Feasibility of diffusion-weighted imaging with DWIBS in staging Hodgkin lymphoma in pediatric patients: comparison with PET/CT

Objective

The aim of the study was to evaluate feasibility of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) method in diagnosing Hodgkin lymphoma in pediatric patients and to compare it with 18F-FDG PET/CT as a gold standard.

Materials and methods

Eleven patients (median age 14) with newly diagnosed Hodgkin lymphoma were examined with 18F-FDG PET/CT and MRI including whole-body DWIBS sequence (b = 0, 800 s/mm²), before the oncologic treatment. About 26 locations of lymphatic tissues were evaluated visually and quantitatively using ADC_mean (DWIBS) and SUV_max (18F-FDG PET/CT), respectively.

Results

All affected lymph node regions (n = 134) diagnosed in 18F-FDG PET/CT were found with DWIBS, presenting decreased diffusion. Significant correlation was found between ADC and SUV values (R² = − 0.37; p = 0.0001). Nevertheless, additional 33 regions were recognized only by DWIBS. They were significantly smaller than regions diagnosed by both methods.

Discussion

Agreement between DWIBS and 18F-FDG PET/CT for detection and staging of malignant lymphoma is high. DWIBS can be used for the evaluation of pediatric Hodgkin lymphoma.

     

Synthesis and temperature-dependent optical properties of Eu3+-doped NaYSiO4 red-emitting phosphors

Abstract

Novel Eu³⁺-activated orthosilicate NaYSiO₄:xEu³⁺ (x?=?0.02, 0.05, and 0.20) red-emitting phosphors were developed for white light emitting diode applications. The X-ray diffraction (XRD), photoluminescence excitation and emission spectra, temperature-dependent curves were applied to characterize the samples. The red emission of the NaYSiO₄:Eu³⁺ phosphor corresponding to ⁵D₀→⁷F₂ (614?nm) transition was observed under the excitation of 394?nm wavelength, which is suitable for UV LED chip. The quenching temperature for NaYSiO₄:0.05Eu³⁺ was found to be over 500 K. The CIE chromaticity coordinates of NaYSiO₄:0.05Eu³⁺ are very close to the National Television System Committee (NTSC) standard red.     

Clinical assessment of myocardial viability using MRI during a constant infusion of Gd-DTPA

This study assessed the accuracy and feasibility of magnetic resonance imaging (MRI) during a constant infusion of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) for the determination of myocardial viability in patients with recent acute myocardial infarction (AMI). Nine patients were studied within 10 days of AMI. Rest-redistribution²⁰¹Thallium (²⁰¹Tl) single photon emission computed tomography (SPECT) was used as a gold standard for viability. Using MRI, regional perfusion was assessed using dynamic imaging during a bolus injection of Gd-DTPA and viability was assessed during a continuous infusion. Finally, cine MR images were acquired at baseline, during low-dose dobutamine infusion and after recovery. To assess viability, the left ventricle was divided into 16 segments and signal intensity in corresponding MRI and redistribution SPECT segments were compared. Wall thickening index (WTI) was determined at each step during the dobutamine study. The results revealed that in five patients, reduced perfusion in infarcted regions was observed qualitatively during dynamic first pass imaging. There was a significant inverse correlation between²⁰¹Tl uptake and MRI signal intensity, i.e. infarcted tissue (low²⁰¹Tl uptake) had increased MR signal intensity. Segments were separated into normal (²⁰¹Tl uptake >90%) and infarcted (<60%). Infarcted MRI segments had greater signal intensity than normal segments (179±50 vs. 102±14%;P<0.0001). WTI in normal segments increased by 18±8.5% (P<0.0001) from baseline to 10 μg/kg per min of dobutamine while infarcted tissue WTI decreased 2.8±7.2% (P=0.17). Thus regions of myocardium that were infarcted as defined by reduced²⁰¹Tl uptake and absent contractile reserve showed greatly increased MRI signal intensity during a constant infusion of Gd-DTPA. The use of MRI during a constant infusion of Gd-DTPA is accurate and feasible for the determination of myocardial necrosis in a clinical setting.     

