapy were analysed. The treatment planning was based on MRI. Time-resolved IVD was performed using a fibre-coupled scintillator. ST was retrospectively performed using the IVD measurements. The ST identified 2D positional shifts of each treatment catheter and thereby inferred updated source positions. For each fraction, the dose was recalculated based on the source-tracked catheter positions and compared with the original plan dose using differences in dose volume histogram indices. Results: Of 352 treatment catheters, 344 had shifts of less than 5 mm. Shifts between 5 and 10 mm were observed for 3 catheters, and shifts greater than 10 mm for 2 catheters. The ST failed for 3 catheters. The maximum relative difference in clinical target volume (prostate + 3 mm isotropic margin) D90% was 5%. In one fraction, the bladder D2cm3 dose increased by 18% (1.4 Gy) due to a single source position being inside the bladder rather than nearby as planned. The max increase in urethra dose was 1.5 Gy (15%). Conclusion: IVD-based 3D dose reconstruction for high-dose-rate prostate brachytherapy is feasible. The dosimetric impact of the observed catheter shifts was limited. Dose reconstruction can therefore aid in determining the dosimetric impact of geometric variations and errors in brachytherapy.

Original languageEnglish (US)
Pages (from-to)62-68
Number of pages7
JournalRadiotherapy and Oncology
Volume171
DOIs
StatePublished - Jun 2022
Externally publishedYes

Keywords

  • Brachytherapy
  • High dose rate
  • In vivo dosimetry
  • Prostate

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Radiology Nuclear Medicine and imaging

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