A two-dimensional (2D) chemical shift correlated MR spectroscopic (COSY) sequence integrated into a new volume localization technique (90°-180°-90°) is proposed for whole-body MR spectroscopy (MRS).Due to the recent improvements in the design of B 0 gradient and RF coils, 1 H MR spectra have been recorded in human brain with excellent water suppression using short TE, as short as 15 ms, and several cerebral metabolites have been identified (1-4). During the past decade alterations in several metabolites, namely, N-acetylaspartate (NAA), glutamate/glutamine (Glx), choline (Ch), creatine (Cr), myo-inositol (mI), and ␥-aminobutyrate (GABA) have been reported in different pathologic states involving the central nervous system (CNS) (5-10). Absolute quantitation of cerebral metabolites in vivo has also been reported for only a few metabolites, albeit with limited success (11-13). Due to severe overlap of these metabolites, an unambiguous assignment of J-coupled metabolite multiplets is severely hindered at 1.5 T field strength.One-dimensional (1D) MR spectral editing techniques to unravel the overlapping resonances rely on J-coupled proton metabolites that have well-separated multiplets. A technique based on subtraction methodology is very sensitive to motion artifacts leading to subtraction errors. An additional drawback is that only one metabolite can be identified at a time. Successful attempts in editing GABA and glutamate using whole-body MRI/MRS scanners have been presented by other researchers (13,14). Single-shotbased multiple-quantum filtered MR spectroscopic sequences have also been implemented on whole-body scanners, but a severe signal loss associated with various coherence transfer pathways made it less attractive to human applications (15)(16)(17).A localized version of a two-dimensional (2D) J-resolved MR spectroscopic (JPRESS) sequence using the PRESS sequence for volume localization was recently proposed (18 -20). Even though the JPRESS sequence retains 100% of the magnetization from a localized volume of interest (VOI), the strong coupling effect inherent at 1.5 T field strength resulted in a complex 2D cross-peak pattern for NAA, glutamate/glutamine, GABA, and other cerebral metabolites (19). Also, some of the 2D cross-peaks were heavily T 2 -weighted during the long incremental delays necessitated by the second dimension of the JPRESS spectrum. An oversampled J-resolved sequence has also been proposed recently (21).Compared to the 2D J-resolved spectra, a COSY spectrum produces a better dispersion of J-cross-peaks, although it requires a larger spectral window to be sampled during the evolution period (22). Different versions of the localized COSY sequence have been implemented by other researchers (23-33). McKinnon and Bosiger (23) proposed a conventional COSY sequence with hard RF pulses (90°-t 1 -90°) followed by three volume selective 180°RF pulses. Haase et al. (24) implemented a COSY combined with an outer volume suppressing sequence, namely, LOCUS. Many previous attempts to develop localiz...

Biochemical changes in the white matter may provide some of the neurobiological substrates to late-life major depression.

These data provide evidence that differences in the concentration of myo-inositol (mmol/liter) in the anterior cingulate cortex in (1)H MRS may differentiate these two populations. Follow-up studies involving larger samples may conclusively estimate the biological specificity between pediatric bipolar disorder and other disorders, which overlap clinically.

