Respiratory motion-corrected proton magnetic resonance spectroscopy of the liver

Purpose

To develop a post-processing, respiratory-motion correction algorithm for magnetic resonance spectroscopy (MRS) of the liver and to determine the incidence and impact of respiratory motion in liver MRS.

Materials and Methods

One hundred thirty-two subjects (27 healthy, 31 with nonalcoholic fatty liver disease and 74 HIV-infected with or without hepatitis C) were scanned with free breathing MRS at 1.5 T. Two spectral time series were acquired on an 8-ml single voxel using TR/TE=2500 ms/30 ms and (1) water suppression, 128 acquisitions, and (2) no water suppression, 8 acquisitions. Individual spectra were phased and frequency aligned to correct for intrahepatic motion. Next, water peaks more than 50% different from the median water peak area were identified and removed, and remaining spectra averaged to correct for presumed extrahepatic motion. Total CH₂+CH₃ lipids to unsuppressed water ratios were compared before and after corrections.

Results

Intrahepatic-motion correction increased the signal to noise ratio (S/N) in all cases (median=11-fold). Presumed extrahepatic motion was present in 41% (54/132) of the subjects. Its correction altered the lipids/water magnitude (magnitude change: median=2.6%, maximum=290%, and was >5% in 25% of these subjects). The incidence and effect of respiratory motion on lipids/water magnitude were similar among the three groups.

Conclusion

Respiratory-motion correction of free breathing liver MRS greatly increased the S/N and, in a significant number of subjects, changed the lipids/water ratios, relevant for monitoring subjects.     

In vivo proton magnetic resonance spectroscopy studies of human brain

In vivo localized proton magnetic resonance spectroscopy (MRS) studies of brain were performed on eighteen normal subjects using the stimulated echo (STE) sequence. The absolute concentrations and proton relaxation times of N-acetyl aspartate (NAA), total creatine (Cr) and choline (Cho) were estimated. The MRS data was quantitatively analyzed for repeatability and intersubject variability. Quantitative analysis indicates excellent spectral repeatability. Significant intersubject variations in [NAA] and [Cr] have been observed while the intersubject variability in [Cho] has been found to be fairly small. Significant intensity distortions have been observed for mixing times longer than 50 msec.     

Brain metabolite alterations demonstrated by proton magnetic resonance spectroscopy in diabetic patients with retinopathy

Due to the homology between retinal and cerebral microvasculatures, retinopathy is a putative indicator of cerebrovascular dysfunction. This study aimed to detect metabolite changes of brain tissue in type 2 diabetes mellitus (T2DM) patients with diabetic retinopathy (DR) using proton magnetic resonance spectroscopy (¹H-MRS). Twenty-nine T2DM patients with DR (DR group), thirty T2DM patients without DR (DM group) and thirty normal controls (NC group) were involved in this study. Single-voxel ¹H-MRS (TR: 2000 ms, TE: 30 ms) was performed at 3.0 T MRI/MRS imager in cerebral left frontal white matter, left lenticular nucleus, and left optic radiation. Our data showed that NAA/Cr ratios of the DR group were significantly lower than those of the DM group in the frontal white matter and optic radiation. In the lenticular nucleus, MI/Cr ratios were significantly higher in the DM group than those in the NC group, while MI/Cr ratios were significantly lower in the DR group than those in the DM group. In the frontal white matter, NAA/Cho ratios were found to be decreased in the DR group as compared to the NC group. Additionally, our finding indicated that NAA/Cr ratios were negatively associated with DR severity in both the frontal white matter and optic radiation. A decrease in NAA indicated neuronal loss and the likely explanation for a decrease in MI was glial loss. In conclusion, we inferred that cerebral neurons and glia cells were damaged in patients with DR. Our data support that DR is associated with brain tissue damage.     

In vivo proton magnetic resonance spectroscopy of alcohol in rhesus monkey brain

Brain alcohol was measured in rhesus monkeys (Macaca mulatta) by proton magnetic resonance spectroscopy (MRS) following acute nasogastric alcohol administration (0.8 g/kg). Monkeys were anesthetized with ketamine and xylazine. A 1.5 T whole body imager and a 3-inch surface coil were used to acquire TE 30 and 270 ms spectra from a 7.5 cc voxel localized with a stimulated echo (STEAM) sequence. Venous blood samples were collected during spectral acquisitions for gas chromatographic determination of temporally concordant blood alcohol levels (BALs). Acute alcohol administration did not alter the resonance areas of N-acetylaspartate/N-acetyl containing compounds (NAA), choline containing compounds, or total creatine. The NAA resonance was used as an internal standard to calculate approximate brain alcohol concentrations, which averaged 27 ± 3% and 27 ± 8% of temporally concordant BALs (T₂-corrected TE 30 and TE 270 ms spectra, respectively). In addition to reconfirming results from prior studies finding incomplete detection of brain alcohol with MRS, these results demonstrate the feasibility of measuring brain alcohol in anesthetized nonhuman primates to examine relationships between alcohol exposure history and MRS-visibility of brain alcohol.     

