PH Imaging Pulse Sequence Design In The Clinical Magnetic Resonance Scanner Based On Chemical Exchange Saturation Transfer

Acid-based balance is altered in a variety of common pathologies, including ischemia, renal failure, cancer and inflammation. It is of importance to rapidly and accurately detect the acid-base environment of human lesions in early disease diagnosis and follow-up treatment.However, It is known that there are few effective tools available to evaluate pH values in vivo.Recently the Magnetic Resonance is found to provide a non-invasive tool of estimating pH value. MRS was first introduced to measure intra- and extracellular pH, but the inherent low resolution of spectroscopy makes it difficult to be applied to clinic. A new technique known as Chemical Exchange Saturation Transfer (CEST) may provide an high-resolution image of the spatial distribution of pH values in humans. In this research, we used the modified MT-SE sequence to scan the tissue-like pH phantom on 1.5T scanner, with the purpose of exploring the feasibility of CEST MR pH imaging on a clinical scanner.This study includes three aspects. Firstly, investigate chemical exchange saturation transfer theory and its relationship with pH value. It is mainly to investigate the Bloch equations of the three-pool model modified, the relationship between pH value and chemical exchange rate, and review the progress of APT pH imaging. Detailed study of on this issue will be of theoretical significance for the design of pulse sequence. Secondly, the pulse sequence design theory and its programming. It is to study the RF pulse and gradient pulse imaging principle. For CEST pH imaging difficulties, the MR pulse sequence program workstation is used to accomplish the magnetization transfer pulse program on the platform of EPIC. Thirdly, the scanning model experiment. The MT-SE sequence scanning three pool model is performed to verify its CEST effect, and the results were compared with the routine SE in the detection of pH value. Ourresults show that MT SE sequence has a greater pH sensitivity than the routine SE sequence. We concluded that it is feasible to get pH imaging map in 1.5T MRI scanner.This subject is a global problem. No "based on CEST pH imaging" related work was reported in China, and there are only a few pH imaging groups abroad, whose studies on pH imaging are still at an initial stage. We successfully implemented MT pulse sequence programming andsimulation in EPIC workstation. In addition, the theoretical description of CEST and the principle of MRI pulse sequence in this thesis will help the follow-up workers to understand and design the new pH-specific pulse sequences.