Magnetic Resonance in Medical Sciences (Magn Reson Med Sci)

Publications in this journal

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  Available from: tsukuba.ac.jp

  Article: In vivo assessment of the trabecular bone microstructure of the distal radius using a compact MRI system.

  Shinya Handa, Sadanori Tomiha, Katsumi Kose, Tomoyuki Haishi
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  ABSTRACT: We repeatedly measured the trabecular bone (TB) microstructure of the distal radius in 5 healthy volunteers using a compact magnetic resonance (MR) imaging system to evaluate the reproducibility of the TB structural parameters. The compact system was specially developed with a 1.0-tesla permanent magnet for the distal radius in a previous study. We measured the distal radius using a 3-dimensional (3D), driven-equilibrium, spin-echo sequence (repetition time/echo time=80 ms/10 ms, number of excitations=1, field of view=76.8 mm x 57.6 mm x 16.0 mm, acquisition time=17 min, matrix size=512 x 384 x 32, voxel size=150 microm x 150 microm x 500 microm) and analyzed the acquired image datasets using the virtual bone biopsy system developed by the University of Pennsylvania. Root mean squares of the coefficients of variance expressed as percentages ranged from 2.9% to 14% for the TB structural parameters. Therefore, we concluded that this compact MR imaging system could be used to assess TB microstructure of the distal radius and provide results consistent with those using a whole-body MR imaging system and showing the promise of this system for evaluating bone quality in clinical settings.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):39-42.
• Article: 3D Hyperpolarized (129)Xe MRI of mouse lung at low xenon concentration using a continuous flow-type hyperpolarizing system: feasibility for quantitative measurement of regional ventilation.

  Yuki Hori, Atsuomi Kimura, Tetsuya Wakayama, Masakazu Kitamoto, Fumito Imai, Hirohiko Imai, Hideaki Fujiwara
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  ABSTRACT: We investigated the feasibility of 3D hyperpolarized (HP) (129)Xe magnetic resonance (MR) imaging at an extremely low concentration of HP (129)Xe supplied from a continuous flow-type hyperpolarizing (CF-HP) system and established a standard procedure for measuring regional lung ventilation of small animals, such as the mouse, as a baseline for further studies. We performed 3D HP (129)Xe MR imaging of the lungs of 2 healthy and 2 emphysematous mice that were spontaneously breathing diluted HP (129)Xe (<1%). From the three 3D MR images acquired by varying the flip angle of the radiofrequency (RF) pulse, we calculated the time constant of regional recovery, tau'(rep), which represents the time required for HP (129)Xe magnetization to be replenished approximately 63% after destruction of hyperpolarization by RF saturation pulse. After calculating the tau'(rep) maps, we examined the validity of our method. We used diluted xenon from the CF-HP system to acquire 3D HP (129)Xe MR images of the mouse lung that were undiminished under spontaneous respiration. The averaged tau'(rep) values were longer for the emphysematous lungs than for the healthy lungs, which reflected ventilation defects in the emphysematous lung. This procedure permitted us to estimate the regional lung ventilation for any arbitrarily set slice, and it will provide a standard for measuring regional lung ventilation as a baseline for further studies.
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):73-9.
• Article: Feasibility of navigator setting on the left diaphragm for whole-heart coronary MRA: a study in healthy volunteers.

  Kunihiro Watanabe, Satoru Morita, Takayoshi Suzuki, Kazuhiro Maruyama, Mayumi Noda, Takahiro Ohnishi, Mitsuo Fujita
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  ABSTRACT: We prospectively compared the quality of images obtained by navigator setting on the left and right diaphragm on whole-heart coronary magnetic resonance angiography (WHCMRA). In 10 healthy volunteers, we performed free-breathing, 3-dimensional segmented true fast imaging with steady-state precession (trueFISP) WHCMRA by setting the navigator on the left and right diaphragm in random order. For the left diaphragm, we set the navigator outside the scope of the heart to avoid the influence on coronary arteries. We compared image acquisition time and visible length of coronary arteries using paired t-test and subjective image quality on a 4-point scale (1, poor; 4, excellent) using Wilcoxon signed-rank test. Mean overall subjective image quality was significantly better in the left diaphragm than the right (3.3+/-0.7 versus 2.9+/-0.9, P=0.02). Mean overall visible length of the coronary arteries was significantly better in the left diaphragm than the right (115.4+/-31.1 vs. 112.6+/-29.9 mm, P=0.02). Mean acquisition time between the left and right diaphragm was not significantly different (15.6+/-5.0 versus 16.0+/-5.7 min, P=0.79). In this small group of healthy volunteers, navigator setting for WHCMRA was superior on the left diaphragm than the right; however, feasibility of the technique requires additional consideration in a larger group of actual patients.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):17-21.
• Article: Appropriate slice location to assess maximal cross-sectional area of individual rotator cuff muscles in normal adults and athletes.