Therapeutic response of tumors by in-vitro proton nuclear magnetic resonance spectroscopy

Proton NMR spectra of perchloric acid extracts of methyl cholantherene induced tumors grown in rats have been analyzed and compared with the normal and the treated tumor tissue samples. Well-resolved resonances from numerous low-molecular weight compounds including various amino acids, nucleotides, choline, creatine, phosphocreatine etc. were observed and assigned using pH titration, 2D NMR and by comparison with the spectra of model compounds. Significant differences were noticed in the spectra of the tumor and the normal tissue samples. Ratios of metabolite levels were calculated for the normal, tumor and treated tumor tissues which are shown as good markers to assess the state of the tumor and their response to treatment.     

High resolution proton magnetic resonance spectroscopy of human brain and liver

Water-suppressed and slice-selective proton spectra of live human brain exhibited several resonances that were tentatively assigned to metabolites such as N-acetylaspartate, glutamate, phosphocreatine and creatine, choline derivatives, and taurine. In the liver spectrum of a healthy volunteer, the major resonance was tentatively assigned to a fatty acyl methylene and the minor resonances to protons in carnitine, taurine, glutamate, and glutamine. In the spectrum of a cancerous liver, resonances in addition to those present in the normal liver were seen. Protein degradation in the liver with cancer was indicated by resonances from urea and from the ring protons in tryptophan, tyrosine, and phenylalanine. Furthermore, increased nucleic acid synthesis was indicated by resonances from nucleotide protons.     

Detection of dimethyl sulfone in the human brain by in vivo proton magnetic resonance spectroscopy

We wish to report the detection of dimethyl sulfone (methylsulfonylmethane, C2H6O2S) in the brain of a normal 62-year-old male using in vivo proton magnetic resonance spectroscopy. The presence of this exogenous metabolite resulted from ingestion of a dietary supplement containing dimethyl sulfone. The concentration of this compound in the brain was measured to be 2.4 mmol, with a washout "half life" of approximately 7.5 days. The in vivo T1 and T2 relaxation times of dimethyl sulfone were measured to be 2180 ms and 385 ms, respectively. The concentration of major brain metabolites, namely N-acetylaspartate, total Creatine and Choline, and myo-Inositol were within normal limits.     

Detection of rectal cancer and response to concurrent chemoradiotherapy by proton magnetic resonance spectroscopy

Introduction

To diagnose rectal cancer and monitor treatment response after preoperative concurrent chemoradiotherapy (CCRT) in rectal cancer patients using proton-1 magnetic resonance spectroscopy (¹H-MRS).

Materials and Methods

We enrolled 134 rectal cancer patients before treatment, of whom 34 underwent preoperative CCRT and follow-up MR spectroscopy before surgery. ¹H-MRS was performed using a six-channel phased-array coil at 3.0 T. We evaluated the presence of a choline peak at 3.2 ppm, and lipid peaks at 0.9 and 1.3 ppm, and glutamine and glutamate peaks at 2.1-2.3 and 2.7 ppm seen at two TEs (40 and 135 ms). We divided MR spectra patterns into two groups (A and B).

Results

A choline peak at 3.2 ppm seen in both TEs was characteristic for rectal cancer before treatment. Of 103 patients, 55 (53%) showed an elevated choline peak before treatment (type A). Type A spectra were seen in 68% of patients (23/34) before preoperative CCRT. After CCRT, the choline peak disappeared, resulting in only the lipid peak at 1.3 ppm (type B) in 97% of patients (33/34).

Discussion

We optimized a localized in vivo¹H-MRS method for detection of rectal adenocarcinoma and monitoring treatment response after preoperative CCRT. The method appears to be a promising and feasible noninvasive modality.     

The role of magnetic resonance spectroscopy in clinical medicine

This article presents a view which emphasises the particular perspective of a clinician who has close involvement in magnetic resonance spectroscopy (MRS) and is directed towards readers who wish to understand the likely role of MRS in clinical medicine. Many more complete reviews already exist, including two review articles from our group. Another review would hardly be justifiable and those readers seeking such an article should consult Refs. 1–5. This will be more in the nature of a personal overview of the topic and one which will touch upon some of the problems which accrue from the interactions of scientists with little appreciation of clinical medicine with clinicians who have little understanding of the complexities of the NMR experiment. Moreover, the discussion will be confined to situations where MRS is likely to impinge directly on problems of day-to-day clinical management, as opposed to situations where the results of MRS research lead to an improved understanding of particular disease states, but where there is no need for each and every patient who is a potential benificiary of the technique to undergo an MRS examination.     