Study of tasin diffusion barrier

Abstract

Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced high-density memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in ¹⁸O₂ at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. ¹⁸O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV of the nuclear reaction ¹⁸O(p,α)¹⁵N.     

Oxidation resistance of TaSiN diffusion barriers

Abstract

Due to his resistance to oxidation, TaSiN is a promising candidate as an electric conductive barrier layer for integration of ferroelectrics and high permittivity oxides in advanced memory devices. Here we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive sputtering using a TaSi₂ target and then processed by rapid thermal annealing (RTA) in ¹⁸O₂ at 650°C. We use RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) to determine film compositions and XRD (X-Ray Diffraction) to study their microstructure. The concentration depth profiles of ¹⁸O was measured after the RTA treatments via the narrow resonances ¹⁸O(p,α)¹⁵N at 151 keV (fwhm=100eV). The relationship between the depth profiles and the excitation curves were deduced with the aid of the SPACES simulation program.     

31P MR spectroscopy and in vitro markers of oxidative capacity in type 2 diabetes patients

Background: Skeletal muscle mitochondrial function in type 2 diabetes (T2D) is currently being studied intensively. In vivo ³¹P magnetic resonance spectroscopy (³¹P MRS) is a noninvasive tool used to measure mitochondrial respiratory function (MIFU) in skeletal muscle tissue. However, microvascular co-morbidity in long-standing T2D can interfere with the ³¹P MRS methodology. Aim: To compare ³¹P MRS-derived parameters describing in vivo MIFU with an in vitro assessment of muscle respiratory capacity and muscle fiber-type composition in T2D patients. Methods: ³¹P MRS was applied in long-standing, insulin-treated T2D patients. ³¹P MRS markers of MIFU were measured in the M. vastus lateralis. Muscle biopsy samples were collected from the same muscle and analyzed for succinate dehydrogenase activity (SDH) and fiber-type distribution. Results: Several ³¹P MRS parameters of MIFU showed moderate to good correlations with the percentage of type I fibers and type I fiber-specific SDH activity (Pearson’s R between 0.70 and 0.75). In vivo and in vitro parameters of local mitochondrial respiration also correlated well with whole-body fitness levels (VO _2peak) in these patients (Pearson’s R between 0.62 and 0.90). Conclusion: Good correlations exist between in vivo and in vitro measurements of MIFU in long-standing insulin-treated T2D subjects, which are qualitatively and quantitatively consistent with previous results measured in healthy subjects. This justifies the use of ³¹P MRS to measure MIFU in relation to T2D.     

A comparison of emulsifiers for the formation of oil-in-water emulsions: stability of the emulsions within 9 h after production and MR signal properties

Objective

To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated.

Materials and methods

Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T₁ mapping and visual control. Signal properties of the emulsifiers were investigated by ¹H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T₁ and T₂) and ADC values of aqueous solutions.

Results

Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T₁ maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in ¹H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r_1,lecithin = 0.11 wt.%⁻¹ s⁻¹, r_2,lecithin = 0.57 wt.%⁻¹ s⁻¹) and ADC value (Δ(ADC)_lecithin =  − 0.18 × 10^–3 mm²/s⋅wt.%) with increasing concentration.

Conclusion

Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.

     

Tissue oxygen tension measurements in the Shionogi model of prostate cancer using 19 F MRS and MRI

