酸碱度平衡是维持机体内环境稳态的重要组成部分之一。肿瘤微环境的酸碱度变化更是直接影响其侵袭性与治疗效果。而对酸碱度的活体无创性成像，目前尚缺乏一种理想的方法。化学交换饱和转移技术在pH成像方面颇有潜力，但其成像序列尚无统一的标准，且难以进行pH的准确定量成像。本课题组在前期创立了化学交换饱和转移成像的信噪比计算公式，优化了该技术的部分重要参数，实现了对化学交换率与交换物质浓度定量校正。本课题将在既往研究基础上，通过理、工、医的结合，进行深入地参数优化校正，确立最优化学交换饱和转移成像序列，并通过建立图像信号与31P-MRS关系图，实现pH成像的准确定量，获取活体脑pH定量成像，并在1.5T、3T及7T上，在多种脑肿瘤模型及病人上进行pH定量成像，通过与病理结合，验证其在对脑肿瘤良恶性、侵袭性判断的准确性。本项目的成功开展将提供一种无创准确的pH定量成像方法，并进一步指导脑肿瘤的诊断与治疗。

Acid-Base Balance is an important part of the human homeostasis. The change of pH value in tumor microenvironment affects its invasion and the therapeutic effects. Nowadays there is no ideal method to image the pH in vivo non-invasively. Chemical exchange saturation transfer technology shows a tremendous potential in pH imaging, but sequences are not uniform and it is hard to quantify the pH imaging. Our team proposed a formula to calculate the signal to noise ratio in CEST imaging. Moreover, we optimized some important parameters and demonstrated quantitative analysis of the exchange rate and labile proton fraction. In this project, combined with science, engineering and medicine, we aim to continue our parameter optimization and establish the optimal CEST sequence. Then, we will demonstrate the relationship between the CEST imaging and 31P-MRS and get the precisely quantitative pH imaging in the brain in vivo. In addition, more pH quantitative imaging will be applied in various kinds of brain tumors at 1.5T, 3T and 7T MR scanners. The classification of benign and malignant brain tumor and the invasion will be proved via histopathology. The success of this project will provide a reliable noninvasive method for quantitative pH imaging, moreover, which can guide the diagnosis and therapy of brain tumors.