Faculty Profiles - NAGANAWA, Shinji

Papers - NAGANAWA, Shinji

Division display 701 - 720 of about 788 ／ All the affair displays >>

Serial evaluation of diffusion tensor brain fiber tracking in a patient with severe diffuse axonal injury. Reviewed

Naganawa S, Sato C, Ishihra S, Kumada H, Ishigaki T, Miura S, Watanabe M, Maruyama K, Takizawa O

AJNR Am J Neuroradiol Vol. 25 ( 9 ) page： 1553-1556 2004.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Serial evaluation of diffusion tensor brain fiber tracking was performed in a 27-year-old female patient with diffuse axonal injury after a traffic accident. Although the result of brain fiber tracking was not necessarily parallel to her clinical symptoms, it may have predicted the neurologic prognosis.

Rad Talk ISMRM2004

長縄慎二

Rad Fan Vol. 2 ( 6 ) page： 47-56 2004.10

High-speed imaging at 3 Tesla: a technical and clinical review with an emphasis on whole-brain 3D imaging. Reviewed

Naganawa S, Kawai H, Fukatsu H, Ishigaki T, Komada T, Maruyama K, Takizawa O

Magn Reson Med Sci Vol. 3 ( 4 ) page： 177-187 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Improvements to the inherently high specific-absorption rate (SAR) of high-speed imaging at 3T are necessary in order to render this method clinically feasible. Various efforts have been undertaken to improve the associated hardware and software. In this review, we focus on whole-brain isotropic 3D imaging with a turbo spin-echo sequence with variable flip-angle echo trains (3D-TSE-VFL) and present its technical and clinical features. This sequence can be used to acquire images of various contrasts including T2-weighted, fat-suppressed T2-weighted, fluid-attenuated inversion recovery (FLAIR), fat-suppressed FLAIR, and STIR (short tau inversion recovery). Various aspects of 3D-TSE-VFL are discussed, including CSF (cerebrospinal fluid) and metal artifacts, STIR contrast, small-part visualization other than brain, and the possibility of serial subtraction. Some images from clinical cases are presented.

Flow ghost artifact in slice-encoding direction mimicking vestibular schwannoma in contrast-enhanced 3D spoiled gradient-echo sequence. Reviewed

Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Aoki I

Eur Radiol Vol. 14 ( 3 ) page： 496-499 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The value of MR imaging by post-contrast T1-weighted 3D spoiled gradient-echo (3D SPGR) is well established for the detection of small vestibular schwannomas in the cerebellopontine angle region. We describe a case in which a flow ghost artifact in the slice-encoding direction mimicked a vestibular schwannoma and heavily T2-weighted MR cisternography and multiplanar reconstruction images helped us to reach the correct diagnosis. In addition, we conducted a volunteer study to demonstrate that changing the k-space trajectory can reduce this artifact in post-contrast 3D SPGR images.

Pre-surgical mapping of primary motor cortex by functional MRI at 3 T: effects of intravenous administration of Gd-DTPA. Reviewed

Naganawa S, Nihashi T, Fukatsu H, Ishigaki T, Aoki I

Eur Radiol Vol. 14 ( 1 ) page： 112-114 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The functional magnetic resonance imaging (fMRI) is often performed at the end of a routine MRI examination during which, dependent on the clinical indication, contrast agent has been administered; however, the effects of Gd-DTPA injection on the results of blood oxygenation level dependent (BOLD)-fMRI remain unknown. The present study was conducted to investigate the effects of the intravenous administration of Gd-DTPA on the results of pre-surgical localization of the primary motor cortex by BOLD-fMRI at 3 T. Eight normal subjects were included in this study. After the anatomical scans, pre- and post-contrast fMRI scanning was performed. The number of significantly activated voxels and the mean percentage signal change were compared. The mean number of significantly activated voxels was 115.0+/-27.0 in pre-contrast runs and 90.8+/-27.1 in post-contrast runs (mean value of all 8 volunteers+/-standard deviation; p<0.05). The mean mean percentage signal change was 4.07+/-0.39 in pre-contrast runs and 3.86+/-1.91 in post-contrast runs ( p=0.16). Pre-surgical localization of the motor area by BOLD-fMRI should be performed before the administration of Gd contrast material.

Optimization of diffusion-tensor MR imaging data acquisition parameters for brain fiber tracking using parallel imaging at 3 T. Reviewed

Naganawa S, Koshikawa T, Kawai H, Fukatsu H, Ishigaki T, Maruyama K, Takizawa O

Eur Radiol Vol. 14 ( 2 ) page： 234-238 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The purpose of this study was to optimize the parameters of diffusion-tensor magnetic resonance imaging (DT MRI) for brain fiber tracking using a slice thickness of 2 mm, a resolution advantage allowed by the high signal-to-noise ratio at 3 T, combined with an 8-channel phased-array head coil. The b-factor, number of motion probing gradient (MPG) directions, and number of averages were varied, and the results of brain fiber tracking for the pyramidal tract and trigeminal nerve were compared qualitatively and quantitatively. The DT MRI data sufficient for brain fiber tracking in healthy subjects can be obtained in <2 min with a 2-mm slice thickness, 700-s/mm2 b-factor, 6 MPG directions, and no averaging (number of averages=1).

