An imaging study to assess displacement between brachytherapy applicator and chestwall during simultaneous thermobrachytherapy of cancer

A conformal surface applicator was developed for simultaneous radiation and hyperthermia treatment of superficial cancer. A preclinical volunteer study was carried out to assess the displacement between the high dose rate (HDR) brachytherapy applicator and the chestwall (CW) of mastectomy volunteers using magnetic resonance imaging (MRI) technique. Image processing algorithms were developed to pre-process 3D MRI data of each volunteer and identify brachytherapy tube positions and CW treatment area. Processed MRI image series of individual volunteer acquired every 15 minutes for 90 minutes were aligned using image registration technique. 3D catheter coordinate positions extracted for the treatment area from the processed 30 and 60 minute MRI data were compared with baseline measurements. Displacement of the brachytherapy tubes from the CW surface measured for 2 cm spaced array of 15 brachytherapy tubes was used to assess applicator positioning errors during simultaneous thermobrachytherapy of superficial cancer. Preclinical results on the displacement between the TBSA and CW were measured for a mastectomy volunteer with 72×280 mm treatment area. Image processing algorithms developed for MRI data analysis were incorporated into a user-friendly graphical user interface (GUI) to analyze remaining volunteer MR data quantitatively for 3D displacement of the TBSA brachytherapy catheters between the 30 and 60 min scans.