Proton T1 Relaxation Times Research Articles

Muscle proton T2 relaxation times and work during repetitive maximal voluntary exercise.

We studied the effects of progressive maximal voluntary handgrip contractions (MVCs) on muscle proton spin-spin (T2) relaxation times and work, measured as the integrated force vs. time curve (FTI). Six healthy volunteers performed 10, 20, 40, and 80 MVCs in a 0.35-T magnet on four separate occasions. Repeated measures analyses of variance of increases in T2 and FTI during successive bouts were significant (P < 0.005 and P < 0.001, respectively). FTI increased with successive bouts to a greater extent than did muscle T2 (P < 0.05). For T2, the Helmert contrast judged the 10-MVC response lower than the mean of the remaining responses (P < 0.005), and the differences between all others compared with the means of subsequent responses were not significant, indicating a "flattening" of the T2 response after the increase from 10 to 20 repetitions. For FTI, all the single degree of freedom Helmert contrasts were significant (P < 0.001), indicating a continual increase in response over increased MVCs. The curved nature of the T2 response conformed best to a hyperbolic function, suggesting that a limit of approximately 32% exists for the change in T2 during progressively longer bouts of MVCs. A limit in the T2 response is consistent with the existence of a limit in the amount of water that muscle can take up from the vasculature during exertion.

Synchronized inversion recovery‐spin echo sequences for precise in vivo T1 measurement of human myocardium: A pilot study on 22 healthy subjects

An ECG-triggered, two-sequence MRI technique is proposed for the precise measurement of proton T1 relaxation times of the human myocardium at a field strength of 0.5 T. The combination of an inversion recovery (IR) sequence and a spin echo (SE) sequence is not new. It is, however, rarely used in quantitative in vivo cardiac studies. Our approach employs a synchronization of the 90 degrees read pulse to the systolic period. In a study of 22 healthy volunteers, the globally measured T1 value was estimated to be 714 +/- 23 ms. Four of the volunteers also underwent additional imaging scans for the purposes of reproducibility assessment. The T1 precision was found to be 3.9 +/- 1.1% for the IR/SE combination and 16.9 +/- 5.3% for a combination of SE sequences. Total imaging time for the IR and SE sequences was 19.2 +/- 3.0 mins. The relative rapidity of this classic technique and the T1 precision obtained give this technique an obvious application in the discrimination of normal and diseased myocardium. In the same study, valuable supplementary tissue characterization is provided by T2, calculated from the SE sequence. T2 was evaluated to be 50 +/- 3 ms.

Muscle water shifts, volume changes, and proton T2 relaxation times after exercise

LETTERS TO THE EDITORMuscle water shifts, volume changes, and proton T2 relaxation times after exerciseJ. L. FleckensteinJ. L. FleckensteinPublished Online:01 Apr 1993https://doi.org/10.1152/jappl.1993.74.4.2047MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Download PDF FiguresReferencesRelatedInformation Cited ByQuantitative Magnetic Resonance Imaging Assessment of the Quadriceps Changes during an Extreme Mountain Ultramarathon12 October 2020 | Medicine & Science in Sports & Exercise, Vol. 53, No. 4Muscle Functional MRI as an Imaging Tool to Evaluate Muscle ActivityJournal of Orthopaedic & Sports Physical Therapy, Vol. 41, No. 11Increased MR Signal Intensity in the Pronator Quadratus Muscle: Does It Always Indicate Anterior Interosseous Neuropathy?American Journal of Roentgenology, Vol. 194, No. 2Entrapment SyndromesUse of Imaging to Assess Normal and Adaptive Muscle FunctionPhysical Therapy, Vol. 87, No. 6Diagnostic Imaging of Skeletal Muscle Exercise Physiology and Pathophysiology More from this issue > Volume 74Issue 4April 1993Pages 2047-2048 Copyright & PermissionsCopyright © 1993 the American Physiological Societyhttps://doi.org/10.1152/jappl.1993.74.4.2047PubMed8390445History Published online 1 April 1993 Published in print 1 April 1993 Metrics

