Amide proton transfer (APT) imaging of brain tumors at 7 T : The role of tissue water T1 -Relaxation properties

NARCIS (Netherlands)

Khlebnikov, V; Polders, Daniel; Hendrikse, J; Robe, Pierre A.; Voormolen, Eduard H; Luijten, Peter R; Klomp, DWJ; Hoogduin, Hans

PURPOSE: To provide insight into the effect of water T1 relaxation (T1wat ) on amide proton transfer (APT) contrast in tumors. Three different metrics of APT contrast-magnetization transfer ratio (MTRRex ), relaxation-compensated MTRRex (AREX), and traditional asymmetry (MTRasym )-were compared in

TOMROP: a sequence for determining the longitudinal relaxation time T1 in NMR

International Nuclear Information System (INIS)

Graumann, R.; Barfuss, H.; Fischer, H.; Hentschel, D.; Oppelt, A.

1987-01-01

We developed the pulse sequence TOMROP (T One by Multiple Read Out Pulses) for determining precisely the spatial distribution of the longitudinal relaxation time T 1 in nuclear magnetic resonance (NMR): a series of small-angle selection pulses is used to read out longitudinal magnetization from its initial state till thermal equilibrium. Hence, one measurement will produce several images with different T 1 weightings whose pixel brilliance depends exponentially from read-out time. T 1 can be determined from these independent of initial magnetization and selection pulse angle. The measuring time corresponds to the time needed in multi-echo imaging for the determination of the transversal relaxation time T 2 . We demonstrate this new method using head images of volunteers produced with a 0.23 T test facility. (orig./HP) [de

Low-Field NMR Spectrometry of Chalk and Argillaceous Sandstones: Rock-Fluid Affinity Assessed from T-1/T-2 Ratio

DEFF Research Database (Denmark)

Katika, Konstantina; Saidian, Milad; Prasad, Manika

2017-01-01

greensand shows different behavior for small and large pores. Small pores (fast-relaxing components) have T-1/T-2 = 2.0 when water saturated, but T-1/T-2 = 3.8 when oil saturated, indicating oil-affinity of chlorite. By contrast, large pores (slow-relaxing components) have significant preference for water...

In vivo measurements of T1 relaxation times of 31P-metabolites in human skeletal muscle

DEFF Research Database (Denmark)

Thomsen, C; Jensen, K E; Henriksen, O

1989-01-01

The T1 relaxation times were estimated for 31P-metabolites in human skeletal muscle. Five healthy volunteers were examined in a 1.5 Tesla wholebody imaging system using an inversion recovery pulse sequence. The calculated T1 relaxation times ranged from 5.517 sec for phosphocreatine to 3.603 sec...

Relaxation times T1, T2, and T2* of apples, pears, citrus fruits, and potatoes with a comparison to human tissues

International Nuclear Information System (INIS)

Werz, Karin; Braun, Hans; Vitha, Dominik; Bruno, Graziano; Martirosian, Petros; Steidle, Guenter; Schick, Fritz

2011-01-01

The aim of the project was a systematic assessment of relaxation times of different fruits and vegetables and a comparison to values of human tissues. Results provide an improved basis for selection of plant phantoms for development of new MR techniques and sequences. Vessels filled with agar gel are mostly used for this purpose, preparation of which is effortful and time-consuming. In the presented study apples, (malus, 8 species), pears, (pyrus, 2 species), citrus fruits (citrus, 5 species) and uncooked potatoes (solanum tuberosum, 8 species) from the supermarket were examined which are easily available nearly all-the-year. T1, T2 and T2 * relaxation times of these nature products were measured on a 1.5 Tesla MR system with adapted examination protocols and mono-exponential fitting, and compared to literature data of human parenchyma tissues, fatty tissue and body fluid (cerebrospinal fluid). Resulting values were as follows: apples: T1: 1486 - 1874 ms, T2: 163 - 281 ms, T2 * : 2,3 - 3,2 ms; pears: T1: 1631 - 1969 ms, T2: 119 - 133 ms, T2 * : 10,1 - 10,6 ms, citrus fruits (pulp) T1: 2055 - 2632 ms, T2: 497 - 998 ms, T2 * : 151 - 182 ms; citrus fruits (skin) T1: 561 - 1669 ms, T2: 93 - 119 ms; potatoes: T1: 1011 - 1459 ms, T2: 166 - 210 ms, T2 * : 20 - 30 ms. All T1-values of the examined objects (except for potatoes and skins of citrus fruits) were longer than T1 values of human tissues. Also T2 values (except for pears and skins of citrus fruits) of the fruits and the potatoes tended to be longer. T2 * values of apples, pears and potatoes were shorter than in healthy human tissue. Results show relaxation values of many fruits to be not exactly fitting to human tissue, but with suitable selection of the fruits and optionally with an adaption of measurement parameters one can achieve suitable contrast and signal characteristics for some purposes. (orig.)

Prolonged T1 relaxation of the hemopoietic bone marrow in patients with chronic leukemia

International Nuclear Information System (INIS)

Jensen, K.E.; Soerensen, P.G.; Thomsen, C.; Christoffersen, P.; Henriksen, O.; Karle, H.; Hvidovre Hospital; Hvidovre Hospital; Gentofte Hospital

1990-01-01

Eleven patients with chronic leukemia (7 with chronic lymphocytic leukemia and 4 with chronic myeloid leukemia) were evaluated with magnetic resonance (MR) imaging and T1 relaxation time measurements by use of a 1.5 tesla whole body MR scanner. Bone marrow biopsies were obtained from the posterior iliac crest (within 72 hours of the MR examination) in order to provide data on bone marrow cellularity and differential counts. The patients with chronic leukemia all showed a significant prolongation of the T1 relaxation times compared with the normal range for hemopoietic bone marrow. (orig.)

Prolonged bone marrow T1-relaxation in acute leukaemia. In vivo tissue characterization by magnetic resonance imaging

DEFF Research Database (Denmark)

Thomsen, C; Sørensen, P G; Karle, H

1987-01-01

In vivo tissue characterization by measurement of T1- and T2-relaxation processes is one of the greatest potentials of magnetic resonance imaging (MRI). This may be especially useful in the evaluation of bone marrow disorders as the MRI-signal from bone marrow is not influenced by the overlying...... osseous tissue. Nine patients with acute leukaemia, one patient with myelodysplastic syndrome, and ten normal volunteers were included in the study. The T1- and T2-relaxation processes were measured in the lumbar spine bone marrow using a wholebody superconductive MR-scanner operating at 1.5 Tesla.......38-0.60 sec.). No significant difference was seen in the T2-relaxation process. In relation to chemotherapy T1 decreased towards the normal range in the patients who obtained complete remission, whereas T1 remained prolonged in the patients who did not respond successfully to the treatment. The results...

Intraindividual comparison of T1 relaxation times after gadobutrol and Gd-DTPA administration for cardiac late enhancement imaging

Energy Technology Data Exchange (ETDEWEB)

Doeblin, Patrick, E-mail: Patrick.doeblin@charite.de [Department of Cardiology, Charité – Universitätsmedizin Berlin, Charité Campus Benjamin Franklin, Berlin (Germany); Schilling, Rene, E-mail: rene.schilling@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Wagner, Moritz, E-mail: moritz.wagner@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Luhur, Reny, E-mail: renyluhur@yahoo.com [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Huppertz, Alexander, E-mail: alexander.huppertz@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Imaging Science Institute, Charité, Berlin (Germany); Hamm, Bernd, E-mail: bernd.hamm@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Taupitz, Matthias, E-mail: matthias.taupitz@harite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); and others

2014-04-15

Purpose: To evaluate T1-relaxation times of chronic myocardial infarction (CMI) using gadobutrol and gadopentetate dimeglumine (Gd-DTPA) over time and to determine the optimal imaging window for late enhancement imaging with both contrast agents. Material and methods: Twelve patients with CMI were prospectively included and examined on a 1.5 T magnetic resonance (MR) system using relaxivity-adjusted doses of gadobutrol (0.15 mmol/kg) and Gd-DTPA (0.2 mmol/kg) in random order. T1-relaxation times of remote myocardium (RM), infarcted myocardium (IM), and left ventricular cavity (LVC) were assessed from short-axis TI scout imaging using the Look–Locker approach and compared intraindividually using a Wilcoxon paired signed-rank test (α < 0.05). Results: Within 3 min of contrast agent administration (CA), IM showed significantly lower T1-relaxation times than RM with both contrast agents, indicating beginning cardiac late enhancement. Differences between gadobutrol and Gd-DTPA in T1-relaxation times of IM and RM were statistically not significant through all time points. However, gadobutrol led to significantly higher T1-relaxation times of LVC than Gd-DTPA from 6 to 9 min (220 ± 15 ms vs. 195 ± 30 ms p < 0.01) onwards, resulting in a significantly greater ΔT1 of IM to LVC at 9–12 min (−20 ± 35 ms vs. 0 ± 35 ms, p < 0.05) and 12–15 min (−25 ± 45 ms vs. −10 ± 60 ms, p < 0.05). Using Gd-DTPA, comparable ΔT1 values were reached only after 25–35 min. Conclusion: This study indicates good delineation of IM to RM with both contrast agents as early as 3 min after administration. However, we found significant differences in T1 relaxation times with greater ΔT1 IM–LVC using 0.15 mmol/kg gadobutrol compared to 0.20 mmol/kg Gd-DTPA after 9–15 min post-CA suggesting earlier differentiability of IM and LVC using gadobutrol.

Electromechanical delay components during skeletal muscle contraction and relaxation in patients with myotonic dystrophy type 1.

Science.gov (United States)

Esposito, Fabio; Cè, Emiliano; Rampichini, Susanna; Limonta, Eloisa; Venturelli, Massimo; Monti, Elena; Bet, Luciano; Fossati, Barbara; Meola, Giovanni

2016-01-01

The electromechanical delay during muscle contraction and relaxation can be partitioned into mainly electrochemical and mainly mechanical components by an EMG, mechanomyographic, and force combined approach. Component duration and measurement reliability were investigated during contraction and relaxation in a group of patients with myotonic dystrophy type 1 (DM1, n = 13) and in healthy controls (n = 13). EMG, mechanomyogram, and force were recorded in DM1 and in age- and body-matched controls from tibialis anterior (distal muscle) and vastus lateralis (proximal muscle) muscles during maximum voluntary and electrically-evoked isometric contractions. The electrochemical and mechanical components of the electromechanical delay during muscle contraction and relaxation were calculated off-line. Maximum strength was significantly lower in DM1 than in controls under both experimental conditions. All electrochemical and mechanical components were significantly longer in DM1 in both muscles. Measurement reliability was very high in both DM1 and controls. The high reliability of the measurements and the differences between DM1 patients and controls suggest that the EMG, mechanomyographic, and force combined approach could be utilized as a valid tool to assess the level of neuromuscular dysfunction in this pathology, and to follow the efficacy of pharmacological or non-pharmacological interventions. Copyright © 2015 Elsevier B.V. All rights reserved.

Changes in T1 relaxation processes in the bone marrow following treatment in children with acute lymphoblastic leukemia

International Nuclear Information System (INIS)

Jensen, K.E.; Thomsen, C.; Henriksen, O.; Hertz, H.; Johansen, H.K.; Yssing, M.

1990-01-01

Magnetic resonance imaging (MRI) and T 1 relaxation time measurements of the vertebral bone marrow were performed in 11 children with acute lymphoblastic leukemia (ALL) at diagnosis. Nine of the children were re-examined after chemotherapeutic treatment. The results were compared with histological data from bone marrow biopsies obtained in close association to the MR examinations. Ten age matched children were examined as a control group. A 1.5 Tesla whole body scanner was used for the measurements. The pretreatment T 1 relaxation times of the bone marrow were significantly prolonged, compared to the age matched controls. After chemotherapy the T 1 relaxation times of the children with ALL decreased significantly towards or into the normal range. A significant correlation was found between the T 1 relaxation time and the content of malignant blast cells in the bone marrow. (orig.)

Magnetic resonance imaging of the bone marrow in patients with acute leukemia during and after chemotherapy. Changes in T1 relaxation

DEFF Research Database (Denmark)

Jensen, K E; Grundtvig Sørensen, P; Thomsen, C

1990-01-01

Twenty-seven patients with acute leukemia were examined at the time of diagnosis with MR imaging and in vivo T1 relaxation time measurements of the hemopoietic bone marrow. A 1.5 T whole body magnetic resonance scanner was used. Twenty of the patients had follow-up examinations in relation...... to chemotherapy. Bone marrow biopsies from the posterior iliac crest were obtained within a short time interval of all MR examinations. At the time of diagnosis, T1 relaxation times were increased significantly in all the leukemic patients, compared with 24 age-matched controls. A decrease in T1 relaxation time......, also showed prolongation of T1 relaxation time in relation to leukemic relapse. The results indicate that changes observed in T1 relaxation times of the hemopoietic bone marrow in patients with acute leukemia reflect changes in disease activity, and, that serial measurements of T1 values may provide...

T1 nuclear magnetic relaxation dispersion of hyperpolarized sodium and cesium hydrogencarbonate-13 C.

Science.gov (United States)

Martínez-Santiesteban, Francisco M; Dang, Thien Phuoc; Lim, Heeseung; Chen, Albert P; Scholl, Timothy J

2017-09-01

In vivo pH mapping in tissue using hyperpolarized hydrogencarbonate- 13 C has been proposed as a method to study tumor growth and treatment and other pathological conditions related to pH changes. The finite spin-lattice relaxation times (T 1 ) of hyperpolarized media are a significant limiting factor for in vivo imaging. Relaxation times can be measured at standard magnetic fields (1.5 T, 3.0 T etc.), but no such data are available at low fields, where T 1 values can be significantly shorter. This information is required to determine the potential loss of polarization as the agent is dispensed and transported from the polarizer to the MRI scanner. The purpose of this study is to measure T 1 dispersion from low to clinical magnetic fields (0.4 mT to 3.0 T) of different hyperpolarized hydrogencarbonate formulations previously proposed in the literature for in vivo pH measurements. 13 C-enriched cesium and sodium hydrogencarbonate preparations were hyperpolarized using dynamic nuclear polarization, and the T 1 values of different samples were measured at different magnetic field strengths using a fast field-cycling relaxometer and a 3.0 T clinical MRI system. The effects of deuterium oxide as a dissolution medium for sodium hydrogencarbonate were also analyzed. This study finds that the cesium formulation has slightly shorter T 1 values compared with the sodium preparation. However, the higher solubility of cesium hydrogencarbonate- 13 C means it can be polarized at greater concentration, using less trityl radical than sodium hydrogencarbonate- 13 C. This study also establishes that the preparation and handling of sodium hydrogencarbonate formulations in relation to cesium hydrogencarbonate is more difficult, due to the higher viscosity and lower achievable concentrations, and that deuterium oxide significantly increases the T 1 of sodium hydrogencarbonate solutions. Finally, this work also investigates the influence of pH on the spin-lattice relaxation of cesium

Instrumentation problems in the measurement of relaxation time T1 in MRI

International Nuclear Information System (INIS)

Leroy-Willig, A.; Roucayrol, J.C.; Bittoun, J.; Courtieu, J.

1986-01-01

Longitudinal relaxation (T 1 ) of protons is a sensitive though non specific tool of tissue characterization. T 1 measurement from magnetic resonance images is unprecise, due to several phenomena that we review: time intervals shorter than in spectroscopic sequences; flip angle inhomogeneity; slice selection and spin echoes. In vivo the molecular inhomogeneity can prevent to measure a true T 1 ; motion and blood flow are important causes of errors. The relative effects of these factors are examined from in vitro and in vivo images acquired at 1.5 T. From a mono-echo single-slice saturation sequence reliable values of T 1 are obtained in vitro, the measurement time being compatible with clinical imaging. In vivo, problems due to various causes of motions are still unresolved [fr

In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome

International Nuclear Information System (INIS)

Jensen, K.E.; Nielsen, H.; Thomsen, C.; Soerensen, P.G.; Karle, H.; Christoffersen, P.; Henriksen, O.; Hvidovre Hospital, Copenhagen; Hvidovre Hospital, Copenhagen

1989-01-01

Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-up examinations. At the time of diagnosis the T1 relaxation times of the vertebral bone marrow were significantly prolonged compared with normal values. The T1 relaxation times of the vertebral bone marrow in patients with MDS showed significantly lower values compared with patients with acute leukemia and did not differ from patients with polycythemia vera. (orig.)

Musculoskeletal MRI at 3.0 T and 7.0 T: A comparison of relaxation times and image contrast

International Nuclear Information System (INIS)

Jordan, Caroline D.; Saranathan, Manojkumar; Bangerter, Neal K.; Hargreaves, Brian A.; Gold, Garry E.

2013-01-01

Objective: The purpose of this study was to measure and compare the relaxation times of musculoskeletal tissues at 3.0 T and 7.0 T, and to use these measurements to select appropriate parameters for musculoskeletal protocols at 7.0 T. Materials and methods: We measured the T 1 and T 2 relaxation times of cartilage, muscle, synovial fluid, bone marrow and subcutaneous fat at both 3.0 T and 7.0 T in the knees of five healthy volunteers. The T 1 relaxation times were measured using a spin-echo inversion recovery sequence with six inversion times. The T 2 relaxation times were measured using a spin-echo sequence with seven echo times. The accuracy of both the T 1 and T 2 measurement techniques was verified in phantoms at both magnetic field strengths. We used the measured relaxation times to help design 7.0 T musculoskeletal protocols that preserve the favorable contrast characteristics of our 3.0 T protocols, while achieving significantly higher resolution at higher SNR efficiency. Results: The T 1 relaxation times in all tissues at 7.0 T were consistently higher than those measured at 3.0 T, while the T 2 relaxation times at 7.0 T were consistently lower than those measured at 3.0 T. The measured relaxation times were used to help develop high resolution 7.0 T protocols that had similar fluid-to-cartilage contrast to that of the standard clinical 3.0 T protocols for the following sequences: proton-density-weighted fast spin-echo (FSE), T 2 -weighted FSE, and 3D-FSE-Cube. Conclusion: The T 1 and T 2 changes were within the expected ranges. Parameters for musculoskeletal protocols at 7.0 T can be optimized based on these values, yielding improved resolution in musculoskeletal imaging with similar contrast to that of standard 3.0 T clinical protocols

In vivo relaxation time measurements on a murine tumor model--prolongation of T1 after photodynamic therapy.

Science.gov (United States)

Liu, Y H; Hawk, R M; Ramaprasad, S

1995-01-01

RIF tumors implanted on mice feet were investigated for changes in relaxation times (T1 and T2) after photodynamic therapy (PDT). Photodynamic therapy was performed using Photofrin II as the photosensitizer and laser light at 630 nm. A home-built proton solenoid coil in the balanced configuration was used to accommodate the tumors, and the relaxation times were measured before, immediately after, and up to several hours after therapy. Several control experiments were performed untreated tumors, tumors treated with Photofrin II alone, or tumors treated with laser light alone. Significant increases in T1s of water protons were observed after PDT treatment. In all experiments, 31P spectra were recorded before and after the therapy to study the tumor status and to confirm the onset of PDT. These studies show significant prolongation of T1s after the PDT treatment. The spin-spin relaxation measurements, on the other hand, did not show such prolongation in T2 values after PDT treatment.

Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Haar, Peter J [Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA (United States); Broaddus, William C; Chen Zhijian; Gillies, George T [Department of Neurosurgery, Virginia Commonwealth University, Richmond, VA (United States); Fatouros, Panos P; Corwin, Frank D, E-mail: wbroaddus@mcvh-vcu.ed [Department of Radiology, Virginia Commonwealth University, Richmond, VA (United States)

2010-06-21

A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s){sup -1} in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

Science.gov (United States)

Haar, Peter J.; Broaddus, William C.; Chen, Zhi-jian; Fatouros, Panos P.; Gillies, George T.; Corwin, Frank D.

2010-06-01

A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s)-1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

International Nuclear Information System (INIS)

Haar, Peter J; Broaddus, William C; Chen Zhijian; Gillies, George T; Fatouros, Panos P; Corwin, Frank D

2010-01-01

A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s) -1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

Diagnostic value of T1 and T2 * relaxation times and off-resonance saturation effects in the evaluation of Achilles tendinopathy by MRI at 3T.

Science.gov (United States)

Grosse, Ulrich; Syha, Roland; Hein, Tobias; Gatidis, Sergios; Grözinger, Gerd; Schabel, Christoph; Martirosian, Petros; Schick, Fritz; Springer, Fabian

2015-04-01

To evaluate and compare the diagnostic value of T1 , T2 * relaxation times and off-resonance saturation ratios (OSR) in healthy controls and patients with different clinical and morphological stages of Achilles tendinopathy. Forty-two healthy Achilles tendons and 34 tendons of 17 patients with symptomatic and asymptomatic tendinopathy were investigated clinically with conventional magnetic resonance imaging (MRI) sequences on a 3T whole-body MR scanner and a dynamic ultrasound examination. In addition, T1 and T2 * relaxation times were assessed using an ultrashort echo time (UTE) imaging sequence with flip angle and echo time variation. For the calculation of OSR values a Gaussian off-resonance saturation pulse (frequency offset: 750-5000 Hz) was used. The diagnostic value of the derived MR values was assessed and compared using receiver operating characteristic (ROC) curves. ROC curves demonstrate the highest overall test performance for OSR values at 2000 Hz off-resonance in differentiating slightly (OSR-2000 [AUC: 0.930] > T2 * [AUC: 0.884] > T1 [AUC: 0.737]) and more severe pathologically altered tendon areas (OSR-2000 [AUC: 0.964] > T2 * [AUC: 0.917] > T1 [AUC: 0.819]) from healthy ones. OSR values at a frequency offset of 2000 Hz demonstrated a better sensitivity and specificity for detecting mild and severe stages of tendinopathy compared to T2 * and particularly when compared to T1 relaxation times. © 2014 Wiley Periodicals, Inc.

Relationship between aging and T1 relaxation time in deep gray matter: A voxel-based analysis.

Science.gov (United States)

Okubo, Gosuke; Okada, Tomohisa; Yamamoto, Akira; Fushimi, Yasutaka; Okada, Tsutomu; Murata, Katsutoshi; Togashi, Kaori

2017-09-01

To investigate age-related changes in T 1 relaxation time in deep gray matter structures in healthy volunteers using magnetization-prepared 2 rapid acquisition gradient echoes (MP2RAGE). In all, 70 healthy volunteers (aged 20-76, mean age 42.6 years) were scanned at 3T magnetic resonance imaging (MRI). A MP2RAGE sequence was employed to quantify T 1 relaxation times. After the spatial normalization of T 1 maps with the diffeomorphic anatomical registration using the exponentiated Lie algebra algorithm, voxel-based regression analysis was conducted. In addition, linear and quadratic regression analyses of regions of interest (ROIs) were also performed. With aging, voxel-based analysis (VBA) revealed significant T 1 value decreases in the ventral-inferior putamen, nucleus accumbens, and amygdala, whereas T 1 values significantly increased in the thalamus and white matter as well (P time vary by location in deep gray matter. 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:724-731. © 2017 International Society for Magnetic Resonance in Medicine.

Relaxation times T1, T2, and T2{sup *} of apples, pears, citrus fruits, and potatoes with a comparison to human tissues; T1-, T2- und T2{sup *}-Relaxationswerte von Aepfeln, Birnen, Zitrusfruechten und Kartoffeln im Vergleich zu menschlichen Geweben

Energy Technology Data Exchange (ETDEWEB)

Werz, Karin; Braun, Hans; Vitha, Dominik; Bruno, Graziano; Martirosian, Petros; Steidle, Guenter; Schick, Fritz [Tuebingen Univ. (Germany). Sektion fuer Experimentelle Radiologie

2011-07-01

The aim of the project was a systematic assessment of relaxation times of different fruits and vegetables and a comparison to values of human tissues. Results provide an improved basis for selection of plant phantoms for development of new MR techniques and sequences. Vessels filled with agar gel are mostly used for this purpose, preparation of which is effortful and time-consuming. In the presented study apples, (malus, 8 species), pears, (pyrus, 2 species), citrus fruits (citrus, 5 species) and uncooked potatoes (solanum tuberosum, 8 species) from the supermarket were examined which are easily available nearly all-the-year. T1, T2 and T2{sup *} relaxation times of these nature products were measured on a 1.5 Tesla MR system with adapted examination protocols and mono-exponential fitting, and compared to literature data of human parenchyma tissues, fatty tissue and body fluid (cerebrospinal fluid). Resulting values were as follows: apples: T1: 1486 - 1874 ms, T2: 163 - 281 ms, T2{sup *}: 2,3 - 3,2 ms; pears: T1: 1631 - 1969 ms, T2: 119 - 133 ms, T2{sup *}: 10,1 - 10,6 ms, citrus fruits (pulp) T1: 2055 - 2632 ms, T2: 497 - 998 ms, T2{sup *}: 151 - 182 ms; citrus fruits (skin) T1: 561 - 1669 ms, T2: 93 - 119 ms; potatoes: T1: 1011 - 1459 ms, T2: 166 - 210 ms, T2{sup *}: 20 - 30 ms. All T1-values of the examined objects (except for potatoes and skins of citrus fruits) were longer than T1 values of human tissues. Also T2 values (except for pears and skins of citrus fruits) of the fruits and the potatoes tended to be longer. T2{sup *} values of apples, pears and potatoes were shorter than in healthy human tissue. Results show relaxation values of many fruits to be not exactly fitting to human tissue, but with suitable selection of the fruits and optionally with an adaption of measurement parameters one can achieve suitable contrast and signal characteristics for some purposes. (orig.)

Surface-NMR measurements of the longitudinal relaxation time T1 in a homogeneous sandy aquifer in Skive, Denmark

Science.gov (United States)

Walbrecker, J.; Behroozmand, A.

2011-12-01

Efficient groundwater management requires reliable means of characterizing shallow groundwater aquifers. One key parameter in this respect is hydraulic conductivity. Surface nuclear magnetic resonance (NMR) is a geophysical exploration technique that can potentially provide this type of information in a noninvasive, cost-effective way. The technique is based on measuring the precession of nuclear spins of protons in groundwater molecules. It involves large loop antennas deployed on Earth's surface to generate electromagnetic pulses tuned to specifically excite and detect groundwater proton spins. Naturally, the excited state of spins is transitory - once excited, spins relax back to their equilibrium state. This relaxation process is strongly influenced by the spin environment, which, in the case of groundwater, is defined by the aquifer. By employing empirical relations, changes in relaxation behavior can be used to identify changes in aquifer hydraulic conductivity, making the NMR relaxation signal a very important piece of information. Particularly, efforts are made to record the longitudinal relaxation parameter T1, because it is known from laboratory studies that it often reliably correlates with hydraulic conductivity, even in the presence of magnetic species. In surface NMR, T1 data are collected by recording the NMR signal amplitude following two sequential excitation pulses as a function of the delay time τ between the two pulses. In conventional acquisition, the two pulses have a mutual phase shift of π. Based on theoretical arguments it was recently shown that T1 times acquired according to this conventional surface-NMR scheme are systematically biased. It was proposed that the bias can be minimized by cycling the phase of the two pulses between π and zero in subsequent double-pulse experiments, and subtracting the resulting signal amplitudes (phase-cycled pseudosaturation recovery scheme, pcPSR). We present the first surface-NMR T1 data set recorded

Role of Thickness Confinement on Relaxations of the Fast Component in a Miscible A/B Blend

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Green, Peter [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sharma, Ravi P. [University of Michigan; Dong, Ban Xuan [University of Michigan

2018-01-18

Spatial compositional heterogeneity strongly influences the dynamics of the A and B components of bulk miscible blends. Its effects are especially apparent in mixtures, such as poly(vinyl methyl ether) (PVME)/polystyrene (PS), where there exist significant disparities between the component glass transition temperatures (Tgs) and relaxation times. The relaxation processes characterized by distinct temperature dependencies and relaxation rates manifest different local compositional environments for temperatures above and below the glass transition temperature of the miscible blend. This same behavior is shown to exist in miscible PS/PVME films as thin as 100 nm. Moreover, in thin films, the characteristic segmental relaxation times t of the PVME component of miscible PVME/PS blends confined between aluminum (Al) substrates decrease with increasing molecular weight M of the PS component. These relaxation rates are film thickness dependent, in films up to a few hundred nanometers in thickness. This is in remarkable contrast to homopolymer films, where thickness confinement effects are apparent only on length scales on the order of nanometers. These surprisingly large length scales and M dependence are associated with the preferential interfacial enrichment - wetting layer formation - of the PVME component at the external Al interfaces, which alters the local spatial blend composition within the interior of the film. The implications are that the dynamics of miscible thin film blends are dictated in part by component Tg differences, disparities in component relaxation rates, component-substrate interactions, and chain lengths (entropy of mixing).

Prolonged T1 relaxation of the hemopoietic bone marrow in patients with chronic leukemia

DEFF Research Database (Denmark)

Jensen, K E; Sørensen, P G; Thomsen, C

1990-01-01

Eleven patients with chronic leukemia (7 with chronic lymphocytic leukemia and 4 with chronic myeloid leukemia) were evaluated with magnetic resonance (MR) imaging and T1 relaxation time measurements by use of a 1.5 tesla whole body MR scanner. Bone marrow biopsies were obtained from the posterior...

T2 relaxation times of irradiated vertebral bone marrow in patients with seminoma.

Science.gov (United States)

Argiris, A; Maris, T; Vlahos, L

1997-01-01

Our purpose was to demonstrate the effects of localized radiotherapy on lumbar vertebral bone marrow with the use of quantitative MRI with measurements of T2 relaxation times. Ten patients with early stage testicular seminoma with a history of radiation therapy to a "dog-leg" field including the lumbar vertebrae underwent MR imaging of their lumbar spine using a 0.5 Tesla magnet. Five healthy subjects and two nonirradiated patients were imaged as well. The intervals from the beginning of radiotherapy to MRI examination varied from 1.5 to 52 months, and the radiation dose ranged from 3000-4200 cGy. The T2 relaxation times of the lumbar vertebral bone marrow and subcutaneous fat were calculated for each subject. Postirradiation bone marrow in irradiated seminoma patients exhibited significantly longer T2 relaxation times than nonirradiated bone marrow in controls (71.1 vs. 63.6 ms, p = 0.047, t-test). The differences between the T2 relaxation times of bone marrow and subcutaneous fat for each subject allowed for even better differentiation between irradiated patients and controls (10.4 vs. 0.4 ms, p = 0.0004, t-test). Postirradiation bone marrow had significantly longer T2 relaxation times than subcutaneous fat in irradiated patients (N = 10, 71.1 vs. 60.7 ms, p = 0.00009, t-test), while nonirradiated bone marrow had T2 relaxation times not statistically different from subcutaneous fat in nonirradiated subjects (N = 7, 63.6 vs. 63.2 ms). Measurements of T2 relaxation times of bone marrow enabled us to differentiate between irradiated seminoma patients and controls. Postirradiation bone marrow undergoes late radiation effects resulting in longer T2 relaxation times than nonirradiated bone marrow and subcutaneous fat.

Topographical Variation of Human Femoral Articular Cartilage Thickness, T1rho and T2 Relaxation Times Is Related to Local Loading during Walking.

Science.gov (United States)

Van Rossom, Sam; Wesseling, Mariska; Van Assche, Dieter; Jonkers, Ilse

2018-01-01

Objective Early detection of degenerative changes in the cartilage matrix composition is essential for evaluating early interventions that slow down osteoarthritis (OA) initiation. T1rho and T2 relaxation times were found to be effective for detecting early changes in proteoglycan and collagen content. To use these magnetic resonance imaging (MRI) methods, it is important to document the topographical variation in cartilage thickness, T1rho and T2 relaxation times in a healthy population. As OA is partially mechanically driven, the relation between these MRI-based parameters and localized mechanical loading during walking was investigated. Design MR images were acquired in 14 healthy adults and cartilage thickness and T1rho and T2 relaxation times were determined. Experimental gait data was collected and processed using musculoskeletal modeling to identify weight-bearing zones and estimate the contact force impulse during gait. Variation of the cartilage properties (i.e., thickness, T1rho, and T2) over the femoral cartilage was analyzed and compared between the weight-bearing and non-weight-bearing zone of the medial and lateral condyle as well as the trochlea. Results Medial condyle cartilage thickness was correlated to the contact force impulse ( r = 0.78). Lower T1rho, indicating increased proteoglycan content, was found in the medial weight-bearing zone. T2 was higher in all weight-bearing zones compared with the non-weight-bearing zones, indicating lower relative collagen content. Conclusions The current results suggest that medial condyle cartilage is adapted as a long-term protective response to localized loading during a frequently performed task and that the weight-bearing zone of the medial condyle has superior weight bearing capacities compared with the non-weight-bearing zones.

Temperature Dependence of Logarithmic-like Relaxational Dynamics of Hydrated tRNA.

Science.gov (United States)

Chu, Xiang-Qiang; Mamontov, Eugene; O'Neill, Hugh; Zhang, Qiu

2013-03-21

The dynamics of RNA within the β-relaxation region of 10 ps to 1 ns is crucial to its biological function. Because of its simpler chemical building blocks and the lack of the side methyl groups, faster relaxational dynamics of RNA compared to proteins can be expected. However, the situation is actually opposite. In this work, the relaxational dynamics of tRNA is measured by quasielastic neutron scattering and analyzed using the mode coupling theory, originally developed for glass-forming liquids. Our results reveal that the dynamics of tRNA follows a log-decay within the β-relaxation region, which is an important trait demonstrated by the dynamics of proteins. The dynamics of hydrated tRNA and lysozyme compared in the time domain further demonstrate that the slower dynamics of tRNA relative to proteins originates from the difference in the folded states of tRNA and proteins, as well as the influence of their hydration water.

Gadolinium-based magnetic resonance contrast agents at 7 Tesla: in vitro T1 relaxivities in human blood plasma.

Science.gov (United States)

Noebauer-Huhmann, Iris M; Szomolanyi, Pavol; Juras, Vladimír; Kraff, Oliver; Ladd, Mark E; Trattnig, Siegfried

2010-09-01

PURPOSE/INTRODUCTION: The aim of this study was to determine the T1 relaxivities (r1) of 8 gadolinium (Gd)-based MR contrast agents in human blood plasma at 7 Tesla, compared with 3 Tesla. Eight commercially available Gd-based MR contrast agents were diluted in human blood plasma to concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. In vitro measurements were performed at 37 degrees C, on a 7 Tesla and on a 3 Tesla whole-body magnetic resonance imaging scanner. For the determination of T1 relaxation times, Inversion Recovery Sequences with inversion times from 0 to 3500 ms were used. The relaxivities were calculated. The r1 relaxivities of all agents, diluted in human blood plasma at body temperature, were lower at 7 Tesla than at 3 Tesla. The values at 3 Tesla were comparable to those published earlier. Notably, in some agents, a minor negative correlation of r1 with a concentration of up to 2 mmol/L could be observed. This was most pronounced in the agents with the highest protein-binding capacity. At 7 Tesla, the in vitro r1 relaxivities of Gd-based contrast agents in human blood plasma are lower than those at 3 Tesla. This work may serve as a basis for the application of Gd-based MR contrast agents at 7 Tesla. Further studies are required to optimize the contrast agent dose in vivo.

Biologically aggressive regions within glioblastoma identified by spin-lock contrast T1 relaxation in the rotating frame (T1ρ MRI

Directory of Open Access Journals (Sweden)

Ramon Francisco Barajas, Jr., MD

2017-12-01

Full Text Available Spin-lattice relaxation in the rotating frame magnetic resonance imaging allows for the quantitative assessment of spin-lock contrast within tissues. We describe the utility of spin-lattice relaxation in the rotating frame metrics in characterizing glioblastoma biological heterogeneity. A 84-year-old man presented to our institution with a right frontal temporal mass. Prior tissue sampling from a peripheral nonenhancing lesion was nondiagnostic. Stereotactic image-guided tissue sampling of the nonenhancing T2-fluid-attenuated inversion recovery hyperintense region involving the anterior cingulate gyrus with elevated spin-lattice relaxation in the rotating frame metrics provided a pathologic diagnosis of glioblastoma. This case illustrates the utility of spin-lattice relaxation in the rotating frame magnetic resonance imaging in identifying biologically aggressive regions within glioblastoma.

Quantum process tomography with informational incomplete data of two J-coupled heterogeneous spins relaxation in a time window much greater than T1

Science.gov (United States)

Maciel, Thiago O.; Vianna, Reinaldo O.; Sarthour, Roberto S.; Oliveira, Ivan S.

2015-11-01

We reconstruct the time dependent quantum map corresponding to the relaxation process of a two-spin system in liquid-state NMR at room temperature. By means of quantum tomography techniques that handle informational incomplete data, we show how to properly post-process and normalize the measurements data for the simulation of quantum information processing, overcoming the unknown number of molecules prepared in a non-equilibrium magnetization state (Nj) by an initial sequence of radiofrequency pulses. From the reconstructed quantum map, we infer both longitudinal (T1) and transversal (T2) relaxation times, and introduce the J-coupling relaxation times ({T}1J,{T}2J), which are relevant for quantum information processing simulations. We show that the map associated to the relaxation process cannot be assumed approximated unital and trace-preserving for times greater than {T}2J.

In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome. A magnetic resonance imaging study

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Jensen, K.E.; Nielsen, H.; Thomsen, C.; Soerensen, P.G.; Karle, H.; Christoffersen, P.; Henriksen, O. (Hvidovre Hospital, Copenhagen (Denmark). Dept. of Magnetic Resonance; Hvidovre Hospital, Copenhagen (Denmark). Dept. of Hematology; Hvidovre Hospital, Copenhagen (Denmark). Dept. of Pathology)

Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-up examinations. At the time of diagnosis the T1 relaxation times of the vertebral bone marrow were significantly prolonged compared with normal values. The T1 relaxation times of the vertebral bone marrow in patients with MDS showed significantly lower values compared with patients with acute leukemia and did not differ from patients with polycythemia vera. (orig.).

Relaxation time T/sub 1/ and bound water fraction of muscle by NMR imager

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Fukuda, N.; Ikehira, H.; Yamane, T.; Tateno, Y.; Torii, S.; Matsumura, K.

1986-05-01

In order to establish the efficacy of NMR-CT in the diagnostic investigation of muscle disorders, proton NMR-CT imaging was performed and muscle longitudinal relaxation (T1) times were measured in 20 Duchenne muscular dystrophy (DMD) patients and normal controls (NC). In addition, the bound water fraction (BWF) was calculated from the measured T1 value in appropriate cases. Results show that in DMD muscle T1 values were above normal in the early clinical stages, declined rapidly with progress of the disease, and reached the same low level as the subcutaneous fat. This decrease of T1 values was not uniform for all muscles, being most prominent in gluteus maximus and least in sartorius and gracilis. In NC muscle BWF increased with maturation under the age of 10 years, and became fixed beyond that. In the early stages of DMD, BWF was below normal.

Spatial characterization of T1 and T2 relaxation times and the water apparent diffusion coefficient in rabbit Achilles tendon subjected to tensile loading.

Science.gov (United States)

Wellen, J; Helmer, K G; Grigg, P; Sotak, C H

2005-03-01

Tendons exhibit viscoelastic mechanical behavior under tensile loading. The elasticity arises from the collagen chains that form fibrils, while the viscous response arises from the interaction of the water with the solid matrix. Therefore, an understanding of the behavior of water in response to the application of a load is crucial to the understanding of the origin of the viscous response. Three-dimensional MRI mapping of rabbit Achilles tendons was performed at 2.0 T to characterize the response of T(1) and T(2) relaxation times and the apparent diffusion coefficient (ADC) of water to tensile loading. The ADC was measured in directions both parallel (ADC( parallel)) and perpendicular (ADC( perpendicular)) to the long axis of the tendon. At a short diffusion time (5.8 ms) MR parameter maps showed the existence of two regions, here termed "core" and "rim", that exhibited statistically significant differences in T(1), T(2), and ADC( perpendicular) under the baseline loading condition. MR parameter maps were also generated at a second loading condition of approximately 1 MPa. At a diffusion time of 5.8 ms, there was a statistically significant increase in the rim region for both ADC( perpendicular) (57.5%) and ADC( parallel) (20.5%) upon tensile loading. The changes in core ADC(( perpendicular), ( parallel)), as well as the relaxation parameters in both core and rim regions, were not statistically significant. The effect of diffusion time on the ADC(( perpendicular), ( parallel)) values was investigated by creating maps at three additional diffusion times (50.0, 125.0, 250.0 ms) using a diffusion-weighted, stimulated-echo (DW-STE) pulse sequence. At longer diffusion times, ADC(( perpendicular), ( parallel)) values increased rather than approaching a constant value. This observation was attributed to T(1) spin-editing during the DW-STE pulse sequence, which resulted in the loss of short-T(1) components (with correspondingly lower ADCs) at longer diffusion times

Molecular order and T1-relaxation, cross-relaxation in nitroxide spin labels

Science.gov (United States)

Marsh, Derek

2018-05-01

Interpretation of saturation-recovery EPR experiments on nitroxide spin labels whose angular rotation is restricted by the orienting potential of the environment (e.g., membranes) currently concentrates on the influence of rotational rates and not of molecular order. Here, I consider the dependence on molecular ordering of contributions to the rates of electron spin-lattice relaxation and cross relaxation from modulation of N-hyperfine and Zeeman anisotropies. These are determined by the averages and , where θ is the angle between the nitroxide z-axis and the static magnetic field, which in turn depends on the angles that these two directions make with the director of uniaxial ordering. For saturation-recovery EPR at 9 GHz, the recovery rate constant is predicted to decrease with increasing order for the magnetic field oriented parallel to the director, and to increase slightly for the perpendicular field orientation. The latter situation corresponds to the usual experimental protocol and is consistent with the dependence on chain-labelling position in lipid bilayer membranes. An altered dependence on order parameter is predicted for saturation-recovery EPR at high field (94 GHz) that is not entirely consistent with observation. Comparisons with experiment are complicated by contributions from slow-motional components, and an unexplained background recovery rate that most probably is independent of order parameter. In general, this analysis supports the interpretation that recovery rates are determined principally by rotational diffusion rates, but experiments at other spectral positions/field orientations could increase the sensitivity to order parameter.

