Feasibility of Two-Dimensional Radiation Dose Distribution Simulation Through Ultrasound Tracking of Respiratory Motion

Abstract

This study applied an ultrasound image tracking algorithm (UITA) for tracking respiration and developed a 2D dose distribution simulation program (DDSP) for simulating a dose distribution map. We evaluated the feasibility of a 2D respiratory motion simulation system combined with the UITA during radiotherapy for tracking respiration. The recorded respiration signals were input to the DDSP to generate a simulated dose distribution map and verify the effectiveness of the Gafchromic Film EBT3 (EBT3 film) as a measured dose distribution map (MDDM), to validate the DDSP. A radiation dose was delivered to EBT3 film and the film response was quantified using the isodose area rate (IAR), average dose rate within the field (ADFR), conformity index rate (CIR), and gamma passing rate. The tracking performance was evaluated by calculating the root mean squared error (RMSE). The calculated RMSEs were 1.67–5.34 and 0.42–2.53 mm in superior–inferior and right–left directions, respectively. The ADFR was 0.93–1.21 and the IARs at 20, 50, 70, and 80% were 0.87–1.29, 0.84–1.16, 0.79–1.61, and 0.48–6.64, respectively. The CIRs at 50, 70, and 80% were 0.87–1.23, 0.84–1.29, and 0.81–4.40, respectively. The human respiration patterns exhibited a 3%/3 mm gamma passing rate of 76.56–96.94%. This study successfully used an ultrasound imaging system to capture human respiration signals and transmit them to the DDSP for simulating radiation dose distributions, thus demonstrating the feasibility of the system.