  Osamu Yanagisawa, Michiko Dohi, Toru Okuwaki, Noriyuki Tawara, Mamoru Niitsu, Hideyuki Takahashi
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  ABSTRACT: We investigated appropriate slice locations for magnetic resonance (MR) imaging evaluation of the maximal cross-sectional area (CSA) of individual rotator cuff (RC) muscles in normal adults and athletes. We used a 1.5-tesla MR system with body-array and spine coils to obtain oblique sagittal T(1)-weighted shoulder images of 29 normal adults (16 men, 13 women); 6 national-level competitive swimmers (4 men, 2 women); 10 collegiate-level female badminton players; and 7 collegiate-level male rowers. We calculated the supraspinatus, infraspinatus, teres minor, and subscapularis CSAs at the 0-1 locations on the scapula (dividing scapula width into 11 locations), 0 representing the medial border of the scapula and 1, the glenoid fossa surface. We evaluated the differences in CSAs at relative locations on the scapula for each muscle in normal adults, swimmers, badminton players, and rowers using a one-way analysis of variance followed by the Tukey test (P<0.05). The supraspinatus CSAs were maximal at 0.7 for all groups. The infraspinatus CSAs were maximal at 0.5 for normal men and women and badminton players, 0.4- and 0.5 locations for swimmers, and 0.4 for rowers. The teres minor CSAs were maximal at 0.9 for all groups except the swimmers (1 location). The subscapularis CSAs were maximal at 0.7 in men, swimmers, and badminton players and 0.6 in women and rowers. The appropriate slice locations for evaluating maximal CSAs are slightly lateral to the center of the scapula for the supraspinatus and subscapularis, at approximately the center of the scapula for the infraspinatus, and near the glenoid fossa for the teres minor. These slice locations should be clinically useful for morphological and/or function-related assessments of shoulder RC muscles.
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):65-71.
• Article: Corticospinal tract extraction combining diffusion tensor tractography with FMRI in patients with brain diseases.

  Yuichi Suzuki, Kazuo Yagi, Takashi Kodama, Nobusada Shinoura
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  ABSTRACT: Our goal was to visualize diffusion tensor tractography (DTT) of the corticospinal tract (CST) with areas of activation on functional magnetic resonance imaging (fMRI) to acquire useful, highly accurate preoperative information. We investigated the usefulness of the technique and our method of precisely evaluating the depicted DTT in patients with brain disease. Nineteen subjects underwent 3-dimensional T(1)-weighted imaging for anatomical reference; gradient-echo, echo-planar imaging (EPI) for fMRI; and single-shot, diffusion-weighted EPI for DTT. The target point for DTT was placed within activated areas in the primary motor area on fMRI, and the seed point was placed in the cerebral peduncle. DTT was depicted with the seed and target points. We examined the precision of DTT using this method by assessing the anteroposterior relationship of depicted DTTs of the upper and lower extremities in the posterior limb of the internal capsule. DTT was depicted in 18 of 19 cases of the upper extremity and in 12 of 19 cases of the lower extremity. In the evaluation of precision, DTT reflected the posterior limb of the internal capsule in all cases. In terms of the anteroposterior relationship of DTTs, nine of 12 cases showed that fibers in the upper extremities passed in front of fibers in the lower extremities. This technique allows depiction of DTT associated with a local brain function in the CST in patients with brain disease and may be useful for operative planning. Our method of evaluating precision is also likely to prove useful.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):9-16.
• Article: Endolymphatic hydrops of the labyrinth visualized on noncontrast MR imaging: a case report.

