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Objective:To provide a new morning check method for the output dose stability of the multileaf collimator (MLC) of the CyberKnife M6 (CK-M6) system.Methods:The CT images of a verification phantom with a size of 20 cm × 20 cm × 10 cm were transmitted into the Precision Treatment Plan ning System (ver. 1.1.1.1). The high-precision alignment between the accelerator output front and the fixed position of the phantom surface was achieved using the fiducial tracking method. A 10 cm × 10 cm radiation field was formed by the MLC and a DailyCheck plan with an output of 200 MU was designed. The repeatability, sensitivity, and accuracy of the DailyCheck plan were measured, and the CK-M6 system was continuously tested for one month using the artificial fixed method and the DailyCheck plan designed in this study. Results:The average and the standard deviation of 10 repeated measurements by the DailyCheck plan were 492.28 pC and 0.09, respectively, indicating good stability. There was a linear correlation between the measured values and the output dose, with a correlation coefficient of R2 > 0.999. Moreover, there was a position deviation of 2 mm between the phantom and the accelerator output front, and the result ant effect on the measured values was equivalent to a dose deviation caused by an output of 1.24 MU. The result from the continuous measurement of both the artificial fixed method and the DailyCheck plan fell within permissible limits, showing high consistency. Conclusions:The DailyCheck plan established through the fiducial tracking of a verification phantom can achieve the convenient, quick, and accurate daily detection of the output dose stability of the MLC of CK-M6. Therefore, this method can be widely applied in the clinical quality control of the CK-M6 system.
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Objective To evaluate the safety and effectiveness of ultra-hypofractionated stereotactic body radiotherapy in the treatment of prostate cancer.Methods A total of 26 patients with prostate cancer treated with Cyber-Knife from May 2010 to May 2018 were analyzed retrospectively.The median age of the patients was 69 years old (range,57 to 87).Ultra-hypofractionated radiotherapy was delivered in five fractions of 7.0-7.5 Gy for a total dose of 35.0-37.5 Gy.Androgen deprivation therapy (ADT) was administered in combination with the Cyber-Knife.The primary endpoints were radiation toxicity,PSA-response,local control and symptom alleviation,while the secondary endpoints were progression-free survival and overall survival.Results No graded ≥ 3 acute and late radiation toxicities occurred during follow-up.The acute toxicity of Grades 1 and 2 was 38.4％ and 19.2％,while the late toxicity of Grades 1 and 2 was 30.8％ and 3.8％,respectively.At a median follow-up of 22.44 months,for patients with localized stage,PSA level was decreased significantly after radiotherapy (Z =2.900,2.794,2.510,2.090,P＜0.05).However,there was no statistically significant difference for the metastatic group (P＞ 0.05).Conclusions Ultra-hypofractionated stereotactic body radiotherapy is a safe and effective treatment for patients with prostate cancer.
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Objective To compare the dosimetrics of the plan target volume (PTV) and organs at risk (OARs) between two treatment planning approaches for patients with multiple brain metastases from non-small cell lung cancer on CyberKnife.Methods 20 patients with multiple metastases from lung carcinoma were reviewed and analyzed,who had been treated by CyberKnife from December 2017 to December 2018.The CyberKnife stereotactic radiotherapy plans of the 20 cases were re-planed with single plan for multiple lesions and multiple plans per lesion.The dosimetry differences of PTV and OARs isodose disribution,conformity index (CI),total beam counts and total monitor units (MUs) were compared in the two types of plans.Results The two types of plans could satisfy over 95％ PTV coverage of the prescription dose.The maximum and mean dose of normal brain adjacent to the PTV were reduced in multiple plan approach effectively.Moreover,the maximum and mean dose of OARs (brainstem) dropped by 1.62％ and 5.57％ (t =1.09,P＜0.01) respectively.The number of treatment nodes and total MU declined by 4.63％ (t=1.87,P＜0.01) and 1.06％ in multiple plan approach,which could significantly shorten the clinical treatment time.The differences in CI index between these two types of plans was of no statistical significance.Conclusions For patients with multiple brain metastases of similar diameter and volume from non-small cell lung cancer to be treated on CyberKnife,multiple plans per lesion could not only reduce dose to normal brain tissue and OARs,but also improve the treatment efficiency.
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Objective@#To compare the dosimetrics of the plan target volume (PTV) and organs at risk (OARs) between two treatment planning approaches for patients with multiple brain metastases from non-small cell lung cancer on CyberKnife.@*Methods@#20 patients with multiple metastases from lung carcinoma were reviewed and analyzed, who had been treated by CyberKnife from December 2017 to December 2018. The CyberKnife stereotactic radiotherapy plans of the 20 cases were re-planed with single plan for multiple lesions and multiple plans per lesion. The dosimetry differences of PTV and OARs isodose disribution, conformity index (CI), total beam counts and total monitor units (MUs) were compared in the two types of plans.@*Results@#The two types of plans could satisfy over 95% PTV coverage of the prescription dose. The maximum and mean dose of normal brain adjacent to the PTV were reduced in multiple plan approach effectively. Moreover, the maximum and mean dose of OARs (brainstem) dropped by 1.62% and 5.57% (t=1.09, P<0.01) respectively. The number of treatment nodes and total MU declined by 4.63% (t=1.87, P<0.01)and 1.06% in multiple plan approach, which could significantly shorten the clinical treatment time. The differences in CI index between these two types of plans was of no statistical significance.@*Conclusions@#For patients with multiple brain metastases of similar diameter and volume from non-small cell lung cancer to be treated on CyberKnife, multiple plans per lesion could not only reduce dose to normal brain tissue and OARs, but also improve the treatment efficiency.
ABSTRACT
Objective To analyze the radiation dose to the normal lung tissue of patients with early stage of non-small cell lung cancer treated by Cyberknife. Methods A retrospective analysis was conducted by summarizing the treatment plans of 264 patients with early stage non-small cell lung cancer from January 2011 to December 2013 in Tianjin Medical University Cancer Institute and Hospital. Sorted by the tumor volumes and locations, the Cyberknife plans were evaluated by means of dose volume histograms ( DVH) , homogeneity indexes ( HI) , percentage volumes receiving at least x Gy ( Vx ) of dose, i. e. , V5 , V10 , V20 , and V30 of the ipsilateral and contralateral lungs. For the tumors approximate to the hilus, the contralateral lungs were included in the optimization process, and the dose-volume metrics were analyzed for the contralateral and bilateral lungs. Results For the tumors close to the chest wall, V5≥(15. 21 ± 3. 12)％ in ipsilateral lung tissue and V5≥(1. 34 ± 0. 67)％ in contralateral lung tissue were observed. For the tumors near the hilus, V5≥(39. 4 ± 11. 90) ％ in ipsilateral lung tissue and V5≥(1. 48 ± 0. 34) ％ in contralateral lung tissue were observed. The irradiated volume ratios of both ipsilateral and contralateral lung tissue increased with the enlargement of tumor sizes. After including the contralateral lung tissue into the optimization, the irradiated volume ratios of the contralateral and bilateral lung tissue (V5,V10) decreasedsignificantly(t=2.44,4.81,3.53,3.17,P<0.05). Conclusions Higherriskof radiation injury in both ipsilateral and contralateral lung tissue can be expected for tumors near the hilus than near the chest wall. After including contralateral lung tissue into the planning optimization, lower dose to the contralateral and whole lung tissue was achieved, indicating a better protection of normal lung tissue.