SU-F-T-535: An Android App and Windows Executable with GUI for the Monitor Unit Calculation in KV X-Ray Therapy




We created two applications, one for use on Android and one for use on Windows, to carry out monitor unit (MU) calculations. These applications carried out these long calculations quickly, while avoiding the potential for human error.


A general formula for calculating MU for an orthovoltage x-ray machine was used and implemented in two programs created for Android and Windows. The formula relies on the prescribed dose and fractionation. Other values the formula relies upon are relative exposure factor (REF) and backscatter factor (BSF). These factors are specific to each unit and head in use, and are measured and tabulated prior to use. In the case of a BSF not falling on already known values, the programs were made to automatically use linear interpolation to find an appropriate BSF. The programs also allow for a stand-off correction, calculated using the inverse-square law, and an attenuator value that can be arbitrarily input by the user.


The two programs were built using C#, and use essentially the same types of backends to do their calculations. Differences in the programs are mainly in the graphical user interfaces. The backend was made to mimic the way a human does the same calculations. Previously measured REF and BSF tables for three different x-ray energies and field size types were loaded into the program beforehand for testing. Both applications were easy to use, and produced the exact same results in all situations. These results matched the same calculations done by hand. Differences were only found when hand calculations use shortcuts to find BSF values that lie outside of the pre-measured values.


Our programs can efficiently and effectively calculate MU as well as or better than by hand. The Android version can be useful in the future for emergency situations.