  Shinji Naganawa, Michihiko Sone, Hironao Otake, Tsutomu Nakashima
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  ABSTRACT: We admitted an 11-year-old girl with enlarged endolymphatic duct and sac syndrome to our hospital with severe nausea and vertigo. Three-dimensional constructive interference in steady state (3D-CISS) and fluid-attenuated inversion recovery (3D-FLAIR) images revealed a reflux of proteinous or hemorrhagic fluid into enlarged endolymphatic space in the labyrinth. This is the first imaging report to show endolymphatic hydrops visualized by noncontrast-enhanced MR imaging in a living human patient.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):43-6.
• Article: Functional T(2) mapping of the trunkal muscle.

  Noriyuki Tawara, Osamu Nitta, Hironobu Kuruma, Mamoru Niitsu, Atsuto Hoshikawa, Toru Okuwaki, Akiyoshi Itoh
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):81-3.
• Article: Mucinous cystadenocarcinoma of the urachus associated with pseudomyxoma peritonei with emphasis on MR findings.

  Kouichi Sugiyama, Naoto Ito
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  ABSTRACT: Urachal mucinous cystadenocarcinoma associated with pseudomyxoma peritonei is extremely rare; only 11 cases are reported. We describe the characteristic imaging findings of this disorder and correlate imaging features by computed tomography, magnetic resonance imaging, and ultrasonography with operative findings and histopathologic specimens.
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):85-9.
• Article: Visualization of coronary arterial wall based on maximum intensity fusion of whole-heart MR angiograms and water suppression SPIR 3D T(1) TFE images.

  Shigeko Tanaka, Masuki Mori, Kazuhisa Kitazaki, Koichi Nakahira, Hiroki Nakatsuka, Yasutaka Maeda, Hisashi Madono, Yukari Naito, Yuko Sugimori, Yuichi Inoue
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  ABSTRACT: We estimated the coronary artery wall using maximum intensity fusion (MIF) of whole-heart magnetic resonance (MR) angiography (WHCA) and water suppression-spectral presaturation with inversion recovery (WS-SPIR) 3D T(1)-weighted turbo field echo (3DT(1) TFE). We created a phantom using a wall of plastic bottles varied with plastic tapes measuring 0.4 to 3.0 mm thick (0-14 sheets) by vernier caliper and compared widths with those on profile curves. In 3 patients, to clarify the capacity to visualize the coronary wall in vulnerable plaque, we acquired WS-SPIR 3D T(1) TFE and WS-spectral attenuation with inversion recovery (SPAIR) (inversion time [TI] 400 ms) 3D T(1) TFE images of carotid vulnerable plaque; also termed "lipid-rich plaque," vulnerable plaque is considered to be visualized in high intensity. We utilized the same geometric parameters and rest period on WHCA as for WS-SPIR 3D T(1) TFE. We obtained MIF of WHCA and WS-SPIR 3D T(1) TFE and measured thickness of the right coronary artery (RCA) wall on the profile curve in 18 cases. The widths of the dip of the lower third of the bottom to head on the profile curve were consistent with actual measurement at 1-2 mm, the usual coronary artery wall thickness. Carotid plaques of high intensity by T(1)-weighted black-blood (T(1)BB) and T(2)-weighted BB (T(2)BB) methods showed high intensity on WS-SPAIR (TI 400 ms) 3D T(1) TFE and low intensity on WS-SPIR 3D T(1) TFE. With or without vulnerable plaque in the coronary artery wall, MIF of WHCA and WS-SPIR 3D T(1) TFE reflected the coronary artery wall. We obtained bands of low intensity in MIF between epicardial fat of WS-SPIR 3D T(1) TFE and coronary artery lumen of WHCA all but mid RCA in all 18 cases. We were unable to detect mid RCA in 5 cases. The outline of the obstructed mid RCA in 1 case was clear in WS-SPIR 3D T(1) TFE. The higher velocity of RCA movement caused blurring in another 4 cases in both WHCA and WS-SPIR 3D T(1) TFE. Those wall thickness of proximal or mid RCA averaged 1.3+/-0.2 mm. Bands of low intensity between epicardial fat and coronary artery lumen on MIF of WHCA and WS-SPIR 3D T(1) TFE can reflect the coronary artery wall.
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):55-63.
• Article: Enlargement of the hippocampal angle: a new index of Alzheimer disease.