Menstrual variation of breast volume and T2 relaxation times in cyclical mastalgia

International Nuclear Information System (INIS)

Hussain, Zainab; Brooks, Jonathan; Percy, Dave

2008-01-01

Purpose: Hormonal activity causes breast volume to change during the menstrual cycle. One possible cause of this volume change is thought to be due to water retention or oedema within the tissues. We used magnetic resonance imaging (MRI) to study the variation in breast volume and 1 H Magnetic Resonance Spectroscopy (MRS) to measure T 2 relaxation times which are known to increase with increasing tissue water content. We hypothesised that an increase in breast volume will elevate T 2 relaxation due to the presence of an increased water content within the breast. T 2 Relaxation time and volume were studied in fifteen control subjects and in a cohort of eight patients with cyclical mastalgia in order to determine whether changes in breast volume and T 2 relaxation times differed in controls and patients during menses, ovulation and premenses. Method: Breast volume was determined by the Cavalieri method in combination with point counting techniques on MR images and T 2 relaxation times of the water and fat in a voxel of breast tissue were obtained using 1 H Magnetic Resonance Spectroscopy (MRS). Results: Statistical analysis (ANOVA) demonstrated highly significant differences in breast volume between the three stages of the cycle (p 2 of fat or water did not depend on stage of cycle. T-tests demonstrated no significant differences in T 2 of water or fat between patient and control groups. The average T 2 relaxation time of water was lowest in the patient and control groups during ovulation and highest in the patient group during premenses. Conclusion: We have performed the first combined volumetric and spectroscopic study of women with cyclical mastalgia and demonstrated that the global changes in volumes and T 2 were not significantly different from normal menstrual variations

Medial meniscal posterior root/horn radial tears correlate with cartilage degeneration detected by T1ρ relaxation mapping

Energy Technology Data Exchange (ETDEWEB)

Takahashi, Kenji, E-mail: Kenji-am@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Hashimoto, Sanshiro, E-mail: info@msorc.jp [Minami-Shinjuku Orthopaedic Rehabilitation Clinic, 2-16-7 Yoyogi, Shibuya-ku, Tokyo 151-0053 (Japan); Nakamura, Hiroshi, E-mail: nakamura@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Mori, Atsushi, E-mail: atsu@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Sato, Akiko, E-mail: akiko-sato@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Majima, Tokifumi, E-mail: tkmajima@iuhw.ac.jp [Department of Orthopaedic Surgery, International University of Health and Welfare Hospital, 537-3 Iguchi, Nasu-shiobara, Tochigi 329-2763 (Japan); Takai, Shinro, E-mail: takai-snr@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan)

2015-06-15

Highlights: • Posterior radial tears in medial meniscus associate T1ρ values of cartilage. • Posterior radial tears relate to cartilage degeneration even in early-stage osteoarthritis. • Abnormalities in meniscus on MRI are useful for screening early-stage osteoarthritis. - Abstract: Objective: This study aimed to identify factors on routine pulse sequence MRI associated with cartilage degeneration observed on T1ρ relaxation mapping. Materials and methods: This study included 137 subjects with knee pain. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of cartilage, subchondral bone, meniscus and ligaments was performed using routine pulse sequence MRI. Radiographic evaluation for osteoarthritis was also performed. Results: Multiple regression analysis revealed posterior root/horn tears to be independent factors increasing the T1ρ values of the cartilage in the medial compartment of the femorotibial joint. Even when adjusted for radiographically defined early-stage osteoarthritis, medial posterior meniscal radial tears significantly increased the T1ρ values. Conclusions: This study showed that posterior root/horn radial tears in the medial meniscus are particularly important MRI findings associated with cartilage degeneration observed on T1ρ relaxation mapping. Morphological factors of the medial meniscus on MRI provide findings useful for screening early-stage osteoarthritis.

Medial meniscal posterior root/horn radial tears correlate with cartilage degeneration detected by T1ρ relaxation mapping

International Nuclear Information System (INIS)

Takahashi, Kenji; Hashimoto, Sanshiro; Nakamura, Hiroshi; Mori, Atsushi; Sato, Akiko; Majima, Tokifumi; Takai, Shinro

2015-01-01

Highlights: • Posterior radial tears in medial meniscus associate T1ρ values of cartilage. • Posterior radial tears relate to cartilage degeneration even in early-stage osteoarthritis. • Abnormalities in meniscus on MRI are useful for screening early-stage osteoarthritis. - Abstract: Objective: This study aimed to identify factors on routine pulse sequence MRI associated with cartilage degeneration observed on T1ρ relaxation mapping. Materials and methods: This study included 137 subjects with knee pain. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of cartilage, subchondral bone, meniscus and ligaments was performed using routine pulse sequence MRI. Radiographic evaluation for osteoarthritis was also performed. Results: Multiple regression analysis revealed posterior root/horn tears to be independent factors increasing the T1ρ values of the cartilage in the medial compartment of the femorotibial joint. Even when adjusted for radiographically defined early-stage osteoarthritis, medial posterior meniscal radial tears significantly increased the T1ρ values. Conclusions: This study showed that posterior root/horn radial tears in the medial meniscus are particularly important MRI findings associated with cartilage degeneration observed on T1ρ relaxation mapping. Morphological factors of the medial meniscus on MRI provide findings useful for screening early-stage osteoarthritis

T1 relaxation time constants, influence of oxygen, and the oxygen transfer function of the human lung at 1.5 T—A meta-analysis

Energy Technology Data Exchange (ETDEWEB)

Dietrich, Olaf, E-mail: od@dtrx.net [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Gaass, Thomas [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Comprehensive Pneumology Center, German Center for Lung Research, Munich (Germany); Reiser, Maximilian F. [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany)

2017-01-15

Purpose: To pool and summarize published data from magnetic resonance longitudinal relaxation measurements of the human lung at 1.5 T to provide a reliable basis of T{sub 1} relaxation time constants of healthy lung tissue both under respiration of room air and of pure oxygen. In particular, the oxygen-induced shortening of T{sub 1} was evaluated. Materials and methods: The PubMed database was comprehensively searched up to June 2016 for original publications in English containing quantitative T{sub 1} data (at least mean values and standard deviations) of the lung parenchyma of healthy subjects (minimum subject number: 3) at 1.5 T. From all included publications, T{sub 1} values of the lung of healthy subjects were extracted (inhaling room air and, if available, inhaling pure oxygen). Weighted mean values and standard deviations of all extracted data and the oxygen transfer function (OTF) were calculated. Results: 22 publications were included with a total number of 188 examined healthy subjects. 103 of these subjects (from 13 studies) were examined while breathing pure oxygen and room air; 85 subjects were examined only under room-air conditions. The weighted mean value (weighted sample standard deviation) of the room-air T{sub 1} values over all 22 studies was 1196 ms (152 ms). Based on studies with room-air and oxygen results, the mean T{sub 1} value at room-air conditions was 1172 ms (161 ms); breathing pure oxygen, the mean T{sub 1} value was reduced to 1054 ms (138 ms). This corresponds to a mean T{sub 1} reduction by 118 ms (35 ms) or 10.0 % (2.3 %) and to a mean OTF value of 1.22 (0.32) × 10{sup −3} s{sup −1}/(%O{sub 2}). Conclusion: This meta-analysis with data from 188 subjects indicates that the average T{sub 1} relaxation time constant of healthy lung tissue at 1.5 T is distributed around 1200 ms with a standard deviation of about 150 ms; breathing pure oxygen reduces this value significantly by 10 % to about 1050 ms.

Inherited MST1 deficiency underlies susceptibility to EV-HPV infections.

Directory of Open Access Journals (Sweden)

Amandine Crequer

Full Text Available Epidermodysplasia verruciformis (EV is characterized by persistent cutaneous lesions caused by a specific group of related human papillomavirus genotypes (EV-HPVs in otherwise healthy individuals. Autosomal recessive (AR EVER1 and EVER2 deficiencies account for two thirds of known cases of EV. AR RHOH deficiency has recently been described in two siblings with EV-HPV infections as well as other infectious and tumoral manifestations. We report here the whole-exome based discovery of AR MST1 deficiency in a 19-year-old patient with a T-cell deficiency associated with EV-HPV, bacterial and fungal infections. MST1 deficiency has recently been described in seven patients from three unrelated kindreds with profound T-cell deficiency and various viral and bacterial infections. The patient was also homozygous for a rare ERCC3 variation. Our findings broaden the clinical range of infections seen in MST1 deficiency and provide a new genetic etiology of susceptibility to EV-HPV infections. Together with the recent discovery of RHOH deficiency, they suggest that T cells are involved in the control of EV-HPVs, at least in some individuals.

Nuclear magnetic resonance studies on brain edema. Time course of /sup 1/H-NMR relaxation times

Energy Technology Data Exchange (ETDEWEB)

Naruse, S; Horikawa, Y; Tanaka, C; Hirakawa, K; Nishikawa, H [Kyoto Prefectural Univ. of Medicine (Japan)

1981-06-01

1. The state of water in normal and edematous brain tissue was studied by measurement of proton longitudinal (T/sub 1/) and transverse (T/sub 2/) relaxation times using pulsed nuclear magnetic resonance (NMR) technique. 2. In control rats, T/sub 1/ and T/sub 2/ of water showed one component, which was more fast in white matter. Those values displayed 1.07 - 1.18 sec. of T/sub 1/ and 75 - 76 msec. of T/sub 2/. 3. When rat brain was injured by cold, T/sub 1/ was observed to become longer (1.18 - 1.27 sec.), and T/sub 2/ was observed be separated into two components, the faster T/sub 2/ (45 - 50 msec.) and slower T/sub 2/ (100 - 105 msec.), in both gray and white matter of the injured side. 4. In triethyltin (TET) induced brain edema, elongation of T/sub 1/ (1.2 sec.) and remarkable separation of T/sub 2/, faster T/sub 2/ (75 msec.) and slower T/sub 2/ (400 - 450 msec.), were observed in white matter. 5. In both cold and TET induced edema, slower T/sub 2/ fraction is suggested to be the extracellular space and faster T/sub 2/ fraction, intracellular. 6. T/sub 2/ changes precede the water content changes in cold injury, and parallel in TET induced edema. Those changes of relaxation times are reversible. 7. T/sub 2/ changes of water is more sensitive than the T/sub 1/ for the detection of production and disappearance of brain edema. 8. These results disclose the dynamic movements of water during the course of brain edema and offered significant information of the clinical application of NMR-CT.

Magnetic resonance fingerprinting using echo-planar imaging: Joint quantification of T1 and T2∗ relaxation times.

Science.gov (United States)

Rieger, Benedikt; Zimmer, Fabian; Zapp, Jascha; Weingärtner, Sebastian; Schad, Lothar R

2017-11-01

To develop an implementation of the magnetic resonance fingerprinting (MRF) paradigm for quantitative imaging using echo-planar imaging (EPI) for simultaneous assessment of T 1 and T2∗. The proposed MRF method (MRF-EPI) is based on the acquisition of 160 gradient-spoiled EPI images with rapid, parallel-imaging accelerated, Cartesian readout and a measurement time of 10 s per slice. Contrast variation is induced using an initial inversion pulse, and varying the flip angles, echo times, and repetition times throughout the sequence. Joint quantification of T 1 and T2∗ is performed using dictionary matching with integrated B1+ correction. The quantification accuracy of the method was validated in phantom scans and in vivo in 6 healthy subjects. Joint T 1 and T2∗ parameter maps acquired with MRF-EPI in phantoms are in good agreement with reference measurements, showing deviations under 5% and 4% for T 1 and T2∗, respectively. In vivo baseline images were visually free of artifacts. In vivo relaxation times are in good agreement with gold-standard techniques (deviation T 1 : 4 ± 2%, T2∗: 4 ± 5%). The visual quality was comparable to the in vivo gold standard, despite substantially shortened scan times. The proposed MRF-EPI method provides fast and accurate T 1 and T2∗ quantification. This approach offers a rapid supplement to the non-Cartesian MRF portfolio, with potentially increased usability and robustness. Magn Reson Med 78:1724-1733, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

T(2) relaxation time of hyaline cartilage in presence of different gadolinium-based contrast agents.

Science.gov (United States)

Wiener, Edzard; Settles, Marcus; Diederichs, Gerd

2010-01-01

The transverse relaxation time, T(2), of native cartilage is used to quantify cartilage degradation. T(2) is frequently measured after contrast administration, assuming that the impact of gadolinium-based contrast agents on cartilage T(2) is negligible. To verify this assumption the depth-dependent variation of T(2) in the presence of gadopentetate dimeglumine, gadobenate dimeglumine and gadoteridol was investigated. Furthermore, the r(2)/r(1) relaxivity ratios were quantified in different cartilage layers to demonstrate differences between T(2) and T(1) relaxation effects. Transverse high-spatial-resolution T(1)- and T(2)-maps were simultaneously acquired on a 1.5 T MR scanner before and after contrast administration in nine bovine patellae using a turbo-mixed sequence. The r(2)/r(1) ratios were calculated for each contrast agent in cartilage. Profiles of T(1), T(2) and r(2)/r(1) across cartilage thickness were generated in the absence and presence of contrast agent. The mean values in different cartilage layers were compared for global variance using the Kruskal-Wallis test and pairwise using the Mann-Whitney U-test. T(2) of unenhanced cartilage was 98 +/- 5 ms at 1 mm and 65 +/- 4 ms at 3 mm depth. Eleven hours after contrast administration significant differences (p cartilage thickness were close to 1.0 (range 0.9-1.3). At 1.5 T, T(2) decreased significantly in the presence of contrast agents, more pronounced in superficial than in deep cartilage. The change in T(2) relaxation rate was similar to the change in T(1). Cartilage T(2) measurements after contrast administration will lead to systematic errors in the quantification of cartilage degradation. 2010 John Wiley & Sons, Ltd.

Sup(1)H n.m.r. relaxation of radiation induced crosslinking in polyester-styrene systems

International Nuclear Information System (INIS)

Andreis, M.; Veksli, Z.; Ranogajec, F.; Hedvig, P.

1989-01-01

The structure and dynamics of a network formed by radiation induced crosslinking of polyesters based on 1,6-hexane diol and 1,2-propylene glycol and maleic anhydride (HDF and PGF, respectively) with styrene is studied by proton pulsed n.m.r. spectroscopy. The dependence of spin-lattice, T 1 , and spin-spin, T 2 , relaxation times on the structure of polyester chain, molar ratios of styrene to polyester unsaturations and the radiation doses are analysed in terms of network formation and structure, and their effect on molecular motion. Above the gel point, at temperatures above the glass transition, the presence of two T 2 components reflects the heterogeneity of the network structure in both resins. Parallel with the n.m.r. relaxation measurements the crosslink density was determined from the extracted gel phase or double bonds (fumaric and styrene) participating in the crosslinking process. (author)

The influence of temperature, viscosity and pH on the relaxation time T1 in flowing liquids

International Nuclear Information System (INIS)

Toczylowska, B.

1995-01-01

The designed and constructed at the Institute of Biocybernetics and Biomedical Engineering facility for the relaxation time (T 1 ) measurements of liquids flow has been presented. The influence of temperature, viscosity and pH has been determined for several liquids, especially physiological fluids

Musculoskeletal MRI at 3.0 T and 7.0 T: a comparison of relaxation times and image contrast.

Science.gov (United States)

Jordan, Caroline D; Saranathan, Manojkumar; Bangerter, Neal K; Hargreaves, Brian A; Gold, Garry E

2013-05-01

The purpose of this study was to measure and compare the relaxation times of musculoskeletal tissues at 3.0 T and 7.0 T, and to use these measurements to select appropriate parameters for musculoskeletal protocols at 7.0 T. We measured the T₁ and T₂ relaxation times of cartilage, muscle, synovial fluid, bone marrow and subcutaneous fat at both 3.0 T and 7.0 T in the knees of five healthy volunteers. The T₁ relaxation times were measured using a spin-echo inversion recovery sequence with six inversion times. The T₂ relaxation times were measured using a spin-echo sequence with seven echo times. The accuracy of both the T₁ and T₂ measurement techniques was verified in phantoms at both magnetic field strengths. We used the measured relaxation times to help design 7.0 T musculoskeletal protocols that preserve the favorable contrast characteristics of our 3.0 T protocols, while achieving significantly higher resolution at higher SNR efficiency. The T₁ relaxation times in all tissues at 7.0 T were consistently higher than those measured at 3.0 T, while the T₂ relaxation times at 7.0 T were consistently lower than those measured at 3.0 T. The measured relaxation times were used to help develop high resolution 7.0 T protocols that had similar fluid-to-cartilage contrast to that of the standard clinical 3.0 T protocols for the following sequences: proton-density-weighted fast spin-echo (FSE), T₂-weighted FSE, and 3D-FSE-Cube. The T₁ and T₂ changes were within the expected ranges. Parameters for musculoskeletal protocols at 7.0 T can be optimized based on these values, yielding improved resolution in musculoskeletal imaging with similar contrast to that of standard 3.0 T clinical protocols. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Quantitative Study of Longitudinal Relaxation (T 1) Contrast Mechanisms in Brain MRI

Science.gov (United States)

Jiang, Xu

Longitudinal relaxation (T1) contrast in MRI is important for studying brain morphology and is widely used in clinical applications. Although MRI only detects signals from water hydrogen ( 1H) protons (WPs), T1 contrast is known to be influenced by other species of 1H protons, including those in macromolecules (MPs), such as lipids and proteins, through magnetization transfer (MT) between WPs and MPs. This complicates the use and quantification of T1 contrast for studying the underlying tissue composition and the physiology of the brain. MT contributes to T1 contrast to an extent that is generally dependent on MT kinetics, as well as the concentration and NMR spectral properties of MPs. However, the MP spectral properties and MT kinetics are both difficult to measure directly, as the signal from MPs is generally invisible to MRI. Therefore, to investigate MT kinetics and further quantify T1 contrast, we first developed a reliable way to indirectly measure the MP fraction and their exchange rate with WPs, with minimal dependence on the spectral properties of MPs. For this purpose, we used brief, highpower radiofrequency (RF) NMR excitation pulses to almost completely saturate the magnetization of MPs. Based on this, both MT kinetics and the contribution of MPs to T1 contrast through MT were studied. The thus obtained knowledge allowed us to subsequently infer the spectral properties of MPs by applying low-power, frequencyselective off-resonance RF pulses and measuring the offset-frequency dependent effect of MPs on the WP MRI signal. A two-pool exchange model was used in both cases to account for direct effects of the RF pulse on WP magnetization. Consistent with earlier works using MRI at low-field and post-mortem analysis of brain tissue, our novel measurement approach found that MPs constitute an up to 27% fraction of the total 1H protons in human brain white matter, and their spectrum follows a super-Lorentzian line with a T2 of 9.6+/-0.6 mus and a resonance

Isotropic morphometry and multicomponent T1 ρ mapping of human knee articular cartilage in vivo at 3T.

Science.gov (United States)

Baboli, Rahman; Sharafi, Azadeh; Chang, Gregory; Regatte, Ravinder R

2018-05-02

The progressive loss of hyaline articular cartilage due to osteoarthritis (OA) changes the functional and biochemical properties of cartilage. Measuring the T 1 ρ along with the morphological assessment can potentially be used as noninvasive biomarkers in detecting early-stage OA. To correlate the biochemical and morphological data, submillimeter isotropic resolution for both studies is required. To implement a high spatial resolution 3D-isotropic-MRI sequence for simultaneous assessment of morphological and biexponential T 1 ρ relaxometry of human knee cartilage in vivo. Prospective. Ten healthy volunteers with no known inflammation, trauma, or pain in the knee. Standard FLASH sequence and customized Turbo-FLASH sequence to acquire 3D-isotropic-T 1 ρ-weighted images on a 3T MRI scanner. The mean volume and thickness along with mono- and biexponential T 1 ρ relaxations were assessed in the articular cartilage of 10 healthy volunteers. Nonparametric rank-sum tests. Bland-Altman analysis and coefficient of variation. The mean monoexponential T 1 ρ relaxation was 40.7 ± 4.8 msec, while the long and short components were 58.2 ± 3.9 msec and 6.5 ± 0.6 msec, respectively. The mean fractions of long and short T 1 ρ relaxation components were 63.7 ± 5.9% and 36.3 ± 5.9%, respectively. Statistically significant (P ≤ 0.03) differences were observed in the monoexponential and long components between some of the regions of interest (ROIs). No gender differences between biexponential components were observed (P > 0.05). Mean cartilage volume and thickness were 25.9 ± 6.4 cm 3 and 2.2 ± 0.7 mm, respectively. Cartilage volume (P = 0.01) and thickness (P = 0.03) were significantly higher in male than female participants across all ROIs. Bland-Altman analysis showed agreement between two morphological methods with limits of agreement between -1000 mm 3 and +1100 mm 3 for volume, and -0.78 mm and +0.46 mm for

T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study

Energy Technology Data Exchange (ETDEWEB)

Mamisch, Tallal Charles [University Bern, Department of Orthopedic Surgery, Inselspital, Bern (Switzerland); University Bern, Magnetic Resonance Spectroscopy and Methodology, Department of Clinical Research, Bern (Switzerland); Hughes, Timothy [Siemens Medical Solutions, Erlangen (Germany); Mosher, Timothy J. [Penn State University College of Medicine, Musculoskeletal Imaging and MRI, Department of Radiology, Hershey, PA (United States); Mueller, Christoph [University of Erlangen, Department of Trauma Surgery, Erlangen (Germany); Trattnig, Siegfried [Medical University of Vienna, MR Center - High Field MR, Department of Radiology, Vienna (Austria); Boesch, Chris [University Bern, Magnetic Resonance Spectroscopy and Methodology, Department of Clinical Research, Bern (Switzerland); Welsch, Goetz Hannes [University of Erlangen, Department of Trauma Surgery, Erlangen (Germany); Medical University of Vienna, MR Center - High Field MR, Department of Radiology, Vienna (Austria)

2012-03-15

T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage. The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue. There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX. Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface. (orig.)

Menstrual variation of breast volume and T{sub 2} relaxation times in cyclical mastalgia

Energy Technology Data Exchange (ETDEWEB)

Hussain, Zainab [Department of Medical Imaging, University of Liverpool, Johnstone Building, Brownlow Hill, P.O. Box 147, Liverpool, Merseyside L69 3GB (United Kingdom); Magnetic Resonance and Image Analysis Research Centre, University of Liverpool, Johnstone Building, Brownlow Hill, P.O. Box 147, Liverpool, Merseyside L69 3GB (United Kingdom)], E-mail: zay@liverpool.ac.uk; Brooks, Jonathan [Magnetic Resonance and Image Analysis Research Centre, University of Liverpool, Johnstone Building, Brownlow Hill, P.O. Box 147, Liverpool, Merseyside L69 3GB (United Kingdom); Department of Human Anatomy and Genetics, University of Oxford, Oxford (United Kingdom); Percy, Dave [Centre for Operational Research and Applied Statistics, University of Salford, Salford, Greater Manchester M5 4WT (United Kingdom)

2008-02-15

Purpose: Hormonal activity causes breast volume to change during the menstrual cycle. One possible cause of this volume change is thought to be due to water retention or oedema within the tissues. We used magnetic resonance imaging (MRI) to study the variation in breast volume and {sup 1}H Magnetic Resonance Spectroscopy (MRS) to measure T{sub 2} relaxation times which are known to increase with increasing tissue water content. We hypothesised that an increase in breast volume will elevate T{sub 2} relaxation due to the presence of an increased water content within the breast. T{sub 2} Relaxation time and volume were studied in fifteen control subjects and in a cohort of eight patients with cyclical mastalgia in order to determine whether changes in breast volume and T{sub 2} relaxation times differed in controls and patients during menses, ovulation and premenses. Method: Breast volume was determined by the Cavalieri method in combination with point counting techniques on MR images and T{sub 2} relaxation times of the water and fat in a voxel of breast tissue were obtained using {sup 1}H Magnetic Resonance Spectroscopy (MRS). Results: Statistical analysis (ANOVA) demonstrated highly significant differences in breast volume between the three stages of the cycle (p < 0.0005) with breast volume being greatest premenstrually. Patients did not exhibit an increase in volume premenstrually, significantly above controls. T{sub 2} of fat or water did not depend on stage of cycle. T-tests demonstrated no significant differences in T{sub 2} of water or fat between patient and control groups. The average T{sub 2} relaxation time of water was lowest in the patient and control groups during ovulation and highest in the patient group during premenses. Conclusion: We have performed the first combined volumetric and spectroscopic study of women with cyclical mastalgia and demonstrated that the global changes in volumes and T{sub 2} were not significantly different from normal

Statistical foundation of the Kubo-Tomita theory of magnetic relaxation

International Nuclear Information System (INIS)

Yul'met'ev, R.M.

1974-01-01

With the aim to give the statistical foundation of the Kubo-Tomita theory the theoretical-functional method of the projection operators is applied to the phenomenon of magnetic relaxation. The exact nonmarkov nonlinear kinetic equations are found for the time correlation functions (TCF) of the longitudinal and transversal components of the spin magnetization of a system including the spin-lattice interaction lambda H' in a general form. The markov kinetic equations of the well-known Bloch-type are derived in the weak coupling Van Hove limits t → infinity, lambda → 0, lambda 2 t=const., and the rate of the spin-lattice (T 1 -1 ) and spin-spin (T 2 -1 ) relaxation is obtained from the relaxation coefficients. It is found that the formulas of the Kubo-Tomita for T 1 -1 and T 2 -1 are correct only in the case of rapid thermal motions when ω 0 tau 0 0 is the resonance frequency and tau 0 is the typical correlation time of the molecular thermal motions). In the other limiting case (ω 0 tau 0 >>1) of slow motion, the effective spectral densities which enter T 1 and T 2 are determined by a set of relaxation times Tsub(β)sup(n) of the spin irreducible operators Vsub(β)sup(n) from the spin-lattice interaction lambda H'. It is found that the time dependence of the transversal component of magnetization had been left out in the collision integral of Kubo-Tomita's theory. Precisely considering this circumstance the frequency dependence of T 2 -1 on the resonance frequency must be changed. (author)

Transverse water relaxation in whole blood and erythrocytes at 3T, 7T, 9.4T, 11.7T and 16.4T; determination of intracellular hemoglobin and extracellular albumin relaxivities.

Science.gov (United States)

Grgac, Ksenija; Li, Wenbo; Huang, Alan; Qin, Qin; van Zijl, Peter C M

2017-05-01

Blood is a physiological substance with multiple water compartments, which contain water-binding proteins such as hemoglobin in erythrocytes and albumin in plasma. Knowing the water transverse (R 2 ) relaxation rates from these different blood compartments is a prerequisite for quantifying the blood oxygenation level-dependent (BOLD) effect. Here, we report the Carr-Purcell-Meiboom-Gill (CPMG) based transverse (R 2CPMG ) relaxation rates of water in bovine blood samples circulated in a perfusion system at physiological temperature in order to mimic blood perfusion in humans. R 2CPMG values of blood plasma, lysed packed erythrocytes, lysed plasma/erythrocyte mixtures, and whole blood at 3 T, 7 T, 9.4 T, 11.7 T and 16.4 T were measured as a function of hematocrit or hemoglobin concentration, oxygenation, and CPMG inter-echo spacing (τ cp ). R 2CPMG in lysed cells showed a small τ cp dependence, attributed to the water exchange rate between free and hemoglobin-bound water to be much faster than τ cp . This was contrary to the tangential dependence in whole blood, where a much slower exchange between cells and blood plasma applies. Whole blood data were fitted as a function of τ cp using a general tangential correlation time model applicable for exchange as well as diffusion contributions to R 2CPMG , and the intercept R 20blood at infinitely short τ cp was determined. The R 20blood values at different hematocrit and the R 2CPMG values of lysed erythrocyte/plasma mixtures at different hemoglobin concentration were used to determine the relaxivity of hemoglobin inside the erythrocyte (r 2Hb ) and albumin (r 2Alb ) in plasma. The r 2Hb values obtained from lysed erythrocytes and whole blood were comparable at full oxygenation. However, while r 2Hb determined from lysed cells showed a linear dependence on oxygenation, this dependence became quadratic in whole blood. This possibly suggests an additional relaxation effect inside intact cells, perhaps due to hemoglobin

The dielectric α relaxation at a temperature close to T sub(g)

International Nuclear Information System (INIS)

Gomez Ribelles, J.L.; Diaz Calleja, R.

1985-01-01

It is shown in this work how the dependence of the mean relaxation times of the dielectric α relaxation on temperature deviates from the Williams, Landel and Ferry model at a temperature close to T sub(g). In some cases, an Arrhenius-like relationship for this relaxation can be observed for temperatures below T sub(g)

Preparation of EVA/silica nano composites characterized with solid state nuclear magnetic resonance; Obtencao de nanocomposito de EVA/SILICA e caracterizacao por ressonancia magnetica nuclear no estado solido

Energy Technology Data Exchange (ETDEWEB)

Passos, Adriano A; Tavares, Maria I.B.; Neto, Roberto C.P.; Moreira, Leonardo A; Ferreira, Antonio G., E-mail: mibt@ima.ufrj.br [Centro de Tecnologia, Instituto de Macromoleculas Professora Eloisa Mano, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil)

2011-07-01

Nano composites of poly(ethylene-co-vinyl acetate)/silica (SiO{sub 2}) with dimensions of ca. 40 nm were prepared via solution intercalation employing chloroform as a solvent. They were mainly characterized with nuclear magnetic resonance spectroscopy (NMR) employing carbon-13 (polymeric matrix), silicon-29 (nanoparticles) and through the determination of the proton spin-lattice relaxation time in the rotating frame (T{sub 1{rho}H}) (polymer matrix). From the NMR results it was inferred that up to 5% of silica in mass a well dispersed nano composite was obtained, owing to a strong interaction between silica and the EVA matrix. (author)

The impact of fibre orientation on T1-relaxation and apparent tissue water content in white matter.

Science.gov (United States)

Schyboll, Felix; Jaekel, Uwe; Weber, Bernd; Neeb, Heiko

2018-02-20

Recent MRI studies have shown that the orientation of nerve fibres relative to the main magnetic field affects the R 2 *(= 1/T 2 *) relaxation rate in white matter (WM) structures. The underlying physical causes have been discussed in several studies but are still not completely understood. However, understanding these effects in detail is of great importance since this might serve as a basis for the development of new diagnostic tools and/or improve quantitative susceptibility mapping techniques. Therefore, in addition to the known angular dependence of R 2 *, the current study investigates the relationship between fibre orientation and the longitudinal relaxation rate, R 1 (= 1/T 1 ), as well as the apparent water content. For a group of 16 healthy subjects, a series of gradient echo, echo-planar and diffusion weighted images were acquired at 3T from which the decay rates, the apparent water content and the diffusion direction were reconstructed. The diffusion weighted data were used to determine the angle between the principle fibre direction and the main magnetic field to examine the angular dependence of R 1 and apparent water content. The obtained results demonstrate that both parameters depend on the fibre orientation and exhibit a positive correlation with the angle between fibre direction and main magnetic field. These observations could be helpful to improve and/or constrain existing biophysical models of brain microstructure by imposing additional constraints resulting from the observed angular dependence R 1 and apparent water content in white matter.

Hyaline articular cartilage: relaxation times, pulse-sequence parameters and MR appearance at 1.5 T

Energy Technology Data Exchange (ETDEWEB)

Chalkias, S.M. [Dept. of Radiology, A.H.E.P.A. General Hospital of the Aristotelian Univ., Thessaloniki (Greece); Pozzi-Mucelli, R.S. [Dept. of Radiology, Univ. of Trieste (Italy); Pozzi-Mucelli, M. [Orthopaedic Clinic, Univ. of Trieste (Italy); Frezza, F. [Dept. of Radiology, Univ. of Trieste (Italy); Longo, R. [Dept. of Radiology, Univ. of Trieste (Italy)

1994-08-01

In order to optimize the parameters for the best visualization of the internal architecture of the hyaline articular cartilage a study both ex vivo and in vivo was performed. Accurate T1 and T2 relaxation times of articular cartilage were obtained with a particular mixed sequence and then used for the creation of isocontrast intensity graphs. These graphs subsequently allowed in all pulse sequences (spin echo, SE and gradient echo, GRE) the best combination of repetition time (TR), echo time (TE) and flip angle (FA) for optimization of signal differences between MR cartilage zones. For SE sequences maximum contrast between cartilage zones can be obtained by using a long TR (> 1,500 ms) with a short TE (< 30 ms), whereas for GRE sequences maximum contrast is obtained with the shortest TE (< 15 ms) combined with a relatively long TR (> 400 ms) and an FA greater than 40 . A trilaminar appearance was demonstrated with a superficial and deep hypointense zone in all sequences and an intermediate zone that was moderately hyperintense on SE T1-weighted images, slightly more hyperintense on proton density Rho and SE T2-weighted images and even more hyperintense on GRE images. (orig.)

T2 relaxation time analysis in patients with multiple sclerosis: correlation with magnetization transfer ratio

International Nuclear Information System (INIS)

Papanikolaou, Nickolas; Papadaki, Eufrosini; Karampekios, Spyros; Maris, Thomas; Prassopoulos, Panos; Gourtsoyiannis, Nicholas; Spilioti, Martha

2004-01-01

The aim of the current study was to perform T2 relaxation time measurements in multiple sclerosis (MS) patients and correlate them with magnetization transfer ratio (MTR) measurements, in order to investigate in more detail the various histopathological changes that occur in lesions and normal-appearing white matter (NAWM). A total number of 291 measurements of MTR and T2 relaxation times were performed in 13 MS patients and 10 age-matched healthy volunteers. Measurements concerned MS plaques (105), NAWM (80), and ''dirty'' white matter (DWM; 30), evenly divided between the MS patients, and normal white matter (NWM; 76) in the healthy volunteers. Biexponential T2 relaxation-time analysis was performed, and also possible linearity between MTR and mean T2 relaxation times was evaluated using linear regression analysis in all subgroups. Biexponential relaxation was more pronounced in ''black-hole'' lesions (16.6%) and homogeneous enhancing plaques (10%), whereas DWM, NAWM, and mildly hypointense lesions presented biexponential behavior with a lower frequency(6.6, 5, and 3.1%, respectively). Non-enhancing isointense lesions and normal white matter did not reveal any biexponentional behavior. Linear regression analysis between monoexponential T2 relaxation time and MTR measurements demonstrated excellent correlation for DWM(r=-0.78, p<0.0001), very good correlation for black-hole lesions(r=-0.71, p=0.002), good correlation for isointense lesions(r=-0.60, p=0.005), moderate correlation for mildly hypointense lesions(r=-0.34, p=0.007), and non-significant correlation for homogeneous enhancing plaques, NAWM, and NWM. Biexponential T2 relaxation-time behavior is seen in only very few lesions (mainly on plaques with high degree of demyelination and axonal loss). A strong correlation between MTR and monoexponential T2 values was found in regions where either inflammation or demyelination predominates; however, when both pathological conditions coexist, this linear

Efficient and robust relaxation procedures for multi-component mixtures including phase transition

International Nuclear Information System (INIS)

Han, Ee; Hantke, Maren; Müller, Siegfried

2017-01-01

We consider a thermodynamic consistent multi-component model in multi-dimensions that is a generalization of the classical two-phase flow model of Baer and Nunziato. The exchange of mass, momentum and energy between the phases is described by additional source terms. Typically these terms are handled by relaxation procedures. Available relaxation procedures suffer from efficiency and robustness resulting in very costly computations that in general only allow for one-dimensional computations. Therefore we focus on the development of new efficient and robust numerical methods for relaxation processes. We derive exact procedures to determine mechanical and thermal equilibrium states. Further we introduce a novel iterative method to treat the mass transfer for a three component mixture. All new procedures can be extended to an arbitrary number of inert ideal gases. We prove existence, uniqueness and physical admissibility of the resulting states and convergence of our new procedures. Efficiency and robustness of the procedures are verified by means of numerical computations in one and two space dimensions. - Highlights: • We develop novel relaxation procedures for a generalized, thermodynamically consistent Baer–Nunziato type model. • Exact procedures for mechanical and thermal relaxation procedures avoid artificial parameters. • Existence, uniqueness and physical admissibility of the equilibrium states are proven for special mixtures. • A novel iterative method for mass transfer is introduced for a three component mixture providing a unique and admissible equilibrium state.

Evaluation of biexponential relaxation behaviour in the human brain by magnetic resonance imaging

DEFF Research Database (Denmark)

Kjaer, L; Thomsen, C; Henriksen, O

1989-01-01

Quantitative estimation of individual biologic components in relaxation curves obtained in vivo may increase the specificity of tissue characterization by magnetic resonance imaging. In this study, the potential of biexponential curve analysis was evaluated in T1 and T2 measurements on the human...... brain at 1.5 tesla. Optimal experimental conditions were carefully observed, including the use of long TR values and a very small voxel size. T1 determination was based on a 12-points partial saturation inversion recovery pulse sequence. T2 determination involved a multiple spin echo sequence with 32...... echoes. No genuine biexponentiality was demonstrated in the T1 and T2 relaxation processes of white matter, cortical grey matter, or cerebrospinal fluid. Thus, a monoexponential model seems adequate for description of the relaxation behaviour in these cases. Furthermore, the results suggest...

Longitudinal evaluation of T1ρ and T2 spatial distribution in osteoarthritic and healthy medial knee cartilage.

Science.gov (United States)

Schooler, J; Kumar, D; Nardo, L; McCulloch, C; Li, X; Link, T M; Majumdar, S

2014-01-01

To investigate longitudinal changes in laminar and spatial distribution of knee articular cartilage magnetic resonance imaging (MRI) T1ρ and T2 relaxation times, in individuals with and without medial compartment cartilage defects. All subjects (at baseline n = 88, >18 years old) underwent 3-Tesla knee MRI at baseline and annually thereafter for 3 years. The MR studies were evaluated for presence of cartilage defects (modified Whole-Organ Magnetic Resonance Imaging Scoring - mWORMS), and quantitative T1ρ and T2 relaxation time maps. Subjects were segregated into those with (mWORMS ≥2) and without (mWORMS ≤1) cartilage lesions at the medial tibia (MT) or medial femur (MF) at each time point. Laminar (bone and articular layer) and spatial (gray level co-occurrence matrix - GLCM) distribution of the T1ρ and T2 relaxation time maps were calculated. Linear regression models (cross-sectional) and Generalized Estimating Equations (GEEs) (longitudinal) were used. Global T1ρ, global T2 and articular layer T2 relaxation times at the MF, and global and articular layer T2 relaxation times at the MT, were higher in subjects with cartilage lesions compared to those without lesions. At the MT global T1ρ relaxation times were higher at each time point in subjects with lesions. MT T1ρ and T2 became progressively more heterogeneous than control compartments over the course of the study. Spatial distribution of T1ρ and T2 relaxation time maps in medial knee OA using GLCM technique may be a sensitive indicator of cartilage deterioration, in addition to whole-compartment relaxation time data. Copyright © 2013 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Simultaneous acquisition for T2 -T2 Exchange and T1 -T2 correlation NMR experiments

Science.gov (United States)

Montrazi, Elton T.; Lucas-Oliveira, Everton; Araujo-Ferreira, Arthur G.; Barsi-Andreeta, Mariane; Bonagamba, Tito J.

2018-04-01

The NMR measurements of longitudinal and transverse relaxation times and its multidimensional correlations provide useful information about molecular dynamics. However, these experiments are very time-consuming, and many researchers proposed faster experiments to reduce this issue. This paper presents a new way to simultaneously perform T2 -T2 Exchange and T1 -T2 correlation experiments by taking the advantage of the storage time and the two steps phase cycling used for running the relaxation exchange experiment. The data corresponding to each step is either summed or subtracted to produce the T2 -T2 and T1 -T2 data, enhancing the information obtained while maintaining the experiment duration. Comparing the results from this technique with traditional NMR experiments it was possible to validate the method.

The immediate effect of long-distance running on T2 and T2* relaxation times of articular cartilage of the knee in young healthy adults at 3.0 T MR imaging.

