Image Selected In Vivo Spectroscopy Research Articles

Localized 31P MR spectroscopy of the transplanted human kidney in situ shows altered metabolism in rejection and acute tubular necrosis

The purpose of this study was to investigate the function of transplant kidneys in situ, and to detect pathologic changes, using volume-selective phosphorous NMR spectroscopy (31P MRS). Localized 31P MR spectra were obtained from 37 patients using a whole-body MR scanner with a combination of surface coils, adiabatic excitation pulses, and a modified image-selected in vivo spectroscopy (ISIS) sequence. Seventeen patients with pathologic changes after renal transplant were compared with a control group of 20 patients with no evidence of transplant dysfunction. The transplant kidneys with rejection reaction showed higher ratios of inorganic phosphate (P2i) to adenosine triphosphate-alpha (ATP-alpha) than the normal control group (.4 +/- .16 compared with .22 +/- .11, P = .01) and reduced pH. The spectra of transplant kidneys with tubular necrosis had lower phosphomonoester (PME)/phosphodiester (PDE) ratios than the control group (.65 +/- .35 compared with .96 +/- .5, P = .04). The pathologies of rejection and tubular necrosis could be differentiated from each other by pH (6.93 +/- .1 in rejection versus 7.14 +/- .19 in tubular necrosis, P = .04). Preliminary results indicate that localized image-guided 31P MR spectroscopy of transplant kidneys in situ can detect rejection reactions and acute tubular necrosis noninvasively, providing an incentive for further research.

31P-MR-Spektroskopie der menschlichen Leber - spektrale Hinweise auf eine Lymphominfiltration

To evaluate whether phosphorus magnetic resonance spectroscopy (31P-MRS) enables a non-invasive detection of liver involvement in systemic diseases like Hodgkin's lymphoma. Using a clinical 1.5 Tesla whole-body MR system image-guided localised phosphorus MR spectra from the anatomically defined volumes of interests were measured. A combination of surface coil, adiabatic excitation pulse and modified image-selected in vivo spectroscopy (ISIS)-sequence was applied. The spectroscopy data were evaluated quantitatively with a time-domain fit programme using non-linear optimisation algorithms to quantify peak areas. After establishment of the examination protocol, 22 healthy volunteers and 13 patients with suspected lymphoma infiltration of the liver were examined. Liver spectra of patients suffering from lymphoma infiltration differed significantly from spectra of persons with normal liver: 1. The peak area ratio of phosphomonoesters (PME) to beta-NTP was elevated in all patients with histologically confirmed liver lymphoma. 2. Patients suffering from Hodgkin's disease with specific or unspecific liver infiltration (n = 7) could be differentiated from patients without liver involvement. In case of infiltrated liver, the peak area ratio PME to beta-NTP was increased, and the pH value was shifted to lower values. Unambiguous differentiation between non-specific (n = 3) and specific (n = 4) infiltration of the liver was not possible. 3. In patients after cytostatic treatment (n = 3), an increase of the peak area ratio of inorganic phosphate to beta-NTP was observed. Our preliminary results indicate that 31P-MRS can yield pointers to liver involvement in patients with systemic diseases such as Hodgkin's disease, which may be hardly detected by imaging methods.

Signal profile measurements for evaluation of the volume‐selection performance of ISIS

High-resolution signal profiles obtained with a test phantom were used in this study to evaluate the volume-selection performance of an implementation of ISIS (Image Selected In vivo Spectroscopy). The phantom simulated the brain with regard to volume and loading of coil. A remotely controlled, movable signal source inside the phantom was filled with orthophosphoric acid. Signal profiles of the volume of interest (VOI) were measured in three perpendicular directions. Special interest was focused on the transition zones, the position of the profiles, and the effects of off-resonance and T1 smearing. The transition zones were on average 5.6 mm wide and the full width at half maximum (FWHM) was 35 mm for a VOI of 40 x 40 x 40 mm3. The positions of the centre of the signal profiles were x = 3.2, y = -0.7 and z = 3.3 mm off-centre. The deviation of the volume position could be explained by off-resonance effects during imaging and spectroscopy. These data illustrate the importance of detailed knowledge of the volume-selection performance when attempting precision measurements using image-guided in vivo MRS.