Metabolism of the colonic mucosa in patients with inflammatory bowel diseases: an in vitro proton magnetic resonance spectroscopy study

Metabolism of the colonic mucosa of patients with ulcerative colitis (UC; n=31) and Crohn's disease (CD; n=26) and normal mucosa (control, n=26) was investigated using in vitro high-resolution proton magnetic resonance spectroscopy. Of the 31 UC patients, 20 were in the active phase and 11 were in the remission phase of the disease. Out of 26 CD patients, 20 were in the active phase, while 6 were in the remission phase of the disease. Twenty-nine metabolites were assigned unambiguously in the perchloric acid extract of colonic mucosa. In the active phase of UC and CD, significantly lower (P相似文献   

Brain metabolite changes in alcoholism: An in vivo proton magnetic resonance spectroscopy (MRS) study

Image-guided, single voxel, localized proton magnetic resonance (MR) spectroscopy was performed to assess the brain metabolite changes in 10 (n = 10) alcoholic patients in the frontal lobe, cerebellum, and thalamus regions. The spectra obtained were characterized by a reduced N-acetyl-aspartate (NAA) to choline (Cho) (p < .01) and NAA to total creatine (Cr + PCr) (p < .01) ratios relative to age-matched (n = 27) controls. These decreased ratios correspond to depleted concentration of the metabolite levels such as NAA and Cho. Reduction of NAA is consistent with the neuronal loss while reduction in Cho suggests significant changes in the membrane lipids of alcoholics.     

Low temperature behaviour of proton magnetic resonance in metallocenes

Proton magnetic resonance of polycrystalline nickelocene and chromocene has been observed at temperatures between 20 and 1.6 K. It confirms that these metallocenes have temperature-independent paramagnetism in this temperature region. The origin of the observed line shape and position characteristic at low temperature is discussed.     

Therapeutic efficacy of a case of pyruvate dehydrogenase complex deficiency monitored by localized proton magnetic resonance spectroscopy

We experienced a case of pyruvate dehydrogenase deficiency observed by proton magnetic resonance spectroscopy(¹H MRS). This case was diagnosed as West syndrome by characteristic convulsion and the periodic hypsarrhythmia pattern of EEG. At the age of 11 months, the first examination of ¹H MRS revealed a high peak of lactate, and the high concentration of lactate and pyruvate was confirmed in sampled cerebrospinal fluid (CSF). Deficiency of pyruvate dehydrogenase complex was finally diagnosed by genetic examination. Dichloroacetate was administered to the patient as therapy. Decrease of lactate in the brain was found by ¹H MRS. Lactate and pyruvate in the CSF was also decreased. In accordance with the suspension of dichloroacetate, increase of lactate in the brain was detected and the convulsions reappeared. After readministration of dichloroacetate, the patient was almost symptom free and lactate in the brain and CSF had decreased to the normal extent. We considered that ¹H MRS provides useful information for screening metabolic disorders of infants and assessing the efficacy of therapy.     

Quantification of neurons in Alzheimer and control brains with ex vivo high resolution magic angle spinning proton magnetic resonance spectroscopy and stereology

Samples from human brains were examined with both stereologic methods for neuronal counting and high resolution magic angle spinning (HRMAS) proton magnetic resonance spectroscopy (1HMRS) for quantification of cellular metabolites. A statistically significant linear correlation between neuronal density and the concentration of N-acetylaspartate (NAA) in the superior temporal sulcus (STS) area was observed. Although NAA has been widely utilized as a neuronal marker in in vivo MRS, an emerging sub-discipline of diagnostic neuroradiology, the experimental proof of the unilateral relationship between NAA and neurons has yet to be confirmed. The observed correlation provides experimental evidence that NAA concentration is proportional to the neuronal density. Metabolite ratios measured from the STS area were compared to those from frontal association cortex for their sensitivities in differentiating Alzheimer disease brains from control brains.     