In vivo NMR imaging and spectroscopic investigation of renal pathology in lean and obese rat kidneys

Diabetic nephropathy is a major cause of end-stage renal failure. While our understanding of the pathogenesis of nephropathy is incomplete, progressive glomerular injury appears to play a significant role in the decline of renal function. Proton NMR spectroscopy and imaging techniques were used to address changes in renal pathology associated with glomerular mesangial expansion in vivo in kidneys from spontaneously obese and lean (control) littermate Zucker rats. Fully functioning rat kidneys were surgically exposed and externalized for direct NMR signal detection via a coil placed around the organ. High-resolution (78 microns in plane) proton images were obtained at 4.7 T magnetic field strength revealing fine structure within the well-defined cortical and medullary regions. The obese rat kidney images were distinct in appearance from the lean kidney images and exhibited marked cortical expansion as well as increased overall kidney size. Enlargement of mean glomerular diameter was verified histologically in the obese kidneys as compared with the lean kidneys. Proton T1 and T2 relaxation times were determined from the entire kidney using standard spectroscopic techniques, and from specific regions within the kidney from multiple T1- and T-2 weighted images. Additionally, image contrast enhancement resulting from saturation transfer between protons in restricted-mobility environments and mobile water protons within the kidney was investigated in the lean and obese rat kidneys using magnetization-transfer imaging techniques. At the early stage of renal injury examined in this study, diseased and healthy kidneys could not be differentiated on the basis of relaxation times alone. The magnitude of saturation transfer obtained in cortical tissue in the lean and obese kidneys was also not statistically significantly different. However, the magnitude of saturation transfer achieved in the medullary tissue of obese kidneys was statistically significantly less than that achieved in lean kidneys.

Molecular mobility in mixtures of absorbed water and solid poly(vinylpyrrolidone).

Poly(vinylpyrrolidone) (PVP) was used as model system to examine molecular mobility in mixtures of absorbed water with solid amorphous polymers. Water vapor absorption isotherms were determined, along with diffusion and proton NMR relaxation measurements of absorbed water. Concurrently, measurements of glass transition temperatures (Tg) and carbon-13 NMR relaxation times for PVP were determined as a function of water content. Two water contents were used as reference points: Wm, obtained from the fit of water absorption isotherms to the BET equation, corresponding to the first shoulder in the sigmoid isotherm; and Wg, the amount of water necessary to depress Tg to the isotherm temperature. Translational diffusion coefficients of water, along with proton T1 relaxation time constants, show that both the translational and the rotational mobility of the water is hindered by the presence of the solid polymer and that the absorbed water is most likely represented by two or more populations of water with different modes or time scales of motion. The presence of "tightly bound" or immobilized water at levels corresponding to Wm, however, is unlikely, since water molecules maintain a high degree of mobility, even at the lowest levels of water. Above Wg, water shows an increase in mobility with increasing water content, but it is always less mobile than bulk water. With increasing water content, carbon-13 T1 relaxation time constants for PVP, measured under the same conditions as above, indicate a major increase in the molecular mobility of carbon atoms associated with the pyrrolidone side chains.

Proton magnetic resonance relaxation times and biomechanical properties of human vascular wall. In vitro study at 4 MHz.

Previous studies have suggested a relationship between tissue magnetic resonance (MR) relaxation times and its biomechanical behavior. To further investigate this relationship, the authors studied 41 human vascular wall samples from different anatomic localizations, including systemic and pulmonary arterial, as well as venous tissues. The authors measured water content, proton MR T1 and T2 relaxation times, and two viscoelastic parameters of the samples at 4 MHz. T2, water content, and both viscoelastic variables significantly differed among the five anatomic localizations (P less than .05). Both T1 and T2 were significantly (P less than .05) and linearly related to viscoelastic parameters. Multiple linear regression showed that both viscoelastic parameters of a sample can be predicted from the measured values of T1 and T2. These results provide a basis for characterizing the mechanical stress of a tissue by knowing its MR relaxation times.

