The Verification of the Monitor Unit Calculations
*Duong Thanh Tai1,2, Truong Thiet Dung1 and Nguyen van Hai3
1Department of Radiation Oncology, Dong Nai General Hospital, Vietnam
2Faculty of Physics & Engineering physics, University of Science, Vietnam
3Dalat Vocational training College, Vietnam
Submission: January 05, 2017; Revised: January 25, 2017;
Accepted: February 10, 2017; Published: March 06, 2017
*Corresponding author: Mr. Duong Thanh Tai, Full postal address: Department of Radiation Oncology, Dong Nai General Hospital, 810000 Bien Hoa, Vietnam, Tel:+84945569139;Email:thanhtai_phys@yahoo.com
How to cite this article: Duong T T, Truong T D, Nguyen v H, The Verification of the Monitor Unit Calculations. Canc Therapy & Oncol Int J. 2017; 3(4): 555616. DOI: 10.19080/CTOIJ.2017.03.555616
Abstract
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
Introduction
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 [1]. 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.
Materials and Methods
Treatment planning
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).
A ‘‘hand’’ Calculations
The monitor units are verified using Microsoft office excel 2010 program which have the formalism described by Khan [2-5]. A general equation describing this calculation is as follows:
D: Prescription dose
X: the number of MU TPS calculations
a: the number of MU a ‘‘hand’’ calculations
Results and Discussion
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).
Case 1: Plan of rectum cancer
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.
conclusion
The MU verification calculation should be performed before treatment by an independent physicist. Our calculation showed that 3D-CRT treatment plans were accurate for treatment delivery.
References
- Jackson Chan, Comparison of monitor unit calculations performed with a 3D computerized planning system and independent ‘‘hand’’ calculations: Results of three years clinical experience, Department of Medical Physics, Hamilton Regional Cancer Centre, 699 Concession St., Hamilton, Ontario, Canada L8V 5C2, 2002.
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- W.P.M. Mayles (1999) Physics Aspects of Quality Control in Radiotherapy, Institute of Physics and Engineering Medicine.
- Prowess, Prowess Panther User Manual, 2013.
- Georg D, Nyholm T, Olofsson J, Kjaer-Kristoffersen F, Schnekenburger B, Winkler P, et al. (2007) Clinical evaluation of monitor unit software and the application of action levels. Radiother Oncol 85(2): 306-315.