Objectives: To investigate changes in tumour tissue oxygenation throughout the tumour growth–regression–relapse cycle in an androgen-dependent animal tumour model. Materials and methods: ¹⁹F T₁ relaxometry of Perfluoro-15-Crown-5-Ether was used to measure in vivo partial oxygen pressure (pO₂) of Shionogi tumours on a 2.35-T MR scanner. Perfluoro-15-Crown-5-Ether was administered as an emulsion injected intravenously or as a neat compound injected directly into the tumour. Non-localized, tumour ¹⁹F T₁ measurements, made at multiple time points throughout the tumour cycle, were translated into pO₂ levels. Results: No correlation between tumour size and pO₂ values was found. Values of pO₂ for growing tumours (50 ± 30 torr) were significantly lower than for regressing and relapsing tumours after 9 days post-castration (70 ± 10 torr, p<0.05). Maximum pO₂ values (90 ± 30 torr) were reached between fifth and eighth day post-castration, when tumour pO₂ was significantly higher than both pre-castration (p<0.001) and after 9 days post-castration (p<0.05). Conclusion: We demonstrate that longitudinal pO₂ measurements in vivo are feasible. Values of pO₂ for growing androgen-dependent tumours were significantly lower than for regressing and relapsing androgen-independent tumours. These results have potential clinical importance in optimizing the timing of chemotherapy and/or radiotherapy of hormone dependent tumours.     

1H magnetic resonance spectroscopy of the brains of normal infants and after perinatal hypoxia-ischemia

The aims of this study were to define proton (¹H) metabolite peak-area ratios in the brains of normal infants and to investigate abnormalities after perinatal hypoxia-ischemia. Point-resolved spectroscopy (PRESS) data were collected at 2.4 T with an echo time (TE) of 270 ms from 8-ml voxels located in the thalamus or occipito-parietal region. Fourteen normal and 9 asphyxiated infants were studied. The gestational plus postnatal ages (GPA) of these two groups were 31–41 (median 36) and 27–41 (37) weeks, respectively, and the asphyxiated infants were studied aged 0–10 (2) days. Peak-area ratios were determined in the normal infants for choline-containing compounds (Cho), creatine plus phosphocreatine (Cr),N-acetylaspartate (NAA) and lactate (Lac). Lactate was detected in all the normal infants and Lac/NAA was higher in the occipito-parietal region than in the thalamus (p<0.005). Lac/NAA decreased with increasing GPA in both the thalamus (p=0.014) and the occipito-parietal region (p=0.033). In six of the nine asphyxiated infants, Lac/NAA was above 95% confidence intervals for either the thalamus and/or the occipito-parietal region. Of these six infants, two died and three were neurologically abnormal aged 2 months, indicating that elevated Lac/NAA after perinatal hypoxia-ischemia may convey a poor prognosis. Propan-l,2-diol (the phenobarbitone injection medium) was detected at 1.1 ppm in three infants.     

Calculation of energy band and optical properties of CuInTe2 with doping

Abstract

Chalcopyrite CuInTe₂ is a direct band gap semiconductor with 1.1?eV energy gap which can be adjusted by doping Ga or Al to match the solar spectrum. The theoretical calculations for CuInTe₂ doping are performed using Cambridge serial total energy package (CASTEP) in Materials Studio under the PBE pseudopotential of the generalized gradient approximation (GGA). The calculation results show that the cell volumes of CuInTe₂, CuGaTe₂ and CuAlTe₂ become larger after the structure optimization. After optimization of doping with Ga or Al in CuInTe₂, the cell volume of CuInTe₂ becomes smaller, and the larger the doping amount, the smaller the cell volume; It was found that as the doping amount increase of Ga or Al, the band gap becomes greater which can be continuously adjusted by changing the doping amount. Absorption rate of CuInTe₂ doping reaches its peak at a wavelength of 250?nm, which orders of magnitude is up to 10⁵. With the increase of the doping amount, the top peak has an increasing tendency. In the range of visible light wavelengths, the absorption rate keeps better, basically reaching 4.0?×?10⁴ cm^?1.     

