New techniques of HI spectroscopy on the liver: Reworking of NMR sequences

摘要

Magnetic resonance spectroscopy (MRS) allows to quantify non-invasively the molecular structure of the compound under examination by measuring the level of absorption of electromagnetic field. Although NMR is widely applied in neuroradiology, this technique has the potential to study diseases of the liver. The goal of the present study is to present a novel NMR technique for the study of liver and related diseases by adapting sequences generally used for neuroradiologic screening. Specifically, the PRESS SV and STEAM SV sequences were adapted to quantify the changes of chemical compounds in liver diseases such as the hepatocellular carcinoma (HCC). Our results shows that the level of choline, which is usually high in malignant HCC, is altered after chemioembolization treatment performed in our hospital. Using NMR, we demonstrated the importance of the spectroscopic investigation in the quantification and differentiation of molecules involved in the metabolism of liver lesions. Magnetic resonance spectroscopy (MRS) is an analytic instrumental technique, which permits to evaluate detailed information on the molecular structure of the compound under examination.1'2 This can be performed measuring the absorption of radio-frequency electromagnetic radiation in the molecules subjected to a static magnetic field.3 These radiations cause transitions of nuclear spin in atoms such as H-l or C-13. First applications of NMR in-vivo have been applied in the neuroradiology field.4"6 With the advent of new powerful technology, it is possible to extend the potentiality of MRS for the diagnosis of diseases in complex organs such as the liver. In this paper, we present a novel MRS technique as it determined by fitting sequences generally used for neuroradiologic screening for the evaluation of metabolite content.7 Specifically, the PRESS SV and STEAM SV sequences were optimized to estimate key metabolites such as the choline in the liver of 28 patients with hepatocellular carcinoma (HCC). A short description of physical and chemical principles of NMR as well as the changes in the acquisition technique (sequences, calibration, tuning FID and triggering) will be also discussed.