The test-retest reliability of two-dimensional (2D) correlated spectroscopy (COSY) was studied on a whole-body 1.5T MRI scanner. Single-voxel localized 2D proton spectra were recorded in vitro as well as in vivo using a recently implemented localized chemical shift correlated spectroscopic (L-COSY) sequence. A total of 40 in vitro and 40 human brain (10 volunteers, four times each) 2D L-COSY spectra were recorded. The coefficients of variation (CVs) of selected brain metabolites (raw volume integrals) recorded in 10 healthy volunteers were less than 9% for creatine, choline, and N-acetyl aspartate, and less than 17% for myo-inositol, glutamine/glutamate, aspartate, and threonine/lactate. The 2D metabolite ratios and the raw volume integrals of 2D diagonal and cross peaks in healthy human brain were very well reproduced. The intraclass correlation coefficients were greater than 0.4 (P < 0.05) for the major metabolites, indicating that the 2D peak volumes were stable enough within individuals to detect reliable differences between normal subjects. In the past decade, MR spectroscopy (MRS) has become a reliable clinical tool for the diagnosis of selected diseases (1-7). An important feature of any diagnostic tool is its reproducibility. Many studies on the reproducibility of one-dimensional (1D) 1 H MRS have reported the ratios and absolute concentrations of the metabolites (8 -13). Although these studies have shown small errors (3-6%) in the measurement of metabolites in vitro (8,9), the in vivo studies showed higher coefficients of variation (7-26%) in a maximum of only five metabolites (9 -13). Severe overlap of brain metabolites is a major hindrance in 1D MRS.Localized and nonlocalized versions of 2D MRS were reported a decade ago (14 -18); however, only recently have 2D proton spectra been recorded in healthy human subjects and patients with brain tumors (19 -25). Compared to 1D MRS, 2D MR spectra allow less ambiguous assignment of several metabolite resonances in human brain and prostate (25)(26)(27). In a previous study (25), the resonances caused by glutamine/glutamate (Glx) were clearly separated from the dominant singlet resulting from N-acetyl aspartate (NAA) and myo-inositol (mI) in the human brain. Even though identification of "free" aspartate (Asp) was not possible with 1D MRS, the peaks were separated from NAA in 2D MRS (25). 2D cross peaks caused by phosphoethanolamine and ethanolamine (PE), phosphoryl choline (PCh), threonine and lactate (Thr/Lac), and ␥-aminobutyric acid (GABA) were also identified in the 2D L-COSY spectra of the brain. However, to date there has been no report on the reproducibility of 2D MRS. The goal of this work was to investigate the reproducibility of 2D peak volumes and 2D metabolite ratios recorded in phantom solutions and healthy brain using the L-COSY sequence (25). MATERIALS AND METHODS A 1.5 T GE Horizon (5.8) MRI/MRS scanner (GE MedicalSystems, Waukesha, WI) with echo-speed gradients was used with a body coil for transmission and a 3-inch surface coil for reception. ...

A localized 2D correlation spectroscopic sequence (L-COSY) was implemented and applied in human breast cancer in vivo to evaluate the water to fat (both saturated and unsaturated) ratios and also to identify choline. Being in agreement with the conventional 1D magnetic resonance spectroscopy (MRS) results, elevated water to lipids ratios were found in breast cancers and choline was observed only in a few cancer patients. J. Index terms: 1 H MR spectroscopy; saturated fatty acid; unsaturated fatty acids; water; choline DIAGNOSIS AND TREATMENT of the breast tumor, the second most common cancer among women, remain a significant medical challenge. The high priorities of breast cancer are early detection, diagnosis, and timely treatment. The clinical needs with respect to lesion characterization and staging have not been well addressed by mammography and other conventional imaging and diagnostic tools.Proton magnetic resonance spectroscopy ( 1 H MRS) of surgically excised breast tumors was first performed by Chu et al. with differences between the malignant and uninvolved healthy tissues reported, but malignant and benign tissues were indistinguishable with 1 H MRS (1). Kaplan and Cohen investigated 1 H MRS of breast cancer cells; peaks due to various choline groups (Cho), creatine/phosphocreatine (Cr/PCr), and lactate (Lac) were reported (2). MRS of 108 plasma samples from patients with breast tumors and from healthy subjects showed significant line width changes in methylene peaks (3). The water to fat ratios were calculated in patients with malignancy and benign tumors, and the ratios were high in the affected side, compared to the unaffected side (4 -6). Cho levels have been recently investigated in breast carcinomas and unaffected breasts (5-7). Mackinnon et al. used 1 H MRS ex vivo to differentiate the fine-needle biopsy specimens of benign breast lesions from invasive cancer (8).A major concern with 1D MRS is that the spectral peaks severely overlap each other. In particular, the dominant peaks due to lipids in the breast overlap with those of metabolites. Spectral editing and multiple quantum (MQ) techniques can be used to differentiate lactate and other metabolites from the overlapping lipids (9 -12). A drawback of the spectral editing technique is that only one metabolite can be selectively detected (9,10). Reduced signal strength of metabolites is a primary concern with MQ techniques (11,12). Several versions of localized 2D MRS have been successfully implemented on a whole-body 1.5T MR imaging (MRI) scanner (13-17). Due to an added dimension, a localized 2D MR spectrum has a better resolution than a conventional 1D MR spectrum (13-18). The objectives of this work were threefold: 1) to implement and evaluate a localized 2D correlated MR spectroscopic sequence (L-COSY) in the human breast and to quantitate the levels of lipids (saturated and unsaturated), water, and metabolites using a dedicated phased-array breast coil; 2) to investigate the regional variations of lipids, metabolites, and water using the 2...