Clinical implementation of multisequence MRI‐based adaptive intracavitary brachytherapy for cervix cancer

Jacqueline E Zoberi,Pawel Dyk,Carol G Bertelsman,Perry W Grigsby,Baozhou Sun,Julie K Schwarz,Yanle Hu,Jose Garcia‐Ramirez

doi:10.1120/jacmp.v17i1.5736

Jacqueline E Zoberi, Pawel Dyk + Show 6 more

Open Access

https://doi.org/10.1120/jacmp.v17i1.5736

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Abstract

The purpose of this study was to describe the clinical implementation of a magnetic resonance image (MRI)‐based approach for adaptive intracavitary brachytherapy (ICBT) of cervix cancer patients. Patients were implanted with titanium tandem and colpostats. MR imaging was performed on a 1.5‐T Philips scanner using T2‐weighted (T2W), proton‐density weighted (PDW), and diffusion‐weighted (DW) imaging sequences. Apparent diffusion coefficient (ADC) maps were generated from the DW images. All images were fused. T2W images were used for the definition of organs at risk (OARs) and dose points. ADC maps in conjunction with T2W images were used for target delineation. PDW images were used for applicator definition. Forward treatment planning was performed using standard source distribution rules normalized to Point A. Point doses and dose‐volume parameters for the tumor and OARs were exported to an automated dose‐tracking application. Brachytherapy doses were adapted for tumor shrinkage and OAR variations during the course of therapy. The MRI‐based ICBT approach described here has been clinically implemented and is carried out for each brachytherapy fraction. Total procedure time from patient preparation to delivery of treatment is typically 2 hrs. Implementation of our technique for structure delineation, applicator definition, dose tracking, and adaptation is demonstrated using treated patient examples. Based on published recommendations and our clinical experience in the radiation treatment of cervix cancer patients, we have refined our standard approach to ICBT by 1) incorporating a multisequence MRI technique for improved visualization of the target, OARs, and applicator, and by 2) implementing dose adaptation by use of automated dose tracking tools.PACS numbers: 87.61.‐c, 87.53.Jw, 87.19.xj

Highlights

Three-dimensional (3D)-based intracavitary brachytherapy (ICBT) treatment planning for cervical cancer was implemented by the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO) working group, providing guidelines on the use of magnetic resonance imaging (MRI), primarily T2-weighted (T2W) sequences, for target definition.[1,2] These guidelines have been implemented at some institutions with access to MRI units and, over time, have facilitated a transition from Point A-based dose prescriptions to dose-volume adaptation.[3,4,5,6,7] An increase in local control and improvement in overall survival using MRI-assisted, dose-volume adaptation for ICBT, combined with 3D conformal EBRT, has been reported by one of these institutions.[8,9]
We have found that T2W-MRI fused with other MRI sequences can assist with target volume delineation and with applicator reconstruction.[11,12,13] We have used this multisequence MRI technique for ICBT treatment planning in addition to FDG-PET/CT imaging for IMRT treatment planning, and have reported our analysis of dose-volume parameters predicting gross tumor volume (GTV) control using this treatment technique.[14]. Total dose delivered to the GTV from combined MRI-based high dose rate (HDR) and PET/CT-guided IMRT was found to be highly correlated with local tumor control.[14]. With this information in hand, we have further refined our brachytherapy treatment technique to include dose tracking and adaptation, similar to what has been done by institutions that have implemented GEC-ESTRO recommendations.[8,15]
Due to the otherwise poor image quality of the Apparent diffusion coefficient (ADC) maps, the ADC maps cannot be used for the delineation of organs at risk (OAR), which is limited to the T2W images

Summary

Introduction

We have found that T2W-MRI fused with other MRI sequences can assist with target volume delineation (via diffusion-weighted imaging, DWI) and with applicator reconstruction (via proton density-weighted imaging, PDW).(11-13) We have used this multisequence MRI technique for ICBT treatment planning in addition to FDG-PET/CT imaging for IMRT treatment planning, and have reported our analysis of dose-volume parameters predicting gross tumor volume (GTV) control using this treatment technique.[14] Total dose delivered to the GTV from combined MRI-based HDR and PET/CT-guided IMRT was found to be highly correlated with local tumor control.[14] With this information in hand, we have further refined our brachytherapy treatment technique to include dose tracking and adaptation, similar to what has been done by institutions that have implemented GEC-ESTRO recommendations.[8,15]. We describe how we perform brachytherapy dose adaptation by tracking tumor volumes, tumor doses, and organs at risk (OAR) doses over the course of treatment, using an automated dose-tracking application. [16] We have clinically implemented these methods at our facility and, using treated patients as examples, we demonstrate features of our MRI-based technique for adaptive ICBT

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