[Impact on reproducibility of the treatment position by improving immobilization device in image guided radiation therapy].

Abstract

The immobilization device for treatment becomes important to obtain fixation and reproducibility of the treatment position. It was confirmed that reproducibility of the treatment position obtains higher accuracy by the method of using immobilization device. Methods: We divided into three terms by the methods of immobilization. An infrared reflective marker performs the setup of a position at the start of treatment, and setup of the patient in a fixed implement is performed by ExacTrac. Difference between coordinates of the immobilization device and the patient position was calculated by the vector in three directions. We estimated the position error index (PE(index)) by using the square root of the sum of square of each vectors, and evaluated the amount of differences of patient position at three terms. Results: Mean and standard deviation of index values were 9.53 ± 7.21, 8.50 ± 5.93, and 6.42 ± 3.80 at each three terms. With every passing year, the amount of gap and difference of the patient fixation has decreased. Conclusion: By the improvement of the use of the immobilization device, gap and difference of fixation has decreased. Accordingly, we could obtain better accuracy of fixation.