Development of monitor unit calculation program for integration with radiation therapy information system

Introduction: Monitor unit (MU) calculation is the main process of 2D technique teletherapy planning. Using of monitor unit calculation program will increase the performance and reduce errors of 2D technique teletherapy. Objectives: To develop a monitor unit (MU) calculation program for integration with an in-house radiation therapy information system (RTIS). The developed program was used for 6 MV photon MU calculation in 2D technique teletherapy. Materials and methods: MU calculation program was based on the Clarkson’s integration method and divided into two parts. The first part was for scatter sector radius determination from 2D simulation images. This part was programmed based on JAVA language. The second part was MU calculation using Clarkson’s irregular field method. The latter part was programmed based on Microsoft Visual Foxpro language. Calculated MU was verified by dose measurement following the test cases (1a, 1b, 1c, 2a, 2b and 7) of IAEA TECDOC 1540. After dose difference between the calculation and the measurement was within acceptance criteria, the program was integrated to the RTIS. Results: The scatter sector radius determination program workflow included selecting of the angle between each radius, calibrating of image distance, defining of isocenter, field size edge defining and equivalent square field. The program generated radius distance and exported to a text file. The MU calculation part workflow included input of prescription dose and tumor depth. Following TECDOC 1540, dose different ranging between calculation and measurement was -1.98% to 1.40% for Test case 1a, 1b, 1c, 2a and 2b, and -3.02% to 0.08% for Test case 7. The program was integrated to dosimetry menu in RTIS which could help calculate MU for each field size of each patient and record to patient database. Conclusion: MU calculation computer program was developed, verified and integrated to RTIS. The program was used for 6 MV photon monitor unit calculation in 2D technique irradiation.