PASADENA hyperpolarization of 13C biomolecules: equipment design and installation

Object  The PASADENA method has achieved hyperpolarization of 16–20% (exceeding 40,000-fold signal enhancement at 4.7 T), in liquid samples of biological molecules relevant to in vivo MRI and MRS. However, there exists no commercial apparatus to perform this experiment conveniently and reproducibly on the routine basis necessary for translation of PASADENA to questions of biomedical importance. The present paper describes equipment designed for rapid production of six to eight liquid samples per hour with high reproducibility of hyperpolarization. Materials and methods  Drawing on an earlier, but unpublished, prototype, we provide diagrams of a delivery circuit, a laminar-flow reaction chamber within a low field NMR contained in a compact, movable housing. Assembly instructions are provided from which a computer driven, semi-automated PASADENA polarizer can be constructed. Results  Together with an available parahydrogen generator, the polarizer, which can be operated by a single investigator, completes one cycle of hyperpolarization each 52 s. Evidence of efficacy is presented. In contrast to competing, commercially available devices for dynamic nuclear polarization which characteristically require 90 min per cycle, PASADENA provides a low-cost alternative for high throughput. Conclusions  This equipment is suited to investigators who have an established small animal NMR and wish to explore the potential of heteronuclear (¹³ C and ¹⁵ N) MRI, MRS, which harnesses the enormous sensitivity gain offered by hyperpolarization.     

Experimental31p nmr study of the influence of ionic strength on the apparent dissociation constant of mgatp

The classical method for³¹P NMR determination of intracellular free magnesium concentration ([Mg _free ²⁺ ]) requires an accurate knowledge of the apparent dissociation constant (K _D ) of MgATP. There is a large difference between the previously determined values ofK _D . Although the value of 50 µM, determined by a³¹P NMR method, is now largely accepted, a value of 86 µM has more recently been measured with a fitting method derived from the original one, and with a different ionic strength. The purpose of our study was to assess if the cause of the difference between these two previously reportedK _D values was due to the measuring method or to the ionic strength value used.Working at pH=7.2,T=37°C, and [KCl]=0.25 M, we performedK _D measurements with the original³¹P NMR method and with the fitting method. The results (67±13 µM and 61±20 µM, respectively) were not significantly different. Then, with the first method, we measured K_D at [KCl]=0.12 M and found a value of 19±5 µM. We conclude that the main cause of difference between theK _D values measured by³¹P NMR reside in the disparity of ionic strength values used for their measurement. OurK _D measurements at [KCl]=0.25 and 0.12 M demonstrate the importance of the ionic strength value used for imitating the intracellular medium on the absolute value of ([Mg _free ²⁺ ]) measured by³¹P NMR spectroscopy.Address for correspondence: Université Catholique de Louvain, Unité CPMC, Bâtiment Lavoisier, Place Louis Pasteur n°1, B-1348 Louvain-la-Neuve, Belgium. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY 10119.     

Titanium Dioxide Wrapped MOFs-Derived Cobalt-Doped Porous Carbon Polyhedrons as Sulfur Hosts for Advanced Lithium–Sulfur Batteries

Abstract

To overcome the shortcomings (low-activity materials and the poor cycle stability) of lithium-sulfur (Li-S) batteries, rational design of cathode host materials is critical. Herein, we developed core-shell Co@NPC@TiO₂ nanostructures, coating titanium dioxide (TiO₂) on cobalt-doped nanoporous carbon (Co@NPC) derived from the thermal decomposition of zeolitic imidazolate framework-67 (ZIF-67) for sulfur electrodes. The synthesized Co@NPC@TiO₂ has excellent electrical conductivity and strong restrictions on polysulfides, the sulfur cathodes with core-shell structure demonstrate a high initial discharge capacity of 1400 mAh g^?1 at 0.1 C, compared with porous carbon, the electrical conductivity and cyclic stability are improved obviously.     

