Distinction of benign from malignant brain lesions in magnetic resonance spectroscopy
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Localized proton MR spectroscopy (MRS) of the human brain, first reported more than 20 years ago,(1–3) is a mature methodology that is used clinically in many medical centers worldwide for the evaluation of brain tumors.(4) While there have been studies of human brain tumors using heteronuclei such as phosphorus (31P) and sodium (11Na),(5,6) by far the most spectroscopy studies use the proton (1H) nucleus, because of both its high sensitivity and ease of implementation on commercial MRI scanners. This review will therefore focus on proton MRS in human brain tumors.
There are two classes of spatial localization techniques for MR spectroscopy; single-voxel (SV) techniques (commonly used methods includes ‘PRESS’(7) and ‘STEAM’(8)) which record spectra from one region of the brain at a time, or multi-voxel techniques (‘MR spectroscopic imaging’ (MRSI), also called ‘Chemical Shift Imaging’ (CSI)(9)) which simultaneously record spectra from multiple regions and thereby map out the spatial distribution of metabolites within the brain. MRSI is typically performed in 2- or 3-dimensions, but does not usually include full brain coverage. While SV-MRS and MRSI each have their own advantages and disadvantages (e.g. in terms of spectral quality, scan time, spatial resolution, spatial coverage, and ease of use/interpretation), a key consideration for brain tumors is their metabolic inhomogeneity. For instance, the spectrum from the necrotic core of a high-grade brain tumor is quite different from a spectrum from the actively growing rim, while peri-tumoral edema is different from tumor invasion into surrounding brain tissue; for these reasons and others, high-resolution MRSI is often favored for evaluating brain tumor metabolism. For a detailed discussion of the relative merits of SV-MRS and MRSI, please see reference.(10)
There are two classes of spatial localization techniques for MR spectroscopy; single-voxel (SV) techniques (commonly used methods includes ‘PRESS’(7) and ‘STEAM’(8)) which record spectra from one region of the brain at a time, or multi-voxel techniques (‘MR spectroscopic imaging’ (MRSI), also called ‘Chemical Shift Imaging’ (CSI)(9)) which simultaneously record spectra from multiple regions and thereby map out the spatial distribution of metabolites within the brain. MRSI is typically performed in 2- or 3-dimensions, but does not usually include full brain coverage. While SV-MRS and MRSI each have their own advantages and disadvantages (e.g. in terms of spectral quality, scan time, spatial resolution, spatial coverage, and ease of use/interpretation), a key consideration for brain tumors is their metabolic inhomogeneity. For instance, the spectrum from the necrotic core of a high-grade brain tumor is quite different from a spectrum from the actively growing rim, while peri-tumoral edema is different from tumor invasion into surrounding brain tissue; for these reasons and others, high-resolution MRSI is often favored for evaluating brain tumor metabolism. For a detailed discussion of the relative merits of SV-MRS and MRSI, please see reference.(10)
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Localized proton MR spectroscopy (MRS) of the human brain, first reported more .... (38) Examples of benign and malignant lesions from this study are shown in figures 4 and ...
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