An assessment of artefacts in localized and non-localized 31P MRS studies of phosphate metabolites and pH in rat tumours.

UA hepatomas, GH3 prolactinomas and N-methyl-N-nitrosourea-induced mammary tumours, which were subcutaneously grown in rats, have been studied by 31P MRS using non-localized pulse-acquire, image selected in vivo spectroscopy (ISIS) and one-dimensional chemical shift imaging (1-D CSI) techniques. Comparisons have been made with measurements from acid extracts of these tumour types and surrounding tissues (i.e., muscle and skin). Since muscle containing high concentrations of phosphocreatine (PCr) is often found adjacent to the tumour, we have compared the ratio of the PCr to gamma-NTP peaks in the spectra with the same ratio calculated from the acid extract data, and have used deviations between the two sets of data to assess the discrimination of the MRS localization technique to signals from the tissue surrounding the tumour. Extract data showed an average NTP content of 1.25 mumol/g wet wt for all three tumour types. PCr (at 0.42 mumol/g wet wt), was significant only in the GH3 prolactinoma whereas it was negligible in the other tumour types (< 0.1 mumol/g wet wt). There was good agreement between the ISIS PCr/gamma-NTP ratio and the extract data for all tumours. However, the 1-D CSI data showed an unexpectedly large contamination of the tumour spectrum with PCr signals from the skin which was shown by subsequent phantom experiments to be due to the curved geometry of tumour and skin rather than Fourier bleed. In pH measurements by MRS it was found that biological variability was greater than the effects of artefacts (due to either the chemical shift artefact in the ISIS technique or partial volume effects) in the localization technique. An average pH of 7.2 was observed for all tumours. By initially comparing data from different localization schemes with that from chemical extracts potential sources of error have been highlighted and show that phantom studies alone are not sufficient to fully assess the accuracy of localized MRS data.

31P localized spectroscopy of fetal brain in utero.

31-Phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy of fetal brain in utero was obtained entirely noninvasively in rat utilizing image selected in vivo spectroscopy (ISIS). The results were in excellent agreement with the data obtained using the surface coil method in the late stage fetus, namely, high phosphomonoester (PME), low phosphocreatine (PCr), and high intracellular pH. Localized spectroscopy provides unprecedented opportunities for the investigation of fetal brain metabolism in utero.

Effect of hypothyroidism on phosphorus metabolism in muscle and liver: in vivo P-31 MR spectroscopy study.

Hypothyroidism is known to affect nearly every organ and organ system of the human body. The goal of the present study was to gain insight into the phosphorus metabolism and bioenergetic function of striated (calf) muscle and liver in patients with hypothyroidism before and after thyroid hormone treatment. With an ISIS (image-selected in vivo spectroscopy) magnetic resonance (MR) technique for volume selection, phosphorus-31 metabolism of the calf muscle in 10 patients and of the liver in seven patients with severe hypothyroidism was studied before and after treatment. In addition, spectra from the calf muscle and liver were obtained in 10 healthy volunteers. Relative to those from the healthy subjects, the P-31 MR spectra from patients with hypothyroidism showed a significantly diminished phosphocreatine/inorganic phosphate ratio (P less than .01). After thyroid hormone substitution therapy, this ratio returned to normal values within several weeks. No statistically significant changes in the spectra of liver tissue could be detected. The results support the theory that hypothyroidism induces a hormone-dependent, fully reversible impairment of the energy metabolism of striated muscle. Changes in liver metabolism observed with biochemical methods are apparently not detectable with state-of-the-art P-31 MR spectroscopy.

High-energy phosphate metabolism of the myocardium in normal subjects and patients with various cardiomyopathies--the study using ECG gated MR spectroscopy with a localization technique.

