Department of Radiation Oncology and Radiation Therapy, University Medical Center of the Johannes Gutenberg-University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.
Department of Radiation Oncology, University Hospital Rostock, Südring 75, 18059, Rostock, Germany.
Radiat Oncol. 2021 Dec 20;16(1):241. doi: 10.1186/s13014-021-01965-5.
Cardiac effects after breast cancer radiation therapy potentially affect more patients as survival improves. The heart's heterogeneous radiation exposure and composition of functional structures call for establishing individual relationships between structure dose and specific late effects. However, valid dosimetry requires reliable contouring which is challenging for small volumes based on older, lower-quality computed tomography imaging. We developed a heart atlas for robust heart contouring in retrospective epidemiologic studies.
The atlas defined the complete heart and geometric surrogate volumes for six cardiac structures: aortic valve, pulmonary valve, all deeper structures combined, myocardium, left anterior myocardium, and right anterior myocardium. We collected treatment planning records from 16 patients from 4 hospitals including dose calculations for 3D conformal tangential field radiation therapy for left-sided breast cancer. Six observers each contoured all patients. We assessed spatial contouring agreement and corresponding dosimetric variability.
Contouring agreement for the complete heart was high with a mean Jaccard similarity coefficient (JSC) of 89%, a volume coefficient of variation (CV) of 5.2%, and a mean dose CV of 4.2%. The left (right) anterior myocardium had acceptable agreement with 63% (58%) JSC, 9.8% (11.5%) volume CV, and 11.9% (8.0%) mean dose CV. Dosimetric agreement for the deep structures and aortic valve was good despite higher spatial variation. Low spatial agreement for the pulmonary valve translated to poor dosimetric agreement.
For the purpose of retrospective dosimetry based on older imaging, geometric surrogate volumes for cardiac organs at risk can yield better contouring agreement than anatomical definitions, but retain limitations for small structures like the pulmonary valve.
随着癌症患者生存率的提高，乳腺癌放射治疗后的心脏效应可能会影响更多的患者。心脏的不均匀辐射暴露和功能结构组成需要建立结构剂量与特定迟发性效应之间的个体关系。然而，有效的剂量测定需要可靠的轮廓绘制，而基于较旧、较低质量的计算机断层成像的小体积轮廓绘制具有挑战性。我们开发了一种心脏图谱，用于在回顾性流行病学研究中进行稳健的心脏轮廓绘制。
该图谱定义了完整的心脏和六个心脏结构的几何替代体积：主动脉瓣、肺动脉瓣、所有较深的结构组合、心肌、左前心肌和右前心肌。我们从 4 家医院的 16 名患者中收集了治疗计划记录，包括左侧乳腺癌 3D 适形切线野放射治疗的剂量计算。六名观察者分别对所有患者进行了轮廓绘制。我们评估了空间轮廓绘制的一致性和相应的剂量学变异性。
完整心脏的轮廓绘制一致性很高，平均 Jaccard 相似系数（JSC）为 89%，体积变异系数（CV）为 5.2%，平均剂量 CV 为 4.2%。左（右）前心肌的 JSC 为 63%（58%），体积 CV 为 9.8%（11.5%），平均剂量 CV 为 11.9%（8.0%），具有可接受的一致性。尽管空间变化较大，但深部结构和主动脉瓣的剂量学一致性较好。肺瓣的空间一致性低导致剂量学一致性差。
对于基于较旧成像的回顾性剂量测定，心脏危险器官的几何替代体积可以比解剖定义获得更好的轮廓绘制一致性，但对于肺瓣等小结构仍存在局限性。