Science.gov (United States)

Behzadi, Cyrus; Welsch, Goetz H; Laqmani, Azien; Henes, Frank O; Kaul, Michael G; Schoen, Gerhard; Adam, Gerhard; Regier, Marc

2016-08-01

To quantitatively assess the immediate effect of long-distance running on T2 and T2* relaxation times of the articular cartilage of the knee at 3.0 T in young healthy adults. 30 healthy male adults (18-31 years) who perform sports at an amateur level underwent an initial MRI at 3.0 T with T2 weighted [16 echo times (TEs): 9.7-154.6 ms] and T2* weighted (24 TEs: 4.6-53.6 ms) relaxation measurements. Thereafter, all participants performed a 45-min run. After the run, all individuals were immediately re-examined. Data sets were post-processed using dedicated software (ImageJ; National Institute of Health, Bethesda, MD). 22 regions of interest were manually drawn in segmented areas of the femoral, tibial and patellar cartilage. For statistical evaluation, Pearson product-moment correlation coefficients and confidence intervals were computed. Mean initial values were 35.7 ms for T2 and 25.1 ms for T2*. After the run, a significant decrease in the mean T2 and T2* relaxation times was observed for all segments in all participants. A mean decrease of relaxation time was observed for T2 with 4.6 ms (±3.6 ms) and for T2* with 3.6 ms (±5.1 ms) after running. A significant decrease could be observed in all cartilage segments for both biomarkers. Both quantitative techniques, T2 and T2*, seem to be valuable parameters in the evaluation of immediate changes in the cartilage ultrastructure after running. This is the first direct comparison of immediate changes in T2 and T2* relaxation times after running in healthy adults.

Microwave Amplitude Modulation Technique to Measure Spin-Lattice (T 1) and Spin-Spin (T 2) Relaxation Times

Science.gov (United States)

Misra, Sushil K.

The measurement of very short spin-lattice, or longitudinal, relaxation (SLR) times (i.e., 10-10 Misra, 1998), and polymer resins doped with rare-earth ions (Pescia et al., 1999a; Pescia et al. 1999b). The ability to measure such fast SLR data on amorphous Si and copper-chromium-tin spinel led to an understanding of the role of exchange interaction in affecting spin-lattice relaxation, while the data on polymer resins doped with rare-earth ions provided evidence of spin-fracton relaxation (Pescia et al., 1999a, b). But such fast SLR times are not measurable by the most commonly used techniques of saturation- and inversion-recovery (Poole, 1982; Alger, 1968), which only measure spin-lattice relaxation times longer than 10-6 s. A summary of relevant experimental data is presented in Table 1.

Enhancement effects and relaxivities of gadolinium-DTPA at 1.5 versus 3 tesla. A phantom study

International Nuclear Information System (INIS)

Sasaki, Makoto; Shibata, Eri; Kanbara, Yoshiyuki; Ehara, Shigeru

2005-01-01

The purpose of this study was to investigate the difference in enhancement effects and relaxivities of the gadolinium chelate at 1.5 and 3 Tesla (T) and to elucidate the contribution of the high magnetic field to contrast enhancement in spin-echo (SE) and gradient-echo (GRE) images. Phantoms containing water with or without gadopentetate dimeglumine (Gd-DTPA) at different concentrations were scanned using 1.5T and 3T MRI scanners of the same manufacturer and under the same temperature conditions and scanning parameters. Relaxivities of gadolinium, R 1 and R 2 , were estimated from serial T 1 and T 2 values of the phantoms using linear regression. Contrast enhancement ratios in SE and GRE T 1 -weighted images were compared at 1.5 and 3T. The R 1 and R 2 of Gd-DTPA at 1.5 and 3T were 4.79 and 5.14, and 4.50 and 5.09, respectively. Although the relaxivities at 3T were slightly lower than those at 1.5T, the contrast enhancement ratio improved in both SE and GRE images as a result of T 1 prolongation of the water at 3T. The decrease in relaxivities of the Gd-DTPA at 3T appears to be so small that T 1 prolongation of the water improves contrast enhancement, suggesting a potential clinical advantage in administration of Gd-DTPA at high field strength. (author)

A suite of Mathematica notebooks for the analysis of protein main chain 15N NMR relaxation data

International Nuclear Information System (INIS)

Spyracopoulos, Leo

2006-01-01

A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain 15 N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of 15 N-T 1 and -T 2 relaxation decays to a two parameter exponential decay, calculation of the principal components of the inertia tensor from protein structural coordinates, nonlinear optimization of the principal components and orientation of the axially symmetric rotational diffusion tensor, model-free analysis of 15 N-T 1 , -T 2 , and { 1 H}- 15 N NOE data, and reduced spectral density analysis of the relaxation data. The principle features of the notebooks include use of a minimal number of input files, integrated notebook data management, ease of use, cross-platform compatibility, automatic visualization of results and generation of high-quality graphics, and output of analyses in text format

The effect of control of diabetes mellitus on plasma T4, T3, rT3 levels and half muscle relaxation period

International Nuclear Information System (INIS)

Ismail, A.A.; Hafiez, A.A.; Sayed, S.N.; Abbas, E.Z.; Halawa, F.A.; Youssef, M.M.

1984-01-01

25 diabetics of the maturity onset type who showed no clinical evidence of either peripheral neruropathy or diabetic amyotrophy were selected for this study. All patients were subjected to the following investigations: estimation of half muscle relaxation period of the quadriceps muscle knee-jerk, measurement of plasma levels of thyroxine (T 4 ), triiodothyronine (T 3 ) and reverse triiodothronine (rT 3 ), determination of fasting and two hours postprandial blood sugar levels. The quadriceps muscle relaxation period in uncontrolled diabetics was significantly longer than in normals. Control of diabetes by glibenclamide or gliclazide did not cause a significant change in muscle relaxation period. There was also no significant difference between the effects of the two drugs. (author)

TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

International Nuclear Information System (INIS)

Lemen, L.

2015-01-01

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common

TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

Energy Technology Data Exchange (ETDEWEB)

Lemen, L. [Univ Cincinnati (United States)

2015-06-15

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common

T2 relaxation time in MR imaging of normal and abnormal lung parenchyma

International Nuclear Information System (INIS)

Mayo, J.R.; McKay, A.; Mueller, N.L.

1990-01-01

To measure the T2 relaxation times of normal and abnormal lung parenchyma and to evaluate the influence of field strength and lung inflation on T2. Five healthy volunteers and five patients with diffuse lung disease were imaged at 0.15 and 1.5 T. Excised normal pig lung was imaged at 0.15 and 1.5 T and analyzed in a spectrometer at 2.0 T. Single-echo (Hahn) pulse sequences (TR, 2,000 msec; TE, 20, 40, 60, 80, and 100 msec) were compared with multiecho trains (Carr-Purcell-Meiboom-Gill [CPMG] at 0.15 T (TR, 2,000 msec; TE, 20-40-60... 240 msec) and 2.0 T (TR, 2,000 msec; TE, 1, 2, 3,..., 10msec). T2 relaxation times calculated from single-echo sequences showed considerable variation between 0.15 and 2.0 T. T2 also changed with lung inflation. However, the T2 measurements on CPMG sequences did not change significantly (P > .05) with field strength and were only minimally affected by lung inflation. The mean ± SD T2 values for normal lung were 99 ± 8 and for abnormal lung were 84 ± 17. Lung parenchyma T2 measurements obtained with the use of conventional single-echo pulse sequences are variable and inaccurate because of inflation and field strength dependent magnetic susceptibility effects that lead to rapid nonrecoverable dephasing. The results indicate that multiecho sequences with appropriately short echo spacings yield more reproducible determinations of T2, which are independent of field strength and less dependent on lung inflation

Temperature dependence of 1H NMR relaxation time, T2, for intact and neoplastic plant tissues

Science.gov (United States)

Lewa, Czesław J.; Lewa, Maria

Temperature dependences of the spin-spin proton relaxation time, T2, have been shown for normal and tumorous tissues collected from kalus culture Nicotiana tabacum and from the plant Kalanchoe daigremontiana. For neoplastic plant tissues, time T2 was increased compared to that for intact plants, a finding similar to that for animal and human tissues. The temperature dependences obtained were compared to analogous relations observed with animal tissues.

A general model to calculate the spin-lattice (T1) relaxation time of blood, accounting for haematocrit, oxygen saturation and magnetic field strength.

Science.gov (United States)

Hales, Patrick W; Kirkham, Fenella J; Clark, Christopher A

2016-02-01

Many MRI techniques require prior knowledge of the T1-relaxation time of blood (T1bl). An assumed/fixed value is often used; however, T1bl is sensitive to magnetic field (B0), haematocrit (Hct), and oxygen saturation (Y). We aimed to combine data from previous in vitro measurements into a mathematical model, to estimate T1bl as a function of B0, Hct, and Y. The model was shown to predict T1bl from in vivo studies with a good accuracy (± 87 ms). This model allows for improved estimation of T1bl between 1.5-7.0 T while accounting for variations in Hct and Y, leading to improved accuracy of MRI-derived perfusion measurements. © The Author(s) 2015.

Rapid parametric mapping of the longitudinal relaxation time T1 using two-dimensional variable flip angle magnetic resonance imaging at 1.5 Tesla, 3 Tesla, and 7 Tesla.

Science.gov (United States)

Dieringer, Matthias A; Deimling, Michael; Santoro, Davide; Wuerfel, Jens; Madai, Vince I; Sobesky, Jan; von Knobelsdorff-Brenkenhoff, Florian; Schulz-Menger, Jeanette; Niendorf, Thoralf

2014-01-01

Visual but subjective reading of longitudinal relaxation time (T1) weighted magnetic resonance images is commonly used for the detection of brain pathologies. For this non-quantitative measure, diagnostic quality depends on hardware configuration, imaging parameters, radio frequency transmission field (B1+) uniformity, as well as observer experience. Parametric quantification of the tissue T1 relaxation parameter offsets the propensity for these effects, but is typically time consuming. For this reason, this study examines the feasibility of rapid 2D T1 quantification using a variable flip angles (VFA) approach at magnetic field strengths of 1.5 Tesla, 3 Tesla, and 7 Tesla. These efforts include validation in phantom experiments and application for brain T1 mapping. T1 quantification included simulations of the Bloch equations to correct for slice profile imperfections, and a correction for B1+. Fast gradient echo acquisitions were conducted using three adjusted flip angles for the proposed T1 quantification approach that was benchmarked against slice profile uncorrected 2D VFA and an inversion-recovery spin-echo based reference method. Brain T1 mapping was performed in six healthy subjects, one multiple sclerosis patient, and one stroke patient. Phantom experiments showed a mean T1 estimation error of (-63±1.5)% for slice profile uncorrected 2D VFA and (0.2±1.4)% for the proposed approach compared to the reference method. Scan time for single slice T1 mapping including B1+ mapping could be reduced to 5 seconds using an in-plane resolution of (2×2) mm2, which equals a scan time reduction of more than 99% compared to the reference method. Our results demonstrate that rapid 2D T1 quantification using a variable flip angle approach is feasible at 1.5T/3T/7T. It represents a valuable alternative for rapid T1 mapping due to the gain in speed versus conventional approaches. This progress may serve to enhance the capabilities of parametric MR based lesion detection and

Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers

International Nuclear Information System (INIS)

Galley, J.; Maestretti, G.; Koch, G.; Hoogewoud, H-M.

2017-01-01

Purpose: To measure the real T1 relaxation time of the lumbar intervertebral discs in a young and healthy population, using different inversion recovery times, and assess diurnal variation. Material and methods: Intervertebral discs from D12 to S1 of 50 healthy volunteers from 18 to 25 years old were evaluated twice the same day, in the morning and in the late afternoon. Dedicated MRI sequences with different inversion recovery times (from 100 to 2500 ms) were used to calculate the real T1 relaxation time. Three regions of interest (ROIs) were defined in each disc, the middle representing the nucleus pulposus (NP) and the outer parts the annulus fibrosus (AF) anterior and posterior. Diurnal variation and differences between each disc level were analyzed. Results: T1 mean values in the NP were 1142 ± 12 ms in the morning and 1085 ± 13 ms in the afternoon, showing a highly significant decrease of 57 ms (p < 0.001). A highly significant difference between the levels of the spine was found. The mean T1 of the anterior part of the AF was 577 ± 9 ms in the morning and 554 ± 8 ms in the afternoon. For the posterior part, the mean values were 633 ± 8 ms in the morning and 581 ± 7 ms in the evening. It shows a highly significant decrease of 23 ms for the anterior part and 51 ms for the posterior part (all p < 0.001). Conclusion: T1 mapping is a promising method of intervertebral disc evaluation. Significant diurnal variation and difference between levels of the lumbar spine were demonstrated. A potential use for longitudinal study in post-operative follow up or sport medicine needs to be evaluated.

Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers

Energy Technology Data Exchange (ETDEWEB)

Galley, J., E-mail: galleyjulien@gmail.com [Department of Radiology, HFR Fribourg, Hôpital Cantonal (Switzerland); Maestretti, G. [Department of Orthopedic Surgery, HFR Fribourg, Hôpital Cantonal (Switzerland); Koch, G.; Hoogewoud, H-M. [Department of Radiology, HFR Fribourg, Hôpital Cantonal (Switzerland)

2017-02-15

Purpose: To measure the real T1 relaxation time of the lumbar intervertebral discs in a young and healthy population, using different inversion recovery times, and assess diurnal variation. Material and methods: Intervertebral discs from D12 to S1 of 50 healthy volunteers from 18 to 25 years old were evaluated twice the same day, in the morning and in the late afternoon. Dedicated MRI sequences with different inversion recovery times (from 100 to 2500 ms) were used to calculate the real T1 relaxation time. Three regions of interest (ROIs) were defined in each disc, the middle representing the nucleus pulposus (NP) and the outer parts the annulus fibrosus (AF) anterior and posterior. Diurnal variation and differences between each disc level were analyzed. Results: T1 mean values in the NP were 1142 ± 12 ms in the morning and 1085 ± 13 ms in the afternoon, showing a highly significant decrease of 57 ms (p < 0.001). A highly significant difference between the levels of the spine was found. The mean T1 of the anterior part of the AF was 577 ± 9 ms in the morning and 554 ± 8 ms in the afternoon. For the posterior part, the mean values were 633 ± 8 ms in the morning and 581 ± 7 ms in the evening. It shows a highly significant decrease of 23 ms for the anterior part and 51 ms for the posterior part (all p < 0.001). Conclusion: T1 mapping is a promising method of intervertebral disc evaluation. Significant diurnal variation and difference between levels of the lumbar spine were demonstrated. A potential use for longitudinal study in post-operative follow up or sport medicine needs to be evaluated.

Magnetization transfer and spin lock MR imaging of patellar cartilage degeneration at 0.1 T

International Nuclear Information System (INIS)

Koskinen, S.K.; Ylae-Outinen, H.; Komu, M.E.S.; Aho, H.J.

1997-01-01

Purpose: To investigate magnetization transfer (MT) parameters and rotating frame relaxation time T1ρ in patellar cartilage at different levels of degeneration. Material and Methods: Thirty cadaveric patellae were examined at 0.1 T using the time-dependent saturation-transfer MT technique and the spin lock (SL) technique. In an SL experiment, nuclear spins are locked with a radiofrequency (RF) field, and the locked nuclear magnetization relaxes along the magnetic component of the locking RF field. The specimens were divided into three groups according to the level of cartilage degeneration. MT parameters and T1ρ were measured. Results: The MT effect was greater in degenerated cartilage than in normal cartilage. T1ρ was longer in advanced cartilage degeneration than in intermediate cartilage degeneration. Conculsion: The results suggest that more studies are needed to fully establish the value of SL imaging in cartilage degeneration. (orig.)

Non-invasive evaluation of blood oxygen saturation and hematocrit from T1 and T2 relaxation times: In-vitro validation in fetal blood.

Science.gov (United States)

Portnoy, Sharon; Seed, Mike; Sled, John G; Macgowan, Christopher K

2017-12-01

We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO 2 ) from measurements of its T 1 and T 2 relaxation times. Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO 2 in terms of R 1 and R 2 . Resulting solutions for Hct and sO 2 are the roots of cubic polynomials. Feasibility of the method was established by comparison of Hct and sO 2 estimates obtained from relaxometry measurements (at 1.5 Tesla) in cord blood specimens to ground-truth values obtained by blood gas analysis. Monte Carlo simulations were also conducted to assess the effect of T 1 , T 2 measurement uncertainty on precision of Hct and sO 2 estimates. Good agreement was observed between estimated and ground-truth blood properties (bias = 0.01; 95% limits of agreement = ±0.13 for Hct and sO 2 ). Considering the combined effects of biological variability and random measurement noise, we estimate a typical uncertainty of ±0.1 for Hct, sO 2 estimates. Results demonstrate accurate quantification of Hct and sO 2 from T 1 and T 2 . This method is applicable to noninvasive fetal vessel oximetry-an application where existing oximetry devices are unusable or require risky blood-sampling procedures. Magn Reson Med 78:2352-2359, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Electronic relaxation processes in polyatomic molecules. Progress report, October 1, 1975--September 30, 1976

International Nuclear Information System (INIS)

Lim, E.C.

1976-09-01

Excitation energy dependence of radiationless decay rate under collision-free conditions was utilized as a probe of intramolecular vibrational relaxation in tetracene and pentacene. The results give evidence of vibrational relaxation which competes with electronic relaxation. The substitution dependence of T 1 (nπ*) → S 0 radiationless transition in monocyclic diazines and the temperature dependence of S 1 non-radiative decay rate in alcoholic solutions of polycyclic monoazines indicate that the vibronic interaction between the lowest energy nπ* and ππ* states leads to a rapid radiationless deactivation of the lower of the two electronic states. Finally, a photon-counting spectrofluorometer of very high sensitivity was constructed, and it was used to record T 2 → T 1 fluorescence in bromoanthracenes and S 2 → S 1 fluorescence in azulene. These spectra represent the first bona-fide, or the most convincing, observation of fluorescence between excited electronic states

Characterizing the microstructural basis of “unidentified bright objects” in neurofibromatosis type 1 : A combined in vivo multicomponent T2 relaxation and multi-shell diffusion MRI analysis

NARCIS (Netherlands)

Billiet, T.; Mädler, B.; D'Arco, F.; Deprez, S.; Plasschaert, E.; Leemans, A.; Zhang, H.; Van Den Bergh, B.R.H.; Vandenbulcke, M.; Legius, E.; Sunaert, S.; Emsell, L.

2014-01-01

Introduction The histopathological basis of “unidentified bright objects” (UBOs) (hyperintense regions seen on T2-weighted magnetic resonance (MR) brain scans in neurofibromatosis-1 (NF1)) remains unclear. New in vivo MRI-based techniques (multi-exponential T2 relaxation (MET2) and diffusion MR

Changes in T1 relaxation processes in the bone marrow following treatment in children with acute lymphoblastic leukemia. A magnetic resonance imaging study

DEFF Research Database (Denmark)

Jensen, K E; Thomsen, C; Henriksen, O

1990-01-01

data from bone marrow biopsies obtained in close association to the MR examinations. Ten age matched children were examined as a control group. A 1.5 Tesla whole body scanner was used for the measurements. The pretreatment T1 relaxation times of the bone marrow were significantly prolonged, compared...

7 Tesla quantitative hip MRI: T1, T2 and T2* mapping of hip cartilage in healthy volunteers

Energy Technology Data Exchange (ETDEWEB)

Lazik, Andrea; Theysohn, Jens M.; Geis, Christina [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); Johst, Soeren; Kraff, Oliver [University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Ladd, Mark E. [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); German Cancer Research Center (DKFZ), Medical Physics in Radiology, Heidelberg (Germany); Quick, Harald H. [University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); University Hospital Essen, High Field and Hybrid MR Imaging, Essen (Germany)

2016-05-15

To evaluate the technical feasibility and applicability of quantitative MR techniques (delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 mapping, T2* mapping) at 7 T MRI for assessing hip cartilage. Hips of 11 healthy volunteers were examined at 7 T MRI with an 8-channel radiofrequency transmit/receive body coil using multi-echo sequences for T2 and T2* mapping and a dual flip angle gradient-echo sequence before (T1{sub 0}) and after intravenous contrast agent administration (T1{sub Gd}; 0.2 mmol/kg Gd-DTPA{sup 2-} followed by 0.5 h of walking and 0.5 h of rest) for dGEMRIC. Relaxation times of cartilage were measured manually in 10 regions of interest. Pearson's correlations between R1{sub delta} = 1/T1{sub Gd} - 1/T1{sub 0} and T1{sub Gd} and between T2 and T2* were calculated. Image quality and the delineation of acetabular and femoral cartilage in the relaxation time maps were evaluated using discrete rating scales. High correlations were found between R1{sub delta} and T1{sub Gd} and between T2 and T2* relaxation times (all p < 0.01). All techniques delivered diagnostic image quality, with best delineation of femoral and acetabular cartilage in the T2* maps (mean 3.2 out of a maximum of 4 points). T1, T2 and T2* mapping of hip cartilage with diagnostic image quality is feasible at 7 T. To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted. (orig.)

Relaxation phenomena in the high temperature S-1 spheromak

International Nuclear Information System (INIS)

Ono, Y.; Ellis, R.A. Jr.; Janos, A.C.; Levinton, F.M.; Mayo, R.M.; Motley, R.W.; Ueda, Y.; Yamada, M.

1988-06-01

Operation of the S-1 device in a high current density (j/n/sub e/ ≥ 2 /times/ 10 -14 A/center dot/m) regime has created high electron temperature spheromaks (50eV ≤ T/sub e/ ≤ 130eV). The mechanisms and causes of the periodic relaxation events often observed in these hotter spheromak plasmas were made clear. Also, a relationship between the MHD relaxation cycle and confinement characteristics was revealed for the first time. Resistive loss at the outer edge of the plasma causes a departure from the initial force-free minimum-energy Taylor state to a MHD profile unstable to low-n ideal MHD modes; a relaxation event then returns the configuration to nearly a Taylor state. 11 refs., 5 figs

In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome. A magnetic resonance imaging study

DEFF Research Database (Denmark)

Jensen, K E; Nielsen, H; Thomsen, C

1989-01-01

Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-...... not differ from patients with polycythemia vera....

Estimation of T2 relaxation time of breast cancer: Correlation with clinical, imaging and pathological features

Energy Technology Data Exchange (ETDEWEB)

Seo, Mirinae; Sohn, Yu Mee [Dept. of Radiology, Kyung Hee University Hospital, College of Medicine, Kyung Hee University, Seoul (Korea, Republic of); Ryu, Jung Kyu; Jahng, Geon Ho; Rhee, Sun Jung; Oh, Jang Hoon; Won, Kyu Yeoun [Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University, Seoul (Korea, Republic of)

2017-01-15

The purpose of this study was to estimate the T2* relaxation time in breast cancer, and to evaluate the association between the T2* value with clinical-imaging-pathological features of breast cancer. Between January 2011 and July 2013, 107 consecutive women with 107 breast cancers underwent multi-echo T2*-weighted imaging on a 3T clinical magnetic resonance imaging system. The Student's t test and one-way analysis of variance were used to compare the T2* values of cancer for different groups, based on the clinical-imaging-pathological features. In addition, multiple linear regression analysis was performed to find independent predictive factors associated with the T2* values. Of the 107 breast cancers, 92 were invasive and 15 were ductal carcinoma in situ (DCIS). The mean T2* value of invasive cancers was significantly longer than that of DCIS (p = 0.029). Signal intensity on T2-weighted imaging (T2WI) and histologic grade of invasive breast cancers showed significant correlation with T2* relaxation time in univariate and multivariate analysis. Breast cancer groups with higher signal intensity on T2WI showed longer T2* relaxation time (p = 0.005). Cancer groups with higher histologic grade showed longer T2* relaxation time (p = 0.017). The T2* value is significantly longer in invasive cancer than in DCIS. In invasive cancers, T2* relaxation time is significantly longer in higher histologic grades and high signal intensity on T2WI. Based on these preliminary data, quantitative T2* mapping has the potential to be useful in the characterization of breast cancer.

Evaluation of iron deposits in the reticuloendothelial system using T2-relaxation rate of MRI. Relation with serum ferritin and Fe concentration

International Nuclear Information System (INIS)

Ootsuka, Kae; Togami, Izumi; Kitagawa, Takahiro

1996-01-01

MR imaging is a useful non-invasive technique to detect iron deposits in many organs, but it is difficult to evaluate quantitatively. This study was performed to determine the possibility whether T2 relaxation rate (1/T2) could quantify iron deposits in the reticuloendothelial system (liver, spleen and bone marrow) of 11 patients and four normal volunteers. A moderate correlation was obtained between T2-relaxation rate and the serum ferritin level. These results suggest that T2-relaxation rate may provide useful information for the repeated quantitative evaluation of patients with iron-overload-syndromes. (author)

Multiscale approach to mechanical behavior of polymeric nanocomposites: an application of T1.rho.(13C) relaxation experiments at variable spin-locking fields

Czech Academy of Sciences Publication Activity Database

Kotek, Jiří; Brus, Jiří

2014-01-01

Roč. 59, č. 9 (2014), s. 662-666 ISSN 0032-2725 R&D Projects: GA ČR(CZ) GA13-29009S Institutional support: RVO:61389013 Keywords : polyamide 6 * nanocomposite * T1ρ(13C) relaxation Subject RIV: JI - Composite Materials Impact factor: 0.633, year: 2014

Variable setpoint as a relaxing component in physiological control.

Science.gov (United States)

Risvoll, Geir B; Thorsen, Kristian; Ruoff, Peter; Drengstig, Tormod

2017-09-01

Setpoints in physiology have been a puzzle for decades, and especially the notion of fixed or variable setpoints have received much attention. In this paper, we show how previously presented homeostatic controller motifs, extended with saturable signaling kinetics, can be described as variable setpoint controllers. The benefit of a variable setpoint controller is that an observed change in the concentration of the regulated biochemical species (the controlled variable) is fully characterized, and is not considered a deviation from a fixed setpoint. The variation in this biochemical species originate from variation in the disturbances (the perturbation), and thereby in the biochemical species representing the controller (the manipulated variable). Thus, we define an operational space which is spanned out by the combined high and low levels of the variations in (1) the controlled variable, (2) the manipulated variable, and (3) the perturbation. From this operational space, we investigate whether and how it imposes constraints on the different motif parameters, in order for the motif to represent a mathematical model of the regulatory system. Further analysis of the controller's ability to compensate for disturbances reveals that a variable setpoint represents a relaxing component for the controller, in that the necessary control action is reduced compared to that of a fixed setpoint controller. Such a relaxing component might serve as an important property from an evolutionary point of view. Finally, we illustrate the principles using the renal sodium and aldosterone regulatory system, where we model the variation in plasma sodium as a function of salt intake. We show that the experimentally observed variations in plasma sodium can be interpreted as a variable setpoint regulatory system. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Rapid simultaneous high-resolution mapping of myelin water fraction and relaxation times in human brain using BMC-mcDESPOT.

Science.gov (United States)

Bouhrara, Mustapha; Spencer, Richard G

2017-02-15

A number of central nervous system (CNS) diseases exhibit changes in myelin content and magnetic resonance longitudinal, T 1 , and transverse, T 2 , relaxation times, which therefore represent important biomarkers of CNS pathology. Among the methods applied for measurement of myelin water fraction (MWF) and relaxation times, the multicomponent driven equilibrium single pulse observation of T 1 and T 2 (mcDESPOT) approach is of particular interest. mcDESPOT permits whole brain mapping of multicomponent T 1 and T 2 , with data acquisition accomplished within a clinically realistic acquisition time. Unfortunately, previous studies have indicated the limited performance of mcDESPOT in the setting of the modest signal-to-noise range of high-resolution mapping, required for the depiction of small structures and to reduce partial volume effects. Recently, we showed that a new Bayesian Monte Carlo (BMC) analysis substantially improved determination of MWF from mcDESPOT imaging data. However, our previous study was limited in that it did not discuss determination of relaxation times. Here, we extend the BMC analysis to the simultaneous determination of whole-brain MWF and relaxation times using the two-component mcDESPOT signal model. Simulation analyses and in-vivo human brain studies indicate the overall greater performance of this approach compared to the stochastic region contraction (SRC) algorithm, conventionally used to derive parameter estimates from mcDESPOT data. SRC estimates of the transverse relaxation time of the long T 2 fraction, T 2,l , and the longitudinal relaxation time of the short T 1 fraction, T 1,s , clustered towards the lower and upper parameter search space limits, respectively, indicating failure of the fitting procedure. We demonstrate that this effect is absent in the BMC analysis. Our results also showed improved parameter estimation for BMC as compared to SRC for high-resolution mapping. Overall we find that the combination of BMC analysis

Coaxial helicity injection and n=1 relaxation activity in the HIST spherical torus

International Nuclear Information System (INIS)

Nagata, M.

2002-01-01

Coaxial Helicity Injection (CHI) has demonstrated non-inductive current generation of spherical tokamak (ST) and spheromak plasmas on several devices. In order to understand comprehensively the role of the n=1 instability and relaxation on current generation processes in helicity-driven spherical systems, we have investigated dynamics of ST plasmas produced in the HIST device (major radius R=0.30 m, minor radius a=0.24 m, aspect ratio A=1.25, toroidal field B t t <150 kA and discharge time t<5 ms in the ST configuration) by decreasing the external toroidal field (TF) and reversing its sign in time. In results, we have discovered that the ST relaxes towards flipped ST configurations through formation of reversed-field pinches (RFPs)-like magnetic field profiles. Surprisingly, it has been observed that not only toroidal flux but also poloidal flux reverses sign spontaneously during the relaxation process. This self-reversal of the poloidal field is thought to be evidence for 'global helicity conservation'. Furthermore, we have first demonstrated that a flipped ST plasma can be successfully sustained by CHI. (author)

Discuss the value of T2 relaxation time in the research of femorotibial joint biological tissue

International Nuclear Information System (INIS)

Zhong Jinglian; Song Lingling; Liang Biling; Ye Ruixin; Yun Wenjuan

2009-01-01

Objective: To discuss the value of T 2 relaxation time in the research of the biomechanics and function of cartilage of knee joint. Methods: Knees of 20 healthy adults and 19 osteoarthritis patients were examined with sagittal 8-echo sequence. The T 2 value of cartilage was calculated. The T 2 values in the superficial and deeper cartilage of femoral and tibial joint were compared, so did between the osteoarthritis patients and healthy adults. Results: The T 2 values in the superficial and the deeper tibital cartilage were (48.8±6.3) ms, (44.3±5.7) ms, respectively. The T 2 values in the superficial and deeper femoral cartilage were (52.1±5.7) ms, (47.7±5.3) ms, respectively. There was a significant difference between superficial and deeper femoral cartilage (t=3.148 and t=3.384, P 2 value in the tibial cartilage of osteoarthritis patients was (56.0±9.1) ms and was higher than that of healthy adults. There was a significant difference between osteoarthritis patients and healthy adults (t=-3.446, P 2 relaxation time can be used in the research of the biomechanics and function of cartilage and has a application value in clinical diagnosis. (authors)

A study of spin-lattice relaxation rates of glucose, fructose, sucrose and cherries using high-T c SQUID-based NMR in ultralow magnetic fields

Science.gov (United States)

Liao, Shu-Hsien; Wu, Pei-Che

2017-08-01

We study the concentration dependence of spin-lattice relaxation rates, T 1 -1, of glucose, fructose, sucrose and cherries by using high-T c SQUID-based NMR at magnetic fields of ˜97 μT. The detected NMR signal, Sy (T Bp), is fitted to [1 - exp(-T Bp/T 1)] to derive T 1 -1, where Sy (T Bp) is the strength of the NMR signal, T Bp is the duration of pre-polarization and T 1 -1 is the spin-lattice relaxation rate. It was found that T 1 -1 increases as the sugar concentrations increase. The increased T 1 -1 is due to the presence of more molecules in the surroundings, which increases the spin-lattice interaction and in turn enhances T 1 -1. The T 1 -1 versus degrees Brix curve provides a basis for determining unknown Brix values for cherries as well as other fruits.

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair.

Science.gov (United States)

Chang, Zhiwei; Halle, Bertil

2013-10-14

In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water (1)H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft

Thermodynamic scaling of α-relaxation time and viscosity stems from the Johari-Goldstein β-relaxation or the primitive relaxation of the coupling model.

Science.gov (United States)

Ngai, K L; Habasaki, J; Prevosto, D; Capaccioli, S; Paluch, Marian

2012-07-21

By now it is well established that the structural α-relaxation time, τ(α), of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τ(α) is a function Φ of the product variable, ρ(γ)/T, where ρ is the density and T the temperature. The constant γ as well as the function, τ(α) = Φ(ρ(γ)/T), is material dependent. Actually this dependence of τ(α) on ρ(γ)/T originates from the dependence on the same product variable of the Johari-Goldstein β-relaxation time, τ(β), or the primitive relaxation time, τ(0), of the coupling model. To support this assertion, we give evidences from various sources itemized as follows. (1) The invariance of the relation between τ(α) and τ(β) or τ(0) to widely different combinations of pressure and temperature. (2) Experimental dielectric and viscosity data of glass-forming van der Waals liquids and polymer. (3) Molecular dynamics simulations of binary Lennard-Jones (LJ) models, the Lewis-Wahnström model of ortho-terphenyl, 1,4 polybutadiene, a room temperature ionic liquid, 1-ethyl-3-methylimidazolium nitrate, and a molten salt 2Ca(NO(3))(2)·3KNO(3) (CKN). (4) Both diffusivity and structural relaxation time, as well as the breakdown of Stokes-Einstein relation in CKN obey thermodynamic scaling by ρ(γ)/T with the same γ. (5) In polymers, the chain normal mode relaxation time, τ(N), is another function of ρ(γ)/T with the same γ as segmental relaxation time τ(α). (6) While the data of τ(α) from simulations for the full LJ binary mixture obey very well the thermodynamic scaling, it is strongly violated when the LJ interaction potential is truncated beyond typical inter-particle distance, although in both cases the repulsive pair potentials coincide for some distances.

Off-resonance R1ρ relaxation outside of the fast exchange limit: An experimental study of a cavity mutant of T4 lysozyme

International Nuclear Information System (INIS)

Korzhnev, Dmitry M.; Orekhov, Vladislav Yu.; Dahlquist, Frederick W.; Kay, Lewis E.

2003-01-01

An 15 N off-resonance R 1ρ spin relaxation study of an L99A point mutant of T4 lysozyme is presented. Previous CPMG-based relaxation dispersion studies of exchange in this protein have established that the molecule interconverts between a populated ground state and an excited state (3.4%) with an exchange rate constant of 1450 s -1 at 25 deg. C. It is shown that for the majority of residues in this protein the offset dependence of the R 1ρ relaxation rates cannot be well fit using models which are only valid in the fast exchange regime. In contrast, a recently derived expression by Trott and Palmer (J. Magn. Reson., 154, 157-160, 2002) which is valid over a wider window of exchange than other relations, is shown to fit the data well. Values of (signed) chemical shift differences between exchanging sites have been extracted and are in reasonable agreement with shift differences measured using CPMG methods. A set of simulations is presented which help establish the exchange regimes that are best suited to analysis by off-resonance R 1ρ techniques

T2 relaxation time is related to liver fibrosis severity

Science.gov (United States)

Siqueira, Luiz; Uppal, Ritika; Alford, Jamu; Fuchs, Bryan C.; Yamada, Suguru; Tanabe, Kenneth; Chung, Raymond T.; Lauwers, Gregory; Chew, Michael L.; Boland, Giles W.; Sahani, Duhyant V.; Vangel, Mark; Hahn, Peter F.; Caravan, Peter

2016-01-01

Background The grading of liver fibrosis relies on liver biopsy. Imaging techniques, including elastography and relaxometric, techniques have had varying success in diagnosing moderate fibrosis. The goal of this study was to determine if there is a relationship between the T2-relaxation time of hepatic parenchyma and the histologic grade of liver fibrosis in patients with hepatitis C undergoing both routine, liver MRI and liver biopsy, and to validate our methodology with phantoms and in a rat model of liver fibrosis. Methods This study is composed of three parts: (I) 123 patients who underwent both routine, clinical liver MRI and biopsy within a 6-month period, between July 1999 and January 2010 were enrolled in a retrospective study. MR imaging was performed at 1.5 T using dual-echo turbo-spin echo equivalent pulse sequence. T2 relaxation time of liver parenchyma in patients was calculated by mono-exponential fit of a region of interest (ROI) within the right lobe correlating to histopathologic grading (Ishak 0–6) and routine serum liver inflammation [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)]. Statistical comparison was performed using ordinary logistic and ordinal logistic regression and ANOVA comparing T2 to Ishak fibrosis without and using AST and ALT as covariates; (II) a phantom was prepared using serial dilutions of dextran coated magnetic iron oxide nanoparticles. T2 weighed imaging was performed by comparing a dual echo fast spin echo sequence to a Carr-Purcell-Meigboom-Gill (CPMG) multi-echo sequence at 1.5 T. Statistical comparison was performed using a paired t-test; (III) male Wistar rats receiving weekly intraperitoneal injections of phosphate buffer solution (PBS) control (n=4 rats); diethylnitrosamine (DEN) for either 5 (n=5 rats) or 8 weeks (n=4 rats) were MR imaged on a Bruker Pharmascan 4.7 T magnet with a home-built bird-cage coil. T2 was quantified by using a mono-exponential fitting algorithm on multi-slice multi

Novel spin dynamics in ferrimagnetic molecular chains from {sup 1}H NMR and {mu}SR spin-lattice relaxation measurements

Energy Technology Data Exchange (ETDEWEB)

Micotti, E. E-mail: micotti@fisicavolta.unipv.it; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L

2004-05-01

The spin dynamics in the helical chain Co(hfac){sub 2}NITPhOMe has been investigated by {sup 1}H NMR and {mu}SR relaxation. In the temperature range 15<T<60 K, the results are consistent with the relaxation of the homogeneous magnetization. For T{<=}15 K, NMR and {mu}SR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived.

Opposing roles for RhoH GTPase during T-cell migration and activation

DEFF Research Database (Denmark)

Baker, Christina M; Comrie, William A; Hyun, Young-Min

2012-01-01

T cells spend the majority of their time perusing lymphoid organs in search of cognate antigen presented by antigen presenting cells (APCs) and then quickly recirculate through the bloodstream to another lymph node. Therefore, regulation of a T-cell response is dependent upon the ability of cells...

Relaxation dispersion in MRI induced by fictitious magnetic fields.

Science.gov (United States)

Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J; Garwood, Michael; Michaeli, Shalom

2011-04-01

A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 2. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T(₁ρ) experiments. As compared with the off-resonance spin lock T(₁ρ) method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable. Copyright © 2011 Elsevier Inc. All rights reserved.

Rapid T1 quantification based on 3D phase sensitive inversion recovery

Directory of Open Access Journals (Sweden)

Warntjes Marcel JB

2010-08-01

Full Text Available Abstract Background In Contrast Enhanced Magnetic Resonance Imaging fibrotic myocardium can be distinguished from healthy tissue using the difference in the longitudinal T1 relaxation after administration of Gadolinium, the so-called Late Gd Enhancement. The purpose of this work was to measure the myocardial absolute T1 post-Gd from a single breath-hold 3D Phase Sensitivity Inversion Recovery sequence (PSIR. Equations were derived to take the acquisition and saturation effects on the magnetization into account. Methods The accuracy of the method was investigated on phantoms and using simulations. The method was applied to a group of patients with suspected myocardial infarction where the absolute difference in relaxation of healthy and fibrotic myocardium was measured at about 15 minutes post-contrast. The evolution of the absolute R1 relaxation rate (1/T1 over time after contrast injection was followed for one patient and compared to T1 mapping using Look-Locker. Based on the T1 maps synthetic LGE images were reconstructed and compared to the conventional LGE images. Results The fitting algorithm is robust against variation in acquisition flip angle, the inversion delay time and cardiac arrhythmia. The observed relaxation rate of the myocardium is 1.2 s-1, increasing to 6 - 7 s-1 after contrast injection and decreasing to 2 - 2.5 s-1 for healthy myocardium and to 3.5 - 4 s-1 for fibrotic myocardium. Synthesized images based on the T1 maps correspond very well to actual LGE images. Conclusions The method provides a robust quantification of post-Gd T1 relaxation for a complete cardiac volume within a single breath-hold.

