Methodological consensus on clinical proton MRS of the brain: Review and recommendations.

Proton MRS (1 H 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.

In vivo 1 H MRS of human gallbladder bile in understanding the pathophysiology of primary sclerosing cholangitis (PSC): Immune-mediated disease versus bile acid-induced injury.

Primary sclerosing cholangitis (PSC) has been considered to be either an "autoimmune disease" or a "bile acid-induced injury." In vitro MRS studies on PSC patients have limitations due to the contamination of bile with contrast agent (commonly administered during endoscopic retrograde cholangiopancreatography) and/or the use of patient cohorts with other diseases as controls. The objective of this study was to quantify biliary metabolites using in vivo 1 H MRS and gain insight into the pathogenesis of PSC. Biliary metabolites in 10 PSC patients and 14 healthy controls were quantified in vivo using 1 H MRS on a 3 T MR scanner. The concentrations of total bile acids plus cholesterol, glycine-conjugated bile acids, taurine-conjugated bile acids, and choline-containing phospholipids (chol-PLs) were compared between the two groups. There were statistically significant decreases in the levels of the above mentioned biliary metabolites in the PSC patients compared with controls. The reduction in bile acid secretion in bile of PSC patients indicates accumulation of bile acids in hepatocytes. Moreover, reduction in the levels of chol-PLs in bile may increase the toxic effects of bile acids. Our findings suggest that the bile duct injury in PSC patients is most likely due to "bile acid-induced injury."

Clinical proton MR spectroscopy in central nervous system disorders.

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.

In vivo 1H MRS of human gallbladder bile at 3 T in one and two dimensions: detection and quantification of major biliary lipids.

In vitro (1)H MRS of human bile has shown potential in the diagnosis of various hepatopancreatobiliary (HPB) diseases. Previously, in vivo (1)H MRS of human bile in gallbladder using a 1.5 T scanner demonstrated the possibility of quantification of choline-containing phospholipids (chol-PLs). However, other lipid components such as bile acids play an important role in the pathophysiology of the HPB system. We have employed a higher magnetic field strength (3 T), and a custom-built receive array coil, to improve the quality of in vivo (1)H MRS of human bile in the gallbladder. We obtained significant improvement in the quality of 1D spectra (17 healthy volunteers) using a respiratory-gated PRESS sequence with well distinguished signals for total bile acids (TBAs) plus cholesterol resonating at 0.66 ppm, taurine-conjugated bile acids (TCBAs) at 3.08 ppm, chol-PLs at 3.22 ppm, glycine-conjugated bile acids (GCBAs) at 3.74 ppm, and the amide proton (-NH) arising from GCBAs and TCBAs in the region 7.76-8.05 ppm. The peak areas of these signals were measured by deconvolution, and subsequently the molar concentrations of metabolites were estimated with good accuracy, except for that of TBAs plus cholesterol. The concentration of TBAs plus cholesterol was overestimated in some cases, which could be due to lipid contamination. In addition, we report the first 2D L-COSY spectra of human gallbladder bile in vivo (obtained in 15 healthy volunteers). 2D L-COSY spectra will be helpful in differentiating various biliary chol-PLs in pathological conditions of the HPB system.

Absence of glycochenodeoxycholic acid (GCDCA) in human bile is an indication of cholestasis: a 1H MRS study.

The utility of (1)H MR spectroscopy in detecting chronic cholestasis has been investigated. The amide proton region of the (1)H MR spectrum of human bile plays a major role in differentiating cholestatic (Ch) patterns from the normal ones. Bile obtained from normal bile ducts contains both taurine and glycine conjugates of bile acids--cholic acid (CA), chenodeoxycholic acid (CDCA), and deoxycholic acid (DCA). Absence of a glycine-conjugated bile acid glycochenodeoxycholic acid (GCDCA) has been observed in bile samples obtained from primary sclerosing cholangitis (PSC) patients. A total of 32 patients with various hepatobiliary diseases were included in the study. Twenty-one patients had PSC and 11 had normal cholangiograms. One PSC patient was excluded from the study because of a bad spectrum. Seventeen out of the 20 PSC patients showed an absence of GCDCA in their (1)H MR spectrum of bile. Six of the 11 reference patients with normal cholangiogram also showed spectra similar to those of PSC, indicating the possibility of cholestasis. DQF-COSY and TOCSY experiments performed on bile samples from PSC patients also revealed absence of phosphatidylcholine (PC) in some of the bile samples, suggesting possible damage to the cholangiocytes by the toxic bile. These observations suggest that analysis of human bile by (1)H MRS could be of value in the diagnosis of chronic Ch liver disorders.

Detection and quantification of D-glucuronic acid in human bile using 1H NMR spectroscopy: relevance to the diagnosis of pancreatic cancer.

