Okoukoni Catherine, Lynch Sarah K, McTyre Emory R, Randolph David M, Weaver Ashley A, Blackstock A William, Lally Brian E, Munley Michael T, Willey Jeffrey S
Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, USA; Department of Biomedical Engineering, Wake Forest School of Medicine, Winston-Salem, USA.
Department of Biomedical Engineering, Wake Forest School of Medicine, Winston-Salem, USA; Virginia Tech-Wake Forest University Center for Injury Biomechanics, Winston-Salem, USA.
Radiother Oncol. 2016 Jun;119(3):449-53. doi: 10.1016/j.radonc.2016.03.023. Epub 2016 Apr 9.
High rates of spontaneous rib fractures are associated with thoracic stereotactic body radiation therapy (SBRT). These fractures likely originate within the cortical bone and relate to the cortical thickness (Ct.Th). We report the development and application of a novel Ct.Th and radiation dose mapping technique to assess early site-specific changes of cortical bone in ribs.
Rib Ct.Th maps were constructed from pre-SBRT and 3month post-SBRT CT scans for 28 patients treated for peripheral lung lesions. The Ct.Th at approximately 50,000 homologous points within the entire rib cage was determined pre- and post-SBRT. Each rib was then divided into 30 homologous regions. The mean dose and thinning were determined per section.
Regions of ribs that received ⩾10Gy exhibited significant thinning of cortical bone (p=0.001). The mean Ct.Th percent difference (95% CI) in regions receiving 10-20Gy, 20-30Gy, 30-40Gy, and ⩾40Gy were -7% (-4%,-11%), -14% (-18%,-11%), -15% (-19%,-11%), and -18% (-22%,-15%) respectively. Regions receiving >20Gy experienced significantly more thinning than regions receiving lower doses.
Substantial early cortical bone thinning was observed post-SBRT in regions of ribs that received ⩾10Gy. The rapid thinning of ribs may predispose ribs to fracture after SBRT.
自发性肋骨骨折的高发生率与胸部立体定向体部放射治疗（SBRT）相关。这些骨折可能起源于皮质骨，并与皮质厚度（Ct.Th）有关。我们报告了一种新型的Ct.Th和放射剂量映射技术的开发与应用，以评估肋骨皮质骨早期特定部位的变化。
对28例接受外周肺病变治疗的患者，在SBRT前和SBRT后3个月的CT扫描中构建肋骨Ct.Th图。在SBRT前后确定整个胸廓内约50,000个同源点的Ct.Th。然后将每根肋骨分为30个同源区域。确定每个区域的平均剂量和变薄情况。
接受≥10Gy照射的肋骨区域显示皮质骨明显变薄（p = 0.001）。接受10 - 20Gy、20 - 30Gy、30 - 40Gy和≥40Gy照射区域的平均Ct.Th百分比差异（95% CI）分别为-7%（-4%，-11%）、-14%（-18%，-11%）、-15%（-19%，-11%）和-18%（-22%，-15%）。接受>20Gy照射的区域比接受较低剂量照射的区域变薄更明显。
在接受≥10Gy照射的肋骨区域，SBRT后观察到早期皮质骨显著变薄。肋骨的快速变薄可能使肋骨在SBRT后易发生骨折。