Nuclear magnetic resonance spectroscopy (MRS) is a new technique for the evaluation of myocardial metabolism. Recently, localized MRS has been clinically available to measure by a non-invasive method the relative concentrations of the high-energy phosphate metabolites in the myocardium. We performed ECG gated P-31 MRS using ISIS (image-selected in vivo spectroscopy) in 15 normal volunteers, 12 patients with hypertrophic cardiomyopathy, 12 with left ventricular hypertrophy, 6 with dilated cardiomyopathy and 11 with specific heart muscle disease. Myocardial peak height ratios of PCr/gamma-ATP, Pi/gamma-ATP and PCr/Pi were measured. Myocardial P-31 MRS demonstrated a significant decrease in the ratio PCr/ATP in patients with hypertrophic cardiomyopathy and specific heart muscle disease as compared with normal subjects, indicating myocardial metabolic disturbance in these patients. The ratio of PCr/ATP in patients with dilated cardiomyopathy did not differ significantly from that of normal subjects. However, exercise MRS revealed a marked decrease of PCr peak in an asymptomatic patient with dilated cardiomyopathy, which may indicate a latent metabolic disturbance in the myocardium of dilated cardiomyopathy.

2. MRI 装置によるスペクトロスコピーの基礎的検討(MRS の現状と技術的課題)

Technical aspects of image selected in vivo spectroscopy (ISIS) and fast rotating gradient spectroscopy (FROGS) are reported. Experiments were performed on a 1.5 T MRI system for human body by using a surface coil tuned to phosphorus-31. Phantoms filled with phosphoricacid solustions and normal ten volunteers were examined. We focused on the dependence of the signal intensity on RF transmitter power, volume selectivity, and the positional shift due to chemical shift. Results are as follows : Transmitter power to excite spins increased with conductivity and volume of phantoms. The peak hight of the spectrum of the heart of human volunteers changed depending on the transmitter power and repetition time. In ISIS, volume selectivity was good in large volume selection. While, in FROGS, it was good in thin slice selection. Positional shift due to chemical shift was not negligible in both techniques, but the distance changed depending on the strength of the gradient field used.

Stable Isotopically-Enriched D-Glucose: Strategies to Introduce Carbon, Hydrogen and Oxygen Isotopes at Various Sites

INTRODUCTION For many years stable isotopes were confined to the chemical laboratory, where they were used primarily to study reaction rates,1 reaction mechanisms,2 and molecular conformation.3,4 Recently, stable isotopically-enriched molecules have been playing increasing roles in biochemical studies, particularly as probes of in vitro biological metabolism5,6 and of biomacromolecular structure.7,8 These modern applications have been stimulated, in large part, by dramatic technical developments in nuclear magnetic resonance (NMR) spectroscopy9 and mass spectrometry (MS).10 Very-high field multinuclear high-resolution NMR in one-, two- and three- dimensions,11,12 and various volume-selective forms of NMR derived from topical magnetic resonance (TMR) spectroscopy,13 have become important analytical methods in the study of biological phenomena. TMR and related techniques such as ISIS (Image Selected In-Vivo Spectroscopy)14 and Spatially Resolved Spectroscopy (SPARS)15 are particularly attractive, as they pe...

Nuclear magnetic resonance imaging-guided phosphorus-31 spectroscopy of the human heart

Phosphorus-31 nuclear magnetic resonance spectroscopy can determine the status of high energy phosphates in vivo. However, its application to human cardiac studies requires precise spatial localization without significant contamination from other tissues. Using image-selected in-vivo spectroscopy (ISIS), a technique that allows three-dimensional localization of the volume of interest, 12 subjects were studied to determine the feasibility and reproducibility of phosphorus-31 spectroscopy of the human heart. Nuclear magnetic resonance imaging was performed using a commercial 1.5 tesla system to define the volume of interest. Phosphorus-31 spectra were obtained from the septum and anteroapical region of the left ventricle in 10 studies. Relative peak heights and areas were determined for high energy phosphates. The mean phosphocreatine to adenosine triphosphate ratio was 1.33 +/- 0.19 by height analysis and 1.23 +/- 0.27 by area analysis. Duplicate measurements in four subjects showed a reproducibility of less than or equal to 10% in three of the subjects. All spectra showed significant signal contribution from the 2,3 diphosphoglycerate in chamber red cells without evidence of skeletal muscle contamination. These results demonstrate the feasibility of image-guided phosphorus-31 spectroscopy for human cardiac studies and indicate the potential of this technique to study metabolic disturbances in human myocardial disease.

