DWI联合热成像实时评估MRI引导下肝癌射频消融效果的研究

Radiofrequency thermal ablation is a major minimally invasive therapeutic method for unresectable hepatic tumors, the therapeutic effectiveness of which depends on whether the lesion is completely ablated. Therefore, real-time and accurate evaluation of the extent of the necrotic area during ablation is necessary. Proton resonance frequency based MR thermometry can be useful in dynamic detection of the temperature of the ablative region, and in generation of thermal dose map which can evaluate the necrotic area indirectly (also called the TD240 area on thermal dose map). However, it is difficult in charactering the necrosis associated with hemodynamic changes or accumulated thermal effect due to overlap of several adjacent ablated regions. With the ADC values, DWI can be used to evaluate the mid- and long-term therapeutic responses of the ablated regions. However, due to the fluctuation of ADC values caused by inhomogeneous distribution of temperature in the ablated regions, there is no study regarding the real-time evaluation of necrotic area with DWI during ablation. Our project is to combine the MR thermometry and DWI in real-time evaluation of the radiofrequency thermal ablation, including: real-time acquisition of temperature mapping by MR thermometry; DWI scanning and correction of ADC according to the temperature distribution; differentiation of necrotic area from hyperemic and edematous area with corrected ADC; comparison between the necrotic areas seen on corrected ADC maps, the TD240 areas and pathological findings. This project intends to find out a potential real-time quantitative method in convenient, noninvasive and accurate evaluation of the extent of necrotic areas in radiofrequency ablation of hepatic cancer.

射频消融是无法手术切除肝肿瘤的一种主要微创治疗方式，其疗效取决于病灶是否消融完全，因此术中实时准确评估组织坏死范围十分必要。基于质子共振频率的热成像可以实时动态监测术区温度，并生成热剂量图间接评估坏死区的范围（TD240区域），却难以准确反映术中血流动力学改变或多个重叠的消融区边缘由于热量累积造成的坏死区范围改变。DWI可通过ADC值评价射频消融术后中远期的治疗反应，然而由于术区温度分布造成的ADC值波动，目前仍缺乏术中使用DWI实时评估坏死区的相关研究。本研究拟联合热成像与DWI对射频消融进行实时评估，具体包括以下四方面的内容：热成像温度图的实时获取；DWI扫描与ADC值校正；校正后的ADC值对凝固性坏死区与充血水肿区的鉴别分析；校正后ADC值预测的凝固性坏死区、TD240区域与病理标本凝固性坏死区的比较。以期为肝癌射频消融术实时评估组织坏死区提供一种简便、无创、准确的定量评价方式。

肝细胞肝癌是严重威胁国人健康最主要的疾病之一。在我国，2020年HCC新发病例数位居第五，死亡病例数位居第二。影像引导下消融可通过提高消融针周围局部温度，使邻近组织产生凝固性坏死，从而达到类似手术切除的效果，是局灶性实性肝脏病灶的一种有效治疗方案。然而，消融效果受到多种因素制约，如病灶大小、不同消融方案下产生的消融灶形态、病灶周围血流带来的热量丢失等等。由于临床上消融患者难以取得手术切除病理标本，而术后即时增强CT或MRI图像上消融灶周围充血水肿带可能会掩盖残余瘤灶，因此，目前在实践中疗效评估仍高度依赖于术后长期动态影像学随访，缺乏无创性的即时评价手段。针对以上问题，本项目主要探究了不同消融方案对肝脏消融灶形态与IVIM-DWI参数的即时影响，并发现消融结束的坏死区的瞬时温度（与消融方案有关）可影响IVIM-DWI 的D值及ADC值，而与灌注相关的参数f更不容易受到消融方案波动影响，且可重复性更高，在术后即时评估消融坏死区范围较有前景；同时，我们在初步发现热成像TD240剂量图所示消融范围较其他常规序列与消融区相关性、一致性更高。此外，在项目开展期间，研究团队亦进行了如下相关研究：1）针对组织标本图像数字化过程中带来的颜色误差，开发出基于深度学习的结构不变的病理图像颜色标准化方法；2）开发并验证了一种基于多闭环标定方法的光学导航穿刺系统；3）利用影像组学对肝细胞肝癌治疗临床结局的早期预测方法进行探究。目前本项目研究成果包括SCI研究论文4篇（其中以共同第一作者身份完成2篇），申请发明专利1项等，有望为肝细胞肝癌治疗提供与消融疗效相关的无创性定量评估手段，实时指导消融方案，提高消融有效率，减少肿瘤局部复发。