Development of an automated radiotherapy dose accumulation workflow for locally advanced high‐risk prostate cancer – A technical report

Abstract

An automated dose accumulation and contour propagation workflow using daily cone beam computed tomography (CBCTs) images for prostate cases that require pelvic lymph nodes irradiation (PLNs) was developed. This workflow was constructed using MIMâ software with the intention to provide accurate dose transformations for plans with two different isocentres, whereby two sequential treatment phases were prescribed. The pre-processing steps for data extractions from treatment plans, CBCTs, determination of couch shift information and management of missing CBCTs are described. To ensure that the imported translational couch shifts were in the correct orientation and readable in MIM, phantom commissioning was performed. For dose transformation, rigid registration with corrected setup shifts and scaled fractional dose was performed for pCT to daily CBCTs, which were then deformed onto CBCT 1 . Fractional dose summation resulted in the final accumulated dose for the patient allowing differences in dosimetry between the planned and accumulated dose to be analysed. Contour propagations of the prostate, bladder and rectum were performed within the same workflow. Transformed contours were then deformed onto daily CBCTs to generate trending reports for analysis, including Dice Similarity Coefficient (DSC) and Mean Distance to Agreement (MDA). Results obtained from phantom commissioning (DSC = 0.96, MDA = 0.89 mm) and geometrical analysis of the propagated contours for twenty patients; prostate (DSC: 0.9 AE 0.0, MDA: 1.0 AE 0.3 mm), rectum (DSC: 0.8 AE 0.1, mm, MDA: 1.7 AE 0.6 mm) and bladder (DSC: 0.8 AE 0.1, MDA: 2.8 AE 1.0 mm) were within clinically accepted tolerances for both DSC (>0.8) and MDA (< 0.3 mm). The developed workflow is being performed on a larger patient cohort for predictive model building, with the goal of correlating observed toxicity with the actual accumulated dose received by the patient.

Application of an automated dose accumulation workflow in high-risk prostate cancer - validation and dose-volume analysis between planned and delivered dose

“…14 , 15 A customized dose accumulation and contour propagation workflow was developed using MIM and was operated in MIM Assistant's interface for automation of data transfer and workflow management. 16 Details of the workflow construction and CBCT contour preparation have been reported 8 , and can be referred to in the supplementary material A.…”

“…7 The development of a dose accumulation and contour propagation workflow for HR-PCa that involves a two-phase treatment technique with two different isocentres has been described in our recent publication. 8 This workflow is essential, as treating the PLNs includes irradiating the centralised OARs to low-intermediate doses (30 to 50 Gy), 9 and the impact of inter-fractional organ deformations affect the actual dose received by the OARs. 10 Accurate dose estimates can be achieved by accumulating the delivered dose received by the patient onto a reference CT, based on daily acquired CBCTs, to account for organ changes.…”

Cone beam CT-based dose accumulation and analysis of delivered dose to the dominant intraprostatic lesion in primary radiotherapy of prostate cancer

“…Dose accumulation for prostate radiotherapy in general has been evaluated before: In a recent analysis, Ong et al presented a workflow for dose accumulation of prostate and pelvic lymph node radiotherapy with two isocenters. Due to different coordinate systems in the utilized MIM v.6.9 (MIMVista Corp., Cleveland OH) and MosaiQ (Elekta AB, Stockholm, Sweden) software Ong et al had to perform phantom measurements for couch shift commissioning which allowed the import of MosaiQ extracted, correctly aligned shift information into the contouring software [ 17 ]. In our current analysis, the RayStation TPS allowed the direct import and usage of couch shift data and therefore phantom measurements were omitted.…”

Dose-volume analysis of planned versus accumulated dose as a predictor for late gastrointestinal toxicity in men receiving radiotherapy for high-risk prostate cancer

“…A total of 37–39 CBCTs images were available per patient to perform dose accumulation. A customised dose accumulation workflow was developed using MIM (MIMVista® v6.9, MIM Software Inc., Cleveland OH, USA) [20] . Details of the workflow construction and validation of an intensity-based deformable image registration (DIR) algorithm used in MIM have been described in our recent publication [17] .…”