Gd-EOB-DTPA-Enhanced MR Imaging of the Liver: The Effect on T2 Relaxation Times and Apparent Diffusion Coefficient (ADC)

International Nuclear Information System (INIS)

Cieszanowski, Andrzej; Podgórska, Joanna; Rosiak, Grzegorz; Maj, Edyta; Grudziński, Ireneusz P.; Kaczyński, Bartosz; Szeszkowski, Wojciech; Milczarek, Krzysztof; Rowiński, Olgierd

2016-01-01

To investigate the effect of gadoxetic acid disodium (Gd-EOB-DTPA) on T2 relaxation times and apparent diffusion coefficient (ADC) values of the liver and focal liver lesions on a 1.5-T system. Magnetic resonance (MR) studies of 50 patients with 35 liver lesions were retrospectively analyzed. All examinations were performed at 1.5T and included T2-weighted turbo spin-echo (TSE) and diffusion-weighted (DW) images acquired before and after intravenous administration of Gd-EOB-DTPA. To assess the effect of this hepatobiliary contrast agent on T2-weighted TSE images and DW images T2 relaxation times and ADC values of the liver and FLLs were calculated and compared pre- and post-injection. The mean T2 relaxation times of the liver and focal hepatic lesions were lower on enhanced than on unenhanced T2-weighted TSE images (decrease of 2.7% and 3.6% respectively), although these differences were not statistically significant. The mean ADC values of the liver showed statistically significant decrease (of 4.6%) on contrast-enhanced DW images, compared to unenhanced images (P>0.05). The mean ADC value of liver lesions was lower on enhanced than on unenhanced DW images, but this difference (of 2.9%) did not reach statistical significance. The mean T2 relaxation times of the liver and focal liver lesions as well as the mean ADC values of liver lesions were not significantly different before and after administration of Gd-EOB-DTPA. Therefore, acquisition of T2-weighted and DW images between the dynamic contrast-enhanced examination and hepatobiliary phase is feasible and time-saving

Effect of extender oils on the stress relaxation behavior of thermoplastic vulcanizates

Directory of Open Access Journals (Sweden)

2008-11-01

Full Text Available The long term mechanical behavior of oil extended thermoplastic vulcanizates (TPV based on polypropylene (PP and acrylonitrile-butadiene rubber (NBR has been characterized by means of stress relaxation experiments. The morphology of TPV and the phase specific oil distribution which depend on the content and type of oil as well as on the mixing regime have been characterized by means of Atomic Force Microscopy (AFM, Dynamic Mechanical Thermal Analysis (DMTA and Differential Scanning Calorimetrie (DSC. The discussion of the stress relaxation behavior was carried out using the two-component model, which allows splitting the initial stress into two components: a thermal activated stress component and an athermal one. A master curve was created by shifting the relaxation curves vertically and horizontally towards the reference curve. The vertical shift factor bT is a function of the temperature dependence of the athermal stress components. It was found that the oil distribution strongly affects the athermal stress component which is related to the contribution of the structural changes, e.g. crystallinity of the PP phase and the average molecular weight between the crosslinks of the NBR phase. From the temperature dependence of the horizontal shift factor aT the main viscoelastic relaxation process was determined as the α-relaxation process of the crystalline PP phase. It is not dependent on the polarity and content of the oil as well as the mixing regime.

Magnetic Resonance Fingerprinting with short relaxation intervals.

Science.gov (United States)

Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter

2017-09-01

The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T 1 and T 2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T 1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T 2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially

T2 Relaxation Time Mapping of the Cartilage Cap of Osteochondromas

OpenAIRE

Kim, Hee Kyung; Horn, Paul; Dardzinski, Bernard J.; Kim, Dong Hoon; Laor, Tal

2016-01-01

Objective Our aim was to evaluate the cartilage cap of osteochondromas using T2 maps and to compare these values to those of normal patellar cartilage, from age and gender matched controls. Materials and Methods This study was approved by the Institutional Review Board and request for informed consent was waived. Eleven children (ages 5-17 years) with osteochondromas underwent MR imaging, which included T2-weighted fat suppressed and T2 relaxation time mapping (echo time = 9-99/repetition tim...

T2 relaxation time in patellar cartilage - global and regional reproducibility at 1.5 Tesla and 3 Tesla

International Nuclear Information System (INIS)

Glaser, C.; Horng, A.; Mendlik, T.; Weckbach, S.; Hoffmann, R.T.; Wagner, S.; Raya, J.G.; Reiser, M.; Horger, W.

2007-01-01

Purpose: Evaluation of the global and regional reproducibility of T2 relaxation time in patellar cartilage at 1.5 T and 3 T. Materials and Methods: 6 left patellae of 6 healthy volunteers (aged 25-30, 3 female, 3 male) were examined using a fat-saturated multiecho sequence and a T1-w 3D-FLASH sequence with water excitation at 1.5 Tesla and 3 Tesla. Three consecutive data sets were acquired within one MRI session with the examined knee being repositioned in the coil and scanner between each data set. The segmented cartilage (FLASH sequence) was overlaid on the multiecho data and T2 values were calculated for the total cartilage, 3 horizontal layers consisting of a superficial, intermedial and deep layer, 3 facets consisting of a medial, median (ridge) and lateral facet (global T2 values) and 27 ROIs/MRI slices (regional T2 value). The reproducibility (precision error) was calculated as the root mean square average of the individual standard deviations [ms] and coefficients of variation (COV) [%]. Results: The mean global reproducibility error for T2 was 3.53% (±0.38%) at 1.5 Tesla and 3.25% (±0.61%) at 3 Tesla. The mean regional reproducibility error for T2 was 8.62% (±2.61%) at 1.5 Tesla and 9.66% (±3.37%) at 3 Tesla. There was no significant difference with respect to absolute reproducibility errors between 1.5 Tesla and 3 Tesla at a constant spatial resolution. However, different reproducibility errors were found between the cartilage layers. One third of the data variability could be attributed to the influence of the different cartilage layers, and another 10% to the influence of the separate MRI slices. Conclusion: Our data provides an estimation of the global and regional reproducibility errors of T2 in healthy cartilage. In the analysis of small subregions, an increase in the regional reproducibility error must be accepted. The data may serve as a basis for sample size calculations of study populations and may contribute to the decision regarding the

Cerebral abnormalities: use of calculated T1 and T2 magnetic resonance images for diagnosis

International Nuclear Information System (INIS)

Mills, C.M.; Crooks, L.E.; Kaufman, L.; Brant-Zawadzki, M.

1984-01-01

The potential clinical importance of T1 and T2 relaxation times in distinguishing normal and pathologic tissue with magnetic resonance (MR) is discussed and clinical examples of cerebral abnormalities are given. Five patients with cerebral infarction, 15 with multiple sclerosis, two with Wilson disease, and four with tumors were imaged. Hemorrhagic and ischemic cerebrovascular accidents were distinguished using the spin echo technique. In the patients with multiple sclerosis, lesions had prolonged T1 and T2 times, but the definition of plaque was limited by spatial resolution. No abnormalities in signal intensity were seen in the patient with Wilson disease who was no longer severly disabled; abnormal increased signal intensity in the basal ganglia was found in the second patient with Wilson disease. Four tumors produced abnormal T1 and T2 relaxation times but these values alone were not sufficient for tumor characterization

Relaxation of fibrils in blends with one viscoelastic component: Bulk and confined conditions

NARCIS (Netherlands)

Cardinaels, R.M.; Moldenaers, P.

2010-01-01

Using a counter rotating parallel plate shear flow cell, shape relaxation of fibrils in a quiescent matrix is studied microscopically. Both the effects of geometrical confinement and component viscoelasticity are systematically explored. By applying a supercritical shear flow for varying amounts of

In vivo estimation of transverse relaxation time constant (T2 ) of 17 human brain metabolites at 3T.

Science.gov (United States)

Wyss, Patrik O; Bianchini, Claudio; Scheidegger, Milan; Giapitzakis, Ioannis A; Hock, Andreas; Fuchs, Alexander; Henning, Anke

2018-08-01

The transverse relaxation times T 2 of 17 metabolites in vivo at 3T is reported and region specific differences are addressed. An echo-time series protocol was applied to one, two, or three volumes of interest with different fraction of white and gray matter including a total number of 106 healthy volunteers and acquiring a total number of 128 spectra. The data were fitted with the 2D fitting tool ProFit2, which included individual line shape modeling for all metabolites and allowed the T 2 calculation of 28 moieties of 17 metabolites. The T 2 of 10 metabolites and their moieties have been reported for the first time. Region specific T 2 differences in white and gray matter enriched tissue occur in 16 of 17 metabolites examined including single resonance lines and coupled spin systems. The relaxation time T 2 is regions specific and has to be considered when applying tissue composition correction for internal water referencing. Magn Reson Med 80:452-461, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

Measurement of alveolar oxygen partial pressure in the rat lung using Carr-Purcell-Meiboom-Gill spin-spin relaxation times of hyperpolarized 3He and 129Xe at 74 mT.

Science.gov (United States)

Kraayvanger, Ryan J; Bidinosti, Christopher P; Dominguez-Viqueira, William; Parra-Robles, Juan; Fox, Matthew; Lam, Wilfred W; Santyr, Giles E

2010-11-01

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, (3) He and (129) Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R(2) ) of (3) He at low magnetic field strengths (oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R(2) values of hyperpolarized (3) He and (129) Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for (3) He and (129) Xe were determined to be (5.2 ± 0.6) × 10(-6) Pa(-1) sec(-1) and (7.3 ± 0.4) × 10(-6) Pa(-1) s(-1) compared with spin-lattice relaxivity constants of (4.0 ± 0.4) × 10(-6) Pa(-1) s(-1) and (4.3 ± 1.3) × 10(-6) Pa(-1) s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using (3) He in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For (129) Xe, multicomponent relaxation was observed with one component exhibiting an increase in R(2) with decreasing alveolar oxygen partial pressure. Copyright © 2010 Wiley-Liss, Inc.

Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3(NIT(C6H4OPh))]: A μ+ spin relaxation study

International Nuclear Information System (INIS)

Arosio, Paolo; Orsini, Francesco; Corti, Maurizio; Mariani, Manuel; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

2015-01-01

The spin dynamics of the molecular magnetic chain [Dy(hfac) 3 (NIT(C 6 H 4 OPh))] were investigated by means of the Muon Spin Relaxation (μ + SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac) 3 (NIT(C 6 H 4 OPh))] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ + SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λ interm (T), associated with the intermediate relaxing component. The experimental λ interm (T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ 0 exp(Δ/k B T), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state

Rotational dynamics of benzene and water in an ionic liquid explored via molecular dynamics simulations and NMR T1 measurements.

Science.gov (United States)

Yasaka, Yoshiro; Klein, Michael L; Nakahara, Masaru; Matubayasi, Nobuyuki

2012-02-21

The rotational dynamics of benzene and water in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride are studied using molecular dynamics (MD) simulation and NMR T(1) measurements. MD trajectories based on an effective potential are used to calculate the (2)H NMR relaxation time, T(1) via Fourier transform of the relevant rotational time correlation function, C(2R)(t). To compensate for the lack of polarization in the standard fixed-charge modeling of the IL, an effective ionic charge, which is smaller than the elementary charge is employed. The simulation results are in closest agreement with NMR experiments with respect to the temperature and Larmor frequency dependencies of T(1) when an effective charge of ±0.5e is used for the anion and the cation, respectively. The computed C(2R)(t) of both solutes shows a bi-modal nature, comprised of an initial non-diffusive ps relaxation plus a long-time ns tail extending to the diffusive regime. Due to the latter component, the solute dynamics is not under the motional narrowing condition with respect to the prevalent Larmor frequency. It is shown that the diffusive tail of the C(2R)(t) is most important to understand frequency and temperature dependencies of T(1) in ILs. On the other hand, the effect of the initial ps relaxation is an increase of T(1) by a constant factor. This is equivalent to an "effective" reduction of the quadrupolar coupling constant (QCC). Thus, in the NMR T(1) analysis, the rotational time correlation function can be modeled analytically in the form of aexp (-t/τ) (Lipari-Szabo model), where the constant a, the Lipari-Szabo factor, contains the integrated contribution of the short-time relaxation and τ represents the relaxation time of the exponential (diffusive) tail. The Debye model is a special case of the Lipari-Szabo model with a = 1, and turns out to be inappropriate to represent benzene and water dynamics in ILs since a is as small as 0.1. The use of the Debye model would result in

Articular Cartilage of the Human Knee Joint: In Vivo Multicomponent T2 Analysis at 3.0 T

Science.gov (United States)

Choi, Kwang Won; Samsonov, Alexey; Spencer, Richard G.; Wilson, John J.; Block, Walter F.; Kijowski, Richard

2015-01-01

Purpose To compare multicomponent T2 parameters of the articular cartilage of the knee joint measured by using multicomponent driven equilibrium single-shot observation of T1 and T2 (mcDESPOT) in asymptomatic volunteers and patients with osteoarthritis. Materials and Methods This prospective study was performed with institutional review board approval and with written informed consent from all subjects. The mcDESPOT sequence was performed in the knee joint of 13 asymptomatic volunteers and 14 patients with osteoarthritis of the knee. Single-component T2 (T2Single), T2 of the fast-relaxing water component (T2F) and of the slow-relaxing water component (T2S), and the fraction of the fast-relaxing water component (FF) of cartilage were measured. Wilcoxon rank-sum tests and multivariate linear regression models were used to compare mcDESPOT parameters between volunteers and patients with osteoarthritis. Receiver operating characteristic analysis was used to assess diagnostic performance with mcDESPOT parameters for distinguishing morphologically normal cartilage from morphologically degenerative cartilage identified at magnetic resonance imaging in eight cartilage subsections of the knee joint. Results Higher cartilage T2Single (P cartilage FF (P cartilage T2F (P = .079) and T2S (P = .124) values were seen in patients with osteoarthritis compared with those in asymptomatic volunteers. Differences in T2Single and FF remained significant (P cartilage (P cartilage T2Single and significantly lower cartilage FF than did asymptomatic volunteers, and receiver operating characteristic analysis results suggested that FF may allow greater diagnostic performance than that with T2Single for distinguishing between normal and degenerative cartilage. © RSNA, 2015 Online supplemental material is available for this article. PMID:26024307

Synthesis of Tumor-avid Photosensitizer-Gd(III)DTPA conjugates: impact of the number of gadolinium units in T1/T2 relaxivity, intracellular localization, and photosensitizing efficacy.

Science.gov (United States)

Goswami, Lalit N; White, William H; Spernyak, Joseph A; Ethirajan, Manivannan; Chen, Yihui; Missert, Joseph R; Morgan, Janet; Mazurchuk, Richard; Pandey, Ravindra K

2010-05-19

To develop novel bifunctional agents for tumor imaging (MR) and photodynamic therapy (PDT), certain tumor-avid photosensitizers derived from chlorophyll-a were conjugated with variable number of Gd(III)aminobenzyl DTPA moieties. All the conjugates containing three or six gadolinium units showed significant T(1) and T(2) relaxivities. However, as a bifunctional agent, the 3-(1'-hexyloxyethyl)pyropheophorbide-a (HPPH) containing 3Gd(III) aminophenyl DTPA was most promising with possible applications in tumor-imaging and PDT. Compared to HPPH, the corresponding 3- and 6Gd(III)aminobenzyl DTPA conjugates exhibited similar electronic absorption characteristics with a slightly decreased intensity of the absorption band at 660 nm. However, compared to HPPH, the excitation of the broad "Soret" band (near 400 nm) of the corresponding 3Gd(III)aminobenzyl-DTPA analogues showed a significant decrease in the fluorescence intensity at 667 nm.

Osteosarcoma: correlation of T1 map and histology map

International Nuclear Information System (INIS)

Suh, Jin Suck; Yun, Mi Jin; Jeong, Eun Kee; Shin, Kyoo Ho; Yang, Woo Ick

1999-01-01

To determine whether T1 mapping shows regional differences between viable and necrotic regions of osteosarcomas after anticancer chemotherapy and to assess whether this mapping is able to express the characteristics of various intramural tissue components. Eleven of 20 osteosarcomas were included in this study, while the remaining nine were excluded because the tumor site was inappropriate for comparison of T1 map and tumor macrosection. All patients underwent MR imaging for the purpose of T1 mapping, followed by pre-operative chemotherapy and subsequent limb-salvage surgery. Spin echo pulse sequencing was used with varying TR (100, 200, 400, 800, 1600, and 2400 msec) and a constant TE of 20 msec. Using a C-language software program, T1 relaxation time was calculated on a pixel-by-pixel basis and then a T1 map was generated by using a post-processing program, NIH Image. We attempted correlation of the T1 map and histologic findings, particularly in regions of interest(ROI) if certain areas were different from other regions on either the T1 or histologic map. Value was expressed as an average of the ratio of T1 of ROI and T1 of fat tissue, and this was used as an internal reference for normalization of the measurement. Tumor necrosis was 100 %(Grade IV) in six specimens, and over 90 % (Grade III) in five. Viable tumor cells were found mostly in regions with chondroid matrix and seldom in regions with osteoid matrix. Regardless of cell viability, values ranged from 0.9 to 9.87(mean, 4.02) in tumor necrotic area with osteoid matrices, and from 3.04 to 3.9(mean, 3.55) in areas with chondroid matrices. Other regions with fibrous tissue proliferation, hemorrhage, and fatty necrosis showed values of 2.92-9.83(mean, 7.20), 2.65-5.96(mean,3.59), and 1.43-3.11(mean, 2.68) respectively. The values of various tissues overlapped. No statistically significant difference was found between regions in which tumors were viable and those with tumor necrosis. Although we hypothesized

NMR relaxation times of natural rubber latex

International Nuclear Information System (INIS)

Harun, S.; Aziz, H.; Basir, Z.

1994-01-01

NMR relaxation times T sub 1 and T sub 2 of natural rubber latex have been measured at 25 degree C on a pulsed NMR spectrometer. The work focuses on the variation of the relaxation times with the amount of water content from 0% to 50%. The water content was adjusted by centrifuging and removing a certain amount of water from the sample. The data were analysed using a biexponential fitting procedure which yields simultaneously either T sub 1a and T sub 1b or T sub 2a and T sub 2b. The amount of solid was compared with the known amount of dry rubber content

Novel spin dynamics in ferrimagnetic molecular chains from 1H NMR and μSR spin-lattice relaxation measurements

International Nuclear Information System (INIS)

Micotti, E.; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L.

2004-01-01

The spin dynamics in the helical chain Co(hfac) 2 NITPhOMe has been investigated by 1 H NMR and μSR relaxation. In the temperature range 15< T<60 K, the results are consistent with the relaxation of the homogeneous magnetization. For T≤15 K, NMR and μSR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived

Novel spin dynamics in ferrimagnetic molecular chains from 1H NMR and μSR spin-lattice relaxation measurements

Science.gov (United States)

Micotti, E.; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L.

2004-05-01

The spin dynamics in the helical chain Co(hfac) 2NITPhOMe has been investigated by 1H NMR and μSR relaxation. In the temperature range 15<T<60 K, the results are consistent with the relaxation of the homogeneous magnetization. For T⩽15 K, NMR and μSR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived.

Acrolein relaxes mouse isolated tracheal smooth muscle via a TRPA1-dependent mechanism.

Science.gov (United States)

Cheah, Esther Y; Burcham, Philip C; Mann, Tracy S; Henry, Peter J

2014-05-01

Airway sensory C-fibres express TRPA1 channels which have recently been identified as a key chemosensory receptor for acrolein, a toxic and highly prevalent component of smoke. TRPA1 likely plays an intermediary role in eliciting a range of effects induced by acrolein including cough and neurogenic inflammation. Currently, it is not known whether acrolein-induced activation of TRPA1 produces other airway effects including relaxation of mouse airway smooth muscle. The aims of this study were to examine the effects of acrolein on airway smooth muscle tone in mouse isolated trachea, and to characterise the cellular and molecular mechanisms underpinning the effects of acrolein. Isometric tension recording studies were conducted on mouse isolated tracheal segments to characterise acrolein-induced relaxation responses. Release of the relaxant PGE₂ was measured by EIA to examine its role in the response. Use of selective antagonists/inhibitors permitted pharmacological characterisation of the molecular and cellular mechanisms underlying this relaxation response. Acrolein induced dose-dependent relaxation responses in mouse isolated tracheal segments. Importantly, these relaxation responses were significantly inhibited by the TRPA1 antagonists AP-18 and HC-030031, an NK₁ receptor antagonist RP-67580, and the EP₂ receptor antagonist PF-04418948, whilst completely abolished by the non-selective COX inhibitor indomethacin. Acrolein also caused rapid PGE₂ release which was suppressed by HC-030031. In summary, acrolein induced a novel bronchodilator response in mouse airways. Pharmacologic studies indicate that acrolein-induced relaxation likely involves interplay between TRPA1-expressing airway sensory C-fibres, NK₁ receptor-expressing epithelial cells, and EP₂-receptor expressing airway smooth muscle cells. Copyright © 2014 Elsevier Inc. All rights reserved.

Ultrashort Echo Time Magnetic Resonance Imaging of the Lung Using a High-Relaxivity T1 Blood-Pool Contrast Agent

Directory of Open Access Journals (Sweden)

Joris Tchouala Nofiele

2014-10-01

Full Text Available The lung remains one of the most challenging organs to image using magnetic resonance imaging (MRI due to intrinsic rapid signal decay. However, unlike conventional modalities such as computed tomography, MRI does not involve radiation and can provide functional and morphologic information on a regional basis. Here we demonstrate proof of concept for a new MRI approach to achieve substantial gains in a signal to noise ratio (SNR in the lung parenchyma: contrast-enhanced ultrashort echo time (UTE imaging following intravenous injection of a high-relaxivity blood-pool manganese porphyrin T1 contrast agent. The new contrast agent increased relative enhancement of the lung parenchyma by over 10-fold compared to gadolinium diethylene triamine pentaacetic acid (Gd-DTPA, and the use of UTE boosted the SNR by a factor of 4 over conventional T1-weighted gradient echo acquisitions. The new agent also maintains steady enhancement over at least 60 minutes, thus providing a long time window for obtaining high-resolution, high-quality images and the ability to measure a number of physiologic parameters.

A study on magnetic relaxation times of various organs and body fluids using superconducting magnetic resonance imaging system part I: measurement of relative signal intensity and T2 relaxation time in various portions of brain and cerebrospinal fluid

International Nuclear Information System (INIS)

Chang, Kee Hyun; Lee, Ghi Jai; Han, Moon Hee; Kim, Jae Ho; Han, Man Chang; Kim, Chu Wan

1988-01-01

This study was undertake to determine if routine clinical magnetic resonance imaging sequences using only two different repetition times (TRs) and with only two sequential echo times (TEs) can be used to measure reproducible relative signal intensity and T2 relaxation time for normal brain tissues and cerebrospinal fluid using a 2.0T superconducting system. In 47 patients 6 different anatomic sites were measured. For each anatomic location, the mean and standard deviation of these values were determined. On T1-weighted (SE 500msec/30msec) images, in globus pallidus and thalamus, of the CSF, cortical gray matter and retrobulbar fat tissue varied more, with a standard deviation of 11-14% on T1-weighted images. On T2-weighted (SE 3000msec/30msec and 3000msec/80msec) images, the relative signal intensity of all anatomic regions varied more than on T1-weighted images. The standard deviation of T2 relaxation times also varied from 10% (fat tissue) to 18% (CSF). These variations might be due to partial volume averaging, signal alteration of CSF secondary to CSF pulsatile motion, etc. Knowing that relative signal intensity and T2 relaxation times calculated from routine imaging sequences are reproducible in only limited area, these normal ranges can be used to investigate changes occurring in disease states of the limited regions.

Evaluation of biexponential relaxation processes by magnetic resonance imaging. A phantom study

DEFF Research Database (Denmark)

Kjaer, L; Thomsen, C; Larsson, H B

1988-01-01

Despite the complexity of biologic tissues, a monoexponential behaviour is usually assumed when estimating relaxation processes in vivo by magnetic resonance imaging (MRI). This study was designed to evaluate the potential of biexponential decomposition of T1 and T2 relaxation curves obtained at 1...... echoes. Applying biexponential curve analysis, a significant deviation from a monoexponential behaviour was recognized at a ratio of corresponding relaxation rates of about 3 and 2, estimating T1 and T2 relaxation, respectively (p less than 0.01, F-test). Requiring an SD less than or equal to 10 per cent...

Sodium and T1rho MRI for molecular and diagnostic imaging of articular cartilage.

Science.gov (United States)

Borthakur, Arijitt; Mellon, Eric; Niyogi, Sampreet; Witschey, Walter; Kneeland, J Bruce; Reddy, Ravinder

2006-11-01

In this article, both sodium magnetic resonance (MR) and T1rho relaxation mapping aimed at measuring molecular changes in cartilage for the diagnostic imaging of osteoarthritis are reviewed. First, an introduction to structure of cartilage, its degeneration in osteoarthritis (OA) and an outline of diagnostic imaging methods in quantifying molecular changes and early diagnostic aspects of cartilage degeneration are described. The sodium MRI section begins with a brief overview of the theory of sodium NMR of biological tissues and is followed by a section on multiple quantum filters that can be used to quantify both bi-exponential relaxation and residual quadrupolar interaction. Specifically, (i) the rationale behind the use of sodium MRI in quantifying proteoglycan (PG) changes, (ii) validation studies using biochemical assays, (iii) studies on human OA specimens, (iv) results on animal models and (v) clinical imaging protocols are reviewed. Results demonstrating the feasibility of quantifying PG in OA patients and comparison with that in healthy subjects are also presented. The section concludes with the discussion of advantages and potential issues with sodium MRI and the impact of new technological advancements (e.g. ultra-high field scanners and parallel imaging methods). In the theory section on T1rho, a brief description of (i) principles of measuring T1rho relaxation, (ii) pulse sequences for computing T1rho relaxation maps, (iii) issues regarding radio frequency power deposition, (iv) mechanisms that contribute to T1rho in biological tissues and (v) effects of exchange and dipolar interaction on T1rho dispersion are discussed. Correlation of T1rho relaxation rate with macromolecular content and biomechanical properties in cartilage specimens subjected to trypsin and cytokine-induced glycosaminoglycan depletion and validation against biochemical assay and histopathology are presented. Experimental T1rho data from osteoarthritic specimens, animal models

Evaluation of MR imaging with T1 and T2* mapping for the determination of hepatic iron overload.

Science.gov (United States)

Henninger, B; Kremser, C; Rauch, S; Eder, R; Zoller, H; Finkenstedt, A; Michaely, H J; Schocke, M

2012-11-01

To evaluate MRI using T1 and T2* mapping sequences in patients with suspected hepatic iron overload (HIO). Twenty-five consecutive patients with clinically suspected HIO were retrospectively studied. All underwent MRI and liver biopsy. For the quantification of liver T2* values we used a fat-saturated multi-echo gradient echo sequence with 12 echoes (TR = 200 ms, TE = 0.99 ms +  n × 1.41 ms, flip angle 20°). T1 values were obtained using a fast T1 mapping sequence based on an inversion recovery snapshot FLASH sequence. Parameter maps were analysed using regions of interest. ROC analysis calculated cut-off points at 10.07 ms and 15.47 ms for T2* in the determination of HIO with accuracy 88 %/88 %, sensitivity 84 %/89.5 % and specificity 100 %/83 %. MRI correctly classified 20 patients (80 %). All patients with HIO only had decreased T1 and T2* relaxation times. There was a significant difference in T1 between patients with HIO only and patients with HIO and steatohepatitis (P = 0.018). MRI-based T2* relaxation diagnoses HIO very accurately, even at low iron concentrations. Important additional information may be obtained by the combination of T1 and T2* mapping. It is a rapid, non-invasive, accurate and reproducible technique for validating the evidence of even low hepatic iron concentrations. • Hepatic iron overload causes fibrosis, cirrhosis and increases hepatocellular carcinoma risk. • MRI detects iron because of the field heterogeneity generated by haemosiderin. • T2* relaxation is very accurate in diagnosing hepatic iron overload. • Additional information may be obtained by T1 and T2* mapping.

T1-T2 dual-modal MRI of brain gliomas using PEGylated Gd-doped iron oxide nanoparticles.

Science.gov (United States)

Xiao, Ning; Gu, Wei; Wang, Hao; Deng, Yunlong; Shi, Xin; Ye, Ling

2014-03-01

To overcome the negative contrast limitations of iron oxide-based contrast agents and to improve the biocompatibility of Gd-chelate contrast agents, PEGylated Gd-doped iron oxide (PEG-GdIO) NPs as a T1-T2 dual-modal contrast agent were synthesized by the polyol method. The transverse relaxivity (r2) and longitudinal relaxivity (r1) of PEG-GdIO were determined to be 66.9 and 65.9 mM(-1) s(-1), respectively. The high r1 value and low r2/r1 ratio make PEG-GdIO NPs suitable as a T1-T2 dual-modal contrast agent. The in vivo MRI demonstrated a brighter contrast enhancement in T1-weighted image and a simultaneous darken effect in T2-weighted MR image compared to the pre-contrast image in the region of glioma. Furthermore, the biocompatibility of PEG-GdIO NPs was confirmed by the in vitro MTT cytotoxicity and in vivo histological analyses (H&E). Therefore, PEG-GdIO NPs hold great potential in T1-T2 dual-modal imaging for the diagnosis of brain glioma. Copyright © 2013 Elsevier Inc. All rights reserved.

Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3{NIT(C6H4OPh)}]: A μ+ spin relaxation study

Science.gov (United States)

Arosio, Paolo; Corti, Maurizio; Mariani, Manuel; Orsini, Francesco; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

2015-05-01

The spin dynamics of the molecular magnetic chain [Dy(hfac)3{NIT(C6H4OPh)}] were investigated by means of the Muon Spin Relaxation (μ+SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac)3{NIT(C6H4OPh)}] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ+SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λinterm(T), associated with the intermediate relaxing component. The experimental λinterm(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ0 exp(Δ/kBT), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3(NIT(C6H4OPh))]: A μ{sup +} spin relaxation study

Energy Technology Data Exchange (ETDEWEB)

Arosio, Paolo, E-mail: paolo.arosio@guest.unimi.it; Orsini, Francesco [Department of Physics, Università degli Studi di Milano, and INSTM, Milano (Italy); Corti, Maurizio [Department of Physics, Università degli Studi di Pavia and INSTM, Pavia (Italy); Mariani, Manuel [Department of Physics and Astronomy, Università degli Studi di Bologna, Bologna (Italy); Bogani, Lapo [Physikalisches Institut, Universität Stuttgart, Stuttgart (Germany); Caneschi, Andrea [INSTM and Department of Chemistry, University of Florence, Firenze (Italy); Lago, Jorge [Departamento de Quimica Inorganica, Universidad del Pais Vasco, Bilbao (Spain); Lascialfari, Alessandro [Department of Physics, Università degli Studi di Milano, and INSTM, Milano (Italy); Centro S3, Istituto Nanoscienze - CNR, Modena (Italy)

2015-05-07

The spin dynamics of the molecular magnetic chain [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] were investigated by means of the Muon Spin Relaxation (μ{sup +}SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ{sup +}SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λ{sub interm}(T), associated with the intermediate relaxing component. The experimental λ{sub interm}(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ{sub 0} exp(Δ/k{sub B}T), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

Proton NMR relaxation in hydrous melts

International Nuclear Information System (INIS)

Braunstein, J.; Bacarella, A.L.; Benjamin, B.M.; Brown, L.L.; Girard, C.

1976-01-01

Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120 0 C. Although measured in different temperature ranges, spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd 2+ . At temperatures near 50 0 C, mean Arrhenius coefficients Δ H/sub T 1 / (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T 1 and T 2 in Ca(NO 3 ) 2 -2.8 H 2 O between -4 and 120 0 C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T 0 ) of 225 0 K, close to the value of T 0 for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

The freezing of water bonded in the wheat (Triticum aestivum L.) grain studied by means protons magnetic relaxation method

International Nuclear Information System (INIS)

Haranczyk, H.; Jasinski, G.; Strzalka, K.

1994-01-01

Some biological aspects of water freezing in the wheat grain have been studied using NMR methods. Measuring of the relaxation times for freezing and liquid water shown absence of T 2 ∼100 μs and T 2 ∼1 ms separated components what pointed for some different way of water bonding

Solid state {sup 1}H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: The relationship between structure and methyl group and t-butyl group rotation

Energy Technology Data Exchange (ETDEWEB)

Wang, Xianlong, E-mail: WangXianlong@uestc.edu.cn, E-mail: pbeckman@brynmawr.edu [Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Rd., 2nd Section, Chengdu 610054 (China); Mallory, Frank B. [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States); Mallory, Clelia W. [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States); Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 (United States); Odhner, Hosanna R.; Beckmann, Peter A., E-mail: WangXianlong@uestc.edu.cn, E-mail: pbeckman@brynmawr.edu [Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States)

2014-05-21

We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state {sup 1}H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the {sup 1}H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.

Strain relaxation of germanium-tin (GeSn) fins

Science.gov (United States)

Kang, Yuye; Huang, Yi-Chiau; Lee, Kwang Hong; Bao, Shuyu; Wang, Wei; Lei, Dian; Masudy-Panah, Saeid; Dong, Yuan; Wu, Ying; Xu, Shengqiang; Tan, Chuan Seng; Gong, Xiao; Yeo, Yee-Chia

2018-02-01

Strain relaxation of biaxially strained Ge1-xSnx layer when it is patterned into Ge1-xSnx fin structures is studied. Ge1-xSnx-on-insulator (GeSnOI) substrate was realized using a direct wafer bonding (DWB) technique and Ge1-xSnx fin structures were formed by electron beam lithography (EBL) patterning and dry etching. The strain in the Ge1-xSnx fins having fin widths (WFin) ranging from 1 μm down to 80 nm was characterized using micro-Raman spectroscopy. Raman measurements show that the strain relaxation increases with decreasing WFin. Finite element (FE) simulation shows that the strain component in the transverse direction relaxes with decreasing WFin, while the strain component along the fin direction remains unchanged. For various Ge1-xSnx fin widths, transverse strain relaxation was further extracted using micro-Raman spectroscopy, which is consistent with the simulation results.

A novel approach to modelling non-exponential spin glass relaxation

Energy Technology Data Exchange (ETDEWEB)

Pickup, R.M. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)]. E-mail: r.cywinski@leeds.ac.uk; Cywinski, R. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Pappas, C. [Hahn-Meitner Institut, Glienicker Strasse 100, 14109 Berlin (Germany)

2007-07-15

A probabilistic cluster model, originally proposed by Weron to explain the universal power law of dielectric relaxation, is shown to account for the non-exponential relaxation in spin glasses above T {sub g}. Neutron spin echo spectra measured for the cluster glass compound Co{sub 55}Ga{sub 45} are well described by the Weron relaxation function, {phi}(t)={phi} {sub o}(1+k(t/{tau}) {sup {beta}}){sup -1/k}, with the interaction parameter k scaling linearly with the non-Curie-Weiss susceptibility.

Relaxation cracking in the process industry, an underestimated problem

Energy Technology Data Exchange (ETDEWEB)

Wortel, J.C. van [TNO Institute of Industrial Technology, Apeldoorn (Netherlands)

1999-12-31

Austenitic components, operating between 500 and 750 deg C, can fail within 1 year service while the ordinary mechanical properties after failure are still within the code requirements. The intergranular brittle failures are situated in the welded or cold deformed areas. This type of cracking has many names, showing the uncertainty concerning the mechanism for the (catastrophical) failures. A just finished investigation showed that it is a relaxation crack problem, introduced by manufacturing processes, especially welding and cold rolling. Cracking/failures can be expected after only 0.1- 0.2 % relaxation strain. These low strain values can already be generated during relaxation of the welding stresses. Especially coarse grained `age hardening` materials are susceptible. Stabilising and Postweld Heat Treatments are very effective to avoid relaxation crack problems during operation. After these heat treatments the components can withstand more than 2 % relaxation strain. At temperatures between 500 and 750 deg C relaxation cracking is the predominant factor for the safety and lifetime of welded austenitic components. (orig.) 12 refs.

Relaxation cracking in the process industry, an underestimated problem

Energy Technology Data Exchange (ETDEWEB)

Wortel, J.C. van [TNO Institute of Industrial Technology, Apeldoorn (Netherlands)

1998-12-31

Austenitic components, operating between 500 and 750 deg C, can fail within 1 year service while the ordinary mechanical properties after failure are still within the code requirements. The intergranular brittle failures are situated in the welded or cold deformed areas. This type of cracking has many names, showing the uncertainty concerning the mechanism for the (catastrophical) failures. A just finished investigation showed that it is a relaxation crack problem, introduced by manufacturing processes, especially welding and cold rolling. Cracking/failures can be expected after only 0.1- 0.2 % relaxation strain. These low strain values can already be generated during relaxation of the welding stresses. Especially coarse grained `age hardening` materials are susceptible. Stabilising and Postweld Heat Treatments are very effective to avoid relaxation crack problems during operation. After these heat treatments the components can withstand more than 2 % relaxation strain. At temperatures between 500 and 750 deg C relaxation cracking is the predominant factor for the safety and lifetime of welded austenitic components. (orig.) 12 refs.

Usefulness of T1 mapping on Gd-EOB-DTPA-enhanced MR imaging in assessment of non-alcoholic fatty liver disease

International Nuclear Information System (INIS)

Ding, Ying; Rao, Sheng-Xiang; Meng, Tao; Chen, Caizhong; Li, Renchen; Zeng, Meng-Su

2014-01-01

This study evaluates the value of Gd-EOB-DTPA-enhanced MRI for diagnosis and staging of non-alcoholic fatty liver disease (NAFLD) in an animal model by T 1 relaxation time measurement. Thirty-four rabbits were divided into the control group (n = 10) and NAFLD group, which was split into four groups (n = 6) with a high-fat diet for an interval of 3 weeks. A dual flip angle was performed before and at the hepatobiliary phase (HBP). T 1 relaxation times of the liver parenchyma and the decrease rate (∇%) were calculated. Histological findings according to semi-quantitative scoring of steatosis, activity and fibrosis were the standard of reference. HBP and ∇% T 1 relaxation time measurement showed significant differences between normal and NAFLD groups, between non-alcoholic steatohepatitis (NASH) and NAFLD without NASH (p = 0.000-0.049), between fibrosis groups (p = 0.000-0.019), but no difference between F1 and F2 (p = 0.834). The areas under the receiver operating characteristic curves (AUCs) of T 1 relaxation time for HBP and ∇% were 0.86-0.93 for the selection of NASH and activity score ≥2, and 0.86-0.95 for the selection of F ≥ 1, 2, 3. No significant difference was found for diagnostic performance between HBP and ∇% T 1 relaxation time. HBP T 1 relaxation time measurement of Gd-EOB-DTPA-enhanced MRI was useful to evaluate NAFLD according to the SAF score. HBP T 1 relaxation time measurement was as accurate as ∇% T 1 relaxation time. (orig.)

Human whole-blood (1)H2O longitudinal relaxation with normal and high-relaxivity contrast reagents: influence of trans-cell-membrane water exchange.

Science.gov (United States)

Wilson, Gregory J; Woods, Mark; Springer, Charles S; Bastawrous, Sarah; Bhargava, Puneet; Maki, Jeffrey H

2014-12-01

Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R1 ) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions. Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA. In plasma, the (1) H2 O R1 [CR]-dependence was nonlinear for gadobenate and gadofosveset secondary to CR interactions with the serum macromolecule albumin, and was well described by an analytical expression for effective 1:1 binding stoichiometry. In whole blood, the (1) H2 O R1 [CR]-dependence was markedly non-linear for all CRs, and was well-predicted by an expression for equilibrium exchange of water molecules between plasma and intracellular spaces using a priori parameter values only. In whole blood, (1) H2 O R1 exhibits a nonlinear relationship with [CR] over 0 to 18 mM CR. The nonlinearity is well described by exchange of water between erythrocyte and plasma compartments, and is particularly evident for high relaxivity CRs. © 2013 Wiley Periodicals, Inc.

Proton T2 relaxation effect of superparamagnetic iron oxide. Comparison between fast spin echo and conventional spin echo sequence

International Nuclear Information System (INIS)

Tanimoto, Akihiro; Satoh, Yoshinori; Higuchi, Nobuya; Izutsu, Mutsumu; Yuasa, Yuji; Hiramatsu, Kyoichi

1995-01-01

Superparamagnetic iron oxide (SPIO) particles have been known to show a great T 2 relaxation effect in the liver, which contributes to significant liver signal decrease and detection of hepatic neoplasms. Recently, fast spin echo (FSE) sequence with less scanning time than conventional spin echo (SE) sequence has been rapidly introduced in clinical MR imaging. To investigate whether SPIO would show decreased T 2 relaxation effect on FSE, we obtained T 2 relaxivity (R2) of SPIO in vitro and liver signal decrease caused by SPIO in vivo. SPIO showed 20% less R2 on Carr-Purcell-Meiboom-Gill (CPMG) sequence than on SE. Relative liver signal-to-noise ratio (SNR) decrease caused by SPIO was significantly smaller (p 2 relaxation effect on FSE than on SE. However, further studies will be required to assess the diagnostic capability of SPIO on FSE, in the detection of hepatic neoplasms. (author)

Determination of the longitudinal relaxation time (T{sub 1}) of the carbon for the caura-16-E N-19-oic acid; Determinacao do tempo de relaxacao longitudinal (T{sub 1}) do carbono para derivados do acido-caura-16-en-19-oico

Energy Technology Data Exchange (ETDEWEB)

Pinheiro, J A; Rodrigues, A S [Ceara Univ., Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica

1992-12-31

In this work, we analyse, through the {sup 13} C longitudinal relaxation time (T{sub 1}), the solute-solute and solute-solvent interactions in some molecules of the c aura-16-en-19-oic acid such as: c aura-16-en-19-oic acid (I), c aura-15-acetoxy-16-en-19-oic acid (II), methyl esther of the c aura-16-en-19-oic acid (III) and c aura-16-en-19-ol (IV) 5 refs., 1 fig., 1 tab.

