Calugaru Emel, Whiting Zachary, Delacruz Brandon, Ma Daniel, Garcia Barbara, Goenka Anuj, Chang Jenghwa
Radiation Medicine Department, Northwell Health, New Hyde Park, New York 11042, USA.
Department of Physics and Astronomy, Hofstra University, Hempstead, New York 11549, USA.
Med Dosim. 2023;48(1):31-36. doi: 10.1016/j.meddos.2022.09.006. Epub 2022 Dec 8.
The purpose of this study was to directly compare the plan quality of Gamma Knife (GK) (Elekta, Stockholm, Sweden)- vs linear accelerator (LINAC)-based delivery techniques for fractionated stereotactic radiotherapy (fSRT) of large brain metastases. Eighteen patients with clinical target volumes (CTVs) larger than 9.5 cc were selected to generate comparative plans for the prescription dose of 9 Gy × 3 fractions, utilizing the Eclipse (Varian, Palo Alto, US) vs Leksell GammaPlan (LGP) (Elekta, Stockholm, Sweden) treatment planning systems (TPS). Each GK plan was first developed using LGP's automatic planning, followed by manual adjustments/refinements. The same MRI and structures, including CTVs and organs at risk, were then DICOM-transferred to the Eclipse TPS. Volumetric Modulated Arc Therapy (VMAT) and Dynamic Conformal Arc (DCA) plans for a Truebeam, with high-definition multi-leaf collimators (MLCs), were developed on these MR images and structures using a single isocenter and 3 non-coplanar arcs. No planning target volume (PTV) margins were added, and no heterogeneity correction was used for either TPS. GK plans were prescribed to the 50% isodose line, and Eclipse VMAT and DCA plans allowed a maximum dose up to 170% and ∼125%, respectively. Gradient index (GI), Paddick Conformity Index (PCI), VRind, and VRind of all 3 techniques were calculated and compared. One-way analysis of variance (ANOVA) was performed to determine the statistical significance of the differences of these planning indices for the 3 planning techniques. A total of eighteen treatment targets were analyzed. Median CTV volume was 14.4 cc (range 9.5 cc - 55.9 cc). Mean ± standard deviation of PCI were 0.85 ± 0.03, 0.90 ± 0.03, and 0.72 ± 0.11 for GK, VMAT and DCA plans, respectively. They were respectively 2.64 ± 0.17, 2.46 ± 0.18, and 2.83 ± 0.48 for GI; 15.33 ± 8.45 cc, 10.47 ± 4.32 cc and 23.51 ± 16 cc for VRind; and 316.28 ± 138.35 cc, 317.81 ± 108.21 cc, and 394.85 ± 142.16 cc for VRind. The differences were statistically significant with p < 0.01 for all indices, except for VRind (p > 0.129). In conclusion, a direct dosimetric comparison using the same MRI scan and contours was performed to evaluate the plan quality of various fSRT delivery techniques for CTV > 9.5 cc. LINAC VMAT plans provided the best dosimetric outcome in regard to PCI, GI, and VRind. GK outcomes were similar to LINAC VMAT plans while LINAC DCA outcomes were significantly worse. Even though GK has a smaller physical penumbra, LINAC VMAT outperformed GK in this study due to enhanced penumbra sharpening and better beam optimization.
本研究的目的是直接比较伽玛刀(GK)(瑞典斯德哥尔摩医科达公司)与直线加速器(LINAC)为基础的大体积脑转移瘤分次立体定向放射治疗(fSRT)的计划质量。选取18例临床靶体积(CTV)大于9.5 cc的患者,使用瓦里安公司(美国帕洛阿尔托)的Eclipse治疗计划系统(TPS)与医科达公司(瑞典斯德哥尔摩)的Leksell伽玛计划(LGP)TPS,针对9 Gy×3次分割的处方剂量生成对比计划。每个GK计划首先使用LGP的自动计划生成,随后进行手动调整/优化。然后将相同的MRI图像和结构,包括CTV和危及器官,通过DICOM格式传输到Eclipse TPS。在这些MR图像和结构上,使用单个等中心和3个非共面弧,为配备高清多叶准直器(MLC)的Truebeam直线加速器制定容积调强弧形放疗(VMAT)和动态适形弧形放疗(DCA)计划。未添加计划靶体积(PTV)边界,且两种TPS均未使用不均匀性校正。GK计划处方剂量至50%等剂量线,Eclipse VMAT和DCA计划允许的最大剂量分别高达170%和~125%。计算并比较了所有3种技术的梯度指数(GI)、帕迪克适形指数(PCI)、VRind和VRind。进行单因素方差分析(ANOVA)以确定这3种计划技术的这些计划指标差异的统计学意义。共分析了18个治疗靶区。CTV体积中位数为14.4 cc(范围9.5 cc - 55.9 cc)。GK、VMAT和DCA计划的PCI均值±标准差分别为0.85±0.03、0.90±0.03和0.72±0.11。GI分别为2.64±0.17、2.46±0.18和2.83±0.48;VRind分别为15.33±8.45 cc、10.47±4.32 cc和23.51±16 cc;VRind分别为316.28±138.35 cc、317.81±108.21 cc和394.85±14,2.16 cc。除VRind外(p>0.129),所有指标的差异均具有统计学意义(p<0.01)。总之,使用相同的MRI扫描和轮廓进行了直接剂量学比较,以评估CTV>9.5 cc的各种fSRT递送技术的计划质量。就PCI、GI和VRind而言,直线加速器VMAT计划提供了最佳的剂量学结果。GK的结果与直线加速器VMAT计划相似,而直线加速器DCA的结果明显更差。尽管GK的物理半值层较小,但由于半值层锐化增强和束流优化更好,在本研究中直线加速器VMAT的表现优于GK。