Magnetic resonance imaging at 1.5 T with immunospecific contrast agent in vitro and in vivo in a xenotransplant model

Object: Demonstrating the feasibility of magnetic resonance imaging (MRI) at 1.5 T of ultrasmall particle iron oxide (USPIO)-antibody bound to tumor cells in vitro and in a murine xenotransplant model. Methods: Human D430B cells or Raji Burkitt lymphoma cells were incubated in vitro with different amounts of commercially available USPIO-anti-CD20 antibodies and cell pellets were stratified in a test tube. For in vivo studies, D430B cells and Raji lymphoma cells were inoculated subcutaneously in immunodeficient mice. MRI at 1.5 T was performed with T1-weighted three-dimensional fast field echo sequences (17/4.6/13°) and T2-weighted three-dimensional fast-field echo sequences (50/12/7°). For in vivo studies MRI was performed before and 24 h after USPIO-anti-CD20 administration. Results: USPIO-anti-CD20-treated D430B cells, showed a dose-dependent decrease in signal intensity (SI) on T2*-weighted images and SI enhancement on T1-weighted images in vitro. Raji cells showed lower SI changes, in accordance to the fivefold lower expression of CD20 on Raji with respect to D430B cells. In vivo 24 h after USPIO-anti-CD20 administration, both tumors showed an inhomogeneous decrease of SI on T2*-weighted images and SI enhancement on T1-weighted images. Conclusions: MRI at 1.5 T is able to detect USPIO-antibody conjugates targeting a tumor-associated antigen in vitro and in vivo.     

Accuracy of computed tomography and magnetic resonance imaging in staging bronchogenic carcinoma

Sixty-three patients with non-small cell bronchogenic carcinoma were prospectively and independently assessed by computed tomography (CT) and magnetic resonance imaging (MRI) before surgery. Images were interpreted by four radiologists who had no knowledge of other imaging studies, except chest x-ray, and were blinded to surgical findings. The data were compared with pathologic and histologic findings. The accuracies of CT and MRI in determining tumor classification and assessing mediastinal and hilar lymph node metastases were compared. Sensitivity of CT in determining T factor was 78%, and specificity was 96%. The values for MRI were 84% and 96%, respectively. There was no significant difference between CT and MRI in staging tumors. MRI is more accurate than CT in diagnosing mediastinal invasion in staging superior sulcus tumors and complex tumors. There was no significant difference between the accuracies of CT and MRI in detecting mediastinal node metastases; the sensitivities were 82% and 90%, respectively, and specificities were 88% and 93%, respectively.     

Large increases in1H metaboliteT 2's after cerebral hypoxia-ischemia correlate with ATP depletion

In vivo proton (¹H) magnetic resonance spectroscopy (MRS) can measure cerebral metabolite concentrations and nuclear relaxation times. Function of the sodium (Na⁺)/potassium (K⁺) pump in cell membranes depends on adequate adenosine triphosphate (ATP) levels: intracellular Na⁺ is normally extruded in exchange for extracellular K⁺. Low ATP will cause pump dysfunction and loss of K⁺ accompanied by influx of Na⁺and water. Raised intracellular water may increase molecular mobility and this might be detectable as increased apparent transverse relaxation times (T ₂'s).¹H-MRS of the brains of newborn piglets during acute hypoxia-ischemia revealed enigmatic increases in the peak area of creatine + phosphocreatine (Cr) relative to those of choline-containing compounds (Cho) andN-acetylaspartate (NAA). Interleaved¹H and phosphorus (³¹P) MRS showed that theT ₂'s of both Cr and lactate (Lac) increased during acute hypoxia-ischemia and these changes correlated with reductions in nucleotide triphosphate (NTP; largely ATP). Within 50 h of metabolic recovery from the primary insult, as delayed energy failure developed, theT ₂'s of Cho, Cr, NAA, and Lac increased greatly. TheseT ₂ changes also correlated with NTP depletion. These observations demonstrate important relationships betweenT ₂'s and function of the ATP-dependent Na⁺/K⁺ pump.     

Overestimation of grey matter atrophy in glioblastoma patients following radio(chemo)therapy

Objective

Brain atrophy has the potential to become a biomarker for severity of radiation-induced side-effects. Particularly brain tumour patients can show great MRI signal changes over time caused by e.g. oedema, tumour progress or necrosis. The goal of this study was to investigate if such changes affect the segmentation accuracy of normal appearing brain and thus influence longitudinal volumetric measurements.

