To Evaluate the Use of a Homemade Self-Held Respiration Monitoring Device (SHRMD) for Deep Inspiration Breath Hold (DIBH) Radiation Therapy to Left Breast Cancer Patients

Abstract

This prospective observational study is to quantify: 1) the inter-fraction reproducibility; 2) the intra-fraction variability; and 3) the intra-beam variability of patient’s breath-holding ability by using the Self-Held Respiration Monitoring Device (SHRMD). Fifteen patients with left breast cancer underwent breast conservative surgery and plan for tangential opposing chest wall radiotherapy using Deep Inspiration Breath Hold (DIBH) technique were selected. The SHRMD consists of two parts: 1) Mechanical sensor, which was placed between the xiphoid process and umbilicus, connecting with a controller to detect and reflect patient’s chest wall motion and provide mechanical motion data to the computer software. The controller also gave a green light signal together with alarm sound to guide the patient during respiration monitoring by indicating the optimum level of breathing threshold. 2) Computer software, which recorded the patients breathing pattern by transferring the sensor mechanical movement into digital readings. By using this device, patient’s actual breathing motion were detected and monitored. The treatments were delivered in a linear accelerator with 6MV photon for 40Gy to 43.2Gy at 100% isodose level in 15 to 16 daily fractions. Megavoltage cine images were acquired in Beam’s Eye View (BEV) during treatment. The average fractional lung depths were used to evaluate the inter-fraction setup reproducibility; the average lung depths variability between medial and lateral fields were used to evaluate the intra-fraction variability; and range of lung depths within each beam were used to evaluate the intra-beam variability. The median age of the 15 patients was 47.5 (range = 39-63). The inter-fraction overall mean error (M), SD of the systematic error (∑) and SD of the random error (σ) were 0.01 cm, 0.06 cm and 0.2 cm respectively. The intra-fraction overall mean error (M), SD of the systematic error (∑) and SD of the random error (σ) were 0.04 cm, 0.07 cm and 0.2 cm respectively. And the intra-beam SD variability was 0.07cm. Results showed that patients undergoing radiotherapy to left breast cancer are able to perform a stable and reproducible DIBH by using the SHRMD.