Enlarged endolymphatic duct and sac syndrome: relationship between MR findings and genotype of mutation in Pendred syndrome gene. Reviewed

Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Sato E, Sugiura M, Yoshino T, Nakashima T

Magn Reson Imaging Vol. 22 ( 1 ) page： 25-30 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Pendred syndrome (PDS) is characterized by profound deafness in childhood, positive perchlorate challenge, and goiter. PDS is often associated with enlarged endolymphatic duct and sac (EEDS), and recently, PDS gene mutations have been reported even in those patients with EEDS without classic Pendred syndrome. In a previous report, the number of mutant alleles was correlated with the degree of subclinical thyroid abnormality, but not with hearing loss, in patients with missense mutation H723R. It also has been reported that the hearing loss in EEDS was not correlated with the EEDS volume, cochlear modiolar area, or signal intensity of the endolymphatic sac. We evaluated the correlations between the number of mutant alleles and these parameters in patients with EEDS to investigate the mechanisms underlying this condition. The study group was comprised of 16 Japanese patients with EEDS diagnosed by MR imaging. The H723R mutation was homozygous in six patients and heterozygous in six patients, with no mutation found in four patients. The modiolar area, EEDS volume, and signal intensity ratio (sac signal/cerebrospinal fluid signal) were not significantly correlated with the number of mutant alleles. PDS gene mutations may not be the only cause of EEDS, and the mechanisms underlying EEDS remain unclear.

Whole-brain vascular reactivity measured by fMRI using hyperventilation and breath-holding tasks: efficacy of 3D prospective acquisition correction (3D-PACE) for head motion. Reviewed

Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Maruyama K, Takizawa O

Eur Radiol Vol. 14 ( 8 ) page： 1484-1488 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Functional MR imaging (fMRI) study using hyperventilation and breath-holding task has been reported to be one of the non-invasive methods to examine whole-brain vascular reactivity. The purpose of this study was to evaluate the efficacy of a method for 3D prospective detection and correction of head motion (3D-PACE) in a study of whole-brain vascular reactivity using hyperventilation and breath-holding tasks. Eight healthy volunteers were scanned using an fMRI protocol of hyperventilation and breath-holding task blocks at 3 T in separate runs with and without 3D-PACE. In two subjects, two more runs with and without 3D-PACE were repeated. The mean total number of activated voxels +/- standard deviation was 26,405.3+/-1,822.2 in the run with 3D-PACE and 17,329.9+/-2,766.3 in the run without 3D-PACE ( P<0.05), although there is some intersubject variation regarding the effect of 3D-PACE. In the two subjects whose performed two more runs, the number of activated voxels were smaller in the run without 3D-PACE than even in the run with 3D-PACE performed later. We conclude that 3D-PACE is beneficial for fMRI studies of whole-brain vascular reactivity induced by hyperventilation and breath-holding.

Comparison of flow artifacts between 2D-FLAIR and 3D-FLAIR sequences at 3 T. Reviewed

Naganawa S, Koshikawa T, Nakamura T, Kawai H, Fukatsu H, Ishigaki T, Komada T, Maruyama K, Takizawa O

Eur Radiol Vol. 14 ( 10 ) page： 1901-1908 2004

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

It has been reported that 3D-FLAIR can reduce the flow artifact resulting from cerebrospinal fluid (CSF) at 1.5 T compared to 2D-FLAIR. Flow-related artifacts tend to be worse at 3 T than at 1.5 T. The purpose of this study was to compare the CSF flow artifacts of 2D-FLAIR and 3D-FLAIR sequences at 3 T in eight healthy volunteers. The grade of CSF-related artifacts were scored through observing the perimedullary cistern, cerebellopontine angle cisterns, fourth ventricule, prepontine cistern, suprasellar cistern, ambient cisterns, sylvian fissures, third ventricle and lateral ventricles. Grading was performed on either axial or sagittal images. The CSF in-flow artifact scores were significantly higher on axial 2D-FLAIR than on axial 3D-FLAIR MPR images in all areas except the bilateral sylvian fissures, and higher on sagittal 2D-FLAIR than on sagittal 3D-FLAIR MPR images in perimedullary, bilateral CP angle and suprasellar cisterns. The CSF-related flow artifacts were significantly reduced by 3D-FLAIR, while structures in the cistern were depicted more clearly, even at 3 T. Further study is necessary to compare the clinical efficacy between 2D-FLAIR and 3D-FLAIR in depicting subtle abnormalities.

MR imaging of gastric cancer in vitro: accuracy of invasion depth diagnosis.

