Clinical evaluation of synthetic computed tomography methods in adaptive proton therapy of lung cancer patients

Vicki Trier Taasti*, Djoya Hattu, Stephanie Peeters, Anke van der Salm, Judith van Loon, Dirk de Ruysscher, Rasmus Nilsson, Sebastian Andersson, Erik Engwall, Mirko Unipan, Richard Canters

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background and purpose: Efficient workflows for adaptive proton therapy are of high importance. This study evaluated the possibility to replace repeat-CTs (reCTs) with synthetic CTs (sCTs), created based on cone-beam CTs (CBCTs), for flagging the need of plan adaptations in intensity-modulated proton therapy (IMPT) treatment of lung cancer patients. Materials and methods: Forty-two IMPT patients were retrospectively included. For each patient, one CBCT and a same-day reCT were included. Two commercial sCT methods were applied; one based on CBCT number correction (Cor-sCT), and one based on deformable image registration (DIR-sCT). The clinical reCT workflow (deformable contour propagation and robust dose re-computation) was performed on the reCT as well as the two sCTs. The deformed target contours on the reCT/sCTs were checked by radiation oncologists and edited if needed. A dose-volume-histogram triggered plan adaptation method was compared between the reCT and the sCTs; patients needing a plan adaptation on the reCT but not on the sCT were denoted false negatives. As secondary evaluation, dose-volume-histogram comparison and gamma analysis (2%/2mm) were performed between the reCT and sCTs. Results: There were five false negatives, two for Cor-sCT and three for DIR-sCT. However, three of these were only minor, and one was caused by tumour position differences between the reCT and CBCT and not by sCT quality issues. An average gamma pass rate of 93% was obtained for both sCT methods. Conclusion: Both sCT methods were judged to be of clinical quality and valuable for reducing the amount of reCT acquisitions.
Original languageEnglish
Article number100459
Number of pages7
JournalPhysics & Imaging in Radiation Oncology
Volume27
Issue number1
DOIs
Publication statusPublished - 1 Jul 2023

Keywords

  • Adaptive proton therapy
  • Cone-beam CT
  • Efficiency gain
  • Lung cancer
  • Proton therapy
  • Synthetic CT

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