Fast quantification of proton magnetic resonance spectroscopic imaging with artificial neural networks

Accurate quantification of the MRSI-observed regional distribution of metabolites involves relatively long processing times. This is particularly true in dealing with large amount of data that is typically acquired in multi-center clinical studies. To significantly shorten the processing time, an artificial neural network (ANN)-based approach was explored for quantifying the phase corrected (as opposed to magnitude) spectra. Specifically, in these studies radial basis function neural network (RBFNN) was used. This method was tested on simulated and normal human brain data acquired at 3T. The N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, glutamate+glutamine (Glx)/Cr, and myo-inositol (mI)/Cr ratios in normal subjects were compared with the line fitting (LF) technique and jMRUI-AMARES analysis, and published values. The average NAA/Cr, Cho/Cr, Glx/Cr and mI/Cr ratios in normal controls were found to be 1.58+/-0.13, 0.9+/-0.08, 0.7+/-0.17 and 0.42+/-0.07, respectively. The corresponding ratios using the LF and jMRUI-AMARES methods were 1.6+/-0.11, 0.95+/-0.08, 0.78+/-0.18, 0.49+/-0.1 and 1.61+/-0.15, 0.78+/-0.07, 0.61+/-0.18, 0.42+/-0.13, respectively. These results agree with those published in literature. Bland-Altman analysis indicated an excellent agreement and minimal bias between the results obtained with RBFNN and other methods. The computational time for the current method was 15s compared to approximately 10 min for the LF-based analysis.     

In vivo proton magnetic resonance spectroscopy of diseased prostate: spectroscopic features of malignant versus benign pathology.

In vivo Proton Magnetic Resonance Spectroscopy appears potentially useful for non-invasive discrimination between benign prostatic hyperplasia (BPH) and prostate carcinoma (PC). Aiming to delimit the range within which spectra from one or the other pathology should occur, and establish extreme spectroscopic features of malignant versus benign prostate disease, we performed endorectal proton MR spectroscopy on 20 patients severely affected of either benign prostatic hyperplasia (BPH) (n = 10) or prostate cancer (PC) (n = 10). They were selected on the basis of the large volume and homogeneity of their lesions, which were histologically confirmed after spectroscopy. Consequently, high-quality short-TE proton spectra with well-resolved metabolite signals, and practically free of volume averaging issues were obtained in all cases. Apart from the typical citrate, creatine, and choline signals of prostate spectra, both BPH and PC spectra showed a peak centered at 3.6 ppm which was assigned to myo-inositol. The intensity of this contribution was found significantly increased in PC cases compared to BPH. Possible relationships between neoplastic transformation and the metabolic pathways in which myo-inositol participates are discussed. Average spectroscopic profiles were calculated for both advanced pathologies, and showed obvious differentiated features. In quantitative terms, the ratio of citrate to choline peak areas as well as that of creatine to myo-inositol appeared as the most convenient to discriminate between advanced PC cases (both ratios below 1.0) and advanced BPH cases (both ratios above 1.0).     

Paramagnetic enhanced proton magnetic resonance measurement in rats: correlates with renal function

Renal cortical, medullar and papillary T1 and T2 relaxation times were measured in rats with normal (n = 13) and impaired renal function (n = 11) with a Bruker Multispec, 20 MHz at 37 degrees C. In one group of seven rats, decreased renal function was obtained by 50% glycerol solution administration (10 ml/kg-body weight) 24 hours before the experiment, while in another group of four rats the renal function was decreased, by ureteral ligation for 72 hours. Immediately after the excision of one kidney, Gadolinium-DTPA (70 mumole/kg body weight) was injected intravenously. The second kidney was excised 5 min later. From the T1 and T2 relaxation times measured in the cortex, medulla, and papilla, their respective ratios before and after GdDTPA administration were calculated and correlated with GFR determined by creatinine clearance (Ccr range was between 0 and 850 microliters/min/g kidney weight). For T1: the ratios in the cortex, medulla, and papilla the correlation coefficients were r = 0.81 (p less than 0.001), r = 0.85 (p less than 0.001), and r = 0.87 (p less than 0.0001), respectively. The respective correlation coefficient r values for T2 were r = 0.38 (NS), r = 0.76 (p less than 0.001), and r = 0.73 (p less than 0.001). The present study indicates that a combination of MR measurements, with and without GdDTPA paramagnetic enhancement, can offer a new possibility for obtaining information on renal function and suggest the possibility of concomitant anatomo functional magnetic resonance imaging.     

Generalization of the lineshape useful in magnetic resonance spectroscopy

A new lineshape function is derived from the Tsallis distribution to describe electron paramagnetic resonance (EPR) spectra, and possibly nuclear magnetic resonance (NMR) spectra as well. This lineshape generalizes the Gaussian and Lorentzian lineshapes that are widely used in simulations. The main features of this lineshape function are presented: the normalization, moments, and first derivative. A number of experimental EPR spectra are compared with the results of simulations employing the new lineshape function. The results show that the new lineshape often provides a better approximation of the experimental spectrum. It is also shown that the new parameter of the lineshape function can be used to quantify the intermolecular spin-spin interactions.