Comparison of RapidArc and Static Gantry Intensity-modulated Radiotherapy for Nasopharyngeal Carcinoma

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WK Cheung, KH Lee, HC Cheng, CH Cheung, CL Chan, KC Ngan

Hong Kong J Radiol 2010;13:125-32

Objective: RapidArc (Varian Medical Systems, Palo Alto, CA) is a new volumetric-modulated arc radiotherapy technique with continuous modulation of gantry speed, dose rate, and multileaf collimator shape. Taking advantages of dose painting capabilities along with rotational delivery, RapidArc has shown promise in the treatment of a wide range of tumours, including intracranial, head and neck, prostate, and endometrial cancers. However, supportive data on RapidArc therapy for nasopharyngeal carcinoma are scanty. In this study, comparison of the quality of a treatment plan and efficiency of radiation delivery by RapidArc and intensitymodulated radiotherapy for nasopharyngeal carcinoma was evaluated.

Methods: Datasets of 3 nasopharyngeal carcinoma patients were used to design both RapidArc and intensitymodulated radiotherapy plans. Results were analysed in terms of dose distribution and dose-volume histograms.

Results: For all patients, RapidArc plans provided a comparable homogeneity index and adequate organs-atrisk sparing relative to intensity-modulated radiotherapy plans. In terms of target dose conformity, the conformity index favoured intensity-modulated radiotherapy, especially for higher dose targets using a simultaneous integrated boost approach.

Conclusion: Taken together, our preliminary experience in dose optimisation with RapidArc for radiation treatment of nasopharyngeal carcinoma was able to deliver reasonable treatment plans. Development of a sophisticated planning system with a quick optimisation algorithm and adjustable level of modulation appears crucial to take full advantage of RapidArc technology. With the ever-increasing complexity of RapidArc treatment planning and delivery, further parallel efforts in optimising quality assurance are warranted.





目的:快速旋轉強度調控放射治療 (RapidArc) 是一種新容量式的調控旋轉放射治療技術,在旋轉的 過程中不斷對機架速度、放射劑率及葉式準直儀作出調控。通過轉圈及調控放射劑率,快速旋轉強 度調控放射治療已被認為是對醫治多種癌症頗有療效的一項技術,包括顱內、頭頸、前列腺及子宮 內膜的腫瘤。然而,快速旋轉強度調控放射治療技術在鼻咽癌治療方面的數據並不足夠。在本研究 中,我們比較了快速旋轉強度調控放射治療及強度調控放射治療對鼻咽癌的治療計劃及放射效果。

方法:把三名鼻咽癌患者的數據用作設計快速旋轉強度調控放射治療計劃及強度調控放射治療計 劃,利用放射劑量分佈及劑量體積直方圖來分析結果。

結果:對於三位患者,快速旋轉強度調控放射治療提供了與強度調控放射治療相約的劑量均勻指數 及對危及器官的劑量有足夠的減緩。目標劑量適形方面,強度調控放射治療的適形指數較佳,尤其 是在同步加量的高量區下。

結論:我們的初步經驗顯示快速旋轉強度調控放射治療有助為鼻咽癌提供合理的治療設計。要發揮 快速旋轉強度調控放射治療的最佳效果,需要發展一套有快速優化算法及可調節調控水平的完善系 統。隨著快速旋轉強度調控放射治療技術的複雜性不斷提高,優化質量保證也需同步進行。