A comparison of the monitor unit calculations between a commercial treatment planning system (TPS) and ‘‘hand’’ calculations is extremely important in radiation therapy. In this paper, we will recalculate MU of the 3D-CRT plan for Lung and Rectal cancer on the treatment planning system supplied by Prowess Panther 4.6 at Dong Nai General Hospital, Vietnam. The monitor unit of each beams was recalculate by ‘‘hand’’ calculations and compared TPS. In general excellent overall agreement was found between calculations performed with the TPS and “hand” calculations. The MU difference between the monitor unit calculations of TPS and ‘‘hand’’ calculation was 0.144% with a standard deviation of 0.051% for rectal patients and 0.027 with a standard deviation of 0.008% for Lung patients. The result shows that there were no significant differences between recalculation and TPS.
Keywords: Linear Accelerator (LINAC); Monitor Unit Calculations; 3D-CRT
Now a day, there are many accidents occur in radiotherapy because error in monitor unit calculations of TPS. In order to prevent accidents in radiotherapy, the monitor unit recalculations are a prerequisite component of quality assurance (QA) in radiation therapy. Because errors and large uncertainties in dose calculations reduce the quality of a treatment, MU recalculations have been recommended as a routine quality assurance (QA) procedure when verifying individual treatment plans . Even though the validity of the calculation algorithms can be passed during the commissioning of a TPS, verification of the monitor units calculated by the TPS is typically performed using a ‘‘hand’’ calculation based all of standard beam data. In this paper we present a comparison of the monitor unit calculations of our planning system, panther 4.6 (Prowess Inc.) with ‘‘hand’’ calculations for Lung and Rectal cancer of clinical cases. The purpose of study was to evaluate the accuracy of a commercial radiation treatment planning systems.
Lung and Rectal cancer is commonly seen in Vietnam. A plan was completed by a physicist, including an evaluation of the dose distributions and dose-volume histogram (DVH). All plans were created with a high energy level of 15MV photon (Primus, Siemens). The monitor units calculated using our treatment planning system, Prowess panther 4.6, are delivered for treatment (Figure 1).
We analyzed these values for two common treatment sites.
This verification is traditionally based on manual monitor unit
(MU) calculation methods for 3D conformal radiotherapy (3D
CRT) treatments. Tables 2 and 3 summarizes the average MU
difference differences between the prowess panther and a hand
calculation (equation 1).
A plan was completed by a physicist, including an evaluation
of MU. All plans were created with a high energy level of 15MV
photon (Primus, Siemens). The number of beams and beam
angles were 00, 900, 1800, and 2700 (Figures 2 & 3)(Table 2).
The results of this investigation show that the percentage
difference is not significant. There isn’t error in MU calculation
of Prowess panther (Figures 4 & 5).
In general good agreement was found between calculations
performed with the different TPSs and hand calculation.