GEOMETRIC AND DOSIMETRIC APPROACH TO DETERMINE PROBABILITY OF LATE CARDIAC MORTALITY IN LEFT TANGENTIAL BREAST IRRADIATION: COMPARISON BETWEEN WEDGED BEAMS AND FIELD-IN-FIELD TECHNIQUE
GEOMETRIC AND DOSIMETRIC APPROACH TO DETERMINE PROBABILITY OF LATE CARDIAC MORTALITY IN LEFT TANGENTIAL BREAST IRRADIATION: COMPARISON BETWEEN WEDGED BEAMS AND FIELD-IN-FIELD TECHNIQUE
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DOI：
10.1016/j.ijrobp.2010.12.021
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发表时间：
2011-11-01
影响因子：
7
通讯作者：
Portaluri, Maurizio
中科院分区：
文献类型：
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作者：
Pili, Giorgio;Grimaldi, Luca;Portaluri, Maurizio
目的：评估切向野左乳房照射导致晚期心脏死亡的概率，比较楔形射束和射野中射野（FIF）技术之间的这种概率，并研究是否可以确定一些几何/剂量学指标来估计治疗开始前的心脏死亡概率。方法和材料：对于30例患者，计算楔形射束和FIF计划的微分剂量体积直方图，并使用相对序列性模型确定相应的心脏死亡概率。作为剂量分布均匀性的比较指标，两种技术的计划靶体积（PTV）占处方剂量的97-103%。三个几何参数进行测量，为每个病人：最大长度，表示有多少心脏轮廓向PTV位移，角度对着中心的计算机断层扫描切片的PTV轮廓，和胸部的宽度/厚度ratio.Results：评估的差分剂量体积直方图显示，这两种技术之间的均匀性的增益约为1.5。与楔形射束技术相比，FIF技术对心脏、左前降支冠状动脉和肺的平均剂量节省分别为15%（2.5戈伊vs. 2.2戈伊）、21%（11.3戈伊vs. 9.0戈伊）和42%（8.0戈伊vs. 4.6戈伊）。此外，心源性死亡概率降低了40%（从0.9%降至0.5%）。三个几何参数，最大长度，角度对着中心的计算机断层扫描切片的PTV轮廓，和胸部的宽度/厚度比，是决定因素（p = 0.06 FIF，和p = 0.10楔形梁）用于评估心脏死亡率probability.Conclusion：FIF技术似乎产生较低的心脏死亡率概率比传统的楔形梁技术。然而，尽管我们的研究表明FIF技术提高了PTV的剂量覆盖率，但入选患者数量有限且随访时间短，无法评估和比较患者的乳腺癌生存率。(C)2011 Elsevier Inc.
Purpose: To evaluate the probability of late cardiac mortality resulting from left breast irradiation planned with tangential fields and to compare this probability between the wedged beam and field-in-field (FIF) techniques and to investigate whether some geometric/dosimetric indicators can be determined to estimate the cardiac mortality probability before treatment begins.Methods and Materials: For 30 patients, differential dose volume histograms were calculated for the wedged beam and FIF plans, and the corresponding cardiac mortality probabilities were determined using the relative seriality model. As a comparative index of the dose distribution uniformity, the planning target volume (PTV) percentages involved in 97-103% of prescribed dose were determined for the two techniques. Three geometric parameters were measured for each patient: the maximal length, indicates how much the heart contours were displaced toward the PTV, the angle subtended at the center of the computed tomography slice by the PTV contour, and the thorax width/thickness ratio.Results: Evaluating the differential dose volume histograms showed that the gain in uniformity between the two techniques was about 1.5. With the FIF technique, the mean dose sparing for the heart, the left anterior descending coronary artery, and the lung was 15% (2.5 Gy vs. 2.2 Gy), 21% (11.3 Gy vs. 9.0 Gy), and 42% (8.0 Gy vs. 4.6 Gy) respectively, compared with the wedged beam technique. Also, the cardiac mortality probability decreased by 40% (from 0.9% to 0.5%). Three geometric parameters, the maximal length, angle subtended at the center of the computed tomography slice by the PTV contour, and thorax width/thickness ratio, were the determining factors (p = .06 for FIF, and p = .10 for wedged beam) for evaluating the cardiac mortality probability.Conclusion: The FIF technique seemed to yield a lower cardiac mortality probability than the conventional wedged beam technique. However, although our study demonstrated that FIF technique improved the dose coverage of the PTV, the restricted number of patients enrolled and the short follow-up did not allow us to evaluate and compare the breast cancer survival rates of the patients. (C) 2011 Elsevier Inc.