  Takafumi Hayashi, Akihiko Wada, Nobue Uchida, Hajime Kitagaki
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  ABSTRACT: Imaging diagnosis of Alzheimer disease (AD), the leading cause of dementia, requires evaluation of the extent of hippocampal atrophy. Coronal magnetic resonance (MR) images of patients with AD often demonstrate outward rotation of the hippocampus that is altered from a long horizontal elliptical to a long vertical elliptical shape. Such rotation may be related to the disease process of AD. To determine whether hippocampal rotation is associated with AD, we investigated MR images from 11 patients with AD and 11 normal controls, measuring the hippocampal angle (HA) and the volume of the left hippocampus on coronal T(1)-weighted MR images. The HA is the angle between a horizontal line orthogonal to the falx cerebri and the uncal sulcus line between the deepest point of the uncal sulcus and the point nearest to the side of the ambient cistern in the uncal gyrus facing the uncal sulcus. The HA is measured on the most rostral slice in which the uncal sulcus can be identified and increases with hippocampal rotation. We found correlation between the HA and standardized hippocampal volume in the AD group, but not in controls. Hippocampal rotation is a new marker associated with the pathology of AD.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):33-8.
• Article: Brain activation during the spot the differences game.

  Eiji Fukuba, Hajime Kitagaki, Akihiko Wada, Kouji Uchida, Shinji Hara, Takafumi Hayashi, Kazushige Oda, Nobue Uchida
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  ABSTRACT: Spot the Differences is a simple and popular game in which an observer compares a pair of similar pictures to detect the differences between them. Functional activation of the brain while playing this game has not been investigated. We used functional magnetic resonance imaging to investigate the main cortical regions involved in playing this game and compared the sites of cortical activation between a session of playing the game and a session of viewing 2 identical pictures. The right posterior parietal cortex showed more activation during game playing, and cortical activation volume correlated with game-playing accuracy. This cortical region may play an important role in awareness of differences between 2 similar pictures.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):23-32.
• Article: Estimation of cell membrane permeability and intracellular diffusion coefficient of human gray matter.

  Toshikazu Imae, Hiroyuki Shinohara, Masaki Sekino, Shoogo Ueno, Hiroyuki Ohsaki, Kazuo Mima, Kuni Ohtomo
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  ABSTRACT: The signal intensity of diffusion-weighted imaging (DWI) is sensitive to the intra- and extracellular diffusion coefficient of water and cell membrane permeability. We applied a method we proposed in previous papers to estimate noninvasively the membrane permeability and intracellular diffusion coefficient of normal human brain (gray matter) in 3 normal volunteers. We theoretically compared predicted signals and experiment results using a 1.5-tesla magnetic resonance (MR) imaging system. We acquired images using an echo planar imaging (EPI) sequence, applying motion-probing gradient (MPG) pulses in 3 directions. We periodically performed numerical simulations for various combinations of membrane permeability and intracellular diffusion coefficients using the finite-difference method. By minimizing the difference between signals obtained experimentally and those from numerical simulation, we could estimate membrane permeability (76+/-9 mm2/s mum) and intracellular diffusion coefficient (1.0+/-0.0 mm2/s) for the human brain. The estimated membrane permeability was the criterion value for diagnosing disease in gray matter.
  Magnetic Resonance in Medical Sciences 02/2009; 8(1):1-7.
• Article: Evaluation of initial diffusion-weighted image findings in acute stroke patients using a semiquantitative score.

