Evaluation of an MR-only interstitial gynecologic brachytherapy workflow using MR-line marker for catheter reconstruction

Brachytherapy. 2020 Sep-Oct;19(5):642-650. doi: 10.1016/j.brachy.2020.06.007. Epub 2020 Jul 22.

Abstract

Purpose: Magnetic resonance imaging (MRI) offers excellent soft-tissue contrast enabling the contouring of targets and organs at risk (OARs) during gynecological interstitial brachytherapy procedure. Despite its benefit, one of the main challenges toward MRI-only workflows is that the implanted catheters are not reliably visualized on MR images. This study aims to evaluate the feasibility of MR-only workflow using an in-house MR line marker during interstitial gynecological high-dose-rate (HDR) brachytherapy.

Methods and materials: Ten patients diagnosed with locally advanced cervical cancer treated with HDR brachytherapy were included in this study. The hybrid CT/MR-treated plan was used as the study reference plan. Five users manually reconstructed the catheter's path on MR images (3D T1- and T2-weighted). Subsequently, the dwell positions from the users' plans were superimposed on the reference plans to evaluate the dosimetric impact of the using MR-only for catheter reconstruction in comparison with hybrid CT/MR approach. Variability of dwell positions between users and reconstruction time was also evaluated.

Results: More than 96.90% of catheter reconstruction variations were < 2 mm. No statistical differences were reported between MR-only and hybrid CT/MR in gross tumor volume D98 and high-risk clinical target volume D90, respectively. For the OARs (bladder, sigmoid, rectum, and bowel), no significant changes were observed in any dose metrics between MR-only and hybrid CT/MR. The average reconstruction time was 51 ± 10 minutes across all ten patients.

Conclusion: The feasibility of MR-only workflow using MR line marker during interstitial gynecological HDR brachytherapy has been validated in this study. The results show that the MR-only workflow is equivalent to the conventional hybrid CT/MR approach in terms of gross tumor volume and high-risk clinical target volume coverage and respecting of OARs dose limits.

Keywords: Catheters reconstruction; Gynecologic cancer; High-dose-rate; Interstitial brachytherapy; MRI.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Brachytherapy / methods*
  • Catheters*
  • Colon, Sigmoid
  • Endometrial Neoplasms / diagnostic imaging
  • Endometrial Neoplasms / radiotherapy*
  • Female
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging / methods
  • Middle Aged
  • Organs at Risk
  • Radiometry
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Rectum
  • Urinary Bladder
  • Uterine Cervical Neoplasms / diagnostic imaging
  • Uterine Cervical Neoplasms / radiotherapy*
  • Vaginal Neoplasms / diagnostic imaging
  • Vaginal Neoplasms / radiotherapy*
  • Workflow