The use of nuclear magnetic resonance to evaluate muscle injury

Magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are new and powerful tools to study tissue biochemistry, and to provide precise anatomical visualization of soft tissue structures. This review focuses on the use of these techniques to study exercise-induced muscle injury. MRS measurements show an increase in the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) 1-7 d after eccentric exercise. This increase in Pi/PCr could be due to either increases in extracellular Pi or small increases in resting muscle metabolism. Increased Pi/PCr is also seen during training programs and may indicate persistent muscle injury. Increased resting Pi/PCr with injury was not associated with altered metabolism during exercise. Elevations in resting Pi/PCr have been used to show increased susceptibility of dystrophic muscle to exercise-induced injury. Progressive clinical deterioration in dystrophic dogs is marked by impaired muscle metabolism, and the presence of low oxidative muscle fibers not seen in normal dogs. MRI shows increased proton T2 relaxation times following eccentric exercise that last up to 80 d after injury, and can reflect muscle edema as well as longer lasting changes in the characteristics of cell water. MRI demonstrate precise localization of the injured area, with large differences in both location and degree of injury in different subjects following the same exercise protocol. Thus, MRS can provide information on the metabolic response to injury, while MRI provides information regarding the site and extent of the injury. These tools have promise in helping to understand exercise-induced muscle injury.

The Effects of Progressive Abstinence from Alcohol on Red Blood Cell Proton NMR Relaxation Times and Water Content

Red blood cell proton relaxation times T1 and T2 were measured in samples from chronic alcoholic patients abstinent for varying periods from 1 week to over 6 months. T1 and T2 were elevated in the early stages of abstinence and declined to the values of controls after 8 weeks. Changes in the water content of the red blood cells and the mean corpuscular volume paralleled these changes but were more closely associated with T2. It is suggested that T1 and T2 may reflect different aspects in water content and free-to-bound ratio of water. The significance of these findings is discussed in the context of changes previously observed in the brains of alcoholic patients, and in rats fed a diet supplemented with alcohol for 6 months.

The role of membrane water permeability in characterization of pathologically altered human stomach tissues: NMR studies

Comparative NMR studies of normal and pathologically altered human stomach tissues were performed on the basis of proton T1 relaxation time measurements in the presence of high external concentrations of relaxation (contrast) agents manganese ethylenediaminetetraacetic acid (Mn-EDTA) and gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). Diffusion permeability of the cell membrane to water, Pd, was determined by measuring the longest proton T1 component sensitive to the exchange of water molecules through the cell membrane. Pathologically altered tissues showed substantially higher (2 to 10 times) average cell membrane permeabilities to water.

Quantitative studies of hydrodynamic effects and cross‐relaxation in protein solutions and tissues with proton and deuteron longitudinal relaxation times

Longitudinal relaxation times T1 of water protons were measured in 5% protein solutions at different static magnetic fields (0.47, 2, and 7 T), for proteins with molecular weight ranging between 1.4 and 480 kDa and in solvents of varying degrees of deuteration. T1 values were also obtained for rat liver soaked with Krebs-Ringer solutions of varying degrees of deuteration at the above fields. For the samples containing D2O, T1 for deuterium was also measured at fields 2 and 7 T. The deuterium measurements were used to estimate water rotational correlation times which were in turn used to estimate the contribution of so-called "hydrodynamic effects" of macromolecules to proton relaxation. The proton relaxation rates at full deuteration were compared with those in protonated solvent (water) to obtain a second, direct measurement of this effect. Both measurements provide quantitation of the hydrodynamic effects, free from the contributions of other effects that are transparent to deuteration, and results from both measurements agree with each other reasonably well. The cross-relaxation rate between solute and solvent protons, and the contribution of paramagnetic impurities in the samples were also obtained from the proton T1 studies. The experimental results show that the hydrodynamic effects (intramolecular and intermolecular water-water interactions) are about the same magnitude in all the proteins studied as well as in rat liver. However, the cross-relaxation rate generally increases with increasing protein molecular weight. Measurements in soaked rat liver indicate that the cross-relaxation rate per unit mass of solute is much higher in tissues than in simple solutions of proteins of similar mean molecular weight. The results challenge the prevailing concept that the relaxation properties of biological tissues may be treated as a simple superposition of the properties of their constituents.

