左侧乳腺癌调强放疗中心跳对左心室肌及左前降支剂量评估的影响

目的 研究左侧乳腺癌调强放射治疗（IMRT）中，心跳对左心室肌（mLV）及左前降支（LAD）剂量评估的影响。方法 选取15例女性患者平静吸气屏气下的心电门控（ECG-gated）4D-CT图像，参照心动周期以5%间隔进行图像重建，重建0~95%共20个时相的图像。分别勾画mLV及LAD。基于0%时相的图像进行左侧乳腺癌IMRT计划设计。统计各时相mLV的体积并计算相似性指数（dice similarity coefficient，DSC）；计算LAD及mLV剂量-体积指标的变化范围。结果 mLV的DSC变化率最大可达472.07%，其平均变化率约为体积变化率的8倍。mLV的体积与DSC在最大、最小值之间差异均具有统计学意义（t=-6.585、-28.870，P<0.05）。mLV的平均剂量（D_mean）变化率最高可达41.95%。mLV的D_mean、V₁₀、V₂₀、V₃₀、V₄₀在最大、最小值之间差异均有统计学意义（t=-5.260、-4.084、-3.592、-3.273、-2.566，P<0.05）。LAD的D_mean平均变化率最高可达130.14%。LAD的D_mean、V₁₀、V₂₀、V₃₀、V₄₀在最大、最小值之间差异均有统计学意义（t=-9.758、-8.810、-8.682、-7.853、-6.205，P<0.05）。结论 左侧乳腺癌放疗中，心跳对mLV和LAD的剂量评估影响不容忽视。

The impact of heartbeat on the left ventricular myocardial and the left anterior descending coronary arterial dosimetry following intensity modulated radiotherapy for left-sided breast cancer

Objective To study the impact of heartbeat on the left ventricular myocardial (mLV) and the left anterior descending (LAD) coronary arterial dosimetry following intensity modulated radiotherapy (IMRT) for left-sided breast carcinoma. Methods A total of 15 female patients who received electrocardiography gated 4D-CT scan in inspiratory breathing-holding were enrolled. According to cardiac cycle, 20 time-phase images were reconstructed from 0 to 95% at 5% interval. Then, the mLV and the LAD were delineated respectively and the IMRT plans of the left breast carcinoma were generated based on 0% phase CT images. The volume and dice similarity coefficient (DSC) of the mLV were calculated, and the variation range of the mLV and the LAD dose-volume indexes were compared among different phases. Results The average rate of DSC variation of mLV was eightfold of volume, which reached to 472.07%,and the average change rate of mLV (D_mean) was up to 41.95%. The difference of the mLV''s volume and DSC was statistically significant between the maximum and minimum(t=-6.585, -28.870, P<0.05), as well as the D_mean, V₁₀, V₂₀, V₃₀ and V₄₀(t=-5.260, -4.084, -3.592, -3.273, -2.566, P<0.05). The average change rate of the LAD''s D_mean was up to 130.14%. The difference of D_mean, V₁₀, V₂₀, V₃₀ and V₄₀ of LAD was statistically significant between the maximum and minimum(t=-9.758, -8.810, -8.682, -7.853, -6.205,P<0.05). Conclusions The dosimetry impact of heartbeat on mLV and LAD should not be ignored.