Measurement of solute proton spin-lattice relaxation times in water using the 1,3,3,1 sequence

International Nuclear Information System (INIS)

Sankar, S.S.; Mole, P.A.; Coulson, R.L.

1986-01-01

1 H NMR spin-lattice relaxation times (T1) of the N-CH3 proton resonances of phosphocreatine (PCr) and creatine (Cr) in water solutions were obtained using the 1,3,3,1 pulse sequence. These T1 values were equivalent to those obtained in D 2 O and water using either the conventional inversion-recovery experiment or the 1,3,3,1 pulse sequence. Thus, the 1,3,3,1 sequence of proton NMR can provide an independent means along with phosphorous NMR for assess PCr and for the study of the creatine kinase reaction (PCr + ADP in equilibrium ATP + Cr) in aqueous solutions and perhaps in biological preparations

[A study on Korean concepts of relaxation].

Science.gov (United States)

Park, J S

1992-01-01

Relaxation technique is an independent nursing intervention used in various stressful situations. The concept of relaxation must be explored for the meaning given by the people in their traditional thought and philosophy. Korean relaxation technique, wanting to become culturally acceptable and effective, is learning to recognize and develop Korean concepts, experiences, and musics of relaxation. This study was aimed at discovering Korean concepts, experiences and musics of relaxation and contributing the development of the relaxation technique for Korean people. The subjects were 59 nursing students, 39 hospitalized patients, 61 housewives, 21 rural residents and 16 researchers. Data were collected from September 4th to October 24th, 1991 by interviews or questionnaires. The data analysis was done by qualitative research method, and validity assured by conformation of the concept and category by 2 nursing scientists who had written a Master's thesis on the relaxation technique. The results of the study were summarized as follows; 1. The meaning of the relaxation concept; From 298 statements, 107 concepts were extracted and then 5 categories "Physical domain", "Psychological domain", "Complex domain", "Situation", and "environment" were organized. 'Don't have discomforts, 'don't have muscle tension', 'don't have energy (him in Korean)', 'don't have activities' subcategories were included in "Physical domain". 'Don't have anxiety', 'feel good', 'emotional stability', 'don't have wordly thoughts', 'feel one's brain muddled', 'loss of desire' subcategories were included in "physical domain" 'Comfort body and mind', 'don't have tension of body and mind', 'be sagged' 'liveliness of thoughts' subcategories were included in "Complex domain". 'Rest', 'sleep', 'others' subcategories were included in "Situation domain". And 'quite environment' & 'comfortable environment' subcategories were included in "Environmental domain". 2. The experiences of the relaxation; From 151

Usefulness of T1 mapping on Gd-EOB-DTPA-enhanced MR imaging in assessment of non-alcoholic fatty liver disease

Energy Technology Data Exchange (ETDEWEB)

Ding, Ying; Rao, Sheng-Xiang; Meng, Tao; Chen, Caizhong; Li, Renchen; Zeng, Meng-Su [Zhongshan/Hospital of Fudan University, Department of Radiology, Shanghai (China)

2014-04-15

This study evaluates the value of Gd-EOB-DTPA-enhanced MRI for diagnosis and staging of non-alcoholic fatty liver disease (NAFLD) in an animal model by T{sub 1} relaxation time measurement. Thirty-four rabbits were divided into the control group (n = 10) and NAFLD group, which was split into four groups (n = 6) with a high-fat diet for an interval of 3 weeks. A dual flip angle was performed before and at the hepatobiliary phase (HBP). T{sub 1} relaxation times of the liver parenchyma and the decrease rate (∇%) were calculated. Histological findings according to semi-quantitative scoring of steatosis, activity and fibrosis were the standard of reference. HBP and ∇% T{sub 1} relaxation time measurement showed significant differences between normal and NAFLD groups, between non-alcoholic steatohepatitis (NASH) and NAFLD without NASH (p = 0.000-0.049), between fibrosis groups (p = 0.000-0.019), but no difference between F1 and F2 (p = 0.834). The areas under the receiver operating characteristic curves (AUCs) of T{sub 1} relaxation time for HBP and ∇% were 0.86-0.93 for the selection of NASH and activity score ≥2, and 0.86-0.95 for the selection of F ≥ 1, 2, 3. No significant difference was found for diagnostic performance between HBP and ∇% T{sub 1} relaxation time. HBP T{sub 1} relaxation time measurement of Gd-EOB-DTPA-enhanced MRI was useful to evaluate NAFLD according to the SAF score. HBP T{sub 1} relaxation time measurement was as accurate as ∇% T{sub 1} relaxation time. (orig.)

Over-relaxation phenomena during the set-up of RFP plasmas

International Nuclear Information System (INIS)

Nordlund, P.; Mazur, S.

1995-03-01

Experiments on the Extrap T1 reversed field pinch have shown that the formation of the RFP configuration is quite sensitive to the relative programming of the toroidal field and ohmic heating circuits. In this paper, new measurements of the evolution of the current density profile and of the spectral structure of the fluctuations during the set-up phase of RFP plasmas in the T1 experiment are presented. These measurements improve the understanding of the role of different spectral components in the dynamics of RFP formation. Under unfavourable (slow) set-up conditions, comparatively high energy is accumulated in m = 1 internal kinks prior to reversal of the edge toroidal fields. At reversal, nonlinearly driven m = 0 modes trigger a rapid broadening of the m = 1 spectrum. This behaviour is associated with a violent suppression of the current density in the core leading to an over-relaxation of the discharge involving a hollowing of the parallel current density profile. The over-relaxation phenomenon increases the volt-second consumption and plasma/wall interaction during RFP set-up, and degrades the flat-top discharge performance. 15 refs, 5 figs, 1 tab

Over-relaxation phenomena during the set-up of RFP plasmas

Energy Technology Data Exchange (ETDEWEB)

Nordlund, P.; Mazur, S.

1995-03-01

Experiments on the Extrap T1 reversed field pinch have shown that the formation of the RFP configuration is quite sensitive to the relative programming of the toroidal field and ohmic heating circuits. In this paper, new measurements of the evolution of the current density profile and of the spectral structure of the fluctuations during the set-up phase of RFP plasmas in the T1 experiment are presented. These measurements improve the understanding of the role of different spectral components in the dynamics of RFP formation. Under unfavourable (slow) set-up conditions, comparatively high energy is accumulated in m = 1 internal kinks prior to reversal of the edge toroidal fields. At reversal, nonlinearly driven m = 0 modes trigger a rapid broadening of the m = 1 spectrum. This behaviour is associated with a violent suppression of the current density in the core leading to an over-relaxation of the discharge involving a hollowing of the parallel current density profile. The over-relaxation phenomenon increases the volt-second consumption and plasma/wall interaction during RFP set-up, and degrades the flat-top discharge performance. 15 refs, 5 figs, 1 tab.

Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy

Science.gov (United States)

Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Bock, D.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

2017-04-01

We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one

Volumetric B1 (+) mapping of the brain at 7T using DREAM.

Science.gov (United States)

Nehrke, Kay; Versluis, Maarten J; Webb, Andrew; Börnert, Peter

2014-01-01

To tailor and optimize the Dual Refocusing Echo Acquisition Mode (DREAM) approach for volumetric B1 (+) mapping of the brain at 7T. A new DREAM echo timing scheme based on the virtual stimulated echo was derived to minimize potential effects of transverse relaxation. Furthermore, the DREAM B1 (+) mapping performance was investigated in simulations and experimentally in phantoms and volunteers for volumetric applications, studying and optimizing the accuracy of the sequence with respect to saturation effects, slice profile imperfections, and T1 and T2 relaxation. Volumetric brain protocols were compiled for different isotropic resolutions (5-2.5 mm) and SENSE factors, and were studied in vivo for different RF drive modes (circular/linear polarization) and the application of dielectric pads. Volumetric B1 (+) maps with good SNR at 2.5 mm isotropic resolution were acquired in about 20 s or less. The specific absorption rate was well below the safety limits for all scans. Mild flow artefacts were observed in the large vessels. Moreover, a slight contrast in the ventricle was observed in the B1 (+) maps, which could be attributed to T1 and T2 relaxation effects. DREAM enables safe, very fast, and robust volumetric B1 (+) mapping of the brain at ultrahigh fields. Copyright © 2013 Wiley Periodicals, Inc.

Spin dynamics of the itinerant helimagnet MnSi studied by positive muon spin relaxation

International Nuclear Information System (INIS)

Kadono, R.; Matsuzaki, T.; Yamazaki, T.; Kreitzman, S.R.; Brewer, J.H.

1990-03-01

The local magnetic fields and spin dynamics of the itinerant helimagnet MnSi(T c ≅ 29.5 K) have been studied experimentally using positive muon spin rotation/relaxation (μ + SR) methods. In the ordered phase (T c ), zero-field μSR was used to measure the hyperfine fields at the muon sites as well as the muon spin-lattice relaxation time T 1 μ . Two magnetically inequivalent interstitial μ + sites were found with hyperfine coupling constants A hf (1) = -3.94 kOe/μ B and A hf (2) = -6.94 kOe/μ B , respectively. In the paramagnetic phase (T > T c ), the muon-nuclear spin double relaxation technique was used to simultaneously but independently determine the spin-lattice relaxation time T 1 Mn of 55 Mn spins and that of positive muons (T 1 μ ) over a wide temperature range (T c 1 Mn and T 1 μ in both phases shows systematic deviations from the predictions of self-consistent renormalization (SCR) theory. (author)

Appearance of normal brain maturation on 1.5-T MR images

International Nuclear Information System (INIS)

Barkovich, A.J.; Kjos, B.; Jackson, D.E. Jr.; Norman, D.

1987-01-01

To investigate the pattern of normal white-matter maturation as demonstrated by high-field-strength MR imaging, 82 normal infants were examined using a 1.5-T unit with spin-echo T1-weighted and T2-weighted pulse sequences. The infants ranged in age from 4 days to 2 years. The scans were assessed for qualitative changes of white matter relative to gray matter and correlated with the patient's age in 14 anatomic areas of the brain. The MR images showed that changes of brain maturation occur in an orderly manner, commencing in the brain stem and progressing to the cerebellum and the cerebrum. Changes from brain myelination were seen earlier on T1-weighted images than on T2-weighted images, possibly because of T1 shortening by the components of the developing myelin sheaths. The later changes on the T2-weighted images correlated best with the development of myelination, as demonstrated by histochemical methods. T1-weighted images were most useful to monitor normal brain development in the first 6 to 8 months of life; T2-weighted images were more useful after 6 months. The milestones in the MR appearance of normal maturation of the brain are presented. The milestones in the MR appearance of normal maturation of the brain are presented. Persistent areas of long T2 relaxation times are seen superior and dorsal to the ventricular trigone in all infants examined and should not be mistaken for ischemic change

Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains

Science.gov (United States)

Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.

2016-10-01

We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.

Tunneling splitting of magnetic levels in Fe8 detected by 1H NMR cross relaxation

Science.gov (United States)

Furukawa, Y.; Aizawa, K.; Kumagai, K.; Ullu, R.; Lascialfari, A.; Borsa, F.

2003-05-01

Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12]ṡ[Br8ṡ9H2O], in short Fe8, have been performed at 1.5 K in a powder sample aligned along the main anisotropy z axis, as a function of a transverse magnetic field (i.e., perpendicular to the main easy axis z). A big enhancement of 1/T1 is observed over a wide range of fields (2.5-5 T), which can be attributed to the tunneling dynamics; in fact, when the tunneling splitting of the pairwise degenerate m=±10 states of the Fe8 molecule becomes equal to the proton Larmor frequency a very effective spin lattice relaxation channel for the nuclei is opened. The experimental results are explained satisfactorily by considering the distribution of tunneling splitting resulting from the distribution of the angles in the hard xy plane for the aligned powder, and the results of the direct diagonalization of the model Hamiltonian.

Measurements of spin-lattice relaxation time in mixed alkali halide crystals

International Nuclear Information System (INIS)

Tannus, A.

1983-01-01

Using magneto-optic techniques the ground state spin-lattice relaxation times (T1) of 'F' centers in mixed Alkali Halide cristals (KCl-KBr), was studied. A computer assisted system to optically measure short relaxation times (approx. = 1mS), was described. The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. The T1 magnetic field dependency at 2 K (up to 65 KGauss), was obtained as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behaviour of T1 in mixed cristals. The Direct Process results (T approx. = 2.0 K) compared against that theory shows that the main relaxation mecanism, up to 25 KGauss, continues to be phonon modulation of the hiperfine iteraction between F electrons and surrounding nuclei. (Author) [pt

Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T.

Science.gov (United States)

Meloni, Antonella; Hezel, Fabian; Positano, Vincenzo; Keilberg, Petra; Pepe, Alessia; Lombardi, Massimo; Niendorf, Thoralf

2014-06-01

Realizing the challenges and opportunities of effective transverse relaxation rate (R2 *) mapping at high and ultrahigh fields, this work examines magnetic field strength (B0 ) dependence and segmental artifact distribution of myocardial R2 * at 1.5, 3.0, and 7.0 T. Healthy subjects were considered. Three short-axis views of the left ventricle were examined. R2 * was calculated for 16 standard myocardial segments. Global and mid-septum R2 * were determined. For each segment, an artifactual factor was estimated as the deviation of segmental from global R2 * value. The global artifactual factor was significantly enlarged at 7.0 T versus 1.5 T (P = 0.010) but not versus 3.0 T. At 7.0 T, the most severe susceptibility artifacts were detected in the inferior lateral wall. The mid-septum showed minor artifactual factors at 7.0 T, similar to those at 1.5 and 3.0 T. Mean R2 * increased linearly with the field strength, with larger changes for global heart R2 * values. At 7.0 T, segmental heart R2 * analysis is challenging due to macroscopic susceptibility artifacts induced by the heart-lung interface and the posterior vein. Myocardial R2 * depends linearly on the magnetic field strength. The increased R2 * sensitivity at 7.0 T might offer means for susceptibility-weighted and oxygenation level-dependent MR imaging of the myocardium. Copyright © 2013 Wiley Periodicals, Inc.

Comparative study of the sensitivity of ADC value and T2 relaxation time for early detection of Wallerian degeneration

International Nuclear Information System (INIS)

Zhang Fan; Lu Guangming; Zee Chishing

2011-01-01

Background and purpose: Wallerian degeneration (WD), the secondary degeneration of axons from cortical and subcortical injuries, is associated with poor neurological outcome. There is some quantitative MR imaging techniques used to estimate the biologic changes secondary to delayed neuronal and axonal losses. Our purpose is to assess the sensitivity of ADC value and T 2 relaxation time for early detection of WD. Methods: Ten male Sprague-Dawley rats were used to establish in vivo Wallerian degeneration model of CNS by ipsilateral motor-sensory cortex ablation. 5 days after cortex ablation, multiecho-T 2 relaxometry and multi-b value DWI were acquired by using a 7 T MR imaging scanner. ADC-map and T 2 -map were reconstructed by post-processing. ROIs are selected according to pathway of corticospinal tract from cortex, internal capsule, cerebral peduncle, pons, medulla oblongata to upper cervical spinal cord to measure ADC value and T 2 relaxation time of healthy side and affected side. The results were compared between the side with cortical ablation and the side without ablation. Results: Excluding ablated cortex, ADC values of the corticospinal tract were significantly increased (P 2 relaxation time was observed between the affected and healthy sides. Imaging findings were correlated with histological examinations. Conclusion: As shown in this animal experiment, ADC values could non-invasively demonstrate the secondary degeneration involving descending white matter tracts. ADC values are more sensitive indicators for detection of early WD than T 2 relaxation time.

The relaxation phenomena of radicals induced in irradiated fresh mangoes

International Nuclear Information System (INIS)

Kikuchi, Masahiro; Morishita, Norio; Kobayashi, Yasuhiko; Ogawa, Hideyuki; Shimoyama, Yuhei; Ukai, Mitsuko

2009-01-01

Using the γ-irradiated fresh mangoes followed by freeze-drying and powderization, electron spin resonance spectrometry of specimens was performed. As a result, a strong single peak in the flesh, the pericarp and the seed was observed at g=2.004 and attributed to organic free radicals. When relaxation times of the peak was calculated using the method of Lund et al., T 2 showed dose responses according to increasing doses while T 1 was almost constant. Dose responsibility of the relaxation time T 2 obtained from flesh specimens of the mangoes could be measured regardless of the preservation period of 1 to 9 days following γ-irradiation. Therefore, there might be possible to detect the irradiation treatment of fresh mangoes using relaxation time T 2 . (author)

Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis

Science.gov (United States)

Mailhiot, Sarah E.; Zong, Fangrong; Maneval, James E.; June, Ronald K.; Galvosas, Petrik; Seymour, Joseph D.

2018-02-01

Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T1-T2 correlation experiments. By using time domain analysis of T2-T2 exchange spectroscopy, the diffusive exchange time can be quantified by measurements that use a single mixing time. Measured characteristic times for exchange are commensurate with T1 in this material and so impacts the observed T1 behavior. The approach used here allows for reliable quantification of NMR relaxation behavior in cartilage in the presence of diffusive fluid exchange between two environments.

Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

Science.gov (United States)

Marsh, Derek

2016-11-01

Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

Tunneling splitting of magnetic levels in Fe8 detected by 1H NMR cross relaxation

OpenAIRE

Furukawa, Y.; Aizawa, K.; Kumagai, K.; Ullu, R.; Lascialfari, A.; Borsa, F.

2003-01-01

Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12][Br8 9H2O], in short Fe8, have been performed at 1.5 K in a powder sample aligned along the main anisotropy z axis, as a function of a transverse magnetic field (i.e., perpendicular to the main easy axis z). A big enhancement of 1/T1 is observed over a wide range of fields (2.5-5 T), which can be attributed to the tunneling dynamics; in fact, when the tunneling spl...

The age dependence of T2 relaxation times of N-acetyl aspartate, creatine and choline in the human brain at 3 and 4T

Czech Academy of Sciences Publication Activity Database

Jirů, F.; Škoch, A.; Wágnerová, D.; Dezortová, M.; Visková, J.; Profant, Oliver; Syka, Josef; Hájek, M.

2016-01-01

Roč. 29, č. 3 (2016), s. 284-292 ISSN 0952-3480 Institutional support: RVO:68378041 Keywords : MRS * T2 relaxation times of metabolites * age dependence of T2 Subject RIV: FH - Neurology Impact factor: 2.872, year: 2016

13C NMR relaxation times of hepatic glycogen in vitro and in vivo

International Nuclear Information System (INIS)

Zang, Lihsin; Laughlin, M.R.; Rothman, D.L.; Shulman, R.G.

1990-01-01

The field dependence of relaxation times of the C-1 carbon of glycogen was studied in vitro by natural-abundance 13 C NMR. T 1 is strongly field dependent, while T 2 does not change significantly with magnetic field. T 1 and T 2 were also measured for rat hepatic glycogen enriched with [1- 13 C]glucose in vivo at 4.7 T, and similar relaxation times were observed as those obtained in vitro at the same field. The in vitro values of T 1 were 65 ± 5 ms at 2.1 T, 142 ± 10 ms at 4.7 T, and 300 ± 10 ms at 8.4 T, while T 2 values were 6.7 ± 1 ms at 2.1 T, 9.4 ± 1 ms at 4.7 T, and 9.5 ± 1 ms at 8.4 T. Calculations based on the rigid-rotor nearest-neighbor model give qualitatively good agreement with the T 1 field dependence with a best-fit correlation time of 6.4 x 10 -9 s, which is significantly smaller than τ M , the estimated overall correlation time for the glycogen molecule (ca. 10 -5 s). A more accurate fit of T 1 data using a modified Lipari and Szabo approach indicates that internal fast motions dominate the T 1 relaxation in glycogen. On the other hand, the T 2 relaxation is dominated by the overall correlation time τ M while the internal motions are almost but not completely unrestricted

Measurement of the Exchange Rate of Waters of Hydration in Elastin by 2D T(2)-T(2) Correlation Nuclear Magnetic Resonance Spectroscopy.

Science.gov (United States)

Sun, Cheng; Boutis, Gregory S

2011-02-28

We report on the direct measurement of the exchange rate of waters of hydration in elastin by T(2)-T(2) exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported. Using an Inverse Laplace Transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed allowing for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described elsewhere [1]) wherein the net entropy of bulk waters of hydration should increase upon increasing temperature in the inverse temperature transition.

Influence of age, BMI, gender and lumbar level on T1ρ magnetic resonance imaging of lumbar discs in healthy asymptomatic adults

Energy Technology Data Exchange (ETDEWEB)

Guebitz, Raphael [Asklepios Hospital Altona, Hamburg (Germany). Dept. of Radiology and Neuroradiology; Lange, Tobias; Gosheger, Georg [University Hospital Muenster (Germany). Dept. of Orthopaedics and Tumor Orthopaedics; Heindel, Walter; Allkemper, Thomas [University Hospital Muenster (Germany). Dept. of Clinical Radiology; Stehling, Christoph [Sankt-Barbara Hospital Ham-Heessen, Hamm (Germany). Clinic for Radiology and Neuroradiology; Gerss, Joachim [Muenster Univ. (Germany). Inst. of Biostatistics and Clinical Research; Kanthak, Christian [Fraunhofer MEVIS, Bremen (Germany). Inst. for Medical Image Computing; Schulte, Tobias L. [Bochum Univ. St. Josef Hospital (Germany). Dept. of Orthopaedics and Trauma Surgery

2018-02-15

To assess the T1ρ range of lumbar intervertebral discs in healthy asymptomatic individuals at 1.5 T and to investigate the influence of age, body mass index (BMI), gender, and lumbar level on T1ρ relaxation. In a prospective study, a total of 81 volunteers aged 20 - 80 years were included in this study and divided into three age groups (A: 20 - 39y; B: 40 - 59y; C: 60 - 80y). All of the volunteers underwent magnetic resonance imaging (MRI) at 1.5 T with acquisition of sagittal T1ρ images. The calculated T1ρ relaxation times were correlated with age, BMI, gender, and lumbar level relative to the total disc, the annulus fibrosus, and the nucleus pulposus. Age had a significant influence on T1ρ relaxation times at all lumbar levels, with increasing age being associated with reduced relaxation times. There was also a significant difference between age groups A vs. C and B vs. C (P = 0.0008 and P = 0.0149, respectively). No significant differences in T1ρ relaxation time were observed between men and women (P > 0.05). BMI showed a significant negative correlation with T1ρ relaxation times (P < 0.0001). Analysis of the lumbar level revealed a significant decrease in relaxation times from L1/2 to L5 / S1 (P = 0.0013). Increasing age correlated significantly with advanced lumbar disc degeneration in asymptomatic individuals, particularly in those aged 60 or older. Increasing BMI correlated significantly with increasing degeneration. The lower discs showed more degeneration than the upper ones.

Influence of age, BMI, gender and lumbar level on T1ρ magnetic resonance imaging of lumbar discs in healthy asymptomatic adults

International Nuclear Information System (INIS)

Guebitz, Raphael; Lange, Tobias; Gosheger, Georg; Heindel, Walter; Allkemper, Thomas; Stehling, Christoph; Gerss, Joachim; Kanthak, Christian; Schulte, Tobias L.

2018-01-01

To assess the T1ρ range of lumbar intervertebral discs in healthy asymptomatic individuals at 1.5 T and to investigate the influence of age, body mass index (BMI), gender, and lumbar level on T1ρ relaxation. In a prospective study, a total of 81 volunteers aged 20 - 80 years were included in this study and divided into three age groups (A: 20 - 39y; B: 40 - 59y; C: 60 - 80y). All of the volunteers underwent magnetic resonance imaging (MRI) at 1.5 T with acquisition of sagittal T1ρ images. The calculated T1ρ relaxation times were correlated with age, BMI, gender, and lumbar level relative to the total disc, the annulus fibrosus, and the nucleus pulposus. Age had a significant influence on T1ρ relaxation times at all lumbar levels, with increasing age being associated with reduced relaxation times. There was also a significant difference between age groups A vs. C and B vs. C (P = 0.0008 and P = 0.0149, respectively). No significant differences in T1ρ relaxation time were observed between men and women (P > 0.05). BMI showed a significant negative correlation with T1ρ relaxation times (P < 0.0001). Analysis of the lumbar level revealed a significant decrease in relaxation times from L1/2 to L5 / S1 (P = 0.0013). Increasing age correlated significantly with advanced lumbar disc degeneration in asymptomatic individuals, particularly in those aged 60 or older. Increasing BMI correlated significantly with increasing degeneration. The lower discs showed more degeneration than the upper ones.

Relaxation rates of low-field gas-phase ^129Xe storage cells

Science.gov (United States)

Limes, Mark; Saam, Brian

2010-10-01

A study of longitudinal nuclear relaxation rates T1 of ^129Xe and Xe-N2 mixtures in a magnetic field of 3.8 mT is presented. In this regime, intrinsic spin relaxation is dominated by the intramolecular spin-rotation interaction due to persistent xenon dimers, a mechanism that can be quelled by introducing large amounts of N2 into the storage cell. Extrinsic spin relaxation is dominated by the wall-relaxation rate, which is the primary quantity of interest for the various low-field storage cells and coatings that we have tested. Previous group work has shown that extremely long gas-phase relaxation times T1 can be obtained, but only at large magnetic fields and low xenon densities. The current work is motivated by the practical benefits of retaining hyperpolarized ^129Xe for extended periods of time in a small magnetic field.

The effects of bone on proton NMR relaxation times of surrounding liquids

Science.gov (United States)

Davis, C. A.; Genant, H. K.; Dunham, J. S.

1986-01-01

Preliminary attempts by our group at UCSF to assess fat content of vertebral marrow in the lumbar spine using relaxation time information demonstrated that the presence of trabecular bone affects relaxation times. The objective of this work was a thorough study of the effects of bone on NMR relaxation characteristics of surrounding liquids. Trabecular bone from autopsy specimens was ground up and sifted into a series of powders with graded densities ranging from 0.3 gm/cc to 0.8 gm/cc. Each powder was placed first in n-saline and then in cottonseed oil. With spectroscopy, spin-lattice relaxation times (T1) and effective spin-spin relaxation times (T2*) were measured for each liquid in each bone powder. As bone density and surface to volume ratio increased, T1 decreased faster for saline than for oil. T2* decreased significantly for both water and oil as the surface to volume ratio increased. It was concluded that effects of water on T1 could be explained by a surface interaction at the bone/liquid interface, which restricted rotational and translational motion of nearby molecules. The T1s of oil were not affected since oil molecules are nonpolar, do not participate in significant intermolecular hydrogen bonding, and therefore would not be expected to interact strongly with the bone surface. Effects on T2* could be explained by local magnetic field inhomogeneities created by discontinuous magnetic susceptibility near the bone surface. These preliminary results suggest that water in contact with trabecular bone in vivo will exhibit shortened relaxation times.

Spin Diffusion and Spin Lattice Relaxation of Dipolar Order in Solids Containing Paramagnetic Impurities

International Nuclear Information System (INIS)

Furman, G.B.; Panich, A.M.; Goren, S.D.

1998-01-01

The phenomena of spin diffusion and spin lattice relaxation of nuclear dipolar order in solids containing paramagnetic impurities (PI) is considered. We show that at the beginning of the relaxation process the diffusion vanishing regime realizes with non-exponential time dependence, R(t) ∼ exp [- (t/T 1d ) α ], where T 1d ∼ C p -1/α , C p is PI's concentration. For a homogeneous distribution of Pis and nuclear spins, α=Q/6, where Q is the sample dimensionality; for an inhomogeneous distribution, the sample is divided into q-dimensional subsystems, each containing one PI, yield- ing α= (Q + q) /6. This result coincides with experimental data for CaF 2 doped with 0.8 - 10 -3 ωt % of Mn 2+ , where the non-exponential decay of the dipolar signal with α= 0.83 has been observed [3]. Fitting the experimental data yields a good agreement with T 1d = 66 ms . For another independent check of the obtained results we use dependence of the relaxation time on impurities concentration. In accordance that 1/α=1.2 , we have T 1d ∼ C p -1 '. 2 . Exactly this dependence on impurity concentration of the relaxation time has been found in the experiment. Then the relaxation regime starts as a non-exponential time dependent, proceed asymptotically to an to an exponential function of time, to so called diffusion limited relaxation regime with relaxation time T 1d D is inversely depends on impurities concentration. This kind of relaxation behavior of the dipolar order takes place in the experiment [2]. Using experimental results [2] from this two regime we can estimate the diffusion coefficient of the nuclear dipolar order in CaF 2 , which gives for typical values of impurity concentration C p ∼ 10 18 cm 3 the diffusion coefficient of dipolar order in the interval D ∼ 10 -11 -i- 10 -12 cm 2 /sec which is coincide to the case of Zeeman energy spin diffusion

Hydrogen-1 NMR relaxation time studies in membrane: anesthetic systems

International Nuclear Information System (INIS)

Pinto, L.M.A.; Fraceto, L.; Paula, E. de; Franzoni, L.; Spisni, A.

1997-01-01

The study of local anesthetics'(LA) interaction with model phospholipid membranes is justified by the direct correlation between anesthetic's hydrophobicity and its potency/toxicity. By the same reason, uncharged LA species seems to play a crucial role in anesthesia. Most clinically used LA are small amphiphilics with a protonated amine group (pKa around 8). Although both charged (protonated) and uncharged forms can coexist at physiological pH, it has been shown (Lee, Biochim. Biophys. Acta 514:95, 1978; Screier et al. Biochim. Biophys. Acta 769:231, 1984) that the real anesthetic pka can be down-shifted, due to differential partition into membranes, increasing the ratio of uncharged species at pH 7.4. We have measured 1 H-NMR longitudinal relaxation times (T 1 ) for phospholipid and three local anesthetics (tetracaine, lidocaine, benzocaine), in sonicated vesicles at a 3:1 molar ratio. All the LA protons have shown smaller T 1 in this system than in isotropic phases, reflecting LA immobilization caused by insertion in the membrane. T 1 values for the lipid protons in the presence of LA were analyzed, in an attempt to identify specific LA:lipid contact regions. (author)

T-stresses for internally cracked components

International Nuclear Information System (INIS)

Fett, T.

1997-12-01

The failure of cracked components is governed by the stresses in the vicinity of the crack tip. The singular stress contribution is characterised by the stress intensity factor K, the first regular stress term is represented by the so-called T-stress. T-stress solutions for components containing an internal crack were computed by application of the Bundary Collocation Method (BCM). The results are compiled in form of tables or approximative relations. In addition a Green's function of T-stresses is proposed for internal cracks which enables to compute T-stress terms for any given stress distribution in the uncracked body. (orig.) [de

Single-shot T1 mapping of the corpus callosum: A rapid characterization of fiber bundle anatomy

Directory of Open Access Journals (Sweden)

Sabine eHofer

2015-05-01

Full Text Available Using diffusion-tensor MRI and fiber tractography the topographic organization of the corpus callosum (CC has been described to comprise 5 segments with fibers projecting into prefrontal (I, premotor and supplementary motor (II, primary motor (III, and primary sensory areas (IV, as well as into parietal, temporal, and occipital cortical areas (V. In order to more rapidly characterize the underlying anatomy of these segments, this study used a novel single-shot T1 mapping method to quantitatively determine T1 relaxation times in the human CC. A region-of-interest analysis revealed a tendency for the lowest T1 relaxation times in the genu and the highest T1 relaxation times in the somatomotor region of the CC. This observation separates regions dominated by myelinated fibers with large diameters (somatomotor area from densely packed smaller axonal bundles (genu with less myelin. The results indicate that characteristic T1 relaxation times in callosal profiles provide an additional means to monitor differences in fiber anatomy, fiber density, and gray matter in respective neocortical areas. In conclusion, rapid T1 mapping allows for a characterization of the axonal architecture in an individual CC in less than 10 s. The approach emerges as a valuable means for studying neocortical brain anatomy with possible implications for the diagnosis of neurodegenerative processes.

Nuclear spin-lattice relaxation in nitroxide spin-label EPR

DEFF Research Database (Denmark)

Marsh, Derek

2016-01-01

that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), preserves...... of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14N-relaxation: T1 n = 1/Wn. Results are compared and contrasted...

Measuring hepatic functional reserve using T1 mapping of Gd-EOB-DTPA enhanced 3T MR imaging: A preliminary study comparing with 99mTc GSA scintigraphy and signal intensity based parameters.

Science.gov (United States)

Nakagawa, Masataka; Namimoto, Tomohiro; Shimizu, Kie; Morita, Kosuke; Sakamoto, Fumi; Oda, Seitaro; Nakaura, Takeshi; Utsunomiya, Daisuke; Shiraishi, Shinya; Yamashita, Yasuyuki

2017-07-01

To determine the utility of liver T1-mapping on gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) enhanced magnetic resonance (MR) imaging for the measurement of liver functional reserve compared with the signal intensity (SI) based parameters, technetium-99m-galactosyl serum albumin ( 99m Tc-GSA) scintigraphy and indocyanine green (ICG) clearance. This retrospective study included 111 patients (Child-Pugh-A 90; -B 21) performed with both Gd-EOB-DTPA enhanced liver MR imaging and 99m Tc-GSA (76 patients with ICG). Receiver operating characteristic (ROC) curve analysis was performed to compare diagnostic performances of T1-relaxation-time parameters [pre-(T1pre) and post-contrast (T1hb) Gd-EOB-DTPA], SI based parameters [relative enhancement (RE), liver-to-muscle-ratio (LMR), liver-to-spleen-ratio (LSR)] and 99m Tc-GSA scintigraphy blood clearance index (HH15)] for Child-Pugh classification. Pearson's correlation was used for comparisons among T1-relaxation-time parameters, SI-based parameters, HH15 and ICG. A significant difference was obtained for Child-Pugh classification with T1hb, ΔT1, all SI based parameters and HH15. T1hb had the highest AUC followed by RE, LMR, LSR, ΔT1, HH15 and T1pre. The correlation coefficients with HH15 were T1pre 0.22, T1hb 0.53, ΔT1 -0.38 of T1 relaxation parameters; RE -0.44, LMR -0.45, LSR -0.43 of SI-based parameters. T1hb was highest for correlation with HH15. The correlation coefficients with ICG were T1pre 0.29, T1hb 0.64, ΔT1 -0.42 of T1 relaxation parameters; RE -0.50, LMR -0.61, LSR -0.58 of SI-based parameters; 0.64 of HH15. Both T1hb and HH15 were highest for correlation with ICG. T1 relaxation time at post-contrast of Gd-EOB-DTPA (T1hb) was strongly correlated with ICG clearance and moderately correlated HH15 with 99m Tc-GSA. T1hb has the potential to provide robust parameter of liver functional reserve. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of multi-exponential relaxation processes: In vitro and in vivo studies

International Nuclear Information System (INIS)

Henriksen, O.; Thomsen, C.; Kjaer, L.; Ring, P.

1986-01-01

T1 and T2 relaxation values obtained at 1.5 T were measured on 12 inversion-recovery (IR) sequences and a multiple spin-echo (SE) sequence with 32 echoes. Phantom studies were carried out for different CuSO/sub 4/ solutions, using MR imaging and reference spectrometry. The correlation was excellent (r=.98, P>.01;r=1.00, P>.01). T1 and T2 values varied less than 10% in the imaging plane. Then two-compartment phantoms were examined. For T1 and T2, the ratios T1(compartment A)/T1 (compartment B)>6 ant T2(c.A)/T2(c.B) > 6 were essential for reliable estimation. Studies on the normal brain indicate a multiexponential T1 and T2 relaxation process in gray matter

Comparative study of the sensitivity of ADC value and T{sub 2} relaxation time for early detection of Wallerian degeneration

Energy Technology Data Exchange (ETDEWEB)

Zhang Fan [Department of Radiology, Nanjing Jinling Hospital, Clinical School of Medical College of Nanjing University, Nanjing 210002 (China); Lu Guangming, E-mail: cjr.luguangming@vip.163.com [Department of Radiology, Nanjing Jinling Hospital, Clinical School of Medical College of Nanjing University, Nanjing 210002 (China); Zee Chishing, E-mail: chishing@usc.edu [Department of Radiology, USC Keck School of Medicine (United States)

2011-07-15

Background and purpose: Wallerian degeneration (WD), the secondary degeneration of axons from cortical and subcortical injuries, is associated with poor neurological outcome. There is some quantitative MR imaging techniques used to estimate the biologic changes secondary to delayed neuronal and axonal losses. Our purpose is to assess the sensitivity of ADC value and T{sub 2} relaxation time for early detection of WD. Methods: Ten male Sprague-Dawley rats were used to establish in vivo Wallerian degeneration model of CNS by ipsilateral motor-sensory cortex ablation. 5 days after cortex ablation, multiecho-T{sub 2} relaxometry and multi-b value DWI were acquired by using a 7 T MR imaging scanner. ADC-map and T{sub 2}-map were reconstructed by post-processing. ROIs are selected according to pathway of corticospinal tract from cortex, internal capsule, cerebral peduncle, pons, medulla oblongata to upper cervical spinal cord to measure ADC value and T{sub 2} relaxation time of healthy side and affected side. The results were compared between the side with cortical ablation and the side without ablation. Results: Excluding ablated cortex, ADC values of the corticospinal tract were significantly increased (P < 0.05) in affected side compared to the unaffected, healthy side; no difference in T{sub 2} relaxation time was observed between the affected and healthy sides. Imaging findings were correlated with histological examinations. Conclusion: As shown in this animal experiment, ADC values could non-invasively demonstrate the secondary degeneration involving descending white matter tracts. ADC values are more sensitive indicators for detection of early WD than T{sub 2} relaxation time.

Spin relaxation of iron in mixed state hemoproteins

International Nuclear Information System (INIS)

Wajnberg, E.; Kalinowski, H.J.; Bemski, G.; Helman, J.S.

1984-01-01

In pure states hemoproteins the relaxation of iron depends on its spin state. It is found that in both mixed state met-hemoglobin and met-myoglobin, the low and high spin states relax through an Orbach-like process. Also, very short (approx. 1 ns) and temperature independent transverse relaxation times T 2 were estimated. This peculiar behaviour of the relaxation may result from the unusual electronic structure of mixed state hemoproteins that allows thermal equilibrium and interconversion of the spin states. (Author) [pt

Is the T1ρ MRI profile of hyaline cartilage in the normal hip uniform?

Science.gov (United States)

Rakhra, Kawan S; Cárdenas-Blanco, Arturo; Melkus, Gerd; Schweitzer, Mark E; Cameron, Ian G; Beaulé, Paul E

2015-04-01

T1ρ MRI is an imaging technique sensitive to proteoglycan (PG) content of hyaline cartilage. However, normative T1ρ values have not been established for the weightbearing cartilage of the hip, and it is not known whether it is uniform or whether there is topographic variation. Knowledge of the T1ρ profile of hyaline cartilage in the normal hip is important for establishing a baseline against which comparisons can be made to experimental and clinical arthritic subjects. In this diagnostic study, we determined (1) the T1ρ MRI values of hyaline cartilage of the normal hip; and (2) whether the T1ρ MRI profile of the normal hip hyaline cartilage is uniform. Fourteen asymptomatic volunteers (11 men, three women; mean age, 35 years) prospectively underwent 1.5-T T1ρ MRI of a single hip. The weightbearing hyaline cartilage bilayer of the acetabulum and femoral head was evaluated on sagittal images and segmented into four zones: (1) anterior; (2) anterosuperior; (3) posterosuperior; and (4) and posterior. For the full region of interest and within each zone and each sagittal slice, we calculated the mean T1ρ relaxation value, a parameter that indirectly quantifies PG content, where T1ρ is inversely related to PG concentration. There was variation in the T1ρ relaxation values depending on zone (anterior to posterior) and slice (medial to lateral). When combining the most anterior quadrants (Zones 1 and 2), the T1ρ relaxation values were lower than those in the combined posterior quadrants (Zones 3 and 4) (30.4 msec versus 32.2 msec, respectively; p = 0.002), reflecting higher PG concentration. There was a difference between the T1ρ relaxation values of the sagittal slices (p = 0.038), most pronounced anteriorly in Zone 1 (26.6 msec, p = 0.001). With a selective combination of zones and slices, there were lower mean T1ρ values in the anterolateral-most region compared with the remainder of the weightbearing portion of the hip (28.6 msec versus 32.2 msec

Measurements of T1 and T2 over time in formalin-fixed human whole-brain specimens

International Nuclear Information System (INIS)

Tovi, M.; Ericsson, A.

1992-01-01

T1 and T2 were measured in 5 formalin-fixed human whole-brain specimens as a function of time. Gray matter/white matter contrast reversal was observed around the 4th day and was considered to be due to the greater decrease in T1 in gray than in white matter. A possible explanation for this is that the decomposition of the myelin phospholipid structure by formalin somewhat counteracts the general reductive effect of the fixation procedure on relaxation times. (orig.)

Hydration water dynamics in biopolymers from NMR relaxation in the rotating frame.

Science.gov (United States)

Blicharska, Barbara; Peemoeller, Hartwig; Witek, Magdalena

2010-12-01

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme). Copyright © 2010 Elsevier Inc. All rights reserved.

Faster metabolite (1H transverse relaxation in the elder human brain.

