Development of a patient dose verification method that uses the transit dose measured with a glass dosimeter

Abstract

The present study aims to verify patient doses by using a glass dosimeter to measure the radiation penetrating patients during radiation therapy and developing an algorithm based thereon that can simply and accurately calculate the internal doses reserved by the patients. In this study, we developed the algorithm and, as a feasibility study for a clinical test, we verified its accuracy by using a solid water phantom. We developed an algorithm that measured the scatter factor, which represents the correlation between the bottom of the phantoms and the transit-dose measurement unit and calculates the center doses of the phantoms by using the inverse square law and percentage depth dose data. Also, we used a glass dosimeter to measure the transit radiation of 14 patients’ 3D conformal radiation therapy cases and predicted the internal doses of the phantoms by using the results. By comparing these values and those of actual measurements obtained from an ion chamber, we evaluated the accuracy of the developed algorithm. When the developed algorithm was applied for patient dose verification based on the transit doses to 14 patients’ 3D-CRT treatment, as measured using the ion chamber, the average deviation from the measurement values for the phantoms was 0.33% (±0.57%). Based on this result, we confirmed that the algorithm is correct. When the patient doses obtained using a glass dosimeter were verified in the same way, the average deviation was −0.28% (±1.87%). The algorithm for calculating patients’ internal doses based on transit radiation measurements was found to be accurate and is expected to be capable of simply verifying patient doses even when measuring with a glass dosimeter, despite an increased error to a certain degree.