Proton MRS (1H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good‐quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi‐adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.

A large body of published work shows that proton (hydrogen 1 [ 1 H]) magnetic resonance (MR) spectroscopy has evolved from a research tool into a clinical neuroimaging modality. Herein, the authors present a summary of brain disorders in which MR spectroscopy has an impact on patient management, together with a critical consideration of common data acquisition and processing procedures. The article documents the impact of 1 H MR spectroscopy in the clinical evaluation of disorders of the central nervous system. The clinical usefulness of 1 H MR spectroscopy has been established for brain neoplasms, neonatal and pediatric disorders (hypoxia-ischemia, inherited metabolic diseases, and traumatic brain injury), demyelinating disorders, and infectious brain lesions. The growing list of disorders for which 1 H MR spectroscopy may contribute to patient management extends to neurodegenerative diseases, epilepsy, and stroke. To facilitate expanded clinical acceptance and standardization of MR spectroscopy methodology, guidelines are provided for data acquisition and analysis, quality assessment, and interpretation. Finally, the authors offer recommendations to expedite the use of robust MR spectroscopy methodology in the clinical setting, including incorporation of technical advances on clinical units.q RSNA, 2014 Online supplemental material is available for this article. G.O. (e-mail: gulin@cmrr.umn.edu). 2 The complete list of authors and affiliations is at the end of this article.q RSNA, 2014 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. Radiology H MR Spectrum of the Brain: Metabolites and Their Biomarker PotentialMR spectroscopy provides a very different basic "readout" than MR imaging, namely a spectrum rather than an techniques were developed. These early localization techniques included pointresolved spectroscopy (PRESS) (1,2) and stimulated echo acquisition mode (STEAM) (3), methods that are now widely used in clinical MR spectroscopy applications.Preliminary studies revealed large differences in metabolite levels in acute stroke (4), chronic multiple sclerosis (5), and brain tumors compared with healthy brain (6). Although this work stimulated a surge of interest in 1 H MR spectroscopy for diagnosing and assessing CNS disorders during the early days of the "Decade of the Brain" (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999), many suboptimal patient studies (7) and the lack of consistent guidelines have led to a situation where, 20 years later, MR spectroscopy is still considered an "investigational technique" by some medical professionals and health care organizations. However, the ability to make an early, noninvasive diagnosis or to increase confidence in a suspected diagnosis is highly valued by patients and clinicians alike. As a result, an increasing number of imaging centers are incorporating MR spectroscopy into their clinical protocols for brain...

This work describes a methodology for quantifying levels of total choline-containing compounds (tCho) in the breast using in vivo 1 H MR spectroscopy (MRS) at high field (4 Tesla). Water is used as an internal reference compound to account for the partial volume of adipose tissue. Peak amplitudes are estimated by fitting one peak at a time over a narrow frequency band to allow measurement of small metabolite resonances in spectra with large lipid peaks. This quantitative method significantly improves previously reported analysis methods by accounting for the variable sensitivity of breast 1 H MRS measurements. Using this technique, we detected and quantified a tCho peak in 214 of 500 in vivo spectra. tCho levels were found to be significantly higher in malignancies than in benign abnormalities and normal breast tissues, which suggests that this technique could be used to diagnose suspicious lesions and monitor response to cancer treatments. Breast cancer is a very common disease, affecting 11% of American women and causing more than 40000 deaths each year (1). While breast cancer mortality is decreasing, the incidence continues to rise (2). Thus, there is a great need for noninvasive diagnostic tools for both screening and treatment monitoring. The conventional diagnostics-X-ray mammography, sonography, and physical examination-are limited in their sensitivity for detecting disease and their specificity for distinguishing between benign and malignant lesions. Magnetic resonance imaging (MRI) of the breast is being used increasingly because of its high sensitivity, but its reported specificity is widely variable (3).Researchers have recently begun to augment breast MRI studies with MR spectroscopy (MRS) to increase specificity. In vivo MRS can detect a resonance at 3.25 ppm that has contributions from several different compounds, including choline, phosphocholine, glycerophosphocholine, and taurine. High-resolution in vitro and ex vivo studies indicate that the levels of choline compounds increase with malignancy (4 -6). At the lower field strengths used for in vivo work (1.5-4 T), these multiple resonances cannot be spectrally resolved and thus appear as a single peak, termed total choline-containing compounds (tCho).Several studies conducted at 1.5 T have shown that in vivo MRS can be used to distinguish between benign and malignant tissues (7-11). These studies used the hypothesis that tCho is only detectable in malignancies. A pooled analysis of these five studies showed that this tCho detectability criterion can identify malignancies with an 83% sensitivity and 85% specificity (12). This qualitative approach is promising, but it is only applicable if the MRS measurement sensitivity is invariant. In similar studies performed at 4 T, the increased sensitivity allows detection of tCho in benign lesions and normal subjects. A more general approach is to quantify the tCho peak with the expectation that tCho levels are higher in malignancies than in benign lesions or normal tissues. Two groups have reported quanti...