Dose Verification Of Monaco Radiotherapy Treatment Planning System

In the process of tumor radiotherapy treatment,planning is an important part of the connection between the disease diagnosis and implementation of treatment.Along with the rapid development of computer technology,the designing method of treatment plan by the original manual dose calculation has become the automatic optimization process depending on a computer system.But the Treatment Planning System(TPS)is to simulate the process of radiation entering into human body from the linac,and different from the actual dose the patient absorbed.In order to make the patient get the ideal treatment,it is very necessary to verify the accuracy of TPS dose calculation results.And the Elekta medical system is using Mosaiq to connect to the accelerator,the integration and stability of the process also need to check.In 2015,the American Association Physicists Medicine(AAPM)released the fifth practical guideline(Medical Physics Practice Guideline 5.a.,MPPG5)to help physics to complete the commissioning and QA of treatment planning dose calculation.In this paper,we combine the AAPM MPPG5 report and clinical practice to sum up a set of suitable test to verify the accuracy of the Monaco TPS dose calculation for 6MV.Firstly,we carry out the multileaf collimator(Multileaf,MLC)parameters testing.The test is provided by Elekta company named of "ExpressQAPlan".We use it to test the Transmission Probability Filter(TPF)which simulate the jaw and MLC of the linac.We've found that Leaf Transmission and Leaf Offset is very sensitive to dose calculation.Improving the Leaf Transmission and Leaf Offset value can increase the ability of ray through the MLC,making TPS dose improving.Although the effect of Leaf Transmission on the penumbra area is clear,and the influence of Leaf Offset on high dose low gradient area is larger,but any of the two parameters will influence each other.So after comprehensive consideration,the Leaf Transmission value is changed from 0.0050 to 0.0055,the Leaf Offset from 0.12 mm to 0.09 mm.Secondly,we verify the pre-test patient plan.Before the complete test of TPS,in order to guarantee the accuracy of the clinical treatment process,we select a rectal cancer case and design the planning with step&shoot(SS),sliding window(SW),Volumetric Modulated Arc Therapy(VMAT)and then test them with linac and phantom.The point dose deviation in solid water is within 1.5%for SS,SW,VMAT,The result of Mapcheck2 and Arccheck measurement is over 90%for 2 mm/2%and more than 95%for 3 mm/3%.Finally,we use the recommended test of AAPM MPPG5 combining with clinical.practice to complete the accuracy of TPS dose calculation.This part include TPS model test,basic dose algorithm validation,heterogeneity correction validation and advanced technique dose validation.In advanced technique dose validation,we introduce the AAPM TG 119 tests,and calculate the confidence limits,and then compare with recommended value in the TG119.After a series of tests and parameters adjustment,we make every test results within the scope of the recommended value,so as to complete the Monaco TPS dose calculation accuracy validation.