Directory of Open Access Journals (Sweden)

Małgorzata Marjańska

Full Text Available (1H magnetic resonance spectroscopy (MRS is unique among imaging modalities because signals from several metabolites are measured during a single examination period. Each metabolite reflects a distinct intracellular process. Furthermore transverse (T2 relaxation times probe the viability of the cell microenvironment, e.g., the viscosity of the cellular fluids, the microscopic susceptibility distribution within the cells, and the iron content. In this study, T2s of brain metabolites were measured in the occipital lobe of eighteen young and fourteen elderly subjects at a field strength of 4 tesla. The T2s of N-acetylaspartate, total creatine, and total choline were 23%, 16% and 10% shorter in elderly than in young subjects. The findings of this study suggest that noninvasive detection of T2 provides useful biological information on changes in the cellular microenvironment that take place during aging.

Assessing liver function in patients with HBV-related HCC: a comparison of T{sub 1} mapping on Gd-EOB-DTPA-enhanced MR imaging with DWI

Energy Technology Data Exchange (ETDEWEB)

Ding, Ying; Rao, Sheng-Xiang; Chen, Caizhong; Li, Renchen; Zeng, Meng-Su [Zhongshan Hospital of Fudan University, Department of Radiology, 180 Fenglin Road, Xuhui District, Shanghai (China)

2015-05-01

To compare the potential of T{sub 1} mapping on gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) for assessing liver function in patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). One hundred consecutive patients with known HBV-related HCCs were included. T{sub 1} relaxation time and apparent diffusion coefficient (ADC) of the liver were measured, and the reduction rate of T{sub 1} relaxation time (∇%) was calculated. T{sub 1} relaxation time measurements were compared with ADC values according to the Model for End-Stage Liver Disease (MELD) score. Hepatobiliary phase (HBP) and ∇% of T{sub 1} relaxation time measurements showed significant correlations with MELD score (rho = 0.571, p < 0.0001; rho = -0.573, p < 0.0001, respectively). HBP and ∇% of T{sub 1} relaxation time were significantly different between good (MELD ≤8) and poor liver function (MELD ≥9) (p < 0.0001 for both). Areas under the receiver operating characteristic curves (AUCs) of T{sub 1} relaxation time for HBP (AUC 0.84) and ∇% (AUC 0.82) were significantly better than for ADC (AUC 0.53; p < 0.0001). T{sub 1} mapping on Gd-EOB-DTPA-enhanced MRI showed promise for evaluating liver function in patients with HBV-related HCC, while DWI was not reliable. HBP T{sub 1} relaxation time measurement was equally accurate as ∇% measurement. (orig.)

Relaxation of nuclear spin on holes in semiconductors

International Nuclear Information System (INIS)

Gr'ncharova, E.I.; Perel', V.I.

1977-01-01

The longitudienal relaxation time T 1 of nuclear spins due to dipole-dipole interaction with holes in semiconductors is calculated. Expressions for T 1 in cubic and uniaxial semiconductors are obtained for non-degenerate and degenerate cases. On the basis of comparison with available experimental data for silicon the agreement with the theoretical results is obtained. It is demonstrated that in uniaxial semiconductors the time of relaxation on holes for a nuclear spin directed along the c axis is considerably greater than that for a spin in the normal direction

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability.

Science.gov (United States)

Fedorenko, Svetlana V; Grechkina, Svetlana L; Mustafina, Asiya R; Kholin, Kirill V; Stepanov, Alexey S; Nizameev, Irek R; Ismaev, Ildus E; Kadirov, Marsil K; Zairov, Rustem R; Fattakhova, Alfia N; Amirov, Rustem R; Soloveva, Svetlana E

2017-01-01

The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40-55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM -1 s -1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T 1 - weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents. Copyright © 2016 Elsevier B.V. All rights reserved.

Slow relaxation in weakly open rational polygons.

Science.gov (United States)

Kokshenev, Valery B; Vicentini, Eduardo

2003-07-01

The interplay between the regular (piecewise-linear) and irregular (vertex-angle) boundary effects in nonintegrable rational polygonal billiards (of m equal sides) is discussed. Decay dynamics in polygons (of perimeter P(m) and small opening Delta) is analyzed through the late-time survival probability S(m) approximately equal t(-delta). Two distinct slow relaxation channels are established. The primary universal channel exhibits relaxation of regular sliding orbits, with delta=1. The secondary channel is given by delta>1 and becomes open when m>P(m)/Delta. It originates from vertex order-disorder dual effects and is due to relaxation of chaoticlike excitations.

Effects of spin vacancies on the correlated spin dynamics in La2Cu1-xZnxO4 from 63Cu nuclear quadrupole resonance relaxation

International Nuclear Information System (INIS)

Carretta, P.; Rigamonti, A.; Sala, R.

1997-01-01

63 Cu nuclear quadrupole resonance (NQR) relaxation measurements in La 2 CuO 4 doped Zn are used in order to investigate the temperature dependence of the in-plane magnetic correlation length ξ 2D and the effects associated to spin vacancies in two dimensional quantum Heisenberg antiferromagnets (QHAF). The relaxation rates T 1 -1 and T 2 -1 have been related to the static generalized susceptibility χ(q,0) and to the decay rate Γ q of the normal excitations. By using scaling arguments for χ(q,0) and Γ q , the relaxation rates have been expressed in close form in terms of ξ 2D (x,T) and its dependence on temperature and spin doping x thus extracted. The experimental findings are analyzed in light of the renormalized classical (RC) and quantum critical (QC) behaviors predicted for ξ 2D by recent theories for S=1/2 HAF in square lattices. It is first shown that in pure La 2 CuO 4 , ξ 2D is consistent with a RC regime up to about 900 K, with tendency toward the QC regime above. The spin vacancies reduce the Nacute eel temperature according to the law T N (x)∼T N (0)(1 3.5x). From the temperature dependence of 63 Cu NQR relaxation rate T 1 -1 , T 2 -1 and from the composition dependence of T N it is consistently proved that the effect on ξ 2D can be accounted for by the modification of the spin stiffness in a simple dilutionlike model, the system still remaining in the RC regime, at least for T≤900 K. copyright 1997 American Institute of Physics

Contrast visibility for indirect MR arthrography with different protein contents and agent relaxivities at different field strengths: An in vitro model

International Nuclear Information System (INIS)

Nouh, M.R.; Schweitzer, M.E.; Ragatte, Ravinder R.

2011-01-01

Objectives: Protein binding and relaxivity are major determinants of the relative effectiveness of an MR arthrographic contrast agent. We sought to evaluate the optimal concentrations of high and usual relaxivity agents in two different proteinous environments at variable field strength for two MR contrast agents of different relaxivities. Materials and methods: At 1.5, 3.0 and 7.0 T, gadobenate dimeglumine (Multihance) with high-relaxivity in proteinous environment and gadoteridol (Prohance) with more typical behavior were studied at 1.25, 2.5, 5, and 10 mmol in 1.7 g/dL and 3 g/dL albumin (mimicking protein content of normal and inflammatory synovial fluids, respectively) vs. pure normal saline, as a control. Analysis of image signal intensity (SI) and relaxivity values was done. Results: In our study a change in concentration had no significant effect on T1 SI. In contrast, nearly every change in concentration led to a significant change in T2 SI. In 1.25 mmol concentration, there was no effect on T1 SI of either protein concentrations while higher concentrations showed significant decreased SI in either protein carrier compared to saline. The SI of Gadoteridol was significantly higher (p < 0.0001) than that of gadobenate at each of 3 T and 7 T, but was significantly lower (p < 0.001) at 1.5 T in saline solution while this was not significant for either protein carrier. Both protein carriers had significant effect on T1 (p = 0.0124) and T2 (p = 0.0118) relaxivities. Also solution concentration significantly (p < 0.01) affected both T1 and T2 relaxivities. Field strength did not affect T1 relaxivity (p = 0.02511) while it significantly affected T2 relaxivity (p < 0.001). This was significant (p = 0.035) in case of gadoteridol at 3 T. Conclusion: 1.25 mmol concentration of both gadoteridol and gadobenate solutions yields the best diagnostic T1 SI specially in higher fields (3 T and 7 T) and avoid the deleterious effect of increasing concentration on T2 SI

Nuclear Spin relaxation mediated by Fermi-edge electrons in n-type GaAs

Science.gov (United States)

Kotur, M.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Namozov, B. R.; Pak, P. E.; Kusrayev, Yu. G.

2014-03-01

A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T 1 in semiconductors. It was applied to bulk n-type GaAs, where T 1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with n D = 9 × 1016 cm-3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T 1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.

Relaxation of ion energy spectrum just after turbulent heating pulse in TRIAM-1 tokamak

International Nuclear Information System (INIS)

Nakamura, Kazuo; Hiraki, Naoji; Nakamura, Yukio; Itoh, Satoshi

1982-01-01

The temporal evolution and spatial profile of the ion energy spectrum just after the application of a toroidal current pulse for turbulent heating are investigated experimentally in the TRIAM-1 tokamak and also numerically using the Fokker-Planck equation. The two-component ion energy spectrum formed by turbulent heating relaxes to a single one within tausub(i) (the ion collision time). (author)

Relaxation of ion energy spectrum just after turbulent heating pulse in TRIAM-1 tokamak

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Kazuo; Hiraki, Naoji; Nakamura, Yukio; Itoh, Satoshi [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1982-07-01

The temporal evolution and spatial profile of the ion energy spectrum just after the application of a toroidal current pulse for turbulent heating are investigated experimentally in the TRIAM-1 tokamak and also numerically using the Fokker-Planck equation. The two-component ion energy spectrum formed by turbulent heating relaxes to a single one within tausub(i) (the ion collision time).

Effect of Temper Condition on Stress Relaxation Behavior of an Aluminum Copper Lithium Alloy

Science.gov (United States)

Mishra, Sumeet; Beura, Vikrant Kumar; Singh, Amit; Yadava, Manasij; Nayan, Niraj

2018-04-01

Deformation behavior of an Al-Cu-Li alloy in different temper conditions (solutionized and T8) is investigated using stress relaxation tests. Fundamental parameters such as the apparent and physical activation volume, strain rate sensitivity, effective stress, and exhaustion rate of mobile dislocation density are determined from single and multiple relaxation tests. It was found that dislocation-dislocation interaction controls the kinetics of plastic deformation in the solutionized sample, whereas dislocation-precipitate interaction is the overriding factor in the presence of T1 precipitates. The apparent activation volume was found to be significantly lower in the presence of T1 precipitates compared with solutionized samples. Strain rate sensitivity and effective stress were found to be higher in the presence of T1 precipitates. In addition, multiple relaxation tests showed that irrespective of microstructural features (solutes, semi-coherent precipitates), the mobile dislocation density reduces during the relaxation period. Further evidence regarding reduction in mobile dislocation density is obtained from uniaxial tensile tests carried out after stress relaxation tests, where both solutionized and T8 samples show an increase in strength. Additional discussion on relaxation strain is included to provide a complete overview regarding the time-dependent deformation behavior of the Al-Cu-Li alloy in different temper conditions.

T1ρ magnetic resonance: basic physics principles and applications in knee and intervertebral disc imaging

NARCIS (Netherlands)

Wáng, Yì-Xiáng J.; Zhang, Qinwei; Li, Xiaojuan; Chen, Weitian; Ahuja, Anil; Yuan, Jing

2015-01-01

T1ρ relaxation time provides a new contrast mechanism that differs from T1- and T2-weighted contrast, and is useful to study low-frequency motional processes and chemical exchange in biological tissues. T1ρ imaging can be performed in the forms of T1ρ-weighted image, T1ρ mapping and T1ρ dispersion.

Determination of the magnetic impurities contribution to the nuclear relaxation in metals

International Nuclear Information System (INIS)

Cohen, A.M.

1982-01-01

The renormalization group techniques developed by Wilson for the Kondo problem are applied, for the first time, to the calculation of nuclear spin relaxation rates in dilute magnetic alloys. A procedure that calculates the longitudinal relaxation time T 1 over the entire temperature range 0 B T 1 is derived; for distances R between the impurity and the nucleus large compared to the inverse Fermi momentum H f , the result is identical to Korringa's expression for the nuclear spin relaxation rate in the pure metal. For smaller k F R, T 1 increases and becomes infinite as k F R→0. A numerical approach, capable of calculating T 1 at finite temperatures, is presented and tested by calculating T 1 for T→0; the numerical results are in excellent agreement with the analytical expression discussed above. Only for k F R→ infinity do the results for T 1 at T=0 agree with those found by Roshen and Saam, who recently analysed this problem in the light of Nozieres's Fermi liquid theory. The reasons for the discrepancy for finite k F R are discussed. (author) [pt

Enhancement of relaxation rates in the normal state of superconductor PuRhGa5:NQR relaxation study

International Nuclear Information System (INIS)

Sakai, H.; Kambe, S.; Tokunaga, Y.; Fujimoto, T.; Walstedt, R.E.; Yasuoka, H.; Aoki, D.; Homma, Y.; Yamamoto, E.; Nakamura, A.; Shiokawa, Y.; Nakajima, K.; Arai, Y.; Matsuda, T.D.; Haga, Y.; Onuki, Y.

2007-01-01

The spin-lattice relaxation rates (1/T 1 ) have been measured under zero field using nuclear quadrupole resonance (NQR) lines in superconductor PuRhGa 5 and Pauli-paramagnet LuCoGa 5 . In the reference LuCoGa 5 with fully-occupied 4f shell, the 1/T 1 shows the constant behavior of (T 1 T) -1 =0.495+/-0.002(sK) -1 . On the other hand, in PuRhGa 5 , 1/T 1 is much larger than in LuCoGa 5 and the 1/T 1 ∝T behavior below ∼30K is seen, where its (T 1 T) -1 value is 3.27+/-0.005(sK) -1 . These results suggest a development of coherent Fermi liquid state incorporated with 5f electrons below ∼30K in PuRhGa 5

Patellofemoral instability in children: T2 relaxation times of the patellar cartilage in patients with and without patellofemoral instability and correlation with morphological grading of cartilage damage

International Nuclear Information System (INIS)

Kang, Chang Ho; Kim, Hee Kyung; Shiraj, Sahar; Anton, Christopher; Kim, Dong Hoon; Horn, Paul S.

2016-01-01

Patellofemoral instability is one of the most common causes of cartilage damage in teenagers. To quantitatively evaluate the patellar cartilage in patients with patellofemoral instability using T2 relaxation time maps (T2 maps), compare the values to those in patients without patellofemoral instability and correlate them with morphological grades in patients with patellofemoral instability. Fifty-three patients with patellofemoral instability (mean age: 15.9 ± 2.4 years) and 53 age- and gender-matched patients without patellofemoral instability were included. Knee MR with axial T2 map was performed. Mean T2 relaxation times were obtained at the medial, central and lateral zones of the patellar cartilage and compared between the two groups. In the patellofemoral instability group, morphological grading of the patellar cartilage (0-4) was performed and correlated with T2 relaxation times. Mean T2 relaxation times were significantly longer in the group with patellofemoral instability as compared to those of the control group across the patellar cartilage (Student's t-test, P<0.05) with the longest time at the central area. Positive correlation was seen between mean T2 relaxation time and morphological grading (Pearson correlation coefficiency, P<0.001). T2 increased with severity of morphological grading from 0 to 3 (mixed model, P<0.001), but no statistical difference was seen between grades 3 and 4. In patellofemoral instability, patellar cartilage damage occurs across the entire cartilage with the highest T2 values at the apex. T2 relaxation times directly reflect the severity in low-grade cartilage damage, which implies an important role for T2 maps in differentiating between normal and low-grade cartilage damage. (orig.)

Proton relaxation relationships of human and animal tissues in vitro. Changes due to autolysis and fixing

International Nuclear Information System (INIS)

Grodd, W.; Schmitt, W.G.H.

1983-01-01

The results of measurements of proton relaxation times of various tissues from rats, pigs and humans are reported; these were obtained by a resonance spectroscope at 20 MHz and 40 0 C. There were specific differences in both relaxation times (T 1 and T 2 ) of the liver and spleen. There was a difference of more than 150 ms in the longitudinal relaxation time between grey and white cerebral tissue. Autolytic changes show an increase in both relaxation times. Fixation produced a reduction in T 1 only. The significance of these findings for NMR tomography is discussed. (orig.) [de

Ferromagnetism versus slow paramagnetic relaxation in Fe-doped Li3N

Science.gov (United States)

Fix, M.; Jesche, A.; Jantz, S. G.; Bräuninger, S. A.; Klauss, H.-H.; Manna, R. S.; Pietsch, I. M.; Höppe, H. A.; Canfield, P. C.

2018-02-01

We report on isothermal magnetization, Mössbauer spectroscopy, and magnetostriction as well as temperature-dependent alternating-current (ac) susceptibility, specific heat, and thermal expansion of single crystalline and polycrystalline Li2(Li1 -xFex) N with x =0 and x ≈0.30 . Magnetic hysteresis emerges at temperatures below T ≈50 K with coercivity fields of up to μ0H =11.6 T at T =2 K and magnetic anisotropy energies of 310 K (27 meV). The ac susceptibility is strongly frequency-dependent (f =10 -10 000 Hz) and reveals an effective energy barrier for spin reversal of Δ E ≈1100 K (90 meV). The relaxation times follow Arrhenius behavior for T >25 K . For T <10 K , however, the relaxation times of τ ≈1010 s are only weakly temperature-dependent, indicating the relevance of a quantum tunneling process instead of thermal excitations. The magnetic entropy amounts to more than 25 J molFe-1 K-1, which significantly exceeds R ln 2 , the value expected for the entropy of a ground-state doublet. Thermal expansion and magnetostriction indicate a weak magnetoelastic coupling in accordance with slow relaxation of the magnetization. The classification of Li2(Li1 -xFex) N as ferromagnet is stressed and contrasted with highly anisotropic and slowly relaxing paramagnetic behavior.

Stretched Exponential relaxation in pure Se glass

Science.gov (United States)

Dash, S.; Ravindren, S.; Boolchand, P.

A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0 relaxation is a narrowing of the glass transition width from 7.1°C to 1.4°C, and the ΔHnr term increasing from 0.21 cal/gm to 0.92 cal/gm. In bulk GexSe100-x glasses as x increases to 20%, the length of the polymeric Sen chains between the Ge-crosslinks decreases to n = 2. and the striking relaxation effects nearly vanish. J.C. Phillips, Rep.Prog.Phys. 59 , 1133 (1996). Supported by NSF Grant DMR 08-53957.

On the relaxation of cold electrons and hot ions

International Nuclear Information System (INIS)

Potapenko, I.F.; Bobylev, A.V.; Azevedo, C.A. de; Sakanaka, P.H.; Assis, A.S. de

1998-01-01

The relaxation process of a space uniform plasma composed of cold electrons and one species of hot ions is studied numerically using one- and two-dimensional Landau - Fokker - Planck codes. Relaxation of a monoenergetic ion beam is considered in possibly extreme temperature regimes. Special attention is paid to the deviation of the relaxation process from the classical picture, which is characterized by the close initial temperatures T e >(m e /m i ) 1/3 T i . The present results give quite a clear idea of the relaxation picture for any initial temperatures also in extreme temperature regimes. A difference scheme, preserving the number of particles and the energy, gives the possibility of solving the problem numerically without error accumulation, except for machine errors. copyright 1998 American Institute of Physics

Quantitative Assessment of the T2 Relaxation Time of the Gluteus Muscles in Children with Duchenne Muscular Dystrophy: a Comparative Study Before and After Steroid Treatment

International Nuclear Information System (INIS)

Kim, Hee Kyung; Laor, Tal; Wong, Brenda; Horn, Paul S.

2010-01-01

To determine the feasibility of using T2 mapping as a quantitative method to longitudinally follow the disease activity in children with Duchenne muscular dystrophy (DMD) who are treated with steroids. Eleven boys with DMD (age range: 5-14 years) underwent evaluation with the clinical functional score (CFS), and conventional pelvic MRI and T2 mapping before and during steroid therapy. The gluteus muscle inflammation and fatty infiltration were evaluated on conventional MRI. The histograms and mean T2 relaxation times were obtained from the T2 maps. The CFS, the conventional MRI findings and the T2 values were compared before and during steroid therapy. None of the patients showed interval change of their CFSs. On conventional MRI, none of the images showed muscle inflammation. During steroid treatment, two boys showed increased fatty infiltration on conventional MRI, and both had an increase of the mean T2 relaxation time (p < 0.05). The remaining nine boys had no increase in fatty infiltration. Of these, three showed an increased mean T2 relaxation time (p < 0.05), two showed no change and four showed a decreased mean T2 relaxation time (p < 0.05). T2 mapping is a feasible technique to evaluate the longitudinal muscle changes in those children who receive steroid therapy for DMD. The differences of the mean T2 relaxation time may reflect alterations in disease activity, and even when the conventional MRI and CFS remain stable

Quantitative Assessment of the T2 Relaxation Time of the Gluteus Muscles in Children with Duchenne Muscular Dystrophy: a Comparative Study Before and After Steroid Treatment

Energy Technology Data Exchange (ETDEWEB)

Kim, Hee Kyung; Laor, Tal; Wong, Brenda [Cincinnati Children' s Hospital Medical Center, Cincinnati (United States); Horn, Paul S. [University of Cincinnati, Cincinnati (United States)

2010-06-15

To determine the feasibility of using T2 mapping as a quantitative method to longitudinally follow the disease activity in children with Duchenne muscular dystrophy (DMD) who are treated with steroids. Eleven boys with DMD (age range: 5-14 years) underwent evaluation with the clinical functional score (CFS), and conventional pelvic MRI and T2 mapping before and during steroid therapy. The gluteus muscle inflammation and fatty infiltration were evaluated on conventional MRI. The histograms and mean T2 relaxation times were obtained from the T2 maps. The CFS, the conventional MRI findings and the T2 values were compared before and during steroid therapy. None of the patients showed interval change of their CFSs. On conventional MRI, none of the images showed muscle inflammation. During steroid treatment, two boys showed increased fatty infiltration on conventional MRI, and both had an increase of the mean T2 relaxation time (p < 0.05). The remaining nine boys had no increase in fatty infiltration. Of these, three showed an increased mean T2 relaxation time (p < 0.05), two showed no change and four showed a decreased mean T2 relaxation time (p < 0.05). T2 mapping is a feasible technique to evaluate the longitudinal muscle changes in those children who receive steroid therapy for DMD. The differences of the mean T2 relaxation time may reflect alterations in disease activity, and even when the conventional MRI and CFS remain stable.

NMR relaxation induced by iron oxide particles: testing theoretical models.

Science.gov (United States)

Gossuin, Y; Orlando, T; Basini, M; Henrard, D; Lascialfari, A; Mattea, C; Stapf, S; Vuong, Q L

2016-04-15

Superparamagnetic iron oxide particles find their main application as contrast agents for cellular and molecular magnetic resonance imaging. The contrast they bring is due to the shortening of the transverse relaxation time T 2 of water protons. In order to understand their influence on proton relaxation, different theoretical relaxation models have been developed, each of them presenting a certain validity domain, which depends on the particle characteristics and proton dynamics. The validation of these models is crucial since they allow for predicting the ideal particle characteristics for obtaining the best contrast but also because the fitting of T 1 experimental data by the theory constitutes an interesting tool for the characterization of the nanoparticles. In this work, T 2 of suspensions of iron oxide particles in different solvents and at different temperatures, corresponding to different proton diffusion properties, were measured and were compared to the three main theoretical models (the motional averaging regime, the static dephasing regime, and the partial refocusing model) with good qualitative agreement. However, a real quantitative agreement was not observed, probably because of the complexity of these nanoparticulate systems. The Roch theory, developed in the motional averaging regime (MAR), was also successfully used to fit T 1 nuclear magnetic relaxation dispersion (NMRD) profiles, even outside the MAR validity range, and provided a good estimate of the particle size. On the other hand, the simultaneous fitting of T 1 and T 2 NMRD profiles by the theory was impossible, and this occurrence constitutes a clear limitation of the Roch model. Finally, the theory was shown to satisfactorily fit the deuterium T 1 NMRD profile of superparamagnetic particle suspensions in heavy water.

Predicting the effect of relaxation during frequency-selective adiabatic pulses

Science.gov (United States)

Pfaff, Annalise R.; McKee, Cailyn E.; Woelk, Klaus

2017-11-01

Adiabatic half and full passages are invaluable for achieving uniform, B1-insensitive excitation or inversion of macroscopic magnetization across a well-defined range of NMR frequencies. To accomplish narrow frequency ranges with adiabatic pulses (computer-calculated data with experimental results demonstrates that, in non-viscous, small-molecule fluids, it is possible to model magnetization and relaxation by considering standard T1 and T2 relaxation in the traditional rotating frame. The proposed model is aimed at performance optimizations of applications in which these pulses are employed. It differs from previous reports which focused on short high-power adiabatic pulses and relaxation that is governed by dipole-dipole interactions, cross polarization, or chemical exchange.

Patellofemoral instability in children: T2 relaxation times of the patellar cartilage in patients with and without patellofemoral instability and correlation with morphological grading of cartilage damage.

Science.gov (United States)

Kang, Chang Ho; Kim, Hee Kyung; Shiraj, Sahar; Anton, Christopher; Kim, Dong Hoon; Horn, Paul S

2016-07-01

Patellofemoral instability is one of the most common causes of cartilage damage in teenagers. To quantitatively evaluate the patellar cartilage in patients with patellofemoral instability using T2 relaxation time maps (T2 maps), compare the values to those in patients without patellofemoral instability and correlate them with morphological grades in patients with patellofemoral instability. Fifty-three patients with patellofemoral instability (mean age: 15.9 ± 2.4 years) and 53 age- and gender-matched patients without patellofemoral instability were included. Knee MR with axial T2 map was performed. Mean T2 relaxation times were obtained at the medial, central and lateral zones of the patellar cartilage and compared between the two groups. In the patellofemoral instability group, morphological grading of the patellar cartilage (0-4) was performed and correlated with T2 relaxation times. Mean T2 relaxation times were significantly longer in the group with patellofemoral instability as compared to those of the control group across the patellar cartilage (Student's t-test, Ppatellofemoral instability, patellar cartilage damage occurs across the entire cartilage with the highest T2 values at the apex. T2 relaxation times directly reflect the severity in low-grade cartilage damage, which implies an important role for T2 maps in differentiating between normal and low-grade cartilage damage.

Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

Energy Technology Data Exchange (ETDEWEB)

Sachleben, Joseph Robert [Lawrence Berkeley Lab., CA (United States); California Univ., Berkeley, CA (United States). Dept. of Chemistry

1993-09-01

Semiconductor nanocrystals, small biomolecules, and ¹³C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution ¹H and ¹³C liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 Å. Internal motion is estimated to be slow with a correlation time > 10^-8 s^-1. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O₂ and ultraviolet. A method for measuring ¹⁴N-¹H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T₁ and T₂ experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in ¹³C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

Nuclear magnetic resonance relaxation times for human lung cancer and lung tissues

International Nuclear Information System (INIS)

Matsuura, Yoshifumi; Shioya, Sumie; Kurita, Daisaku; Ohta, Takashi; Haida, Munetaka; Ohta, Yasuyo; Suda, Syuichi; Fukuzaki, Minoru.

1994-01-01

We investigated the nuclear magnetic resonance (NMR) relaxation times, T 1 and T 2 , for lung cancer tissue, and other samples of lung tissue obtained from surgical specimens. The samples were nine squamous cell carcinomas, five necrotic squamous cell carcinomas, 15 adenocarcinomas, two benign mesotheliomas, and 13 fibrotic lungs. The relaxation times were measured with a 90 MHz NMR spectrometer and the results were correlated with histological changes. The values of T 1 and T 2 for squamous cell carcinoma and mesothelioma were significantly longer than those of adenocarcinoma and fibrotic lung tissue. There were no significant differences in values of T 1 and T 2 between adenocarcinoma and lung tissue. The values of T 1 and T 2 for benign mesothelioma were similar to those of squamous cell carcinoma, which suggested that increases in T 1 and T 2 are not specific to malignant tissues. (author)

Whole brain MP2RAGE-based mapping of the longitudinal relaxation time at 9.4T.

Science.gov (United States)

Hagberg, G E; Bause, J; Ethofer, T; Ehses, P; Dresler, T; Herbert, C; Pohmann, R; Shajan, G; Fallgatter, A; Pavlova, M A; Scheffler, K

2017-01-01

Mapping of the longitudinal relaxation time (T 1 ) with high accuracy and precision is central for neuroscientific and clinical research, since it opens up the possibility to obtain accurate brain tissue segmentation and gain myelin-related information. An ideal, quantitative method should enable whole brain coverage within a limited scan time yet allow for detailed sampling with sub-millimeter voxel sizes. The use of ultra-high magnetic fields is well suited for this purpose, however the inhomogeneous transmit field potentially hampers its use. In the present work, we conducted whole brain T 1 mapping based on the MP2RAGE sequence at 9.4T and explored potential pitfalls for automated tissue classification compared with 3T. Data accuracy and T 2 -dependent variation of the adiabatic inversion efficiency were investigated by single slice T 1 mapping with inversion recovery EPI measurements, quantitative T 2 mapping using multi-echo techniques and simulations of the Bloch equations. We found that the prominent spatial variation of the transmit field at 9.4T (yielding flip angles between 20% and 180% of nominal values) profoundly affected the result of image segmentation and T 1 mapping. These effects could be mitigated by correcting for both flip angle and inversion efficiency deviations. Based on the corrected T 1 maps, new, 'flattened', MP2RAGE contrast images were generated, that were no longer affected by variations of the transmit field. Unlike the uncorrected MP2RAGE contrast images acquired at 9.4T, these flattened images yielded image segmentations comparable to 3T, making bias-field correction prior to image segmentation and tissue classification unnecessary. In terms of the T 1 estimates at high field, the proposed correction methods resulted in an improved precision, with test-retest variability below 1% and a coefficient-of-variation across 25 subjects below 3%. Copyright © 2016 Elsevier Inc. All rights reserved.

SU-F-I-63: Relaxation Times of Lipid Resonances in NAFLD Animal Model Using Enhanced Curve Fitting

Energy Technology Data Exchange (ETDEWEB)

Song, K-H; Yoo, C-H; Lim, S-I; Choe, B-Y [Department of Biomedical Engineering, and Research Institute of Biomedical Engineering, The Catholic University of Korea College of Medicine, Seoul (Korea, Republic of)

2016-06-15

Purpose: The objective of this study is to evaluate the relaxation time of methylene resonance in comparison with other lipid resonances. Methods: The examinations were performed on a 3.0T MRI scanner using a four-channel animal coil. Eight more Sprague-Dawley rats in the same baseline weight range were housed with ad libitum access to water and a high-fat (HF) diet (60% fat, 20% protein, and 20% carbohydrate). In order to avoid large blood vessels, a voxel (0.8×0.8×0.8 cm{sup 3}) was placed in a homogeneous area of the liver parenchyma during free breathing. Lipid relaxations in NC and HF diet rats were estimated at a fixed repetition time (TR) of 6000 msec, and multi echo time (TEs) of 40–220 msec. All spectra for data measurement were processed using the Advanced Method for Accurate, Robust, and Efficient Spectral (AMARES) fitting algorithm of the Java-based Magnetic Resonance User Interface (jMRUI) package. Results: The mean T2 relaxation time of the methylene resonance in normal-chow diet was 37.1 msec (M{sub 0}, 2.9±0.5), with a standard deviation of 4.3 msec. The mean T2 relaxation time of the methylene resonance was 31.4 msec (M{sub 0}, 3.7±0.3), with a standard deviation of 1.8 msec. The T2 relaxation times of methylene protons were higher in normal-chow diet rats than in HF rats (p<0.05), and the extrapolated M{sub 0} values were higher in HF rats than in NC rats (p<0.005). The excellent linear fit with R{sup 2}>0.9971 and R{sup 2}>0.9987 indicates T2 relaxation decay curves with mono-exponential function. Conclusion: In in vivo, a sufficient spectral resolution and a sufficiently high signal-to-noise ratio (SNR) can be achieved, so that the data measured over short TE values can be extrapolated back to TE = 0 to produce better estimates of the relative weights of the spectral components. In the short term, treating the effective decay rate as exponential is an adequate approximation.

Heteronuclear relaxation in time-dependent spin systems: 15N-T1ρ dispersion during adiabatic fast passage

International Nuclear Information System (INIS)

Konrat, Robert; Tollinger, Martin

1999-01-01

A novel NMR experiment comprising adiabatic fast passage techniques for the measurement of heteronuclear self-relaxation rates in fully 15N-enriched proteins is described. Heteronuclear self-relaxation is monitored by performing adiabatic fast passage (AFP) experiments at variable adiabaticity (e.g., variation of RF spin-lock field intensity). The experiment encompasses gradient- selection and sensitivity-enhancement. It is shown that transverse relaxation rates derived with this method are in good agreement with the ones measured by the classical Carr-Purcell-Meiboom-Gill (CPMG) sequences. An application of this method to the study of the carboxyl-terminal LIM domain of quail cysteine and glycine-rich protein qCRP2(LIM2) is presented

Characterization of structural relaxation in inorganic glasses using length dilatometry

Science.gov (United States)

Koontz, Erick

characterization technique is comprised of three main components: experimental measurements, fitting of configurational length change, and description of glass behavior by analysis of fitting parameters. N-BK7 optical glass from Schott was used as the proof of concept glass but the main scientific interest was in three chalcogenide glasses: As40Se 60, As20Se80, and Ge17.9As19.7 Se62.4. The dilatometric experiments were carried out using a thermomechanical analyzer (TMA) on glass sample that were synthesized by the author, in all cases except N-BK7. Isothermal structural relaxation measurements were done on (12 mm tall x 3 mm x 3 mm) beams placed vertically in the TMA. The samples were equilibrated at a starting temperature (T 0) until structural equilibrium was reached then a temperature down step was initiated to the final temperature (T 1) and held isothermally until relaxation concluded. The configurational aspect of length relaxation, and therefore volume relaxation was extracted and fit with a Prony series. The Prony series parameters indicated a number of relaxation events occurring within the glass on timescales typically an order of magnitude apart in time. The data analysis showed as many as 4 discrete relaxation times at lower temperatures. The number of discrete relaxation decreased as the temperature increased until just one single relaxation was left in the temperature range just at or above Tg. In the case of N-BK7 these trends were utilized to construct a simple model that could be applied to glass manufacturing in the areas of annealing or PGM. A future development of a rather simple finite element model (FEM) would easily be able to use this model to predict the exponential-like, temperature and time dependent relaxation behaviors of the glass. The predictive model was not extended to the chalcogenide glass studied here, but could easily be applied to them in the future. The relaxation time trends versus temperature showed a definite region of transition between a

Objective measurement of minimal fat in normal skeletal muscles of healthy children using T2 relaxation time mapping (T2 maps) and MR spectroscopy.

Science.gov (United States)

Kim, Hee Kyung; Serai, Suraj; Merrow, Arnold C; Wang, Lily; Horn, Paul S; Laor, Tal

2014-02-01

Various skeletal muscle diseases result in fatty infiltration, making it important to develop noninvasive biomarkers to objectively measure muscular fat. We compared T2 relaxation time mapping (T2 maps) and magnetic resonance spectroscopy (MRS) with physical characteristics previously correlated with intramuscular fat to validate T2 maps and MRS as objective measures of skeletal muscle fat. We evaluated gluteus maximus muscles in 30 healthy boys (ages 5-19 years) at 3 T with T1-weighted images, T2-W images with fat saturation, T2 maps with and without fat saturation, and MR spectroscopy. We calculated body surface area (BSA), body mass index (BMI) and BMI percentile (BMI %). We performed fat and inflammation grading on T1-W imaging and fat-saturated T2-W imaging, respectively. Mean T2 values from T2 maps with fat saturation were subtracted from T2 maps without fat saturation to determine T2 fat values. We obtained lipid-to-water ratios by MR spectroscopy. Pearson correlation was used to assess relationships between BSA, BMI, BMI %, T2 fat values, and lipid-to-water ratios for each boy. Twenty-four boys completed all exams; 21 showed minimal and 3 showed no fatty infiltration. None showed muscle inflammation. There was correlation between BSA, BMI, and BMI %, and T2 fat values (P values and lipid-to-water ratios (P skeletal muscles, even in microscopic amounts, and validate each other. Both techniques might enable detection of minimal pathological fatty infiltration in children with skeletal muscle disorders.

The advantage of high relaxivity contrast agents in brain perfusion

International Nuclear Information System (INIS)

Cotton, F.; Hermier, M.

2006-01-01

Accurate MRI characterization of brain lesions is critical for planning therapeutic strategy, assessing prognosis and monitoring response to therapy. Conventional MRI with gadolinium-based contrast agents is useful for the evaluation of brain lesions, but this approach primarily depicts areas of disruption of the blood-brain barrier (BBB) rather than tissue perfusion. Advanced MR imaging techniques such as dynamic contrast agent-enhanced perfusion MRI provide physiological information that complements the anatomic data available from conventional MRI. We evaluated brain perfusion imaging with gadobenate dimeglumine (Gd-BOPTA, MultiHance; Bracco Imaging, Milan, Italy). The contrast-enhanced perfusion technique was performed on a Philips Intera 1.5-T MR system. The technique used to obtain perfusion images was dynamic susceptibility contrast-enhanced MRI, which is highly sensitive to T2* changes. Combined with PRESTO perfusion imaging, SENSE is applied to double the temporal resolution, thereby improving the signal intensity curve fit and, accordingly, the accuracy of the derived parametric images. MultiHance is the first gadolinium MR contrast agent with significantly higher T1 and T2 relaxivities than conventional MR contrast agents. The higher T1 relaxivity, and therefore better contrast-enhanced T1-weighted imaging, leads to significantly improved detection of BBB breakdown and hence improved brain tumor conspicuity and delineation. The higher T2 relaxivity allows high-quality T2*-weighted perfusion MRI and the derivation of good quality relative cerebral blood volume (rCBV) maps. We determined the value of MultiHance for enhanced T2*-weighted perfusion imaging of histologically proven (by surgery or stereotaxic biopsy) intraaxial brain tumors (n=80), multiple sclerosis lesions (n=10), abscesses (n=4), neurolupus (n=15) and stroke (n=16). All the procedures carried out were safe and no adverse events occurred. The acquired perfusion images were of good quality in

Electron paramagnetic relaxation studies of free radicals in. gamma. -irradiated DNA

Energy Technology Data Exchange (ETDEWEB)

Kuwabara, M; Yoshi, G [Hokkaido Univ., Sapporo (Japan)

1980-01-01

Using the continuous microwave power saturation method the T/sub 1/ spin-lattice relaxation time and T/sub 2/ spin-spin relaxation time for DNA radicals (measured at 297/sup 0/K) are reported. Identical experiments carried out on thymidine-5'-monophosphate sodium salt (TMP) and deoxycytidine-5'-monophosphate sodium salt (dCMP) are also reported. Irradiated DNA produces TMP radicals on the base moiety and dCMP radicals on the sugar moiety. Comparing the relaxation times of DNA with those of TMP and dCMP provided a reliable analysis of the nature of DNA radicals.

T2-mapping of the sacroiliac joints at 1.5 Tesla: a feasibility and reproducibility study.

Science.gov (United States)

Albano, Domenico; Chianca, Vito; Cuocolo, Renato; Bignone, Rodolfo; Ciccia, Francesco; Sconfienza, Luca Maria; Midiri, Massimo; Brunetti, Arturo; Lagalla, Roberto; Galia, Massimo

2018-04-20

To evaluate the reproducibility of T2 relaxation time measurements of the sacroiliac joints at 1.5 T. Healthy volunteers underwent an oblique axial multislice multiecho spin-echo sequence of the sacroiliac joints at 1.5 T. Regions of interest were manually drawn using a dedicated software by two musculoskeletal radiologists to include the cartilaginous part of the sacroiliac joints. A senior radiologist performed the measurement twice, while a resident measured once. Intra- and inter-observer reproducibility was tested using the Bland-Altman method. Association between sex and T2 relaxation times was tested using the Mann-Whitney U test. Correlation between T2 relaxation times and body mass index (BMI) was tested using the Spearman's rho. Eighty sacroiliac joints of 40 subjects (mean age: 28 ± 4.8 years, range: 20-43; mean BMI: 23.3 ± 3.1, range: 18.9-30) were imaged. The mean T2 values obtained by the senior radiologist in the first series of measurements were 42 ± 4.4 ms, whereas in the second series were 40.7 ± 4.5 ms. The mean T2 values obtained by the radiology resident were 41.1 ± 4.2 ms. Intra-observer reproducibility was 88% (coefficient of repeatability = 3.8; bias = 1.28; p sacroiliac joints seems to be highly reproducible at 1.5 T. Further studies could investigate the potential clinical application of this tool in the sacroiliac joints.

