Purpose: uRT-Linac 506C, designed and produced by UIH, is the first computerized tomography imaging guided linear accelerator in the world. This study aims to compare the dosimetric parameters of treatment plans designed on Varian Eclipse v13.5 TPS of Varian IX linac and uRT-TPS of uRT-Linac 506C respectively, in condition of intensity-modulated radiation therapy (IMRT).
Method: In this retrospective study, 10 patients with gastric cancer were involved and planned with Varian Eclipse v13.5 TPS and uRT-TPS for IMRT treatment, respectively. All treatment plans were made by the same experienced physicist and were clinically acceptable. To effectively compare the quality of the treatment plans, dosimetry parameters of planing target volume (PTV) andorgans at risk (OARs), and monitoring unit (MU) efficiency are included in the comparison. Quality assurance process were performed to evaluate the delivery accuracy of the accelerator systems with gamma-index parameters.
Result: In terms of dose conformity and coverage of target volume, uRT-TPS (CI =0.89 ± 0.01, HI = 1.04 ± 0.00) was superior to Varian Eclipse TPS (CI =0.87 ± 0.03, HI = 1.06 ± 0.01). The same was the parameter of V45/%, Varian Eclipse TPS equal to 96.40 ± 1.65 and uRT-TPS equal to 97.82 ± 0.78. These differences are statistically significant (PCI = 0.047, PHI = 0.005, PV45 =0.005). Concerning the left kidney, the Dmax of Varian Eclipse TPS was significantly lower than that of uRT-TPS (4132.60±730.54 cGy VS 4291.00±667.99 cGy, PDmax =0.009). However, the Dmean, V10 and V20 of Varian Eclipse TPS (Dmean=807.80±173.21 cGy; V10=23.09%±7.61%; V20=8.77%±5.22%) were significantly higher than uRT-TPS (Dmean=733.90±136.54 cGy, V10 = 20.67%±6.67%; V20=6.30%±3.72%), with the P values of 0.005; 0.022 and 0.017 respectively. For the right kidney, the Dmean and V5 of Varian Eclipse TPS (Dmean=755.00±176.69 cGy; V5=49.03%±8.66%) were significantly higher than that of uRT-TPS (Dmean=687.20±150.94 cGy; V5=45.27%±10.07%), with the P values of 0.009 and 0.047 respectively. As for liver’s Dmax and V5, these of Varian Eclipse TPS (Dmax=4915.40±80.85 cGy; V5=88.47%±4.27%) were significantly higher than those of uRT-TPS (Dmax=4822.90±35.96 cGy; V5=84.90%±5.77%), with the P values of 0.017 and 0.022 respectively.
All uRT - linac 506c treatment plans were recognized as clinically acceptable and had statistically better OAR sparing with higher delivery efficiency. The dose parameters of some target areas and organs at risk of URT-TPS are better than Varian eclipse TPS.