  Naomi Morita, Masafumi Harada, Masaaki Uno, Shunji Matsubara, Shinji Nagahiro, Hiromu Nishitani
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  ABSTRACT: We evaluated the usefulness of rating diffusion-weighted images (DWI) using a semiquantitative score modified from the Alberta Stroke Programme Early CT Score (ASPECTS) to predict deterioration of neurological symptoms in patients with hyperacute ischemic stroke who had undergone thrombolytic therapy with recombinant tissue plasminogen activator (rt-PA). We examined 22 patients with acute stroke (14 men, 8 women, mean age 72.5 years) treated with intravenous rt-PA. All were assessed using the National Institutes of Health Stroke Scale (NIHSS) and underwent emergent magnetic resonance (MR) imaging within 3 hours and 24 hours of stroke onset. Patients were divided into a deteriorated group (16 patients), in which NIHSS scores were increased after thrombolysis, and a non-deteriorated group (6 patients). We compared the DWI score, ASPECTS, and volume of hyperintense ischemic lesion on DWI (DWI volume) of the 2 groups and examined correlations between these scores and initial NIHSS score or DWI volume. The DWI score and ASPECTS tended to be lower in the deteriorated group than the non-deteriorated group. In addition, with a cutoff value<or=7, the DWI score could discriminate the deteriorated group from the non-deteriorated group with a sensitivity of 50% and specificity of 87.5%, whereas for ASPECTS, sensitivity was 50% and specificity, 81.2%. The DWI score, ASPECTS, and DWI volume had no correlation with NIHSS score but weak negative correlations with the DWI volume (P<0.01; Spearman's test). Comparing initial NIHSS score with each DWI score and DWI volume, the non-deteriorated group tended to have higher DWI scores and smaller DWI volumes than the deteriorated group, but there was no statistical difference between initial NIHSS and DWI scores. Though the DWI score was not statistically different, the threshold would be set to 6 points or above. Comparing initial DWI score with volume, patients with low DWI scores tended to show large variation in DWI volume and patients with small DWI volume showed large variation in DWI scores. There was no relation between hemorrhagic change and symptoms in either group. The semiquantitative DWI score easily evaluated extent of acute ischemic lesion on DWI and might be used to predict patient outcome after thrombolytic therapy more accurately than ASPECTS or DWI volume.
  Magnetic Resonance in Medical Sciences 02/2009; 8(2):47-53.
• Article: MR imaging of fetal omphalocele: a case report.

  Yukio Sugai, Takaaki Hosoya, Hirohisa Kurachi
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  ABSTRACT: We report a case of a fetal omphalocele in which the internal structure of the hernia sac was imaged in detail by magnetic resonance (MR) imaging. The hernia sac consisted of amnion, Wharton jelly, and externally, peritoneum. The umbilical vascular channels (2 arteries, one vein) were surrounded by Wharton jelly. Use of MR imaging facilitates a more accurate evaluation of fetal omphalocele with regard to hernial sac, intestinal structure, and differential diagnosis.
  Magnetic Resonance in Medical Sciences 02/2008; 7(4):211-3.
• Article: Usual and unusual MRI findings of ovarian fibroma: correlation with pathologic findings.

  Kazuhiro Kitajima, Yasushi Kaji, Kazuro Sugimura
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  ABSTRACT: Ovarian fibromas typically exhibit low signal intensity on T(2)-weighted images, which reflects their abundant fibrocollagenous stroma. However, the mass of larger tumors often demonstrates high signal intensity on T(2)-weighted images, which reflects varied degenerative changes, such as cystic degeneration, edematous change, hemorrhagic infarction, or necrosis caused by torsion and myxomatous change. We illustrate typical and atypical magnetic resonance (MR) imaging findings of ovarian fibromas and correlate them with histopathologic findings.
  Magnetic Resonance in Medical Sciences 02/2008; 7(1):43-8.
• Article: A case of anti-aquaporin-4 and anti-glutamate receptor antibodies positive myelitis presented with modest clinical signs.

  Kazuhiro Honda, Tatsuhiko Yuasa
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  ABSTRACT: We present a case of anti-aquaporin-4 antibody-positive myelitis, which suggests the high-risk syndrome of neuromyelitis optica, whose modest clinical signs were in conspicuous contrast to the extensive spinal cord lesions demonstrated on magnetic resonance (MR) imaging. Follow-up MR imaging showed marked improvement of lesions. Interestingly, an anti-glutamate receptor antibody, which has been suggested to cause dysfunction of N-methy-D-aspartate receptor on neuron, was detected in the cerebrospinal fluid of the patient. We discuss the case and related literature.
  Magnetic Resonance in Medical Sciences 02/2008; 7(1):55-8.
• Article: Diagnosis of unruptured intracranial aneurysms: 3T MR angiography versus 64-channel multi-detector row CT angiography.

