Luzzara Marco, Santoro Luigi, Brown Kevin
Elekta AB, Stockholm, Sweden.
Istituto Europeo di Oncologia, Milano, Italy.
Phys Imaging Radiat Oncol. 2018 Mar 23;5:88-92. doi: 10.1016/j.phro.2018.03.005. eCollection 2018 Jan.
Several studies have investigated multi leaf collimator (MLC) leaf design. We performed a systematic review and meta-analysis of those studies to compare the impact of MLC leaf width used for different radiotherapy techniques.
We decided to focus on 2.5, 3.0 and 5.0 mm leaf width MLCs as it appeared to be the most contentious area from literature. We adopted Cochrane and PRISMA guidelines and computed the association between MLC leaf width and conformity index (CI) across the selected studies as pooled mean difference (PMD) with 95% confidence interval.
A total of 43 papers were selected from the literature search, of which ten compare MLC leaf width of 2.5 mm or 3.0 mm (MLC2.5 mm) versus 5.0 mm (MLC5 mm) in terms of CI. There was a slight, but significant, difference between MLC2.5 mm and MLC5 mm in favor of the former (mean difference -0.036; 95% confidence interval: -0.068 to -0.005). A subgroup analysis was performed by comparing techniques (intensity modulated radiation therapy vs conformal). In the intensity modulated radiation therapy (IMRT) subgroup, the difference between MLC2.5 mm and MLC5 mm appeared to be negligible (mean difference: -0.006; 95% confidence interval: -0.013 to 0.001) and not significantly different from zero. In the subgroup of studies which used conformal techniques, there was a significant difference between MLC2.5 mm and MLC5 mm (mean difference: -0.054; 95% confidence interval: -0.096 to -0.012).
Introduction of IMRT produced comparable target coverage (CI) between 2.5 or 5.0 mm leaf width MLCs.
多项研究对多叶准直器（MLC）的叶片设计进行了调查。我们对这些研究进行了系统评价和荟萃分析，以比较不同放疗技术中使用的MLC叶片宽度的影响。
鉴于文献中该领域争议最大，我们决定重点关注叶片宽度为2.5、3.0和5.0毫米的MLC。我们采用Cochrane和PRISMA指南，并计算所选研究中MLC叶片宽度与适形指数（CI）之间的关联，以合并均值差（PMD）及95%置信区间表示。
通过文献检索共筛选出43篇论文，其中10篇在CI方面比较了2.5毫米或3.0毫米叶片宽度的MLC（MLC2.5毫米）与5.0毫米叶片宽度的MLC（MLC5毫米）。MLC2.5毫米和MLC5毫米之间存在轻微但显著的差异，前者更具优势（均值差 -0.036；95%置信区间：-0.068至-0.005）。通过比较技术（调强放射治疗与适形放疗）进行了亚组分析。在调强放射治疗（IMRT）亚组中，MLC2.5毫米和MLC5毫米之间的差异似乎可以忽略不计（均值差：-0.006；95%置信区间：-0.013至0.001），且与零无显著差异。在使用适形技术的研究亚组中，MLC2.5毫米和MLC5毫米之间存在显著差异（均值差：-0.054；95%置信区间：-0.096至-0.012）。
调强放射治疗的引入使得叶片宽度为2.5或5.0毫米的MLC在靶区覆盖（CI）方面具有可比性。