OBJECTIVE: There are no specific biomarkers available for the definitive diagnosis of pancreatic cancer. Analysis of D-glucuronic acid (GlcUA) in bile could be valuable in this regard. MATERIALS AND METHODS: Bile samples obtained from patients with pancreatic cancer (n = 4), chronic pancreatitis (n = 3) and control patients with biliary obstruction (n = 10) were analyzed by (1)H NMR spectroscopy. GlcUA was quantified from the peak area of the alpha-(1)CH signal (at 5.24 ppm) obtained by deconvolution. RESULTS: GlcUA was detected in human bile by one-dimensional (1)H NMR and two-dimensional (1)H-(1)H COSY and TOCSY experiments. Quantification of GlcUA was achieved by measuring the peak area of the alpha-(1)CH signal using CPMG experiment, and the quantities of GlcUA were calibrated to account for the attenuation due to T (2) relaxation. GlcUA was observed at elevated levels in bile samples obtained from pancreatic cancer patients, whereas it was either absent or found in negligible amounts in control and chronic pancreatitis patients. The reason for the presence of elevated levels of GlcUA could be the hydrolysis of biliary bilirubin diglucuronide by beta-glucuronidase, released excessively from pancreatic tissue during the course of malignancy. CONCLUSION: Analysis of D-glucuronic acid in bile could be valuable in the detection of pancreatic cancer, and detecting GlcUA by in vivo (1)H MRS has the potential to help in the non-invasive diagnosis of pancreatic cancer. Given that only four cancer patients have been studied so far, the new biomarker is regarded as a preliminary finding, but one that warrants further investigation.

MR metabolomics of fecal extracts: applications in the study of bowel diseases.

NMR-based metabolomics is becoming a useful tool in the study of body fluids and has a strong potential to contribute to disease diagnosis. While applications on urine and serum have been the focus to date, there are a number of other body fluids that are readily available and could potentially be used for metabolomics-based disease diagnosis. One such body fluid is stool or fecal extract. Given its contact with and transient stay in the colon and rectum, stool carries a lot of useful information regarding the health/disease status of both the colon and the rectum. This could be particularly useful for the non-invasive diagnosis of colorectal cancer and inflammatory bowel disease--the two bowel diseases that are very common and pose significant public health problems. Different methodological considerations including the collection of sample, the storage of sample, the preparation of sample, NMR acquisition parameters, experimental conditions and data analysis methods are discussed. Results obtained in the detection of colorectal cancer and in the differentiation of the two major forms of inflammatory bowel disease (i.e. ulcerative colitis and Crohn's disease) are presented. This is concluded with a brief discussion on the future of MR metabolomics of fecal extracts.

Prediction of treatment response in head and neck cancer by magnetic resonance spectroscopy.

BACKGROUND AND PURPOSE: Poor treatment outcome remains high in patients with squamous cell carcinoma (SCC) of the head and neck region. Treatment of head and neck cancer could be improved and perhaps standardized if reliable markers for tumor progression and poor prognosis could be developed. MR spectroscopy has been used previously to differentiate between malignant and adjacent normal specimen in these cancers. This study explores the capability of MR spectroscopy in providing an indication of the aggressiveness of a tumor and its response to treatment. METHODS: Thirty-six SCC patients with treatment failure, and 22 other patients who were treated concurrently at the same center but with no indication of failure for a period of 3 years, were selected for the study. Tumor specimens were kept frozen at -70 degrees C, and later subjected to 1H-MR spectroscopy at 25 degrees C. The resonance areas for 6 spectral regions were determined, and their ratio calculated. The mean values of the ratios were then compared between the 2 groups by using the Student t test. RESULTS: The choline-to-creatine (3.2/3.0 parts per million [ppm]) and the 1.3/0.9 ppm spectral intensity ratios (signal due to lipid or lactic acid) were the 2 most notable ones to be significantly elevated in the group with poor response. Using these ratios, a sensitivity of 83% and a specificity of 82% were obtained in predicting which head and neck cancer patients would fail treatment. CONCLUSIONS: These preliminary results suggest that MR spectroscopy has the potential to contribute to an accurate and early prediction of tumor behavior and response to treatment in squamous cell carcinoma of the head and neck region.

Deriving biomedical diagnostics from NMR spectroscopic data.

Biomedical spectroscopic experiments generate large volumes of data. For accurate, robust diagnostic tools the data must be analyzed for only a few characteristic observations per subject, and a large number of subjects must be studied. We describe here two of the current data analytic approaches applied to this problem: SIMCA (principal component analysis, partial least squares), and the statistical classification strategy (SCS). We demonstrate the application of the SCS by three examples of its use in analyzing 1H NMR spectra: screening for colon cancer, characterization of thyroid cancer, and distinguishing cancer from cholangitis in the biliary tract.

