肝癌三维适形、静态调强与容积旋转调强放射治疗的剂量学研究

Dosimetric Comparison of 3DCRT,Static IMRT,and VMAT for Hepatocellular Carcinoma

【目的】比较三维适形放射治疗(3DCRT)、静态调强(sIMRT)和容积旋转调强(VMAT)技术在肝癌的剂量学差异,评价不同放疗技术的优劣性。【方法】选择20例行4DCT扫描的原发性肝右叶癌,为每例患者制定三套放疗计划:3DCRT、9野sIMRT和VMAT计划。处方剂量统一为50 Gy,分25次照射。比较不同计划的靶区和危及器官剂量学参数、加速器跳数(MU)以及治疗参数等。【结果】三组计划的Dmax无明显差异;IMRT和VMAT计划的靶区覆盖率、均匀性和适形性均显著优于3DCRT。三组计划的肝平均剂量分别为(20.5±4.5)Gy(3DCRT)、(21.1±3.8)Gy(IMRT)、(20.9±3.9)Gy(VMAT),肾脏、胃、小肠、脊髓的受照剂量差异不明显。3DCRT、IMRT、VMAT计划的MU分别为405±99、392±81、438±76(P=0.226),有效治疗时间分别为(2.1±0.2)min、(4.8±0.7)min、(3.0±0.2)min(P=0.000)。【结论】VMAT的剂量分布与IMRT相仿,可显著提高治疗效率。与3DCRT相比,IMRT和VMAT计划均可显著改善肝癌靶区的剂量覆盖,但在正常器官的保护方面并无明显优势。

[Objective] To compare the dose distribution between three-dimensional conformal radiotherapy （3DCRT）, static intensity-modulated radiotherapy （slMRT）, and volumetric modulated arc therapy （VMAT） for hepatocellular carcinoma. [ Methods ] The 4DCT scans of 20 patients with hepatocellular carcinoma in right lobe were selected for this comparative analysis. The 3DCRT, IMRT, and VMAT plans were prepared for each patient. Dose prescription was 50 Gy to the planning target volume （PTV） in 25 fractions. PTV dose coverage, organs at risk （OAR） doses, monitor units （MU）, and treatment delivery parameters were assessed. [ Results ] All three plans achieved comparable Dmax. Both VMAT and IMRT showed significantly better PTV coverage, conformity, and homogeneity than 3DCRT. The mean dose to normal liver was as follows： （20.5 ± 4.5） Gy for 3DCRT, （21.1± 3.8） Gy for IMRT, and （20.9 ± 3.9） Gy for VMAT. Comparable sparing of normal tissues including kidney, stomach, small intestine and spinal cord were achieved with all three plans. The number of MU/fraction was 405 ± 99 for 3DCRT, 392 ± 81 for IMRT, and 438± 76 for VMAT （P = 0.226）. Effective treatment times for 3DCRT, IMRT and VMAT were （2.1 ±0.2） min, （4.8 ±0.7） min, and （3.0 ±0.2） min, respectively （P= 0.000）. [Conclusion] VMAT improved delivery efficiency for equivalent dosimetric quality as IMRT. Compared with 3DCRT, IMRT and VMAT provided favorable tumor coverage, but both IMRT and VMAT were not superior to 3DCRT in terms of normal tissues protection.