Fenglei Du

Objective:This study aims to compare the dosimetric calculationsin standard non-small cell lung cancer (NSCLC) radiotherapy planningusing the Collapsed Cone (CC) algorithm of the RayStation planningsystem on the Varian Halcyon accelerator, with the Analytical AnisotropicAlgorithm (AAA) and Acuros XB algorithms on the Eclipse accelerator.Methods:The RayStation planning system was employed to designthe RapidArc radiotherapy plans for 15 lung cancer patients on theHalcyon accelerator, using the CC algorithm for dose calculation.The plans were then transferred to the Eclipse planning system. Withoutmaking any changes to these plans, doses were computed using bothAAA and Acuros XB algorithms. The differences in dose-volume indicesfor the clinical target volume (CTV), planned target volume (PTV),and other organs at risk were evaluated.Results:Compared with the CC algorithm, the AAA algorithmshowed slightly lower dose-volume indices for both the CTV (D2%,D50%, D95%, D98%, and mean dose) and the PTV (D2%, D50%, andmean dose), with differences within 1%. Specifically, the PTV's D95%and D98% were respectively 1.7% and 2.4% lower, the heart's meandose was 3.2% lower, the lung's V20Gy was 0.2% lower, the averagedose was 0.2% higher, and the spinal cord's maximum dose (representedby D0.1cc) was 0.9% lower. In contrast to the CC algorithm, the AcurosXB algorithm also showed slightly lower dose-volume indices for theCTV and the PTV, with differences within 1.5%. Specifically, thePTV's D95% and D98% were respectively 1.6% and 2.3% lower, theheart's mean dose was 4.4% lower, the lung's V20Gy was 0.3% lower,the average dose was 1.4% lower, and the spinal cord's maximum dosewas 2.3% lower. Paired t-tests indicated that all these results hadsignificant differences (p∼3% lower. The results of this study can serve as a reference for institutionsthat are preparing to use the RayStation planning system for the designand clinical application of plans on the Varian Halcyon accelerator.

Background: Radiotherapy (RT) is the primary treatment for nasopharyngeal carcinoma (NPC). However, it can cause implicit RT-induced injury by irradiating normal brain tissue. To date, there have been no detailed reports on the radiated exact location in the brain, the corresponding radiation dose, and their relationship.Methods: We analyzed 803 Chinese NPC patients treated with RT and used a CT brain template in a Montreal Neurological Institute (MNI) space to compare the group differences in RT dose distribution for different RT technologies (IMRT or VMAT).Results: Brain regions that received high doses (>50 Gy) of radiation were mainly located in parts of the temporal and limbic lobes, where radioactive damage often occurs. Brain regions that accepted higher doses with IMRT were mainly located near the anterior region of the nasopharyngeal tumor, while brain regions that accepted higher doses with VMAT were mainly located near the posterior region of the tumor. No significant difference was detected between IMRT and VMAT for T1 stage patients. For T2 stage patients, differences were widely distributed, with VMAT showing a significant dose advantage in protecting the normal brain tissue. For T3 stage patients, VMAT showed an advantage in the superior temporal gyrus and limbic lobe, while IMRT showed an advantage in the posterior cerebellum. For T4 stage patients, VMAT showed a disadvantage in protecting the normal brain tissue. These results indicate that IMRT and VMAT have their own advantages in sparing different organs at risk (OARs) in the brain for different T stages of NPC patients treated with RT.Conclusion: Our approach for analyzing dosimetric characteristics in a standard MNI space for Chinese NPC patients provides greater convenience in toxicity and dosimetry analysis with superior localization accuracy. Using this method, we found interesting differences from previous reports: VMAT showed a disadvantage in protecting the normal brain tissue for T4 stage NPC patients.