Investigations concerning the potential for using 1h nmr relaxometry or high‐resolution spectroscopy of plasma as a screening test for malignant lung disease

In 158 plasma samples, obtained from patients with lung carcinoma, lung metastases, and infectious or inflammatory lung diseases and from healthy controls, the NMR relaxation times T1 and T2 of water protons were measured at a resonance frequency of 20 MHz by pulsed NMR techniques and adjusted to a standardized total plasma protein concentration. For one-third of these samples water-suppressed 500-MHz 1H NMR spectroscopy at 37 degrees C was used (a) to determine the widths of the composite lipid methyl and methylene signals, and (b) to quantitate individual lipid methylene signal components that could be detected in resolution-enhanced spectra. In addition, hematological parameters and the plasma levels of several acute phase proteins and apolipoprotein-A were monitored. No diagnostically significant differences between lung carcinoma patients and patients with nonmalignant lung disease could be found for any of the plasma NMR parameters, nor could T1 or lipid linewidth data distinguish between any patient group and healthy controls. However, the mean T2 was significantly shortened by about 15% for any kind of lung disease compared to healthy controls. Similar but less significant results were found for apolipoprotein-A levels. A linear discriminant function, calculated from the apolipoprotein-A and T2 data, did not improve the differentiation between malignant and nonmalignant lung disease but did improve the discrimination between tumor patients and healthy controls up to a sensitivity and specificity of 80 and 96.5%, respectively. T2 correlates inversely with plasma fibrinogen levels and the blood sedimentation rate and, therefore, appears to monitor a general inflammatory status of a tumor patient rather than the presence or absence of cancer. For all groups except healthy pregnant women, the lipid methylene composite signal linewidth correlates inversely with the fraction of mobile triglyceride present (mainly as VLDL), as estimated from resolution-enhanced spectra.

The use of magnetic resonance imaging and spectroscopy in the assessment of patients with head and neck and other superficial human malignancies

The proper demarcation of diseased tissue is important for radiation therapy planning and treatment. The volume to be irradiated is usually identified on radiographs or on x-ray computed tomography (CT) sections. Magnetic resonance (MR)-derived images of the proton T2 relaxation times in small pixel elements, typically 0.5 mm2 or less, provide significantly sharper differentiation between normal and diseased tissue. The T2 values in tissue depend on the tissue composition, histologic condition, and physiologic environment within the tumor. Furthermore, for many tumors the histogram of T2 values has a clear biphasic distribution suggesting that T2 maps may be useful for the identification of necrotic or hypoxic regions within tumors. The distribution of T2 values within the tumor bed shows the general pattern that the T2 values are elevated with a range greater than that seen in normal muscle. Elevated T2 values are not by themselves diagnostic of malignancy; however, they demonstrate the heterogeneity of the microenvironment present within a tumor. The spatial distribution of T2 values is being explored as a method for computer assistance in the delineation of the target volume for treatment planning. In addition, MR P-31 spectroscopic examinations were performed on 30 patients with squamous cell carcinomas of the head and neck. Although hampered by muscle contamination in some P-31 spectra obtained with surface coil profile localization techniques, significant trends can still be appreciated in our data. These trends include the following: (1) the P-31 spectra from malignant tissue have well-resolved spectral lines in the upfield region that correspond to Pi, phosphomonoester (PME), and phosphodiester (PDE) not usually seen in normal muscle; (2) the PDE/B-ATP and PME/B-ATP ratios are greater than unity in all cases; and (3) most of the tumors have higher PME peaks than PDE peaks. The P-31 spectra from patients treated with ionizing radiation changed during and after therapy. Some of the changes could be associated with alteration of the tumor metabolic activity or synthesis and breakdown of lipoproteins. These studies suggest that magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) studies may be useful for both radiotherapy treatment planning and the noninvasive monitoring of patients both before and during treatment.

