Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Int J Radiat Oncol Biol Phys. 2012 Feb 1;82(2):708-14. doi: 10.1016/j.ijrobp.2011.01.035. Epub 2011 Mar 26.
Many patients with left-sided breast cancer receive adjuvant radiotherapy during deep-inspiration breath hold (DIBH) to minimize radiation exposure to the heart. We measured the displacement of the left anterior descending artery (LAD) and heart owing to cardiac motion during DIBH, relative to the standard tangential fields for left breast cancer radiotherapy.
A total of 20 patients who had undergone computed tomography-based coronary angiography with retrospective electrocardiographic gating were randomly selected for the present study. The patients underwent scanning during DIBH to control the influence of respiration on cardiac motion. Standard medial and lateral tangential fields were placed, and the LADs were contoured on the systolic- and diastolic-phase computed tomography data sets by the clinicians. Displacement of the LAD during cardiac contractions was calculated in three directions: toward the posterior edge of the treatment fields, left-right, and anteroposterior. Displacement of the entire heart was measured on the maximal and minimal intensity projection computed tomography images.
The mean displacement of the LAD from cardiac contraction without the influence of respiration for 20 patients was 2.3 mm (range, 0.7-3.8) toward the posterior edge of the treatment fields, 2.6 mm (range, 1.0-6.8) in the left-right direction, and 2.3 mm (range, 0.6-6.5) in the anteroposterior direction. At least 30% of the LAD volume was displaced >5 mm in any direction in 2 patients (10%), and <10% of the LAD volume was displaced >5 mm in 10 patients (50%). The extent of displacement of the heart periphery during cardiac motion was negligible near the treatment fields.
Displacement of the heart periphery near the treatment fields was negligible during DIBH; however, displacement of the LAD from cardiac contraction varied substantially between and within patients. We recommend maintaining ≥ 5 mm of distance between the LAD and the field edge for patients undergoing breast cancer radiotherapy during DIBH.
许多左侧乳腺癌患者在深吸气屏气（DIBH）期间接受辅助放疗，以尽量减少心脏受到的辐射。我们测量了左前降支（LAD）和心脏在 DIBH 期间由于心脏运动相对于左侧乳腺癌放疗的标准切线野的位移。
总共随机选择了 20 名接受基于计算机断层扫描的冠状动脉造影术并进行回顾性心电图门控的患者进行本研究。患者在 DIBH 下进行扫描，以控制呼吸对心脏运动的影响。放置标准的内侧和外侧切线野，并由临床医生在收缩期和舒张期计算机断层扫描数据集上描绘 LAD。在三个方向上计算 LAD 在心脏收缩期间的位移：朝向治疗野的后缘、左右和前后。在最大和最小强度投影计算机断层扫描图像上测量整个心脏的位移。
20 名患者在没有呼吸影响的情况下，LAD 在心脏收缩期间的平均位移为 2.3 毫米（范围为 0.7-3.8）朝向治疗野的后缘，2.6 毫米（范围为 1.0-6.8）在左右方向，2.3 毫米（范围为 0.6-6.5）在前后方向。在 2 名患者（10%）中，至少有 30%的 LAD 体积在任何方向上的位移>5 毫米，而在 10 名患者（50%）中，<10%的 LAD 体积的位移>5 毫米。在治疗野附近，心脏周边在心脏运动期间的位移程度可以忽略不计。
在 DIBH 期间，治疗野附近心脏周边的位移可以忽略不计；然而，LAD 从心脏收缩的位移在患者之间和患者内部有很大的差异。我们建议在接受 DIBH 乳腺癌放疗的患者中，LAD 与场边之间保持≥5 毫米的距离。