Simultaneous quantification of glycine- and taurine-conjugated bile acids, total bile acids, and choline-containing phospholipids in human bile using 1H NMR spectroscopy.

Bile acids, phospholipids, and cholesterol are the major lipid components in human bile. The composition of bile is altered in various cholestatic diseases, and determining such alterations will be of great clinical importance in understanding the pathophysiology of these diseases. A robust method for the simultaneous quantification of major biliary lipids--glycine-conjugated bile acids (GCBAs), taurine-conjugated bile acids (TCBAs), total bile acids (TBAs) and choline-containing phospholipids (choline-PLs) has been devised using (1)H NMR spectroscopy. Bile samples were obtained from patients with various hepatopancreatobiliary diseases (n=10) during an endoscopic retrograde cholangiopancreatography (ERCP) examination. Peak areas of metabolite-signals of interest were obtained simultaneously by deconvoluting the experimental spectrum, making the present method robust. GCBAs and TCBAs have been quantified using the peak areas of their characteristic methylene (CH(2)) signals resonating at 3.73 and 3.07 ppm, whereas TBA and choline-PLs were quantified using their methyl (CH(3)) and trimethylammonium (-N(+)(CH(3))(3)) signals resonating at 0.65 and 3.22 ppm respectively. The present method was compared with an NMR-based literature method (which involves dissolving bile in DMSO), and a good correlation was observed between the two methods with regression coefficients - 0.97, 0.99, 0.98 and 0.93 for GCBAs, TCBAs, TBAs, and choline-PLs respectively. This method has the potential to be extended to in vivo applications for the simultaneous quantification of various biliary lipids non-invasively.

Medical diagnosis by high resolution NMR of human specimens.

NMR has progressed relatively recently from a technique used almost exclusively by chemists and physicists to a viable tool for medical diagnosis. NMR applications have developed from analysis of cells, tissues, and biological fluids, to in vivo analysis. We discuss some examples of its clinical successes, as well as some of the challenges encountered along the way.

Statistical classification strategy for proton magnetic resonance spectra of soft tissue sarcoma: an exploratory study with potential clinical utility.

PURPOSE: Histological grading is currently one of the best predictors of tumor behavior and outcome in soft tissue sarcoma. However, occasionally there is significant disagreement even among expert pathologists. An alternative method that gives more reliable and non-subjective diagnostic information is needed. The potential use of proton magnetic resonance spectroscopy in combination with an appropriate statistical classification strategy was tested here in differentiating normal mesenchymal tissue from soft tissue sarcoma. METHODS: Fifty-four normal and soft tissue sarcoma specimens of various histological types were obtained from 15 patients. One-dimensional proton magnetic resonance spectra were acquired at 360 MHz. Spectral data were analyzed by using both the conventional peak area ratios and a specific statistical classification strategy. RESULTS: The statistical classification strategy gave much better results than the conventional analysis. The overall classification accuracy (based on the histopathology of the MRS specimens) in differentiating normal mesenchymal from soft tissue sarcoma was 93%, with a sensitivity of 100% and specificity of 88%.The results in the test set were 83, 92 and 76%, respectively. Our optimal region selection algorithm identified six spectral regions with discriminating potential, including those assigned to choline, creatine, glutamine, glutamic acid and lipid. CONCLUSION: Proton magnetic resonance spectroscopy combined with a statistical classification strategy gave good results in differentiating normal mesenchymal tissue from soft tissue sarcoma specimens ex vivo. Such an approach may also differentiate benign tumors from malignant ones and this will be explored in future studies.

An ex vivo study exploring the diagnostic potential of 1H magnetic resonance spectroscopy in squamous cell carcinoma of the head and neck region.

BACKGROUND: Definitive diagnosis of head and neck cancer is generally made by histopathologic evaluation. Management and prognosis largely depend on accurate and timely diagnosis. We have explored the use of (1)H magnetic resonance spectroscopy in search of a better or complementary diagnostic technique. METHODS: Tumor and adjacent normal tissue specimens (n = 135) from untreated head and neck cancer patients (n = 40) were obtained and subjected to spectroscopic evaluation followed by histopathologic analysis. Data were partitioned into training and test sets and subjected to multivariate analysis. RESULTS: The resonances from taurine, choline, glutamic acid, lactic acid, and lipid were found to have diagnostic potential by our optimal region selection algorithm. Multivariate analysis of the spectral data differentiated between normal and malignant tissues, with an overall accuracy of 92.6% (training set, 97.3%; test set, 87.3%), an overall sensitivity of 93% (test set, 90%), and an overall specificity of 92% (test set, 82.6%). CONCLUSIONS: (1)H magnetic resonance spectroscopy combined with multivariate methods of analysis can distinguish between normal and malignant squamous cell tissue, and this may lead to the development of an objective and noninvasive diagnostic procedure.