Magnetic Resonant Spectroscopy and Spectroscopic Imaging: A Review of Basic Principles and Recent Achievements in Oncology

Abstract

There is a growing appreciation of the possibilities offered by molecular imaging in oncology for early detection, by identifying key changes for the emergence and progression of cancer on the molecular and/or cellular level. Among the potentially most promising of these are Magnetic Resonance Spectroscopy (MRS) and Spectroscopic Imaging (MRSI) that involve the in vivo application of traditional laboratory-based Nuclear Magnetic Resonance (NMR) techniques, and provide, in addition to the anatomic picture, complementary biochemical and physiologic information in the form of spectra. MRS and MRSI have been shown to enhance diagnostics as well as assessment of response to therapy for a number of cancers, most notably brain, prostate and lymphoma, with some encouraging results for breast cancer, hepatic and head and neck tumours. Most striking is that adding spectroscopic information from MRS substantially improves the specificity of MRI in oncology. The combination of anatomic localisation and quantification by metabolite spectra is often decisive in accurate and timely identification of malignancy. This has proven invaluable, especially in the most difficult cases, e.g. differentiating recurrent tumour from radiation necrosis or post-operative changes. These methods also hold promise for screening/primary detection of cancers, particularly since no ionising radiation is involved. These and other features are compared to combined functional and anatomic imaging provided by PET-CT in oncology. In this review article, we outline the basic principles of MRS and MRSI, including some computational aspects, and present the major achievements attained thus far using MRS and MRSI in clinical oncology, highlighting areas where further progress could be of strategic importance in the fight against cancer.