Purpose: To determine a simplified formula to perform hand calculation of monitor unit (MU) for total body irradiation (TBI) for 6 MV photon beams. The formula provides a quick way for physicians, physicists, dosimetrists and therapists to perform a verification calculation for TBI treatment.Methods and Materials: Patient data (123 adult patients and 46 pediatric patients) were accumulated for TBI with 6 MV photon beams between September 2010 and February 2014. The dependence of MU on patient thickness was examined.Results: Among the 123 adult patients examined, the depth varied between 8 and 22.5 cm (mean and sd, 13.86 +/- 2.8 cm). Among the 46 pediatric patients examined, the depth varied between 6.75 and 17.5 cm (mean and sd, 9.22 +/- 1.89 cm). To deliver 200 cGy, the mean and standard deviation of MU*(100/SAD)2 is 94 +/- 7 and 85 +/- 4 for adult and pediatric patient respectively. By linear curve fitting, simplified equations between MU*(100/SAD)2 and patient depth were achieved. The equations are MU*(100/SAD)2 = 2.42 d + 60.2 and MU*(100/SAD)2 = 2.03 d + 60.0 for adult and pediatric patients respectively.Conclusion: Simplified equations between the MU*(100/SAD) 2 and the depth of the patient are concluded by data mining 169 patients in our facility. The equations can be used by the physicians, physicists, dosimetrists and therapists to perform quick verification calculations.
Wang, P,
The Variation of MU for Total Body Irradiation. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14042486.html