Relaxation dynamics of the conductive processes for PbNb2O6 ferroelectric ceramics in the frequency and time domain

International Nuclear Information System (INIS)

Gonzalez, R L; Leyet, Y; Guerrero, F; Guerra, J de Los S; Venet, M; Eiras, J A

2007-01-01

The relaxation dynamics of the conductive process present in PbNb 2 O 6 piezoelectric ceramics was investigated. A relaxation function in the time domain, Φ(t), was found from the frequency dependence of the dielectric modulus (imaginary component, M'') by using a relaxation function in the frequency domain, F*(ω). The best relaxation function, F*(ω), was found to be a Cole-Cole distribution function, in which relaxation characteristic parameters, such as α and τ CC , are involved. On the other hand, the relaxation function, Φ(t), obtained by the time domain method, was found to be a Kohlrausch-Williams-Watts (KWW) function type. The thermal evolution of the characteristics parameters of the KWW function (β and τ*) was analysed. The values of the activation energy (E a ), obtained in the whole investigated temperature interval, suggest the existence of a relaxation mechanism (a conductive process), which may be interpreted by an ion hopping between neighbouring sites within the crystalline lattice. The results are corroborated with the formalism of the AC conductivity

T1 value of hyperplastic and hypoplastic bone marrow

International Nuclear Information System (INIS)

Asai, Sae; Yoshida, Hideo; Yoshikawa, Hiroki; Yashiro, Naofumi; Iio, Masahiro; Takaku, Fumimaro

1985-01-01

Magnetic resonance (MR) images of the bone marrow of 18 patients (11 normal control, 4 aplastic anemia, 2 chronic myelocytic leukemia, 1 polycythemia vera) were discussed. MR imager had 0.15T registive system. Sagittal section of the body was obtained with inversion recovery (TR1,000, 1,600/TI 350, 450/TE 13, 40 msec) and saturation recovery (TR 1,000, 2,000/TE 13,40 msec) sequences. T 1 relaxation time was calculated from those images. T 1 value of the thoracic and lumbar vertebral bone marrow which contains red marrow even in elderly patients was measured. The results were as follows: 1) T 1 values of chronic myelocytic leukemia (CML) and polycythemia vera were longer than that of normal. 2) T 1 values of four aplastic anemia were all shorter than normal. CML and polycythemia vera can be called myeloproliferative disease and their bone marrows are hyperplastic, which may explain elongated T 1 . The bone marrow of aplasticanemia is hypoplastic and shows fatty change which may have decreased T 1 . Our results suggest T 1 value of bone marrow is useful to evaluate hematological disorders. (author)

Nuclear relaxation and critical fluctuations in membranes containing cholesterol

Science.gov (United States)

McConnell, Harden

2009-04-01

Nuclear resonance frequencies in bilayer membranes depend on lipid composition. Our calculations describe the combined effects of composition fluctuations and diffusion on nuclear relaxation near a miscibility critical point. Both tracer and gradient diffusion are included. The calculations involve correlation functions and a correlation length ξ =ξ0T/(T -Tc), where T -Tc is temperature above the critical temperature and ξ0 is a parameter of molecular length. Several correlation functions are examined, each of which is related in some degree to the Ising model correlation function. These correlation functions are used in the calculation of transverse deuterium relaxation rates in magic angle spinning and quadrupole echo experiments. The calculations are compared with experiments that report maxima in deuterium and proton nuclear relaxation rates at the critical temperature [Veatch et al., Proc. Nat. Acad. Sci. U.S.A. 104, 17650 (2007)]. One Ising-model-related correlation function yields a maximum 1/T2 relaxation rate at the critical temperature for both magic angle spinning and quadrupole echo experiments. The calculated rates at the critical temperature are close to the experimental rates. The rate maxima involve relatively rapid tracer diffusion in a static composition gradient over distances of up to 10-100 nm.

Irradiation properties of T0 chopper components

Energy Technology Data Exchange (ETDEWEB)

Itoh, Shinichi, E-mail: shinichi.itoh@kek.jp [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Ueno, Kenji; Ohkubo, Ryuji [Mechanical Engineering Center, Applied Research Laboratory, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Sagehashi, Hidenori [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Funahashi, Yoshisato [Mechanical Engineering Center, Applied Research Laboratory, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Yokoo, Tetsuya [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan)

2011-10-21

We investigated the irradiation properties of the components of a T0 chopper. The organic materials in the rotor bearing grease, the magnetic fluids in seals, and the rubber in the timing belt, as well as the semiconductor materials in the rotation sensor and motor encoder, were all irradiated with high-energy {gamma}-rays up to 100 kGy. No significant damage that shortens the lifetime of a T0 chopper was observed for the mechanical components. However, the semiconductor components were damaged by the irradiation. For the rotation sensor system detecting the rotor phase, the signal from a marker on the rotor shaft was transmitted outside the shielding by an optical fiber with radiation-proofing and the electrical circuits were removed from the beamline shielding. The lifetime of the motor encoder possibly meets the requirement for the maintenance period of the T0 chopper.

Momentum constraint relaxation

International Nuclear Information System (INIS)

Marronetti, Pedro

2006-01-01

Full relativistic simulations in three dimensions invariably develop runaway modes that grow exponentially and are accompanied by violations of the Hamiltonian and momentum constraints. Recently, we introduced a numerical method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint violation and helps improve the quality of the numerical model. We present here a method that controls the violation of the momentum constraint. The method is based on the addition of a longitudinal component to the traceless extrinsic curvature A ij -tilde, generated by a vector potential w i , as outlined by York. The components of w i are relaxed to solve approximately the momentum constraint equations, slowly pushing the evolution towards the space of solutions of the constraint equations. We test this method with simulations of binary neutron stars in circular orbits and show that it effectively controls the growth of the aforementioned violations. We also show that a full numerical enforcement of the constraints, as opposed to the gentle correction of the momentum relaxation scheme, results in the development of instabilities that stop the runs shortly

T20 measurements for 1H(d searrow,γ)3He and the P-wave component of the nucleon-nucleon force

International Nuclear Information System (INIS)

Schmid, G.J.; Chasteler, R.M.; Weller, H.R.; Tilley, D.R.; Fonseca, A.C.; Lehman, D.R.

1996-01-01

Measurements of T 20 (θ lab =90 degree) for 1 H(d searrow,γ) 3 He, in the energy range E d (lab)=12.7 endash 19.8 MeV, have been compared with the results of new exact three-body Faddeev calculations using the Paris and Bonn-A nucleon-nucleon (NN) potentials. This comparison indicates a strong sensitivity of the T 20 observable to the p-wave part of the NN force. In particular, we find that the 3 P 1 component of the P-wave interaction is the dominant P-wave term affecting the value of T 20 (θ lab =90 degree) at these energies. This contrasts with the results of polarized N-D scattering studies where the 3 P 0 component has been found to dominate. cents 1996 The American Physical Society

Nuclear spin relaxation due to chemical shift anisotropy of gas-phase 129Xe.

Science.gov (United States)

Hanni, Matti; Lantto, Perttu; Vaara, Juha

2011-08-14

Nuclear spin relaxation provides detailed dynamical information on molecular systems and materials. Here, first-principles modeling of the chemical shift anisotropy (CSA) relaxation time for the prototypic monoatomic (129)Xe gas is carried out, both complementing and predicting the results of NMR measurements. Our approach is based on molecular dynamics simulations combined with pre-parametrized ab initio binary nuclear shielding tensors, an "NMR force field". By using the Redfield relaxation formalism, the simulated CSA time correlation functions lead to spectral density functions that, for the first time, quantitatively determine the experimental spin-lattice relaxation times T(1). The quality requirements on both the Xe-Xe interaction potential and binary shielding tensor are investigated in the context of CSA T(1). Persistent dimers Xe(2) are found to be responsible for the CSA relaxation mechanism in the low-density limit of the gas, completely in line with the earlier experimental findings.

Electron spin-lattice relaxation in fractals

International Nuclear Information System (INIS)

Shrivastava, K.N.

1986-08-01

We have developed the theory of the spin-fracton interaction for paramagnetic ions in fractal structures. The interaction is exponentially damped by the self-similarity length of the fractal and by the range dimensionality d Φ . The relaxation time of the spin due to the absorption and emission of the fracton has been calculated for a general dimensionality called the Raman dimensionality d R , which for the fractons differs from the Hausdorff (fractal) dimensionality, D, as well as from the Euclidean dimensionality, d. The exponent of the energy level separation in the relaxation rate varies with d R d Φ /D. We have calculated the spin relaxation rate due to a new type of Raman process in which one fracton is absorbed to affect a spin transition from one electronic level to another and later another fracton is emitted along with a spin transition such that the difference in the energies of the two fractons is equal to the electronic energy level separation. The temperature and the dimensionality dependence of such a process has been found in several approximations. In one of the approximations where the van Vleck relaxation rate for a spin in a crystal is known to vary with temperature as T 9 , our calculated variation for fractals turns out to be T 6.6 , whereas the experimental value for Fe 3+ in frozen solutions of myoglobin azide is T 6.3 . Since we used d R =4/3 and the fracton range dimensionality d Φ =D/1.8, we expect to measure the dimensionalities of the problem by measuring the temperature dependence of the relaxation times. We have also calculated the shift of the paramagnetic resonance transition for a spin in a fractal for general dimensionalities. (author)

Relaxation of coupled nuclear spin systems

International Nuclear Information System (INIS)

Koenigsberger, E.

1985-05-01

The subject of the present work is the relaxation behaviour of scalarly coupled spin-1/2 systems. In the theoretical part the semiclassical Redfield equations are used. Dipolar (D), Chemical Shift Anisotropy (CSA) and Random Field (RF) interactions are considered as relaxation mechanisms. Cross correlations of dipolar interactions of different nuclei pairs and those between the D and the CSA mechanisms are important. The model of anisotropic molecular rotational relaxation and the extreme narrowing approximation are used to obtain the spectral density functions. The longitudinal relaxation data are analyzed into normal modes following Werbelow and Grant. The time evolution of normal modes is derived for the AX system with D-CSA cross terms. In the experimental part the hypothesis of dimerization in the cinnamic acid and the methyl cinnamate - AMX systems with DD cross terms - is corroborated by T 1 -time measurements and a calculation of the diffusion constants. In pentachlorobenzene - an AX system - taking into account of D-CSA cross terms enables the complete determination of movements anosotropy and the determination of the sign of the indirect coupling constant 1 Jsub(CH). (G.Q.)

Meniscal T1rho and T2 measured with 3.0T MRI increases directly after running a marathon

Energy Technology Data Exchange (ETDEWEB)

Stehling, Christoph [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); University of Muenster, Department of Clinical Radiology, Muenster (Germany); Luke, Anthony [University of California, Department of Orthopedic Surgery, San Francisco, CA (United States); Stahl, Robert [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Ludwig Maximilians University of Munich, Department of Clinical Radiology, Munich (Germany); Baum, Thomas; Joseph, Gabby; Pan, Judong; Link, Thomas M. [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States)

2011-06-15

To prospectively evaluate changes in T1rho and T2 relaxation time in the meniscus using 3.0 T MRI in asymptomatic knees of marathon runners and to compare these findings with those of age-matched healthy subjects. Thirteen marathon runners underwent 3.0 T MRI including T1rho and T2 mapping sequences before, 48-72 h after, and 3 months after competition. Ten controls were examined at baseline and after 3 months. All images were analyzed by two musculoskeletal radiologists identifying and grading cartilage, meniscal, ligamentous. and other knee abnormalities with WORMS scores. Meniscal segmentation was performed to generate T1rho and T2 maps in six compartments. No differences in morphological knee abnormalities were found before and after the marathon. However, all marathon runners showed a significant increase in T1rho and T2 values after competition in all meniscus compartments (p < 0.0001), which may indicate changes in the biochemical composition of meniscal tissue. While T2 values decreased after 3 months T1rho values remained at a high level, indicating persisting changes in the meniscal matrix composition after a marathon. T2 values in menisci have the potential to be used as biomarkers for identifying reversible meniscus matrix changes indicating potential tissue damage. T1rho values need further study, but may be a valuable marker for diagnosing early, degenerative changes in the menisci following exercise. (orig.)

Earth's magnetic field enabled scalar coupling relaxation of 13C nuclei bound to fast-relaxing quadrupolar 14N in amide groups.

Science.gov (United States)

Chiavazza, Enrico; Kubala, Eugen; Gringeri, Concetta V; Düwel, Stephan; Durst, Markus; Schulte, Rolf F; Menzel, Marion I

2013-02-01

Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., (79)Br-(13)C), can be a very effective relaxation mechanism. While working on hyperpolarized [5-(13)C]glutamine, fast liquid-state polarization decay during transfer to the MRI scanner was observed. This behavior could hypothetically be explained by substantial T(1) shortening due to a scalar coupling contribution (type II) to the relaxation caused by the fast-relaxing quadrupolar (14)N adjacent to the (13)C nucleus in the amide group. This contribution is only effective in low magnetic fields (i.e., less than 800 μT) and prevents the use of molecules bearing the (13)C-amide group as hyperpolarized MRS/MRI probes. In the present work, this hypothesis is explored both theoretically and experimentally. The results show that high hyperpolarization levels can be retained using either a (15)N-labeled amide or by applying a magnetic field during transfer of the sample from the polarizer to the MRI scanner. Copyright © 2012 Elsevier Inc. All rights reserved.

Relaxation parameter estimation and comparison of NLS and LLS methods for DCE MRI in the cervix

DEFF Research Database (Denmark)

Mariager, Christian; Kallehauge, Jesper; Tanderup, Kari

Dynamic Contrast Enhanced (DCE) MRI is a promising tool for tumor treatment planning. However, prior knowledge of the T1 value within each tumor voxel is needed to utilize this technique. Therefore, a T1 relaxation measurement is performed before the DCE experiment to establish a baseline, before...... any injection of contrast agent. This T1 relaxation measurement is often performed using a variable flip angle spoiled gradient recalled echo (SPGR) sequence. T1 can then be estimated using either a linear least squares (LLS) or a non-linear least squares (NLS) fitting algorithm....

Postearthquake relaxation after the 2004 M6 Parkfield, California, earthquake and rate-and-state friction

Science.gov (United States)

Savage, J.C.; Langbein, J.

2008-01-01

An unusually complete set of measurements (including rapid rate GPS over the first 10 days) of postseismic deformation is available at 12 continuous GPS stations located close to the epicenter of the 2004 M6.0 Parkfield earthquake. The principal component modes for the relaxation of the ensemble of those 12 GPS stations were determined. The first mode alone furnishes an adequate approximation to the data. Thus, the relaxation at all stations can be represented by the product of a common temporal function and distinct amplitudes for each component (north or east) of relaxation at each station. The distribution in space of the amplitudes indicates that the relaxation is dominantly strike slip. The temporal function, which spans times from about 5 min to 900 days postearthquake, can be fit by a superposition of three creep terms, each of the form ??l loge(1 + t/??l), with characteristic times ??, = 4.06, 0.11, and 0.0001 days. It seems likely that what is actually involved is a broad spectrum of characteristic times, the individual components of which arise from afterslip on different fault patches. Perfettini and Avouac (2004) have shown that an individual creep term can be explained by the spring-slider model with rate-dependent (no state variable) friction. The observed temporal function can also be explained using a single spring-slider model (i.e., single fault patch) that includes rate-and-state-dependent friction, a single-state variable, and either of the two commonly used (aging and slip) state evolution laws. In the latter fits, the rate-and-state friction parameter b is negative.

Brownian rotational relaxation and power absorption in magnetite nanoparticles

International Nuclear Information System (INIS)

Goya, G.F.; Fernandez-Pacheco, R.; Arruebo, M.; Cassinelli, N.; Ibarra, M.R.

2007-01-01

We present a study of the power absorption efficiency in several magnetite-based colloids, to asses their potential as magnetic inductive hyperthermia (MIH) agents. Relaxation times τ were measured through the imaginary susceptibility component χ ' '(T), and analyzed within Debye's theory of dipolar fluid. The results indicated Brownian rotational relaxation and allowed to calculate the hydrodynamic radius close to the values obtained from photon correlation. The study of the colloid performances as power absorbers showed no detectable increase of temperature for dextran-coated Fe 3 O 4 nanoparticles, whereas a second Fe 3 O 4 -based dispersion of similar concentration could be heated up to 12K after 30min under similar experimental conditions. The different power absorption efficiencies are discussed in terms of the magnetic structure of the nanoparticles

Relaxation of polarized nuclei in superconducting rhodium

DEFF Research Database (Denmark)

Knuuttila, T.A.; Tuoriniemi, J.T.; Lefmann, K.

2000-01-01

Nuclear spin lattice relaxation rates were measured in normal and superconducting (sc) rhodium with nuclear polarizations up to p = 0.55. This was sufficient to influence the sc state of Rh, whose T, and B-c, are exceptionally low. Because B-c ... is unchanged, the nuclear spin entropy was fully sustained across the sc transition. The relaxation in the sc state was slower at all temperatures without the coherence enhancement close to T-c. Nonzero nuclear polarization strongly reduced the difference between the relaxation rates in the sc and normal...

Corroborative evidences of TV γ -scaling of the α-relaxation originating from the primitive relaxation/JG β relaxation

Science.gov (United States)

Ngai, K. L.; Paluch, M.

2017-12-01

Successful thermodynamic scaling of the structural alpha-relaxation time or transport coefficients of glass-forming liquids determined at various temperatures T and pressures P means the data conform to a single function of the product variable TVgamma, where V is the specific volume and gamma is a material specific constant. In the past two decades we have witnessed successful TVgamma-scaling in many molecular, polymeric, and even metallic glass-formers, and gamma is related to the slope of the repulsive part of the intermolecular potential. The advances made indicate TVgamma-scaling is an important aspect of the dynamic and thermodynamic properties of glass-formers. In this paper we show the origin of TVgamma-scaling is not from the structural alpha-relaxation time. Instead it comes from its precursor, the Johari-Goldstein beta-relaxation or the primitive relaxation of the Coupling Model and their relaxation times or tau_0 respectively. It is remarkable that all relaxation times are functions of TVgamma with the same gama, as well as the fractional exponent of the Kohlrausch correlation function of the structural alpha-relaxation. We arrive at this conclusion convincingly based on corroborative evidences from a number of experiments and molecular dynamics simulations performed on a wide variety of glass-formers and in conjunction with consistency with the predictions of the Coupling Model.

Evaluation of the Delta-T SPN1 radiometer for the measurement of solar irradiance components

Science.gov (United States)

Estelles, Victor; Serrano, David; Segura, Sara; Wood, John; Webb, Nick; Utrillas, Maria Pilar

2016-04-01

In this study we analyse the performance of an SPN1 radiometer built by Delta-T Devices Ltd. to retrieve global solar irradiance at ground and its components (diffuse, direct) in comparison with measurements from two Kipp&Zonen CMP21 radiometers and a Kipp&Zonen CHP1 pirheliometer, mounted on an active Solys-2 suntracker at the Burjassot site (Valencia, Spain) using data acquired every minute during years 2013 - 2015. The measurement site is close to sea level (60 m a.s.l.), near the Mediterranean coast (10 km) and within the metropolitan area of Valencia City (over 1.500.000 inhabitants). The SPN1 is an inexpensive and versatile instrument for the measurement of the three components of the solar radiation without any mobile part and without any need to azimuthally align the instrument to track the sun (http://www.delta-t.co.uk). The three components of the solar radiation are estimated from a combination of measurements performed by 7 different miniature thermopiles. The SPN1 pyranometer measures the irradiance between 400 and 2700 nm, and the nominal uncertainty for the individual readings is about 8% ± 10 W/m2 (5% for the daily averages). The pyranometer Kipp&Zonen CMP21 model is a secondary standard for the measurement of broadband solar global irradiance in horizontal planes. Two ventilated CMP21 are used for the measurement of the global and diffuse irradiances. The expected total daily uncertainty of the radiometer is estimated to be 2%. The pirheliometer Kipp&Zonen CHP1 is designed for the measurement of the direct irradiance. The principles are similar to the CMP21 pyranometer. The results of the comparison show that the global irradiance from the SPN1 compares very well with the CMP21, with absolute RMSD and MBD differences below the combined uncertainties (15 W/m2 and -5.4 W/m2, respectively; relative RMSD of 3.1%). Both datasets are very well correlated, with a correlation coefficient higher than 0.997 and a slope and intercept very close to 1 and 0

Gradient-induced longitudinal relaxation of hyperpolarized noble gases in the fringe fields of superconducting magnets used for magnetic resonance.

Science.gov (United States)

Zheng, Wangzhi; Cleveland, Zackary I; Möller, Harald E; Driehuys, Bastiaan

2011-02-01

When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of (3)He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum (3)He relaxation rate of 3.83×10(-3) s(-1) (T(1)=4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T(1) would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T(1) of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient-induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius. Copyright © 2010 Elsevier Inc. All rights reserved.

Lactate and T2 measurements of synovial aspirates at 1.5 T: differentiation of septic from non-septic arthritis

International Nuclear Information System (INIS)

Wiener, Edzard; Zanetti, Marco; Hodler, Juerg; Pfirrmann, Christian W.A.

2008-01-01

The aim of this study was to differentiate septic from non-septic arthritis by measuring lactate concentration with 1 H magnetic resonance spectroscopy (HMRS) and by estimating total protein content with the assessment of T 2 values. In 30 patients with acute arthritis, synovial fluid was aspirated. Lactate concentrations were analyzed with single voxel HMRS at 1.5 T. T 2 relaxation times were mapped with a multi-spin echo sequence. All samples underwent microbiological testing and routine laboratory analysis to quantify lactate concentration and total protein content. Values obtained in septic and non-septic arthritis were compared with a Mann-Whitney U test. Synovial fluid from patients with septic arthritis (n=10) had higher concentrations of lactate (11.4 ± 4.0 mmol/L) and higher total protein content (51.8 ± 10.7 g/L) than fluid obtained in non-septic arthritis (n=20; 5.2±1.1 mmol/L and 40.4±6.9 g/L, respectively, p 2 relaxation times (as an indicator of total protein content) were moderately correlated to laboratory-confirmed lactate concentration (r 2 =0.71) and total protein content (r 2 =0.73). Markedly increased lactate concentrations (>6 mmol/L) in combination with low T 2 values ( 2 may be of value in the differentiation of septic from non-septic arthritis. (orig.)

Influence of dietary components on regulatory T cells

DEFF Research Database (Denmark)

Navikas, Shohreh; Teimer, Roman; Bockermann, Robert

2011-01-01

It is no longer a myth that a balanced diet is fundamental for general health. Common dietary components including vitamins A and D, omega-3 and probiotics are now widely accepted to be essential to protect against many diseases with an inflammatory nature. On the other hand, high fat diets...... components on diseases in which Tregs play a seminal role will be discussed. Among chronic diseases where dietary factors could have a direct influence via modulation of Tregs homeostasis and functions, we will review chronic tissue-specific autoimmune and inflammatory conditions such as IBD, T1D, MS, RA...

Relaxation along a fictitious field (RAFF and Z-spectroscopy using alternating-phase irradiation (ZAPI in permanent focal cerebral ischemia in rat.

Directory of Open Access Journals (Sweden)

Kimmo T Jokivarsi

Full Text Available Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI, were quantified together with conventional relaxation parameters (T1, T2 and T1ρ and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1 Time-dependent changes in RAFF and T1ρ relaxation are not coupled to those in MT. 2 RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3 MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4 ZAPI data suggest alterations in the T2 distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke.

Characterizing the microstructural basis of "unidentified bright objects" in neurofibromatosis type 1: A combined in vivo multicomponent T2 relaxation and multi-shell diffusion MRI analysis.

Science.gov (United States)

Billiet, Thibo; Mädler, Burkhard; D'Arco, Felice; Peeters, Ronald; Deprez, Sabine; Plasschaert, Ellen; Leemans, Alexander; Zhang, Hui; den Bergh, Bea Van; Vandenbulcke, Mathieu; Legius, Eric; Sunaert, Stefan; Emsell, Louise

2014-01-01

The histopathological basis of "unidentified bright objects" (UBOs) (hyperintense regions seen on T2-weighted magnetic resonance (MR) brain scans in neurofibromatosis-1 (NF1)) remains unclear. New in vivo MRI-based techniques (multi-exponential T2 relaxation (MET2) and diffusion MR imaging (dMRI)) provide measures relating to microstructural change. We combined these methods and present previously unreported data on in vivo UBO microstructure in NF1. 3-Tesla dMRI data were acquired on 17 NF1 patients, covering 30 white matter UBOs. Diffusion tensor, kurtosis and neurite orientation and dispersion density imaging parameters were calculated within UBO sites and in contralateral normal appearing white matter (cNAWM). Analysis of MET2 parameters was performed on 24 UBO-cNAWM pairs. No significant alterations in the myelin water fraction and intra- and extracellular (IE) water fraction were found. Mean T2 time of IE water was significantly higher in UBOs. UBOs furthermore showed increased axial, radial and mean diffusivity, and decreased fractional anisotropy, mean kurtosis and neurite density index compared to cNAWM. Neurite orientation dispersion and isotropic fluid fraction were unaltered. Our results suggest that demyelination and axonal degeneration are unlikely to be present in UBOs, which appear to be mainly caused by a shift towards a higher T2-value of the intra- and extracellular water pool. This may arise from altered microstructural compartmentalization, and an increase in 'extracellular-like', intracellular water, possibly due to intramyelinic edema. These findings confirm the added value of combining dMRI and MET2 to characterize the microstructural basis of T2 hyperintensities in vivo.

Determination of Proton Relaxivities of Mn(II, Cu(II and Cr(III added to Solutions of Serum Proteins

Directory of Open Access Journals (Sweden)

Ali Yilmaz

2009-04-01

Full Text Available Relaxometric studies are still of scientific interest due to their use in medicine and biology. In this study, proton T1 and T2 relaxivities of Mn(II, Cu(II and Cr(III in water were determined in the presence and absence of various proteins (albumin, α-globulin, γ-globulin, lysozyme, fibrinogen. The 1/T1 and 1/T2 in all solutions are linearly proportional to the concentration of the paramagnetic ions. Mn(II has the great influence to alter relaxations in all protein solutions, while Cu(II and Cr(III have a poor influence on the relaxations. In addition, Mn(II and Cu(II are bound to each protein, but Cr(III is not bound to any protein.

Proton T2 Relaxation effect of superparamagnetic iron oxide on fast spin echo sequence. Influence of echo number (even or odd) of effective TE

International Nuclear Information System (INIS)

Tsuchihashi, Toshio; Maki, Toshio; Kitagawa, Matsuo; Suzuki, Takeshi; Fujita, Isao

1999-01-01

The T 2 relaxation effect of the fast spin echo sequence (FSE) was investigated using superparamagnetic iron oxide (SPIO) particles. When even echoes were used as the effective TE of FSE, the signal intensity ratio [signal intensity of FSE/signal intensity of conventional spin echo sequence (CSE)] of FSE and CSE increased, whereas the T 2 relaxation effect of SPIO with FSE was reduced. However, when odd echoes were used, neither signal intensity changed, and weakening of the T 2 relaxation effect, considered a problem with FSE, was reduced. This phenomenon was not observed when the refocusing flip angle was changed to 30 and 60 degrees. However, it was observed when the refocusing flip angle was 120 and 150 degrees. Thus, this phenomenon can be considered to be related to oscillation in longitudinal magnetization when using the Carr-Purcell-Meiboom-Gill (CPMG) technique. (author)

Water-selective excitation of short T2 species with binomial pulses.

Science.gov (United States)

Deligianni, Xeni; Bär, Peter; Scheffler, Klaus; Trattnig, Siegfried; Bieri, Oliver

2014-09-01

For imaging of fibrous musculoskeletal components, ultra-short echo time methods are often combined with fat suppression. Due to the increased chemical shift, spectral excitation of water might become a favorable option at ultra-high fields. Thus, this study aims to compare and explore short binomial excitation schemes for spectrally selective imaging of fibrous tissue components with short transverse relaxation time (T2 ). Water selective 1-1-binomial excitation is compared with nonselective imaging using a sub-millisecond spoiled gradient echo technique for in vivo imaging of fibrous tissue at 3T and 7T. Simulations indicate a maximum signal loss from binomial excitation of approximately 30% in the limit of very short T2 (0.1 ms), as compared to nonselective imaging; decreasing rapidly with increasing field strength and increasing T2 , e.g., to 19% at 3T and 10% at 7T for T2 of 1 ms. In agreement with simulations, a binomial phase close to 90° yielded minimum signal loss: approximately 6% at 3T and close to 0% at 7T for menisci, and for ligaments 9% and 13%, respectively. Overall, for imaging of short-lived T2 components, short 1-1 binomial excitation schemes prove to offer marginal signal loss especially at ultra-high fields with overall improved scanning efficiency. Copyright © 2013 Wiley Periodicals, Inc.

T1 value of hyperplastic and hypoplastic bone marrow. Preliminary report

Energy Technology Data Exchange (ETDEWEB)

Asai, Sae; Yoshida, Hideo; Yoshikawa, Hiroki; Yashiro, Naofumi; Iio, Masahiro; Takaku, Fumimaro

1985-03-01

Magnetic resonance (MR) images of the bone marrow of 18 patients (11 normal control, 4 aplastic anemia, 2 chronic myelocytic leukemia, 1 polycythemia vera) were discussed. MR imager had 0.15T registive system. Sagittal section of the body was obtained with inversion recovery (TR1,000, 1,600/TI 350, 450/TE 13, 40 msec) and saturation recovery (TR 1,000, 2,000/TE 13,40 msec) sequences. T1 relaxation time was calculated from those images. T1 value of the thoracic and lumbar vertebral bone marrow which contains red marrow even in elderly patients was measured. T1 values of chronic myelocytic leukemia (CML) and polycythemia vera were longer than that of normal. T1 values of four aplastic anemia were all shorter than normal. CML and polycythemia vera can be called myeloproliferative disease and their bone marrows are hyperplastic, which may explain elongated T1. The bone marrow of aplasticanemia is hypoplastic and shows fatty change which may have decreased T1. Our results suggest T1 value of bone marrow is useful to evaluate hematological disorders. (author).

QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

Science.gov (United States)

Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

2018-02-14

Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

In vivo determination of T1 and T2 in the brain of patients with severe but stable multiple sclerosis

DEFF Research Database (Denmark)

Larsson, H B; Frederiksen, J; Kjaer, L

1988-01-01

investigated, using a whole-body superconductive MR scanner, operating at 1.5 T. By employing 12-point (or 6-point) partial saturation inversion recovery (PSIR) and 32-echo multiple spin-echo sequences we measured T1 and T2 in MS plaques, white matter, and cortical gray matter. We also focused on the issue......, whether T1 and T2 relaxation processes in fact were monoexponential. T1 and T2 in plaques were found to cover a wide range, which could be explained only by inherent biophysical dissimilarity of the plaques, possibly due to differences in disease activity, edema and gliosis. T1 appeared monoexponential...... in all the plaques, but in seven cases T2 showed biexponential behavior. This was found to be most pronounced near the cerebrospinal fluid of the ventricles, probably caused by partial volume effects or increased free water content. The T2 of apparently normal white matter was significantly longer in MS...

Dielectric and mechanical relaxation in isooctylcyanobiphenyl (8*OCB)

Energy Technology Data Exchange (ETDEWEB)

Pawlus, S; Mierzwa, M; Paluch, M; Rzoska, S J [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Roland, C M, E-mail: michal.mierzwa@us.edu.p [Chemistry Division, Naval Research Laboratory, Code 6120, Washington, DC 20375-5342 (United States)

2010-06-16

The dynamics of isooctylcyanobiphenyl (8*OCB) was characterized using dielectric and mechanical spectroscopies. This isomer of the liquid crystalline octylcyanobiphenyl (8OCB) vitrifies during cooling or on application of pressure, exhibiting the typical features of glass-forming liquids: non-Debye relaxation function, non-Arrhenius temperature dependence of the relaxation times, {tau}{sub {alpha}}, a dynamic crossover at T {approx} 1.6T{sub g}. This crossover is evidenced by changes in the behavior of both the peak shape and the temperature dependence of {tau}{sub {alpha}}. The primary relaxation time at the crossover, 2 ns at ambient pressure, is the smallest value reported to date for any molecular liquid or polymer. Interestingly, at all temperatures below this crossover, {tau}{sub {alpha}}and the dc conductivity remain coupled (i.e., conform to the Debye-Stokes-Einstein relation). Two secondary relaxations are observed in the glassy state, one of which is identified as the Johari-Goldstein process. Unlike the case for 8OCB, no liquid crystalline phase could be attained for 8*OCB, demonstrating that relatively small differences in chemical structure can effect substantial changes in the intermolecular potential.

Brownian rotational relaxation and power absorption in magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Goya, G.F. [Institute of Nanoscience of Aragon (INA), University of Zaragoza, 50009 Zaragoza (Spain)]. E-mail: goya@unizar.es; Fernandez-Pacheco, R. [Institute of Nanoscience of Aragon (INA), University of Zaragoza, 50009 Zaragoza (Spain); Arruebo, M. [Institute of Nanoscience of Aragon (INA), University of Zaragoza, 50009 Zaragoza (Spain); Cassinelli, N. [Electronics Division, Bauer and Associates, Buenos Aires (Argentina); Facultad de Ingenieria, UNLP (Argentina); Ibarra, M.R. [Institute of Nanoscience of Aragon (INA), University of Zaragoza, 50009 Zaragoza (Spain)

2007-09-15

We present a study of the power absorption efficiency in several magnetite-based colloids, to asses their potential as magnetic inductive hyperthermia (MIH) agents. Relaxation times {tau} were measured through the imaginary susceptibility component {chi}{sup '}'(T), and analyzed within Debye's theory of dipolar fluid. The results indicated Brownian rotational relaxation and allowed to calculate the hydrodynamic radius close to the values obtained from photon correlation. The study of the colloid performances as power absorbers showed no detectable increase of temperature for dextran-coated Fe{sub 3}O{sub 4} nanoparticles, whereas a second Fe{sub 3}O{sub 4}-based dispersion of similar concentration could be heated up to 12K after 30min under similar experimental conditions. The different power absorption efficiencies are discussed in terms of the magnetic structure of the nanoparticles.

Stress relaxation of bi-disperse polystyrene melts

DEFF Research Database (Denmark)

Hengeller, Ludovica; Huang, Qian; Dorokhin, Andriy

2016-01-01

We present start-up of uniaxial extension followed by stress relaxation experiments of a bi-disperse 50 % by weight blend of 95k and 545k molecular weight polystyrene. We also show, for comparison, stress relaxation measurements of the polystyrene melts with molecular weight 95k and 545k, which...... are the components of the bi-disperse melt. The measurements show three separated relaxation regimes: a fast regime, a transition regime, and a slow regime. In the fast regime, the orientation of the long chains is frozen and the stress relaxation is due to stretch relaxation of the short chains primarily....... Conversely in the slow regime, the long chains have retracted and undergo relaxation of orientation in fully relaxed short chains....

Low-temperature strain ageing in In-Pb alloys under stress relaxation conditions

International Nuclear Information System (INIS)

Fomenko, L.S.

2000-01-01

The dynamic strain ageing (DSA) of In-Pb (6 and 8 at. % Pb) substitutional solid solution single crystals is studied at temperatures 77-205 K under stress relaxation conditions. The dependences of the stress increment after relaxation connected with DSA on stress relaxation time, stress relaxation rate at the end of the relaxation, temperature, alloy content, flow stress, and strain are determined. It is shown that the DSA kinetic is described by a Harper-type equation with the exponent equal to 1/3 and a low activation energy value (0.3-0.34 eV). This provides a low temperature of the DSA onset (∼ 0.17 T m , where T m is the melt temperature) and is evidence of pipe-mode diffusion. It is supposed that the obstacles to dislocation motion in the crystals studied consist of the groups of solutes, and the strength of the obstacles increases during the DSA due to the pipe diffusion of the solute atoms along the dislocations

Quantitative assessment of the T2 relaxation time of the gluteus muscles in children with Duchenne muscular dystrophy: a comparative study before and after steroid treatment.

Science.gov (United States)

Kim, Hee Kyung; Laor, Tal; Horn, Paul S; Wong, Brenda

2010-01-01

To determine the feasibility of using T2 mapping as a quantitative method to longitudinally follow the disease activity in children with Duchenne muscular dystrophy (DMD) who are treated with steroids. ELEVEN BOYS WITH DMD (AGE RANGE: 5-14 years) underwent evaluation with the clinical functional score (CFS), and conventional pelvic MRI and T2 mapping before and during steroid therapy. The gluteus muscle inflammation and fatty infiltration were evaluated on conventional MRI. The histograms and mean T2 relaxation times were obtained from the T2 maps. The CFS, the conventional MRI findings and the T2 values were compared before and during steroid therapy. None of the patients showed interval change of their CFSs. On conventional MRI, none of the images showed muscle inflammation. During steroid treatment, two boys showed increased fatty infiltration on conventional MRI, and both had an increase of the mean T2 relaxation time (p muscle changes in those children who receive steroid therapy for DMD. The differences of the mean T2 relaxation time may reflect alterations in disease activity, and even when the conventional MRI and CFS remain stable.

Non-equilibrium relaxation and near-arrest dynamics in colloidal suspensions

International Nuclear Information System (INIS)

Medina-Noyola, M; RamIrez-Gonzalez, Pedro

2009-01-01

In this work we propose a theory to describe the irreversible diffusive relaxation of the local concentration of a colloidal dispersion that proceeds toward its stable thermodynamic equilibrium state, but which may in the process be trapped in metastable or dynamically arrested states. The central assumption of this theory is that the irreversible relaxation of the macroscopically observed mean value n-bar(r,t) of the local concentration of colloidal particles is described by a diffusion equation involving a local mobility b*(r,t) that depends not only on the mean value n-bar(r,t) but also on the covariance σ(r,r';t)≡δn(r,t)δn(r',t)-bar of the fluctuations δn(r,t)≡n(r,t)-n-bar(r,t). This diffusion equation must hence be solved simultaneously with the relaxation equation for the covariance σ(r,r';t), and here we also derive the corresponding relaxation equation. The dependence of the local mobility b*(r,t) on the mean value and the covariance is determined by a self-consistent set of equations involving now the spatially and temporally non-local time-dependent correlation functions, which in a uniform system in equilibrium reduces to the self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics. The resulting general theory considers the possibility that these relaxation processes occur under the influence of external fields, such as gravitational forces acting in the process of sedimentation. In this paper, however, we describe a simpler application, in which the system remains spatially uniform during the irreversible relaxation process, and discuss the general features of the glass transition scenario predicted by this non-equilibrium theory.

Stress relaxation experiments on a lamellar polystyrene-polyisoprene diblock copolymer melt

DEFF Research Database (Denmark)

Holmqvist, P.; Castelletto, V.; Hamley, I.W.

2001-01-01

The non-linear rheology of the lamellar phase of a polystyrene-polyisoprene diblock copolymer is studied by oscillatory shear experiments. The relaxation of the shear modulus, G(t, gamma) is studied as a function of strain amplitude, gamma, up to large amplitude strains, gamma = 100%. The decay...... of G(t, gamma) is analysed using the model-independent CONTIN inverse Laplace transform algorithm to obtain a series of relaxation times, which reveals multiple relaxation processes. The timescale for the fastest relaxation processes is compared to those previously observed for diblock copolymer melts...... via dynamic light scattering experiments. The slowest relaxation process may be related to the shear-induced orientation of the lamellae. It is shown that time-strain separability G(t, gamma)= G(t)h(gamma) can be applied, and the damping function h(gamma) is consistent with a strongly strain...

Ovarian chocolate cysts. Staging with relaxation time in MR imaging

Energy Technology Data Exchange (ETDEWEB)

Sugimura, Kazuro; Ishida, Tetsuya; Takemori, Masayuki; Kitagaki, Hajime; Tanaka, Yutaka; Yamasaki, Katsuhito; Shimizu, Tadafumi; Kono, Michio

1988-10-01

Accurate preoperative staging of ovarian chocolate cysts is very important because recent hormonal therapy has been effective in low stage patients. However, it has been difficult to assess the preoperative stage of ovarian chocolate cysts. We evaluated the diagnostic potential of MRI in preoperative staging of 15 overian chocolate cysts. It was well known that the older the ovarian chocolate cyst was the more iron content it had. We examined the iron contents effect on T1 and T2 relaxation times in surgically confirmed chocolate cysts (stage II: 3 cases, stage III: 3 cases and stage IV: 9 cases by AFS classification, 1985) employing the 0.15-T MR system and 200 MHz spectrometer. There was a positive linear relation between T1 of the lesion using the MR system (T1) and T1 of the resected contents using the spectrometer (sp-T1); r = 0.93. The same relation was revealed between T2 and sp-T2; r = 0.87. It was indicated that T1 and T2 using the MR system was accurate. There was a negative linear relation between T1 and the iron contents ( r = -0.81) but no relation between T2 and the iron contents. T1 was 412 +- 91 msec for stage II, 356 +- 126 msec for stage III and 208 +- 30 msec for stage IV. T1 for stage IV was shorter than that for stage II and III, statistically significant differences were noted (p < 0.05). Thus, T1 was useful in differentiating a fresh from an old ovarian chocolate cyst. We concluded that T1 relaxation time using the MR system was useful for the staging of an ovarian chocolate cyst without surgery.

Muon-spin-relaxation study of magnetism in ErBa2Cu3O6.2

International Nuclear Information System (INIS)

Lichti, R.L.; Chan, K.B.; Adams, T.R.; Boekema, C.; Dawson, W.K.; Flint, J.A.; Cooke, D.W.; Kwok, R.S.; Willis, J.O.

