Surface imaging for patient setup and monitoring for breast radiotherapy

Abstract

Approximately one in eight women will get breast cancer at some point in their lives. A promising new treatment is partial breast irradiation, in which multiple radiation beams cross at the tumor site within the patient. This method of radiotherapy treats only a portion of the breast for a relatively small number of treatments with a high dose per treatment. This method requires much higher accuracy of patient alignment as the tumor site must be correct targeted. This study examined the possibility of using the VisionRT (London, UK) software and cameras for surface visualization to align patients for this treatment. A portable, single pod, the "Mini Cam" was found to be able to generate images for translations less than 2.5-5.5 cm, depending on the direction of translation. Calibration was a key aspect to ensuring accurate results. Eight patients were studied for deformation, breathing motion and day to day alignment. Surface images were taken at several points during regular treatment. Deformation was found to be small and never exceeded and average value of 2 mm. No correlation was found between the amount of deformation and the breast size or planning treatment volume. The average peak-to-peak breathing motion was 0.99-2.16 mm. Variability was discovered in the gating function of the VisionRT software. Aligning patients based on the first treatment session was found to be more accurate than aligning to a CT image taken weeks earlier.