Dosimetric Study Of SIMRT,VMAT And TOMO In The Treatment Of Nasopharyngeal Carcinoma

Objective: Nasopharyngeal carcinoma(NPC)is one of the most common malignancies in China.Because of the pathological type of NPC,the specificity of biological behavior and anatomy,and the protection of adjacent organs,radiation therapy(Radiation Therapy,RT)is still the treatment of choice for non-far distant metastatic nasopharyngeal carcinoma.Under the demand of precision treatment,intensitymodulated radiation therapy(IMRT)has gradually replaced the previous radiation therapy technology into mainstream technology,and has been widely used in the clinical diagnosis and treatment of NPC.Currently used intensity modulated radiation therapy systems include: fixed field intensity radiation therapy(step and shot intensity modulated radiation therapy,sIMRT),volumetric rotational intensity modulated radiation therapy(VMAT)and spiral tonic intensity modulated radiation therapy system(Tomotherapy,TOMO).This study analyzed the dosimetric characteristics of sIMRT,VMAT and TOMO in the treatment of patients with nasopharyngeal carcinoma,and compared the advantages and disadvantages between the three,in the latest version of the UICC / AJCC staging system of the nose pharyngeal cancer,the difference is different.Direct evidence of nasopharyngeal patients providing optimal radiotherapy options.Methods: Ten patients with nasopharyngeal carcinoma treated by the Department of Thoracic Radiotherapy of Liaoning Provincial Cancer Hospital were selected from the initial diagnosis of pathologically clear and no distant metastasis.The radiotherapy plans of these 10 patients were sIMRT,VMAT and TOMO respectively.These three radiotherapy methods were retrospectively re-staged and re-planned.In order to avoid offset effects,the coverage of the planning target volume(PTV)of the three radiotherapy plans was standardized using the same level.Different types of dose-limiting references are also used in different categories of Organs at risk(OARs)according to the planned limit criteria.All radiotherapy plans are completed by the same qualified physicist.In this study,the Pinnacle treatment planning system and the TOMO treatment planning system were used to redesign the plans for sIMRT,VMAT,and TOMO,and the cumulative doses of PTV and OARs for the three radiotherapy plans were compared for three radiation treatment plans.The method's machine units(MU)are analyzed.Results: The sIMRT,VMAT,and TOMO programs had similar PTV coverage.Among them,in the stratified comparison of clinical stages,TOMO was superior to VMAT and sIMRT in the clinical phase III treatment plan,and in the clinical stage IV treatment plan TOMO and There is no significant difference between the VMATs.However,the TOMO scheme is optimal in terms of the stratification results of the T staging.For the statistical analysis of target comparison parameters,it is clear that for the treatment plan of stage III,TOMO is optimal,VMAT is second,and sIMRT is the worst;there is no significant difference between TOMO and VMAT in the clinical stage IV treatment plan.Regardless of the stratification results from clinical stage and T stage,TOMO can better protect the brainstem and spinal cord than sIMRT and VMAT,but there are advantages and disadvantages in the three specific treatment methods.For patients with locally advanced or large lesions,sIMRT does not recommend a first order compared to the other two.The machine hop count of the VMAT protocol(609±72.94)was shorter than the sIMRT protocol(792.8±75.25;P<0.05)and the TOMO protocol(7850.5±1312.63;P<0.05).Conclusion: Although sIMRT,VMAT and TOMO have similar PTV coverage,their advantages are not the same.TOMO and VMAT have better uniformity and conformity than sIMRT,and TOMO can better protect brainstem and spinal cord.But for patients who can't brake for a long time,VMAT is the best choice.For patients with locally advanced or large tumor lesions,sIMRT does not recommend a first order compared to the other two.This study demonstrates the dose distribution and trends of the three intensity-modulated radiotherapy plans in different structures,and more research is needed to further evaluate.