Preliminary results of nuclear magnetic resonance studies of healthy human saliva

Relaxation times T1 and T2 of water protons for stimulated and unstimulated parotid and submandibular saliva from healthy patients were measured in the conventional way using the Bruker PC 20 Minispec. Some measurements of dispersion were also carried out. An interpretation of the average values for T1 and T2 observed in the 20 MHz range is proposed for these types of saliva in relation to biochemical composition (total proteins, amylase activity, sialic acids and hexosamins) and viscosity. For parotid saliva T2(-1)-T1(-1) correlates significantly with amylase activity. In the submandibular saliva T2(-1)-T1(-1) correlates significantly with both mucins and alpha-amylase activity.

Modeling sickle cell vasoocclusion in the rat leg: quantification of trapped sickle cells and correlation with 31P metabolic and 1H magnetic resonance imaging changes.

We have developed an animal model to elucidate the acute effects of perfusion abnormalities on muscle metabolism induced by different density-defined classes of erythrocytes isolated from sickle cell anemia patients. Technetium-99m (99mTc)-labeled, saline-washed normal (AA), homozygous sickle (SS), or high-density SS (SS4) erythrocytes were injected into the femoral artery of the rat and quantitative 99mTc imaging, 31P magnetic resonance spectroscopy by surface coil at 2 teslas, and 1H magnetic resonance imaging at 0.15 tesla were performed. Between 5 and 25 microliters of SS4 cells was trapped in the microcirculation of the thigh (or 1-6 x 10(7) cells per cubic centimeter of tissue). In contrast, fewer SS discocytes (SS2) or AA cells were trapped (an equivalent packed cell volume of less than 6.7 microliters and 0.3 microliters, respectively). After injection of SS4 cells an initial increase in inorganic phosphate was observed in the region of the thigh served by the femoral artery, intracellular pH decreased, and subsequently the proton relaxation time T1 reached a broad maximum at 18-28 hr. When T1 obtained at this time was plotted against the volume of cells trapped, an increase of T1 over the control value of 411 +/- 48 msec was found that was proportional to the number of cells trapped. We conclude that the densest SS cells are most effective at producing vasoocclusion. The extent of the change detected by 1H magnetic resonance imaging is dependent on the amount of cells trapped in the microcirculation and the magnitude of the initial increase of inorganic phosphate.

Fluid inclusion studies in Ljubija siderite mine in NW Bosnia (Yugoslavia)

The T2 relaxation time of protons in water suspensions of iron-oxide particle clusters is found to increase with the waiting time tw after the sample is inserted in the gap of the magnet with 1.41 T field, owing to field induced cluster aggregation. In order to compare the experimental results with existing theories, the measured T2 has to be extrapolated to tw=0, for which a power-law T2 increment versus tw relation is proposed. The extrapolated T2(0) is found to be inversely proportional to the volume fraction v of iron oxide.

Nuclear magnetic resonance relaxation in experimental brain edema: effects of water concentration, protein concentration, and temperature.

Proton relaxation times T1 and T2 of macromolecular solutions, bovine brain tissues, and experimental cat brain edema tissues were studied as a function of water concentration, protein concentration, and temperature. A linear relation was found between the inverse of the weight fraction of tissue water and the spin-lattice relaxation rate, R1, based on a fast proton exchange model for relaxation. This correlation was also found for the spin-spin relaxation rate, R2, of gray matter samples and macromolecular solutions at low concentrations. Concentrated solutions of protein-water samples showed an enhanced relaxation due to viscosity effects. The T2 of white matter was considerably lengthened with elevated water concentration, but showed no straightforward relation with the total tissue water content. The relaxation times of all samples increased with temperature, supporting the assumption of fast proton exchange in the model for relaxation. This was not found for white matter, in which T2 decreased with increasing temperature, which indicated that intermediate or even slow exchange was present. The relation found between relaxation times and tissue water content can be used to predict the amount of and/or increase in tissue water due to water-elevating processes such as edema.