Application of image-guided surface coil P-31 MR spectroscopy to human liver, heart, and kidney.

Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomplished with surface coils by means of depth-resolved surface coil spectroscopy or rotating frame experiments, in which the extent of tissue sampled critically depends on surface coil placement. The authors' goal was to modify the surface coil image-selected in vivo spectroscopy (ISIS) experiment to accomplish three-dimensional volume selection through application of selective pulses in the presence of B0 gradients. Advantages of ISIS include the ability to use proton images to define the volume of interest (VOI) and reduced dependence on exact positioning of the surface coil. However, rapid replication of the surface coil ISIS experiment can cause spectral contamination from signals originating outside the VOI. A modified version of the ISIS experiment was developed to alleviate contamination under conditions of rapid replication. Applications of localized P-31 MR spectroscopy for observation of high-energy phosphorus metabolites are presented in human liver, heart, and transplanted and normal kidney.

Spatial localization in NMR spectroscopy in vivo.

Spatial localization techniques are necessary for in vivo NMR spectroscopy involving heterogeneous organisms. Localization by surface coil NMR detection alone is generally inadequate for deep-lying organs due to contaminating signals from intervening surface tissues. However, localization to preselected planar volumes can be accomplished using a single selective excitation pulse in the presence of a pulsed magnetic field gradient, yielding depth-resolved surface coil spectra (DRESS). Within selected planes, DRESS are spatially restricted by the surface coil sensitivity profiles to disk-shaped volumes whose radii increase with depth, notwithstanding variations in the NMR signal density distribution. Nevertheless, DRESS is a simple and versatile localization procedure that is readily adaptable to spectral relaxation time measurements by adding inversion or spin-echo refocusing pulses or to in vivo solvent-suppressed spectroscopy of proton (1H) metabolites using a combination of chemical-selective RF pulses. Also, the spatial information gathering efficiency of the technique can be improved to provide simultaneous acquisition of spectra from multiple volumes by interleaving excitation of adjacent planes within the normal relaxation recovery period. The spatial selectivity can be improved by adding additional selective excitation spin-echo refocusing pulses to achieve full, three-dimensional point resolved spectroscopy (PRESS) in a single excitation sequence. Alternatively, for samples with short spin-spin relaxation times, DRESS can be combined with other localization schemes, such as image-selected in vivo spectroscopy (ISIS), to provide complete gradient controlled three-dimensional localization with a reduced number of sequence cycles.

Simulation of selective pulse techniques for localized NMR spectroscopy

The results of a computer simulation investigation delineating the limits of resolution, sensitivity, and accuracy of the depth- resolved suface-coil spectroscopy (DRESS), volume-selective excitation (VSE), and image-selected in vivo spectroscopy (ISIS) methods for achieving spatially localized NMR spectroscopy are presented. A computer program, which numerically solves the Bloch equations for variable input parameters, is used to simulate the spatial localization afforded by each technique. Because the numerical solution of the Bloch equations describes the behavior of the bulk magnetization with great precision, the simulations provide an objective and realistic means of evaluating the performance of the individual localization schemes and reveal nuances and limitations not discussed in the original experimental papers. The results of this computer simulation study should encourage the optimization of localization methodology for use in specific applications.

Image-selected in Vivo spectroscopy (ISIS). A new technique for spatially selective nmr spectroscopy

A method of spatial localization is described which is particularly suitable for the in vivo spectroscopic investigation of biological and medical samples. The technique overcomes most of the technical problems associated with localized NMR spectroscopy and allows the spectrum to be investigated from a cube which can be positioned by reference to an NMR image. The cube can be reduced or enlarged, and can be rapidly moved in space to investigate further volumes of interest within the sample. The first experimental results from a phantom and the human leg are presented.