开创口腔锥形束CT的低剂量综合优化技术研究

Stomatology is developing and flourishing greatly in meeting modern needs. The rise of new cone-beam CT (CBCT) brings in a revolutionary change in this era, but its dose is much larger than traditional dental X-ray machines, which calls for extensive attention for the issue of national medical exposure protection. By observing the development trends of multiple disciplines such as medical applications of nuclear technology and radiation protection, researching on comprehensive optimal solutions for low-dose CBCT is a leading cutting-edge subject. Therefore, in order to make theoretical and fundamental breakthroughs for CBCT achieving high-quality images with optimal minimum dose, great efforts will be devoted into two core aspects in this project: creatively sloving key physical and technical problems of devices and optimizing radiation protection in clinical applications. Upon systematic analysis of data from clinical investigations, we will focus on innovative designs including automatic beam parameter adjustment, spectrum photon counting detector, corresponding image reconstruction methods, ill-posed data processing technology, and etc. These works will lay a solid theoretical foundation for the birth of a new generation of low-dose CBCT. Meanwhile, this project will deeply explore the interaction between image quality and dose by digging information from clinical practice. Meanwhile, with experimental study of head phantoms of both adults and children, we will build up a pioneering evaluation system for image quality and dose, and a guide for their optimal match. The achievements will develop the optimization of radiation protection principles and its applications, as well as provide a scientific basis for the establishment of CBCT system guidance of medical radiation dose levels.

口腔医学适应现代化需求正蓬勃发展，新崛起的锥形束CT（CBCT）为其带来了革命性变化，但所致受检者剂量远大于牙科X射线机而成为全民医疗照射防护焦点。纵观核技术医学应用和辐射防护等诸多学科及社会发展趋势，亟需全方位研究解决CBCT低剂量综合最优化这个前沿课题。故围绕设备关键物理技术问题创新和临床应用防护最优化研究两大方面协同攻关，旨在突破CBCT以最佳低剂量获得高成像质量的理论与应用基础。从系统分析临床调查监测数据出发，着重研究束流参数自动调节、能谱光子计数探测器、相应图像重建方法和病态数据处理等技术以革新设计理念，为催生新一代低剂量CBCT奠定坚实理论基础。同时深入临床实际探究成像质量与所致剂量的制约关系，通过成人儿童的头模实验研究，在国内外率先创建CBCT图像质量和所致剂量的评价体系及二者最优化匹配指南，发展辐射防护最优化原理与应用，并为建立CBCT医疗照射剂量指导水平提供科学依据。

口腔医学适应现代化需求正蓬勃发展，新崛起的锥形束CT（CBCT）为其带来了革命性变化，但所致受检者剂量远大于牙科X射线机而成为全民医疗照射防护焦点。纵观核技术医学应用和辐射防护等诸多学科及社会发展趋势，亟需全方位研究解决CBCT低剂量综合最优化这个前沿课题。从2015年至2019年，项目组围绕设备关键物理技术问题创新和临床应用防护最优化研究两大方面协同攻关，突破了CBCT以最佳低剂量获得高成像质量的理论与应用基础，取得较好成果。项目组针对光子计数探测器的设计与制造问题，基于蒙卡模拟确定了探测器晶体参数，与此相应地完成了ASIC芯片的设计与制造，最后将两者封装测试，成功研制出1cm×1cm，36 × 36像素，像素尺寸0.25mm × 0.25mm的可三面拼接的面阵列模块！针对X射线源的优化方案问题，确定了滤波片的最佳方案，实现了管电流关于角度的自动调制，在保证图像质量的情况下，又针对标准体型患者降低了31%的剂量！针对SPCD的建模问题，提出了一种参数化的探测器响应解析模型，并结合蒙卡模拟和实验测量对其参数进行了标定。针对能谱重建的问题，提出了基于加权子集的前处理算法、基于最大似然的前处理算法、重建物质衰减曲线的后处理算法和基于深度学习的后处理算法等多种方法，实现了准确的能谱重建。针对病态数据校正问题，提出了加权非局部TV极小化的优化算法和两种基于深度学习的图像域优化算法。实验证明了采用能谱CT成像技术，在保证图像质量的情况下扫描剂量降低了30%！项目组进行了大量临床调查，结果显示接受CBCT检查的青少年占40%，中大视野占97%，降低剂量是紧迫的任务。针对口腔CBCT剂量表征量的问题，项目组通过大量剂量测量实验和数学拟合，首次提出了CBCT的剂量表征量，更加精确地表征了CBCT的面吸收剂量和体吸收剂量！针对图像质量评价的问题，项目组提出了一种将主观评价映射到客观评价的图像质量评价方法，在此基础上，提出一种辐射剂量和图像质量的匹配优化方法，推荐扫描参数对于大部分解剖结构都能大幅降低剂量。