San Raffaele Scientific Institute, Milano, Italy.
Radiother Oncol. 2012 Aug;104(2):224-9. doi: 10.1016/j.radonc.2012.06.003. Epub 2012 Jul 16.
Measuring parotid density changes in patients treated with IMRT for head-neck cancer (HNC) and assessing correlation with treatment-related parameters.
Data of 84 patients treated with IMRT for different HNC were pooled from three institutions. Parotid deformation and average Hounsfield number changes (ΔHU) were evaluated through MVCT (with Helical Tomotherapy) or diagnostic kVCT images taken at the treatment start/end. Parotids were delineated in the first image and propagated to the last using a previously validated algorithm based on elastic registration. The correlation between ΔHU and several treatment-related parameters was tested; then, logistic uni- and multi-variate analyses taking "large" ΔHU as end-point were carried out. Due to the better image quality, analyses were repeated considering only kVCT data.
ΔHU was negative in 116/168 parotids (69%; for kVCT patients: 72/92, 78%). The average ΔHU was significantly different from zero (-7.3, 0.20-0.25 HU/fraction, p<0.001). Individual ΔHU was highly correlated with parotid deformation both in terms of volume change and mean value of the Jacobian of the deformation field (Jac_mean), and with neck thickness variation; these correlations were much stronger for kVCT data. Logistic analyses considering ΔHU<-11 (quartile value) as the end-point showed a two-variable model including large deformation (Jac_mean<0.68) and initial neck thickness to be the most predictive variables (p<0.0005, AUC=0.683; AUC=0.776 for kVCT); the odd ratio of large vs moderate/small parotid deformation was 3.8 and 8.0 for the whole and the kVCT population respectively.
Parotid density reduced in most patients during IMRT and this phenomenon was highly correlated with parotid deformation. The individual assessment of density changes was highly reliable just with diagnostic KvCT. Density changes should be considered as an additional objective measurement of early parotid radiation-induced modifications; further research is warranted.
测量接受头颈部癌症（HNC）调强放疗（IMRT）治疗的患者的腮腺密度变化，并评估其与治疗相关参数的相关性。
将三个机构中接受 IMRT 治疗的 84 例不同 HNC 患者的数据汇总。通过 MVCT（螺旋断层放疗）或在治疗开始/结束时拍摄的诊断性千伏 CT 图像评估腮腺变形和平均亨氏单位数变化（ΔHU）。在第一张图像中对腮腺进行勾画，并使用基于弹性配准的先前验证的算法将其传播到最后一张图像。测试了 ΔHU 与几个治疗相关参数之间的相关性；然后，以“大”ΔHU 为终点进行了单变量和多变量逻辑分析。由于图像质量较好，因此仅考虑千伏 CT 数据重复了分析。
168 个腮腺中有 116 个（69%；对于千伏 CT 患者：72/92，78%）的 ΔHU 为负值。平均 ΔHU 与零有显著差异（-7.3，0.20-0.25 HU/分次，p<0.001）。个体 ΔHU 与腮腺变形的体积变化和变形场雅可比均值（Jac_mean）均高度相关，并且与颈部厚度变化相关；这些相关性在千伏 CT 数据中更强。考虑以 ΔHU<-11（四分位值）为终点的逻辑分析表明，包含大变形（Jac_mean<0.68）和初始颈部厚度的两变量模型是最具预测性的变量（p<0.0005，AUC=0.683；对于千伏 CT 人群为 AUC=0.776）；大腮腺变形与中/小腮腺变形的比值在全人群和千伏 CT 人群中分别为 3.8 和 8.0。
在接受 IMRT 治疗的大多数患者中，腮腺密度降低，这种现象与腮腺变形高度相关。仅使用诊断性千伏 CT 即可对密度变化进行高度可靠的个体评估。密度变化应被视为评估早期腮腺放射性损伤改变的附加客观测量指标；需要进一步研究。
