High-­dose rate intraluminal brachytherapy for oesophageal cancer using MR imaging: A clinical implementation

Abstract: Purpose: The aim of this study was to investigate a new methodology for brachytherapy of oesophageal cancer using magnetic resonance (MR) imaging for treatment planning. That includes finding a suitable oesophageal applicator that can be visualised on MR images and to create dose and fraction schedule that should be used brachytherapy treatments. Material and Methods: A total of six patients were involved to determine a suitable MR sequence for visualisation of the oesophageal tumour. The patients were scanned with two different T2-weighted sequences, inversion recovery fast spin echo (IR FSE) and fast recovery fast spin echo (FRFSE). The imaging was performed on a 3.0 T MR scanner from GE Healthcare. Dose planning was performed on MR images using two different methods. In the first method the dose was prescribed at 10 mm from the applicator centre, as currently used at Skåne University Hospital. In the second method the dose planning was performed by manually adjusting the dwell times until tumour coverage was reached. An MR safe oesophageal applicator could not be found on the market. Therefore a duodenal tube was used and modified. Different contrast agents were studied in order to render the tube visible on MR images. Results: The oesophageal tumour was successfully visualised and delineated on T2-weighted images with FRFSE sequences. Furthermore, improved dose coverage to the tumour was observed when the dose planning was manually optimised to the tumour volume, where V100% to the tumour was increased from 70% to 95%. Moreover, the applicator was filled with a saline solution and was visualised on the MR images. Conclusion: Brachytherapy treatment for oesophageal cancer with MR imaging provides an improved tumour visualisation and the manifesting of DVH parameters enables dose coverage to the tumour.