Materials and methods

T1-weighted MR images of 52 glioblastoma patients with unilateral tumours acquired before and three months after the end of radio(chemo)therapy were analysed. GM and WM volumes in the contralateral hemisphere were compared between segmenting the whole brain (full) and the contralateral hemisphere only (cl) with SPM and FSL. Relative GM and WM volumes were compared using paired t tests and correlated with the corresponding mean dose in GM and WM, respectively.

Results

Mean GM atrophy was significantly higher for full segmentation compared to cl segmentation when using SPM (mean ± std: ΔV_GM,full = − 3.1% ± 3.7%, ΔV_GM,cl = − 1.6% ± 2.7%; p < 0.001, d = 0.62). GM atrophy was significantly correlated with the mean GM dose with the SPM cl segmentation (r = − 0.4, p = 0.004), FSL full segmentation (r = − 0.4, p = 0.004) and FSL cl segmentation (r = -0.35, p = 0.012) but not with the SPM full segmentation (r = − 0.23, p = 0.1).

Conclusions

For accurate normal tissue volume measurements in brain tumour patients using SPM, abnormal tissue needs to be masked prior to segmentation, however, this is not necessary when using FSL.

     

Prediction of pathological tumor volume in clinically localized prostate cancer: value of endorectal coil magnetic resonance imaging

The purpose of this study was to determine whether endorectal coil magnetic resonance imaging (MRI) enables accurate assessment of pathologic tumor volume in patients with clinically localized prostate carcinoma. Twenty-four patients with biopsy-proved prostate carcinoma underwent MRI at 0.5 T before radical prostatectomy. Tumor volumes were determined independently on axial fast-spin-echo (SE) T₂-weighted MR images and whole-mount pathology slides of the surgical specimens. At pathology, tumor volumes ranged from 0.17 to 9.42 cm³ (mean±SD, 3.11±2.99 cm³). A strong correlation (r=.944) was found between measurements of tumor volume based on MR images and pathological specimens. The error was less than 0.5 cm³ in 14 cases, in the range of 0.5–1 cm³ in 7 cases, and more than 1 cm³ in 3 cases. By using an MR tumor volume of 2 cm³ as cutoff value, extracapsular tumor spread could be predicted with a sensitivity of 81.2%, a specificity of 100%, and an accuracy of 87.5%. Tumor volume determinations based on MR images seem to be accurate enough to be helpful in clinical decision-making.     

Multinuclear MR-spectroscopy on ion-homeostasis and energetics during ischemia and reperfusion

4. Conclusion Voltage-gated Na⁺-channels constitute a major port of Na⁺ entry in the initial minutes following the onset of ischemia. The persistent component of the Na⁺ current does not play a significant role in the guinea pig heart even thereafter. Due to intracellular acidification. NHE is activate dand forms the dominant influx pathway in the next 30 min of ischemia, but is partially inactivated in the later course of ischemia. Alternative, not yet characterised ports of entry gain importance in this phase. Blocking either voltage-gated Na⁺-channels or NHE improved post-ischemic contractile function. Thus reducing Na⁺-overload in ischemia (and reperfusion) is a promising therapeutical aporoach for cardio-protection.     

Sodium ion distribution in the vitreous body

We have studied the nuclear magnetic resonance (NMR) relaxation behavior, and thus the dynamic properties, of the sodium ion in the vitreous body at different temperatures. The²³Na NMR spectrum exhibits a resonance, the intensity of which accounts for an ion visibility of 100%. The²³Na longitudinal and transverse relaxation times, at all temperatures but the highest, present two components, suggesting that the sodium ions are present in two states of different mobility, whose populations are in slow exchange on the NMR time scale. The correlation times and quadrupole coupling constants for the two sodium pools have been derived. The faster relaxation of a fraction of the vitreal sodium has tentatively been ascribed to the influence of the macromolecular framework of the vitreous body. The reported information may be of use for the understanding of the diagnostic applications of²³Na magnetic resonance imaging of the ocular structures.