  Yoshiyasu Hiratsuka, Hitoshi Miki, Ikuko Kiriyama, Keiichi Kikuchi, Shizue Takahashi, Ichiro Matsubara, Kazuhiko Sadamoto, Teruhito Mochizuki
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  ABSTRACT: We compared 3-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA) using a 3-tesla (T) MR unit with 64-channel multi-detector row computed tomographic angiography (64-MDCTA) for detection and characterization of angiographically proven unruptured intracranial aneurysms. Thirty-eight patients with 47 aneurysms and 8 patients without aneurysms underwent 3T, 3D TOF MRA; 64-MDCTA; and intra-arterial angiography. As a first study, 3 radiologists blinded to pertinent clinical information independently reviewed MRA and CTA images. We evaluated diagnostic accuracy using an alternative free-response receiver operating characteristic (AFROC) analysis and evaluated the sensitivity and specificity of each technique. Next, 2 radiologists used volume-rendering images generated from MRA or CTA data to evaluate the morphology of the 47 aneurysms detected, and MRA and CTA results were compared. Three-dimensional digital angiography (DA) images were used as the standard of reference. On the AFROC analysis, the value of the mean area under the AFROC curve (A(1)) was 0.91 for both modalities. Mean sensitivity of 89% and specificity of 76% for MRA were not significantly different from sensitivity of 87% and specificity of 79% for CTA. Therefore, when used to evaluate aneurysmal morphology, both modalities appear satisfactory for determining these vascular anomalies. Three-tesla, 3D TOF MRA and 64-MDCTA are excellent modalities with high diagnostic accuracy for evaluating unruptured intracranial aneurysms and no significant difference between them in diagnostic performance.
  Magnetic Resonance in Medical Sciences 02/2008; 7(4):169-78.
• Article: Development of a noninvasive method to measure intravascular and intracardiac pressure differences using magnetic resonance imaging.

  Taisuke Nagao, Keita Yoshida, Koji Okada, Shohei Miyazaki, Takashi Ueguchi, Kenya Murase
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  ABSTRACT: We developed a noninvasive method using magnetic resonance (MR) imaging to measure differences in intravascular and intracardiac pressure, and we investigated the feasibility of the method's use in a pulsatile flow phantom and human studies. We measured 3 velocity components using phase contrast MR imaging on a 1.5T MR scanner, used velocity data in Navier-Stokes equations to obtain pressure gradients, and directly integrated the in-plane pressure gradients to calculate pressure differences. To validate our method, we compared the pressure differences obtained by our method with the theoretical values obtained from an axisymmetric model of arterial stenosis. We also estimated the pressure differences in glass-tube phantoms simulating various vascular pathologies and in the left ventricle and aortic arch of a normal volunteer as clinical application. The pressure differences obtained by our method agreed well with theoretical values obtained using the straight-tube phantom with stenosis of 45%, but we observed some differences when stenosis was 65%. We clearly observed variations in pressure differences at specific locations at various phases of a cardiac cycle in both phantom and human studies. This method appears useful for measuring intravascular and intracardiac pressure differences.
  Magnetic Resonance in Medical Sciences 02/2008; 7(3):113-22.
• Article: A simple method for quantitative measurement and analysis of hyperpolarized (129)Xe uptake dynamics in mouse brain under controlled flow.

  Atsuomi Kimura, Hirohiko Imai, Tetsuya Wakayama, Hideaki Fujiwara
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  ABSTRACT: We established a simple method for measuring and quantifying uptake dynamics of hyperpolarized (HP) (129)Xe in mouse brain, which includes application of a saturation recovery pulse sequence under controlled flow of HP (129)Xe. The technique allows pursuit of the time-dependent change in (129)Xe nuclear magnetic resonance signal in the uptake process without effect from radiofrequency destruction of the polarization and the dynamics in mouse lung. The uptake behavior is well described by a simple model that depends only on a decay rate constant comprising cerebral blood flow and the longitudinal relaxation rate of HP (129)Xe in the brain tissue. The improved analysis enabled precise determination of the decay rate constant as 0.107+/-0.013 s(-1) (+/-standard deviation, n=5), leading to estimation of longitudinal relaxation time, T(1i), as 15.3+/-3.5 s.
  Magnetic Resonance in Medical Sciences 02/2008; 7(4):179-85.