Comparative Study On Physical Dose Verification Of Intensity Modulated Radiotherapy

With the rapid development of applied physics and computer science,the advances of many medical fields increasingly depend on their accuracy.In particular,the safety and efficacy of radiotherapy(RT)are knowingly and significantly associated with the dosage delivery quality in term of its magnitude and volume.At present,the intensity modulated radiation therapy(IMRT)new technology is widely used in China and demands higher accuracy of dose delivery and verification.The objectives of this study was to compare the features of three RT dose verification methods or devices and identify the factors associating with the dose delivery accuracy.We randomly selected 20 patients whose IMRT plans were designed to target their head & neck,chest,and abdomen tumors.Then,we conducted three sets of dose measurements-1-deminensioanl(D),2-D,and 3-D ones-for each IMRT plan.First,we used the ionization chamber and Matrixx 2-D matrix for the absolute dose measurement and their comparison.Second,we used the film and Matrixx 2-D matrix methods while all field angles were set at zero for their relative error comparison.Third,we used the 3-D measurement and calculation methods of using the Pinnacle treatment system,Delta4 data collection technology,and Monte Carlo simulation method.Afterward,we conducted the pair-wise comparisons of all results above.In sum,we selected 80 patients with IMRT,including the 20 patients above,for the parameter analyses.The study results showed that compared to Matrixx,the ionization chamber absolute dose measurement was closer to the planned value and more stable but disadvantaged at its higher sensitivity to smaller volumes of subfields.However,the Matrixx method is comparable in term of the overall relative measurement error.There was no significant result differences of using 2-D film and Matrixx methods although the film is knowingly susceptible to environmental factors.Also,there were no difference of results from three3-D methods-the Pinnacle calculation and the Delta4 as well as the Monte Carlo simulation.We concluded that the Delta4 is high reliable for 3-D dose verification measurement and the RT field parameters should be carefully considered given that they are closely associated with dose verification measurements...