摘要
目的了解人体前胸矢状面倾斜度的大小及对放疗剂量分布的影响.方法选择126例患者行胸部CT扫描并予正中矢状面重建.分别测定上中下胸廓层面前后体表中线至脊髓距离及各层上下间距,计算出前胸倾斜度.查TMR表得出中平面深度及脊髓深度处上中胸及中下胸层面剂量误差.结果前野各层面至脊髓距离变化较大,后野变化较小.人体前胸倾斜度范围为25～56°.上中胸段组的上下缘剂量误差较大,躯体中平面平均相差8%,脊髓17%.中下胸段组剂量误差较小,躯体中平面4%,脊髓7%.误差随倾斜角度增加而增加.根据倾斜度得出合适的楔形板修正角度大约为10～35°.结论人体前胸矢状面存在自然倾斜度,这种倾斜影响前野剂量分布,应予以个体化修正.建议根据角度的大小选择合适的头足向楔形板优化.
Objective To measure the inclination in the thorax as a gradient on sngittal plane and evaluate its significance for dose distribution. Methods 126 patients＇ chest CT images were obtained and reconstructed on middle the sngittal plane. The transverse plane at suprasternal notch, carina and the end of xiphisternum were chosen to represent the upper, middle and lower thoracic plane. The distance of each plane between anterior/posterior midline and spinal cord, the distance between each representative planes were measured respectively. The anterior thoracic gradient was then calculated according to these data. The difference of tissue maximum ratio （TMR） at the center of anterior-posterior parallel field and spinal cord between each representative plane was calculated according to a standard 10 cm × 10 cm field. Results The distance between anterior midline and spinal cord of each plane changed obviously, whereas the distance between posterior body midline and spinal cord changed less. The range of anterior thoracic gradient was 25° to 56°. The difference of TMR between upper and middle plane was 8% at the center of anterior-posterior field and 7% at the spinal cord, whereas the value between the middle and lower plane was 4% and 7%. The difference became more apparent while the anterior thoracic gradient increased. The appropriate wedge to correct these differences was 10-35°. Conclusions The inherent anterior thoracic gradient exerts impact on the radiation dose distribution. The dose difference between the upper and lower plane of anterior-posterior parallel field caused by the thoracic gradient can be corrected by an appropriate top to foot wedge.
出处
《中华放射肿瘤学杂志》
CSCD
北大核心
2005年第5期419-421,共3页
Chinese Journal of Radiation Oncology