Proton relaxation study of pure and doped quasi-one-dimensional C6H11NH3CuCl3(CHAC)

The authors have measured the proton relaxation time T1 in pure and Mn-doped C6H11NH3CuCl3 (CHAC) at several frequencies, for different orientations of the static field B0 applied in the (ac) and (bc) planes of these crystals at room temperature and 77 K. These measurements are explained well in terms of 1D spin diffusion process in the spin dynamics and anisotropic exchange cut-off. Both processes are strongly modified by manganese doping.

NMR changes in experimental allergic encephalomyelitis: NMR changes precede clinical and pathological events.

In guinea pigs immunized with myelin basic protein (MBP) in complete Freund's adjuvant, experimental allergic encephalomyelitis (EAE) shows a characteristic clinical and pathological course. This study characterized the proton nuclear magnetic resonance (NMR) properties of the central nervous system prior to the onset of clinical signs of EAE. At this time (Days 7-9), the blood brain barrier is disrupted. The effects of the injection of paramagnetic contrast agents gadolinium-DTPA and gadolinium-deferoxamine on the tissue NMR relaxation times were examined. Both proton T1 and T2 relaxation times were prolonged in the spinal cord and the brain prior to the onset of clinical and pathological changes. The largest change was in the thoracolumbar spinal cord where T2 prolongation was 22.9%. Gadolinium-DTPA produced a moderate (5-11%) or marked (9-19%) decrease in control and MBP-treated animals, respectively. Gadolinium-deferoxamine also decreased proton relaxation times but was toxic to all animals, producing respiratory arrest. Changes in proton T2 relaxation times in cord and cerebellum were sufficiently large (greater than 10%) to suggest that they might be visualized by magnetic resonance imaging techniques. We have previously described the changes in proton relaxation times during the acute phase of EAE (S.J. Karlik, G. Strejan, J.J. Gilbert, and J.H. Noseworthy, Neurology 36, 1112 (1986]. This study indicates that proton relaxation times are significantly altered at a time when blood brain barrier disruption occurs prior to the onset of clinical or pathological signs.

Slice profile effects and their calibration and correction in quantitative NMR imaging

The signal values extracted from an NMR image matrix depend upon the NMR properties of the sample material, i.e. the proton density and relaxation times T1 and T2, and also upon various instrument parameters, one such being the slice shape. It is a common approximation to assume an ideal slice profile: one that is perfectly rectangular and invariant in shape for all applications, but in practice real slice profiles are neither. In this study the effect of the slice is included in signal intensity calculations by means of a computer simulation. Comparison is made between these slice-corrected values and values calculated on the basis of an ideal slice. Four pulse sequences are examined: saturation recovery, inversion recovery, spin echo and inversion recovery followed by spin echo.

Relaxation time study of diammonium hydrazinium (+2) tetraperchlorate

The relaxation times T1, and T1ρ, and T1D of protons in (NH4)2N2H6(ClO4)4 were measured in the temperature range from 77 to 430 K. T1 measurements were made at 36 and 18 MHz, and T1ρ measurements were made as a function of H1. The temperature and frequency dependence of T1 is explained in terms of dipole–dipole interactions within anisotropically reorienting NH3 groups and spin-rotational interactions within reorienting NH+4 ions. The value of the T1ρ minimum due to reorienting NH3 groups is unusually large with weak H1 dependence, possibly due to tunneling motions. The T1ρ measurements exhibit a strong H1 dependence on the high-temperature side of the T1ρ minimum. An analysis of the H1 dispersion in terms of cross relaxation between protons and nitrogen nuclei within the N2H++6 ions has yielded values for the nitrogen T1.