1990-01-01

The copper magnetism of ErBa 2 Cu 3 O 6.2 is examined by transverse-field (TF) and zero-field (ZF) muon-spin relaxation (μSR). These data indicate two magnetic phases with T N1 congruent 330 K and T N2 ∼65 K. The second phase is signaled by deviation of the ZF-μSR frequencies from a standard magnetization curve and an abrupt change in the TF-μSR relaxation rate. A relaxation feature indicates a muon depolarization mechanism with a T 3/2 dependence in the low-temperature phase. Observed fields are compared to those calculated for proposed magnetic structures

Magnetization relaxation in spin glasses above transition point

International Nuclear Information System (INIS)

Zajtsev, I.A.; Minakov, A.A.; Galonzka, R.R.

1988-01-01

Magnetization relaxation of Cd 0.6 Zn 0.4 Cr 2 Se 4 and Cd 0.6 Mn 0.4 Te monocrystalline samples with T g =21 K and T g =12 K respectively and magnetic colloid is investigated. It is shown that magnetization inexponential relaxation detected experimentally in spin and dipole glasses is essentially higher than T g temperature transition. It is found that at temperatures higher than T g the essential difference is observed in behaviour of spin glasses with different Z and disorder types

Dielectric relaxation in Li2SO4 in the intermedia-temperature regime

Science.gov (United States)

Diosa, J. E.; Vargas, R. A.; Fernández, M. E.; Albinsson, I.; Mellander, B.-E.

2005-08-01

The dielectric permittivity of polycrystalline Li2SO4 was measured from 5 Hz to 13 MHz and over the temperature range 235-460 °C. The corrected imaginary part of permittivity, , and its real part vs. frequency clearly show a new dielectric relaxation around fmax = 2 × 104 Hz at T = 256 °C, which shifts to higher frequencies (1 MHz) as the temperatures increases. The relaxation frequency (calculated from the peak position of ) vs. reciprocal T shows an activated relaxation process with activation energy Ea= 0.9 eV, which is very close to that derived from the dc conductivity, E (0.87 eV). We suggest that this dielectric relaxation could be due to the Li+ jump and SO4- reorientation that cause distortion and change of the local lattice polarizability inducing dipoles like LiSO4-.

The freezing of water bonded in the wheat (Triticum aestivum L.) grain studied by means protons magnetic relaxation method; Zamarzanie wody zwiazanej w ziarnach pszenicy (Triticum aestivum L.) badane metoda relaksacji magnetycznej dla protonow

Energy Technology Data Exchange (ETDEWEB)

Haranczyk, H.; Jasinski, G. [Inst. Fizyki, Uniwersytet Jagiellonski, Cracow (Poland); Strzalka, K. [Inst. Biologii Molekularnej, Uniwersytet Jagiellonski, Cracow (Poland)

1994-12-31

Some biological aspects of water freezing in the wheat grain have been studied using NMR methods. Measuring of the relaxation times for freezing and liquid water shown absence of T{sub 2}{approx}100 {mu}s and T{sub 2}{approx}1 ms separated components what pointed for some different way of water bonding. 7 refs, 12 figs, 2 tabs.

Induced magnetic moment in stainless steel components of orthodontic appliances in 1.5 T MRI scanners

Science.gov (United States)

Rollins, Nancy K.; Liang, Hui; Park, Yong Jong

2015-01-01

Purpose: Most orthodontic appliances are made of stainless steel materials and induce severe magnetic susceptibility artifacts in brain MRI. In an effort for correcting these artifacts, it is important to know the value of induced magnetic moments in all parts of orthodontic appliances. In this study, the induced magnetic moment of stainless steel orthodontic brackets, molar bands, and arch-wires from several vendors is measured. Methods: Individual stainless steel brackets, molar bands, and short segments of arch-wire were positioned in the center of spherical flask filled with water through a thin plastic rod. The induced magnetic moment at 1.5 T was determined by fitting the B0 map to the z-component of the magnetic dipole field using a computer routine. Results: The induced magnetic moment at 1.5 T was dominated by the longitudinal component mz, with a small contribution from the transverse components. The mz was insensitive to the orientation of the metal parts. The orthodontic brackets collectively dominated the magnetic dipole moment in orthodontic appliances. In brackets from six vendors, the total induced mz from 20 brackets for nonmolar teeth ranged from 0.108 to 0.158 (median 0.122) A ⋅ m2. The mz in eight molar bands with bracket attachment from two vendors ranged from 0.0004 to 0.0166 (median 0.0035) A ⋅ m2. Several full length arch wires had induced magnetic moment in the range of 0.006–0.025 (median 0.015) A ⋅ m2. Conclusions: Orthodontic brackets collectively contributed most to the total magnetic moment. Different types of brackets, molar bands, and arch wires all exhibit substantial variability in the induced magnetic moment. PMID:26429261

The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method

Science.gov (United States)

Savchenko, D.; Shanina, B.; Kalabukhova, E.; Pöppl, A.; Lančok, J.; Mokhov, E.

2016-04-01

We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation "sandwich method" (SSM) with a donor concentration of about 1017 cm-3 at T = 10-40 K. The donor electrons of the N donors substituting quasi-cubic "k1" and "k2" sites (Nk1,k2) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T1-1), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T9, respectively. The character of the temperature dependence of the T1-1 for the donor electrons of N substituting hexagonal ("h") site (Nh) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (Tm-1) with the temperature increase for the Nh donors in both types of the samples, as well as for the Nk1,k2 donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time Tm for the Nk1,k2 donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at Nh and Nk1,k2 sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.

Cooling-history effects on magnetic relaxation through quantum tunneling

Science.gov (United States)

Fernandez, Julio; Alonso, Juan

2003-03-01

Magnetic clusters, such as Fe8 and Mn_12, that make up the core of large organometallic molecules, behave at low temperatures as large single spins S. In crystals, magnetic anisotropy energies U inhibit magnetic relaxation of these spins, which can then proceed at very small temperatures (at k_BT tunneling (MQT). Magnetic dipolar interactions then play an essential role. We study how an Ising system of spins that interact through magnetic dipolar fields relaxes. A spin is allowed to flip, at rate Γ, only if the magnetic field h acting on it is within some tunnel window -hw < h< h_w. We let (1) this system be initially held for some time at some temperature Ta that is above both the long-range ordering temperature and T ˜ U/S, and (2) apply a magnetic field at t=0, inmediately after the system is quenched to T < 0.1U/S. This is somewhat as in the experiments of Wernsdorfer et al on Fe_8. The time evolution of the magnetiztion m and field distributions after the field is applied at t=0 is studied. For small applied fields H, m ˜= hw HF(Γ t). In addition, F(Γ t)˜= cΓ t for Γ t < 1 and F(Γ t)˜= cΓ t for 1 <Γ t < (h_d/h_w)^2, where hd is a nearest neighbor dipolar field. We will show how c depends on the cooling protocol. Finally, m saturates at m_s˜= 0.13\\varepsilon_aH.

{sup 13}C relaxation in an RNA hairpin

Energy Technology Data Exchange (ETDEWEB)

King, G.C. [Univ. of South Wales, Kensington (Australia)]|[Rice Univ., Houston, TX (United States); Akratos, C. [Univ. of South Wales, Kensington (Australia); Xi, Z.; Michnica, M.J. [Rice Univ., Houston, TX (United States)

1994-12-01

This initial survey of {sup 13}C relaxation in the {triangle}TAR RNA element has generated a number of interesting results that should prove generally useful for future studies. The most readily comparable study in the literature monitored {sup 13}C relaxation of the methyl groups from unusual bases in tRNA{sup Phe}. The study, which used T{sub 1} and NOE data only, reported order parameters for the methyl group axis that ranged between 0.51 and 0.97-a range similar to that observed here. However, they reported a breakdown of the standard order parameter analysis at higher (118-MHz {sup 13}C) frequencies, which should serve to emphasize the need for a thorough exploration of suitable motional models.

Evaluation of the internal structure of articular cartilage in terms of 1H-NMR relaxation behavior

International Nuclear Information System (INIS)

Matsuo, Takeshi

2000-01-01

The structural characteristics of articular cartilage were analyzed using 1 H-longitudinal (T 1 ) and transverse (T 2 ) relaxation times as measured by fast-inversion-recovery and multi-spin-echo magnetic resonance imaging (MRI). Pairs of cartilage-bone plugs from weight bearing and non-weight bearing regions were dissected from 15 medial femoral condyles and were subjected to NMR measurements with and without static loads (0.15-1.0 MPa). The T 1 of the cartilage with no load showed a maximum value just beneath the articular surface and this value decreased gradually towards the deeper zones. The T 2 of the same cartilage showed a maximum value at, or just beneath, the articular surface, decreased rapidly towards the intermediate zone yet increased again in the deepest zone. The increase of T 2 in the deepest zone was more greatly pronounced in the weight bearing region than in the non-weight bearing region. These layer-dependent differences in the T 1 and T 2 could account for the laminar appearance of the articular cartilage in the MR images. Under static loads, the decrease of T 1 in the transitional zone (from just beneath the articular surface to the intermediate zone) was significant. Because T 1 has a positive correlation with the water content, this decrease in T 1 may signify that the largest water loss occurs in the transitional zone. These findings suggest that the transitional zone might attenuate mechanical stress in the joint, and the expressed water from the cartilage could substantially contribute to the lubrication of the joint. (author)

Evaluation of relaxation time measurements by magnetic resonance imaging. A phantom study

DEFF Research Database (Denmark)

Kjaer, L; Thomsen, C; Henriksen, O

1987-01-01

Several circumstances may explain the great variation in reported proton T1 and T2 relaxation times usually seen. This study was designed to evaluate the accuracy of relaxation time measurements by magnetic resonance imaging (MRI) operating at 1.5 tesla. Using a phantom of nine boxes with different...... concentrations of CuSO4 and correlating the calculated T1 and T2 values with reference values obtained by two spectrometers (corrected to MRI-proton frequency = 64 MHz) we found a maximum deviation of about 10 per cent. Measurements performed on a large water phantom in order to evaluate the homogeneity...... in the imaging plane showed a variation of less than 10 per cent within 10 cm from the centre of the magnet in all three imaging planes. Changing the gradient field strength apparently had no influence on the T2 values recorded. Consequently diffusion processes seem without significance. It is concluded...

Preliminary study for differential diagnosis of intracranial tumors using in vivo quantitative proton MR spectroscopy with correction for T2 relaxation time

International Nuclear Information System (INIS)

Isobe, Tomonori; Yamamoto, Tetsuya; Akutsu, Hiroyoshi; Shiigai, Masanari; Shibata, Yasushi; Takada, Kenta; Masumoto, Tomohiko; Anno, Izumi; Matsumura, Akira

2015-01-01

Introduction: The intent of this study was to differentiate intracranial tumors using the metabolite concentrations obtained by quantification with correction for T2 relaxation time, and to analyze whether the spectrum peak was generated by the existence of metabolites in proton magnetic resonance spectroscopy (MRS). Methods: All proton MRS studies were performed on a clinical 1.5T MR system. 7 normal volunteers and 57 patients (gliomas, metastases, meningiomas, acoustic neuromas, and pituitary adenomas) underwent single voxel proton MRS with different echo times (TE: 68, 136, 272 ms) for T2 correction of signal derived from metabolites and tissue water. With tissue water employed as an internal reference, the concentrations of metabolite (i.e. N-acetylaspartate (NAA), total creatine (t-Cr) and choline-containing compounds (Cho)) were calculated. Moreover, proton MRS data of previously published typical literatures were critically reviewed and compared with our data. Results: Extramedullary tumors were characterized by absence of NAA compared with intramedullary tumors. High-grade glioma differed from low-grade glioma by lower t-Cr concentrations. Metastasis differed from cystic glioblastoma by higher Cho concentrations, lower t-Cr concentrations, an absence of NAA, and a prominent Lipids peak. Based on these results and review of previous reports, we suggest a clinical pathway for the differentiation of intracranial tumors. Conclusion: The metabolite concentrations obtained by quantification with correction for T2 relaxation time, and to analyze whether the spectrum peak was generated by the existence of metabolites in proton MRS is useful for the diagnosis of the intracranial tumors

Quantitative MRI T2 relaxation time evaluation of knee cartilage: comparison of meniscus-intact and -injured knees after anterior cruciate ligament reconstruction.

Science.gov (United States)

Li, Hong; Chen, Shuang; Tao, Hongyue; Chen, Shiyi

2015-04-01

Associated meniscal injury is well recognized at anterior cruciate ligament (ACL) reconstruction, and it is a known risk factor for osteoarthritis. To evaluate and characterize the postoperative appearance of articular cartilage after different meniscal treatment in ACL-reconstructed knees using T2 relaxation time evaluation on MRI. Cohort study; Level of evidence, 3. A total of 62 consecutive patients who under ACL reconstruction were recruited in this study, including 23 patients undergoing partial meniscectomy (MS group), 21 patients undergoing meniscal repair (MR group), and 18 patients with intact menisci (MI group) at time of surgery. Clinical evaluation, including subjective functional scores and physical examination, was performed on the same day as the MRI examination and at follow-up times ranging from 2 to 4.2 years. The MRI multiecho sagittal images were segmented to determine the T2 relaxation time value of each meniscus and articular cartilage plate. Differences in each measurement were compared among groups. No patient had joint-line tenderness or reported pain or clicking on McMurray test or instability. There were also no statistically significant differences in functional scores or medial or lateral meniscus T2 values among the 3 groups (P > .05 for both). There was a significantly higher articular cartilage T2 value in the medial femorotibial articular cartilage for the MS group (P T2 value between the MS and MR groups (P > .05) in each articular cartilage plate. The medial tibial articular cartilage T2 value had a significant positive correlation with medial meniscus T2 value (r = 0.287; P = .024) CONCLUSION: This study demonstrates that knees with meniscectomy or meniscal repair had articular cartilage degeneration at 2 to 4 years postoperatively, with higher articular cartilage T2 relaxation time values compared with the knees with an intact meniscus. © 2015 The Author(s).

MR imaging of the stomach and relaxation measurement with intraluminal hyperpolarized 129Xenon gas

International Nuclear Information System (INIS)

Yanagawa, Yasuhiro; Kimura, Atsuomi; Fujiwara, Hideaki; Kinoshita, Yoshimasa; Hattori, Mineyuki; Hiraga, Takashi; Iida, Hidehiro

2001-01-01

Using laser optical pumping, the nuclear spin polarization of noble gases can be strongly enhanced. The purpose of this study was to make a simple apparatus that can provide hyperpolarized 129 Xe gas, which can then be used in an attempt to obtain magnetic resonance imaging (MRI). We would also like to study the relaxation behavior of hyperpolarized 129 Xe gas through the measurement of the relaxation time. First, we demonstrated that hyperpolarized 129 Xe gas can be applied to magnetic resonance imaging of the stomach, by using a rat as a model. This was performed under a 4.7 T magnet field using the following imaging parameters for the hyperpolarized 129 Xe gas: TR=50 ms, TE=15 ms, FOV=10 x 10 cm 2 , matrix size 64 x 64, THK=2.54 cm. By using these parameters, we were able to obtain a hyperpolarized image of the stomach in rats for the first time. Next, we measured the relaxation times of the hyperpolarized 129 Xe gas enclosed in cavities such as the stomach of rats as well as in phantoms created by glass and gelatin bulbs. The cavity size dependency of the relaxation time was analyzed on the basis of the kinetic theory of gases. This analysis showed a linear relationship between the relaxation rate (1/T 1 ) and a square inverse of the cavity diameter (1/d 2 ). From this relationship, the wall effect on the 129 Xe relaxation can be estimated in the novel parameter t 1 , wall . This shows drastic dependency on the material of the wall, suggesting a potential use of the relaxation experiment as a diagnostic tool for organ surfaces in the future. (author)

Ultralow-field and spin-locking relaxation dispersion in postmortem pig brain.

Science.gov (United States)

Dong, Hui; Hwang, Seong-Min; Wendland, Michael; You, Lixing; Clarke, John; Inglis, Ben

2017-12-01

To investigate tissue-specific differences, a quantitative comparison was made between relaxation dispersion in postmortem pig brain measured at ultralow fields (ULF) and spin locking at 7 tesla (T). The goal was to determine whether ULF-MRI has potential advantages for in vivo human brain imaging. Separate specimens of gray matter and white matter were investigated using an ULF-MRI system with superconducting quantum interference device (SQUID) signal detection to measure T1ULF at fields from 58.7 to 235.0 μT and using a commercial MRI scanner to measure T1ρ7T at spin-locking fields from 5.0 to 235.0 μT. At matched field strengths, T1ρ7T is 50 to 100% longer than T1ULF. Furthermore, dispersion in T1ULF is close to linear between 58.7 and 235 µT, whereas dispersion in T1ρ7T is highly nonlinear over the same range. A subtle elbow in the T1ULF dispersion at approximately 140 µT is tentatively attributed to the local dipolar field of macromolecules. It is suggested that different relaxation mechanisms dominate each method and that ULF-MRI has a fundamentally different sensitivity to the macromolecular structure of neural tissue. Ultralow-field MRI may offer distinct, quantitative advantages for human brain imaging, while simultaneously avoiding the severe heating limitation imposed on high-field spin locking. Magn Reson Med 78:2342-2351, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Hydrogen bond network relaxation in aqueous polyelectrolyte solutions: the effect of temperature

International Nuclear Information System (INIS)

Sarti, S; Bordi, F; Truzzolillo, D

2012-01-01

Dielectric spectroscopy data over the range 100 MHz-40 GHz allow for a reliable analysis of two of the major relaxation phenomena for polyelectrolytes (PE) in water. Within this range, the dielectric relaxation of pure water is dominated by a near-Debye process at ν = 18.5 GHz corresponding to a relaxation time of τ = 8.4 ps at 25 °C. This mode is commonly attributed to the cooperative relaxation specific to liquids forming a hydrogen bond network (HBN) and arising from long range H-bond-mediated dipole-dipole interactions. The presence of charged polymers in water partially modifies the dielectric characteristics of the orientational water molecule relaxation due to a change of the dielectric constant of water surrounding the charges on the polyion chain. We report experimental results on the effect of the presence of a standard flexible polyelectrolyte (sodium polyacrylate) on the HBN relaxation in water for different temperatures, showing that the HBN relaxation time does not change by increasing the polyelectrolyte density in water, even if relatively high concentrations are reached (0.02 monomol l -1 ≤ C ≤ 0.4 monomol l -1 ). We also find that the effect of PE addition on the HBN relaxation is not even a broadening of its distribution, rather a decrease of the spectral weight that goes beyond the pure volume fraction effect. This extra decrease is larger at low T and less evident at high T, supporting the idea that the correlation length of the water is less affected by the presence of charged flexible chains at high temperatures. (paper)

Relaxation of helium levels excited by heavy ion impact: III.- Orientation by anisotropic relaxation of excited atoms in previously aligned states

International Nuclear Information System (INIS)

Chamoun, E.; Lombardi, M.; Carre, M.; Gaillard, M.L.

1977-01-01

In the last paper of this series devoted to relaxation phenomena in a low pressure cell of helium excited by an accelerated ion beam, experimental evidence is given for a new mechanism of transfer between alignment and orientation through anisotropic relaxation of initially aligned excited states. The theory predicting this effect is briefly outlined and then description is given of the exact experimental conditions to detect the circularly polarized component of the light emitted by the target excited in the 4 1 D level of He I by Na + impact [fr

Nuclear spin phonon relaxation by Raman process in Na{sub 3}H(SO{sub 4}){sub 2} single crystals with the electric-quadrupole-type interaction using {sup 1}H and {sup 23}Na NMR

Energy Technology Data Exchange (ETDEWEB)

Lim, Ae Ran [Department of Science Education, Jeonju University, Jeonju 560-759, Chonbuk (Korea, Republic of)], E-mail: aeranlim@hanmail.net; Shin, Chang Woo [Solid State Analysis Team, Korea Basic Science Institute, Daegu 702-701 (Korea, Republic of)

2008-11-30

Successive phase transitions in a Na{sub 3}H(SO{sub 4}){sub 2} single crystal were found at 296, 513, and 533 K. To investigate the mechanism of the phase transition at 296 K, the {sup 1}H and {sup 23}Na spin-lattice relaxation time and the spin-spin relaxation time of Na{sub 3}H(SO{sub 4}){sub 2} were measured near the phase transition temperature using a FT NMR spectrometer. The spin-lattice relaxation time, T{sub 1}, for {sup 1}H in Na{sub 3}H(SO{sub 4}){sub 2} crystals exhibits a minimum below T{sub C1} (=296 K) indicating the presence of distinct molecular motion governed by the Bloembergen-Purcell-Pound (BPP) theory. Although the results for the {sup 1}H and {sup 23}Na relaxation times provide no evidence of the phase transition at T{sub C1}, the separation of the {sup 23}Na resonance lines changes abruptly at T{sub C1}. The phase transition at 296 K produces a change in the separation of the Na resonance line that is associated with a change in the atomic positions in the vicinity of the Na ions. Also, the nuclear spin-lattice relaxation process in Na{sub 3}H(SO{sub 4}){sub 2} crystals with the electric-quadrupole-type interaction proceed via Raman process. These results are compared with those obtained for other M{sub 3}H(SO{sub 4}){sub 2} (M=K, Rb, and Cs) crystals, which have similar hydrogen-bonded structures.

¹²⁹ Xe NMR Relaxation-Based Macromolecular Sensing

Energy Technology Data Exchange (ETDEWEB)

Gomes, Muller D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Dao, Phuong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Jeong, Keunhong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Slack, Clancy C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Vassiliou, Christophoros C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Finbloom, Joel A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Francis, Matthew B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Wemmer, David E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Physical Biosciences Division; Pines, Alexander [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

2016-07-29

A ¹²⁹Xe NMR relaxation-based sensing approach is reported on that exploits changes in the bulk xenon relaxation rate induced by slowed tumbling of a cryptophane-based sensor upon target binding. The amplification afforded by detection of the bulk dissolved xenon allows sensitive detection of targets. The sensor comprises a xenon-binding cryptophane cage, a target interaction element, and a metal chelating agent. Xenon associated with the target-bound cryptophane cage is rapidly relaxed and then detected after exchange with the bulk. Here we show that large macromolecular targets increase the rotational correlation time of xenon, increasing its relaxation rate. Upon binding of a biotin-containing sensor to avidin at 1.5 μM concentration, the free xenon T₂ is reduced by a factor of 4.

Synergic nature of dielectric relaxation process in the layered perovskite halide salts: The case of 1,3- diammoniumpropylenetetrabromocadmate compound

Science.gov (United States)

Staśkiewicz, Beata

2018-06-01

The negative thermal expansion (NTE) property was a prototype to discuss the origin of difference between classical Debye relaxation process and the non-Debye behavior in the layered perovskite halide salt of chemical formula NH3(CH2)3NH3CdBr4. The analysis has been taken by dielectric relaxation spectroscopy measurements in almost six decades in frequency 5 × 102 ≤ f(ω) ≤ 1.2 × 108 and in the temperature range 315 ≤ T(K) ≤ 390. It was shown that the investigated sample exhibit an antiferrodistortive nature of phase transition between two orthorhombic structural modifications i.e. Pnma (phase I) and Ima2 (phase II) at Tc1(I → II) = 326 K, leading from an antiferroelectric to a paraelectric phase. The involvement of an odd number of carbon atoms in the alkylammonium chains in dielectric properties of examined sample is proved. Higher structural modifications, i.e. Ima2 (phase II) and P21/m (phase III), have shown significant deviations from a regular circle on the Cole-Cole diagram. Presented experimental observations are essentially important for the theoretical explanation of relaxation processes in analyzed organic - inorganic compound crystallizing in a perovskite-like topology and may provide new perspective on the fundamental aspect of relaxation response in "diammonium" series.

Idiosyncratic reality claims, relaxation dispositions, and ABC relaxation theory: happiness, literal christianity, miraculous powers, metaphysics, and the paranormal.

Science.gov (United States)

Smith, Jonathan C; Karmin, Aaron D

2002-12-01

This study examined idiosyncratic reality claims, that is, irrational or paranormal beliefs often claimed to enhance relaxation and happiness and reduce stress. The Smith Idiosyncratic Reality Claims Inventory and the Smith Relaxation Dispositions Inventory (which measures relaxation and stress dispositions, or enduring states of mind frequently associated with relaxation or stress) were given to 310 junior college student volunteers. Principal components factor analysis with varimax rotation identified five idiosyncratic reality claim factors: belief in Literal Christianity; Magic; Space Aliens: After Death experiences; and Miraculous Powers of Meditation, Prayer, and Belief. No factor correlated with increased relaxation dispositions Peace, Energy, or Joy, or reduced dispositional somatic stress, worry, or negative emotion on the Smith Relaxation Dispositions Inventory. It was concluded that idiosyncratic reality claims may not be associated with reported relaxation, happiness, or stress. In contrast, previous research strongly supported self-affirming beliefs with few paranormal assumptions display such an association.

Volume and structural relaxation in compressed sodium borate glass.

Science.gov (United States)

Svenson, Mouritz N; Youngman, Randall E; Yue, Yuanzheng; Rzoska, Sylwester J; Bockowski, Michal; Jensen, Lars R; Smedskjaer, Morten M

2016-11-21

The structure and properties of glass can be modified through compression near the glass transition temperature (T g ), and such modified structure and properties can be maintained at ambient temperature and pressure. However, once the compressed glass undergoes annealing near T g at ambient pressure, the modified structure and properties will relax. The challenging question is how the property relaxation is correlated with both the local and the medium-range structural relaxation. In this paper, we answer this question by studying the volume (density) and structural relaxation of a sodium borate glass that has first been pressure-quenched from its T g at 1 GPa, and then annealed at ambient pressure under different temperature-time conditions. Using 11 B MAS NMR and Raman spectroscopy, we find that the pressure-induced densification of the glass is accompanied by a conversion of six-membered rings into non-ring trigonal boron (B III ) units, i.e. a structural change in medium-range order, and an increase in the fraction of tetrahedral boron (B IV ), i.e. a structural change in short-range order. These pressure-induced structural conversions are reversible during ambient pressure annealing near T g , but exhibit a dependence on the annealing temperature, e.g. the ring/non-ring B III ratio stabilizes at different values depending on the applied annealing temperature. We find that conversions between structural units cannot account for the pressure-induced densification, and instead we suggest the packing of structural units as the main densification mechanism.

Proton NMR relaxivity of blood samples in the presence of some gadolinium and dysprosium compounds

International Nuclear Information System (INIS)

Coroiu, I.; Darabont, Al.; Bogdan, M.

1999-01-01

The use of some new compounds in MRI tissue and blood characterisation based on nuclear spin relaxation time measurements cannot be sustained until the molecular sources of these variations are understood. Tissues and blood are complex molecular systems with complex NMR properties. A better comprehension of the molecular basis of relaxation offers the possibility to predict the changes expected for a given pathology. The purpose of this contribution is to evidence the different relaxation characteristics of some gadolinium and dysprosium compounds in the presence and absence of the blood and to give a possible explanation about the molecular processes that cause occurrence of changes. Some gadolinium and dysprosium compounds such as: Gd-CIT (gadolinium citrate), Dy-DTPA (DTPA-diethylenetriamine pentaacetic acid), iron oxide - gadolinium oxide (or dysprosium oxide)- dextran complexes were prepared. The longitudinal T 1 -1 and transverse T 2 -1 'relaxation rates' measurements have been carried out as a function of molar concentrations. All measurements have been made at room temperature (about 25 deg.C) and the proton Larmor frequency ν o = 90 MHz. The pulsed NMR spectrometer utilised was a commercial Bruker SXP4/100 spectrometer. Transverse relaxation rate measurements have been made using the Carr-Purcell method, while longitudinal relaxation rate measurements using the inversion recovery pulse sequence, 180 angle-τ-90 angle. The accuracy was about 2-3% for the longitudinal relaxation rates and about 5-7% for the transverse relaxation rates. R 1 and R 2 relaxivities, in mM -1 s -1 were determined from the least square determination of the slopes of plots 1/T 1,2 versus compound molar concentration, using at least five independent measurements at several concentrations between 0 and 2 mM. Increased R 2 relaxivity observed for dysprosium compounds in the blood presence can be explained by PRE effect. The largest gain in R 2 relaxivity seems to imply a noncovalent

Combined Fat Imaging/Look Locker for mapping of lipid spin-lattice (T1) relaxation time

Science.gov (United States)

Jihyun Park, Annie; Yung, Andrew; Kozlowski, Piotr; Reinsberg, Stefan

2012-10-01

Tumor hypoxia is a main problem arising in the treatment of cancer due to its resistance to cytotoxic therapy such as radiation and chemotherapy, and selection for more aggressive tumor phenotypes. Attempts to improve and quantify tumor oxygenation are in development and tools to assess the success of such schemes are required. Monitoring oxygen level with MRI using T1 based method (where oxygen acts as T1 shortening agent) is a dynamic and noninvasive way to study tumor characteristics. The method's sensitivity to oxygen is higher in lipids than in water due to higher oxygen solubility in lipid. Our study aims to develop a time-efficient method to spatially map T1 of fat inside the tumor. We are combining two techniques: Fat/Water imaging and Look Locker (a rapid T1 measurement technique). Fat/Water Imaging is done with either Dixon or Direct Phase Encoding (DPE) method. The combination of these techniques poses new challenges that are tackled using spin dynamics simulations as well as experiments in vitro and in vivo.

Evaluation of creep damage due to stress relaxation in SA533 grade B class 1 and SA508 class 3 pressure vessel steels

International Nuclear Information System (INIS)

Hoffmann, C.L.; Urko, W.

1993-01-01

Creep damage can result from stress relaxation of residual stresses in components when exposed to high temperature thermal cycles. Pressure vessels, such as the reactor vessel of the modular high-temperature gas reactor (MHTGR), which normally operate at temperatures well below the creep range can develop relatively high residual stresses in high stress locations. During short term excursions to elevated-temperatures, creep damage can be produced by the loadings on the vessel. In addition, residual stresses will relax out, causing greater creep damage in the pressure vessel material than might otherwise be calculated. The evaluation described in this paper assesses the magnitude of the creep damage due to relaxation of residual stresses resulting from short term exposure of the pressure vessel material to temperatures in the creep range. Creep relaxation curves were generated for SA533 Grade B, Class 1 and SA508 Class 3 pressure vessel steels using finite element analysis of a simple uniaxial truss loaded under constant strain conditions to produce an initial axial stress equal to 1.25 times the material yield strength at temperature. The strain is held constant for 1000 hours at prescribed temperatures from 700 F to 1000 F. The material creep law is used to calculate the relaxed stress for each time increment. The calculated stress relaxation versus time curves are compared with stress relaxation test data. Creep damage fractions are calculated by integrating the stress relaxation versus time curves and performing a linear creep damage summation using the minimum stress to rupture curves at the respective relaxation temperatures. Cumulative creep damage due to stress relaxation as a function of time and temperature is derived from the linear damage summation

Effective temperature in relaxation of Coulomb glasses.

Science.gov (United States)

Somoza, A M; Ortuño, M; Caravaca, M; Pollak, M

2008-08-01

We study relaxation in two-dimensional Coulomb glasses up to macroscopic times. We use a kinetic Monte Carlo algorithm especially designed to escape efficiently from deep valleys around metastable states. We find that, during the relaxation process, the site occupancy follows a Fermi-Dirac distribution with an effective temperature much higher than the real temperature T. Long electron-hole excitations are characterized by T(eff), while short ones are thermalized at T. We argue that the density of states at the Fermi level is proportional to T(eff) and is a good thermometer to measure it. T(eff) decreases extremely slowly, roughly as the inverse of the logarithm of time, and it should affect hopping conductance in many experimental circumstances.

Assessment of demyelination, edema, and gliosis by in vivo determination of T1 and T2 in the brain of patients with acute attack of multiple sclerosis

DEFF Research Database (Denmark)

Larsson, H B; Frederiksen, J; Petersen, J

1989-01-01

-body superconductive MR-scanner, operating at 1.5 T. The measurements were repeated several times, from onset of the disease and during remission by use of six-point partial saturation inversion recovery and 32-echo multiple spin-echo sequences, giving T1 and T2, respectively. We also focused on the issue, whether T1....... Hendriksen, and J. Olesen, Magn. Reson. Med. 7, 43 (1988)). In some of the acute plaques a slight initial increase in T1 and T2 was seen, when the measurement was repeated in about 10 days. Thereafter T1 decreased slowly in all but one patient as a function of days. In all cases the T1 relaxation process...

Fast T1 and T2 mapping methods: the zoomed U-FLARE sequence compared with EPI and snapshot-FLASH for abdominal imaging at 11.7 Tesla.

Science.gov (United States)

Pastor, Géraldine; Jiménez-González, María; Plaza-García, Sandra; Beraza, Marta; Reese, Torsten

2017-06-01

A newly adapted zoomed ultrafast low-angle RARE (U-FLARE) sequence is described for abdominal imaging applications at 11.7 Tesla and compared with the standard echo-plannar imaging (EPI) and snapshot fast low angle shot (FLASH) methods. Ultrafast EPI and snapshot-FLASH protocols were evaluated to determine relaxation times in phantoms and in the mouse kidney in vivo. Owing to their apparent shortcomings, imaging artefacts, signal-to-noise ratio (SNR), and variability in the determination of relaxation times, these methods are compared with the newly implemented zoomed U-FLARE sequence. Snapshot-FLASH has a lower SNR when compared with the zoomed U-FLARE sequence and EPI. The variability in the measurement of relaxation times is higher in the Look-Locker sequences than in inversion recovery experiments. Respectively, the average T1 and T2 values at 11.7 Tesla are as follows: kidney cortex, 1810 and 29 ms; kidney medulla, 2100 and 25 ms; subcutaneous tumour, 2365 and 28 ms. This study demonstrates that the zoomed U-FLARE sequence yields single-shot single-slice images with good anatomical resolution and high SNR at 11.7 Tesla. Thus, it offers a viable alternative to standard protocols for mapping very fast parameters, such as T1 and T2, or dynamic processes in vivo at high field.

Comparative study of imaging at 3.0 T versus 1.5 T of the knee

Energy Technology Data Exchange (ETDEWEB)

Wong, Scott [University of California, San Francisco, Department of Radiology, San Francisco, CA (United States); University of Miami Miller School of Medicine, Miami, FL (United States); Steinbach, Lynne; Zhao, Jian; Link, Thomas M. [University of California, Department of Radiology, San Francisco, CA (United States); Stehling, Christoph [University of California, Department of Radiology, San Francisco, CA (United States); University of Muenster, Department of Radiology, Muenster (Germany); Ma, C.B. [University of California San Francisco, Department of Orthopedic Surgery, San Francisco, CA (United States)

2009-08-15

The objectives of the study were to compare MR imaging at 1.5 and 3.0 T in the same patients concerning image quality and visualization of cartilage pathology and to assess diagnostic performance using arthroscopy as a standard of reference. Twenty-six patients were identified retrospectively as having comparative 1.5 and 3.0 T MR studies of the knee within an average of 102 days. Standard protocols included T1-weighted and fat-saturated intermediate-weighted fast spin-echo sequences in three planes; sequence parameters had been adjusted to account for differences in relaxation at 3.0 T. Arthroscopy was performed in 19 patients. Four radiologists reviewed each study independently, scored image quality, and analyzed pathological findings. Sensitivities, specificities, and accuracies in diagnosing cartilage lesions were calculated in the 19 patients with arthroscopy, and differences between 1.5 and 3.0 T exams were compared using paired Student's t tests with a significance threshold of p<0.05. Each radiologist scored the 3.0 T studies higher than those obtained at 1.5 T in visualizing anatomical structures and abnormalities (p<0.05). Using arthroscopy as a standard of reference, diagnosis of cartilage abnormalities was improved at 3.0 T with higher sensitivity (75.7% versus 70.6%), accuracy (88.2% versus 86.4%), and correct grading of cartilage lesions (51.3% versus 42.9%). Diagnostic confidence scores were higher at 3.0 than 1.5 T (p<0.05) and signal-to-noise ratio at 3.0 T was approximately twofold higher than at 1.5 T. MRI at 3.0 T improved visualization of anatomical structures and improved diagnostic confidence compared to 1.5 T. This resulted in significantly better sensitivity and grading of cartilage lesions at the knee. (orig.)

Comparative study of imaging at 3.0 T versus 1.5 T of the knee

International Nuclear Information System (INIS)

Wong, Scott; Steinbach, Lynne; Zhao, Jian; Link, Thomas M.; Stehling, Christoph; Ma, C.B.

2009-01-01

The objectives of the study were to compare MR imaging at 1.5 and 3.0 T in the same patients concerning image quality and visualization of cartilage pathology and to assess diagnostic performance using arthroscopy as a standard of reference. Twenty-six patients were identified retrospectively as having comparative 1.5 and 3.0 T MR studies of the knee within an average of 102 days. Standard protocols included T1-weighted and fat-saturated intermediate-weighted fast spin-echo sequences in three planes; sequence parameters had been adjusted to account for differences in relaxation at 3.0 T. Arthroscopy was performed in 19 patients. Four radiologists reviewed each study independently, scored image quality, and analyzed pathological findings. Sensitivities, specificities, and accuracies in diagnosing cartilage lesions were calculated in the 19 patients with arthroscopy, and differences between 1.5 and 3.0 T exams were compared using paired Student's t tests with a significance threshold of p<0.05. Each radiologist scored the 3.0 T studies higher than those obtained at 1.5 T in visualizing anatomical structures and abnormalities (p<0.05). Using arthroscopy as a standard of reference, diagnosis of cartilage abnormalities was improved at 3.0 T with higher sensitivity (75.7% versus 70.6%), accuracy (88.2% versus 86.4%), and correct grading of cartilage lesions (51.3% versus 42.9%). Diagnostic confidence scores were higher at 3.0 than 1.5 T (p<0.05) and signal-to-noise ratio at 3.0 T was approximately twofold higher than at 1.5 T. MRI at 3.0 T improved visualization of anatomical structures and improved diagnostic confidence compared to 1.5 T. This resulted in significantly better sensitivity and grading of cartilage lesions at the knee. (orig.)

Measurement of the exchange rate of waters of hydration in elastin by 2D T2-T2 correlation nuclear magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Sun Cheng; Boutis, Gregory S

2011-01-01

We report on a direct measurement of the exchange rate of waters of hydration in elastin by T 2 -T 2 exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543-59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.

Distinct mechanisms of relaxation to bioactive components from chamomile species in porcine isolated blood vessels

International Nuclear Information System (INIS)

Roberts, R.E.; Allen, S.; Chang, A.P.Y.; Henderson, H.; Hobson, G.C.; Karania, B.; Morgan, K.N.; Pek, A.S.Y.; Raghvani, K.; Shee, C.Y.; Shikotra, J.; Street, E.; Abbas, Z.; Ellis, K.; Heer, J.K.; Alexander, S.P.H.

2013-01-01

German chamomile (Matricaria recutita L.), a widely-used herbal medicine, has been reported to have a wide range of biological effects, including smooth muscle relaxation. The aim of this study was to compare the effects of representative compounds from chamomile (apigenin, luteolin, (−)-α-bisabolol, farnesene, umbelliferone; 3–30 μM) on vascular tone using porcine coronary and splenic arteries mounted for isometric tension recording in isolated tissue baths and precontracted with the thromboxane-mimetic U46619. Apigenin, luteolin, and (−)-α-bisabolol produced slow, concentration-dependent relaxations in both the coronary and splenic arteries that were not blocked by inhibition of nitric oxide synthase or potassium channels. Removal of extracellular calcium inhibited the relaxations to all three compounds, and these compounds also inhibited calcium re-addition-evoked contractions, indicating that the relaxation response may be mediated through inhibition of calcium influx. Apigenin and luteolin, but not (−)-α-bisabolol, enhanced the relaxation to the nitric oxide donor sodium nitroprusside, indicating that apigenin and luteolin may act to regulate cyclic GMP levels. Umbelliferone produced a rapid, transient relaxation in the splenic artery, but not the coronary artery, that was inhibited by L-NAME and removal of the endothelium, suggesting an influence on nitric oxide production. Farnesene, at concentrations up to 30 μM, was without effect in either blood vessel. In conclusion, hydroxylated compounds (apigenin, luteolin and (−)-α-bisabolol) found in chamomile all caused a slow relaxation of isolated blood vessels through an effect on calcium influx. Umbelliferone, on the other hand, produced a rapid, transient relaxation dependent upon release of nitric oxide from the endothelium. - Highlights: • Apigenin, luteolin, and (-)-α-bisabolol are present in chamomile. • They produced slow, concentration-dependent relaxations in arteries. • These

Distinct mechanisms of relaxation to bioactive components from chamomile species in porcine isolated blood vessels

Energy Technology Data Exchange (ETDEWEB)

Roberts, R.E., E-mail: Richard.roberts@nottingham.ac.uk; Allen, S.; Chang, A.P.Y.; Henderson, H.; Hobson, G.C.; Karania, B.; Morgan, K.N.; Pek, A.S.Y.; Raghvani, K.; Shee, C.Y.; Shikotra, J.; Street, E.; Abbas, Z.; Ellis, K.; Heer, J.K.; Alexander, S.P.H., E-mail: steve.alexander@nottingham.ac.uk

2013-11-01