CBCT-Based Dose Monitoring and Adaptive Planning Triggers in Head and Neck PBS Proton Therapy

Abstract

Purpose: To investigate the feasibility of using cone-beam computed tomography (CBCT)-derived synthetic CTs to monitor the daily dose and trigger a plan review for adaptive proton therapy (APT) in head and neck cancer (HNC) patients. Methods: For 84 HNC patients treated with proton pencil-beam scanning (PBS), same-day CBCT and verification CT (vfCT) pairs were retrospectively collected. The ground truth CT (gtCT) was created by deforming the vfCT to the same-day CBCT, and it was then used as a dosimetric baseline and for establishing plan review trigger recommendations. Two different synthetic CT algorithms were tested; the corrected CBCT (corrCBCT) was created using an iterative image correction method and the virtual CT (virtCT) was created by deforming the planning CT to the CBCT, followed by a low-density masking process. Clinical treatment plans were recalculated on the image sets for evaluation. Results: Plan review trigger criteria for adaptive therapy were established after closely reviewing the cohort data. Compared to the vfCT, the corrCBCT and virtCT reliably produced dosimetric data more similar to the gtCT. The average discrepancy in D99 for high-risk clinical target volumes (CTV) was 1.1%, 0.7%, and 0.4% and for standard-risk CTVs was 1.8%, 0.5%, and 0.5% for the vfCT, corrCBCT, and virtCT, respectively. Conclusion: Streamlined APT has been achieved with the proposed plan review criteria and CBCT-based synthetic CT workflow.

Cone-Beam CT Images as an Indicator of QACT During Adaptive Proton Therapy of Extremity Sarcomas

“…There have been a great number of research interests in post-processing CBCT images for adaptive re-planning in head-and-neck (HN), lung and prostate cancers. 7 , 8 , 15 , 19 , 20 , 21 , 22 Yao et. al.…”

“… 15 Deformation of pCT to CBCT and generation of synthetic CT (sCT) from CBCT have been heavily explored as options for automated adaptive proton therapy for HN cancers. 7 , 20 , 21 , 22 However, it involves complex methods and may mislead in contour propagation from pCT to sCT. In another study, Yao et.…”

A review of the clinical introduction of 4D particle therapy research concepts

“…Mobile in-room CT was shown to provide adequate acquisition time, geometric accuracy and image quality as well as SPR conversion as a basis for offline replanning and contour propagation [119] , [120] , [121] . Individual PT offline adaptive procedures can also be triggered by 2D orthogonal X-ray or (synthetic) CBCT in combination with in-house and commercial software tools [122] , [123] , [124] , which are both also relevant image modalities for 4D motion management. Most offline adaptive planning in photon and particle therapy occurs ad-hoc based on anatomical changes noted on control imaging (e.g., CBCT or diagnostic CT scanner installed in or outside the treatment room) or clinical observations by medical doctors, radiation therapy technologists or the patient.…”

The Applications and Pitfalls of Cone-Beam Computed Tomography-Based Synthetic Computed Tomography for Adaptive Evaluation in Pencil-Beam Scanning Proton Therapy

“…Yet, despite these advancements, the integration of synthetic CT into proton therapy-a domain marked by its unique sensitivities-remains circumscribed to limited data across a select few treatment sites. Several literatures [14][15][16][17][18][19] demonstrate that CBCT-based sCT generation methods generally fall into three categories: direct-deformable (DD), image-correction (IC), and artificial intelligence (AI). Veiga et al [15,16] explored the DD method with a focus on adaptive proton therapy for lung cancer patients.…”

“…Concurrently, Kurz et al [17] investigated the IC approach, emphasizing its potential for CBCT-based dose calculation in H&N cancer patients. Reiners et al [18] explored both the DD and IC methods in the RayStation Treatment Planning System (TPS) (version 12A), assessing their utility for daily dose monitoring and triggering plan reviews for H&N cancer. They concluded that synthetic CT is a more efficient and accurate adaptive workflow in proton therapy.…”