Sato C, Naganawa S, Kumada H, Miura S, Ishigaki T

Eur Radiol Vol. 14 ( 9 ) page： 1543-1549 2004

Language：English Publishing type：Research paper (scientific journal)

The purpose of this study was to evaluate the accuracy of grading cancerous invasion of the gastric wall in vitro using magnetic resonance (MR) imaging. Twelve specimens of gastric carcinoma were examined at 1.5-T using a small, loop surface coil. They were imaged within 2 days of fixation in formalin. The field of view was 30 mm; the matrix size was 256x256, and the section thickness was 2 mm. T1-weighted, T2-weighted and short inversion time inversion recovery (STIR) images were obtained. Two radiologists evaluated the MR images independently, and in discrepant cases, consensus was obtained through discussion. Findings on MR images were compared with histopathologic findings. All T1-weighted, T2-weighted and STIR images depicted the normal gastric wall as consisting of six layers. STIR images depicted normal six layers most clearly. Histologically, the cancerous invasion was found to extend into the mucosa in 4 of the 12 specimens, the submucosa in 3, the muscularis propria in 2, the subserosa in 2 and the serosa in 1. The grading by MR imaging matched the histopathologic findings for all 12 tumors. The overall accuracy was 100%. Thus, MR imaging in vitro was sufficiently accurate for grading cancerous invasion of the gastric wall.

MRIの最新トッピックス　3T MRIの臨床

長縄慎二

映像情報メディカル Vol. 36 page： 1056-1060 2004

頭頚部画像診断に必要不可欠な臨床画像解剖（１）側頭骨　（内耳、内耳道）

長縄慎二

画像診断 Vol. 24 ( 11 ) page： 2-4 2004

Magnetic resonance imaging of endolymphatic sac in acute low-tone sensorineural hearing loss without vertigo. Reviewed

Sugiura M, Naganawa S, Nakashima T, Misawa H, Nakamura T

ORL J Otorhinolaryngol Relat Spec Vol. 65 ( 5 ) page： 254-260 2003

Language：English Publishing type：Research paper (scientific journal)

The etiology of acute low-tone sensorineural hearing loss (ALHL) may be associated with deteriorated function of the endolymphatic sac. Using magnetic resonance (MR) imaging on a 1.5-tesla MR system, we evaluated the frequency of visualization and contrast enhancement of the endolymphatic sac in 25 patients (9 men and 16 women; age range 11-64 years) with ALHL and 21 control subjects. The present study demonstrated that the frequency of visualization and enhancement of the endolymphatic sac in patients with ALHL was not significantly higher than in control subjects.

High-resolution T1-weighted 3D real IR imaging of the temporal bone using triple-dose contrast material. Reviewed

Naganawa S, Koshikawa T, Nakamura T, Fukatsu H, Ishigaki T, Aoki I

Eur Radiol Vol. 13 ( 12 ) page： 2650-2658 2003

Contrast enhancement of the cochlear aqueduct in MR imaging: its frequency and clinical significance. Reviewed

Nakamura T, Naganawa S, Fukatsu H, Sakurai Y, Aoki I, Ninomiya A, Nakashima T, Ishigaki T

Neuroradiology Vol. 45 ( 9 ) page： 626-630 2003

Language：English Publishing type：Research paper (scientific journal)

There have been no previous reports on contrast enhancement of the cochlear aqueduct in magnetic resonance imaging. The purpose of the present study was to evaluate the frequency and significance of this finding. Thirty-one patients (15 men and 16 women; age range 18-81 years) with otologic symptoms (sudden sensorineural hearing loss, vertigo, or tinnitus) were examined using contrast-enhanced imaging on a 1.5-T MR scanner. The normal ear served as the control. Two radiologists evaluated contrast enhancement in the area of the cochlear aqueduct. Forty-eight of 62 ears (77.4%) showed contrast enhancement of the cochlear aqueduct, but no significant differences in the frequency of contrast enhancement were observed between patients with and patients without vertigo, tinnitus, sensorineural hearing loss, cerebellopontine angle tumors, or a high-riding jugular bulb. In addition, no gender- or age-related differences were noted. Contrast enhancement of the cochlear aqueduct was frequently observed, but the frequency of enhancement in symptomatic ears was not significantly higher than in control ears. The results of this study may prove helpful in avoiding unnecessary examinations and potential diagnostic confusion.

Disorders of cochlear blood flow. Reviewed

Nakashima T, Naganawa S, Sone M, Tominaga M, Hayashi H, Yamamoto H, Liu X, Nuttall AL

Brain Res Brain Res Rev Vol. 43 ( 1 ) page： 17-28 2003

Language：English Publishing type：Research paper (scientific journal)

The cochlea is principally supplied from the inner ear artery (labyrinthine artery), which is usually a branch of the anterior inferior cerebellar artery. Cochlear blood flow is a function of cochlear perfusion pressure, which is calculated as the difference between mean arterial blood pressure and inner ear fluid pressure. Many otologic disorders such as noise-induced hearing loss, endolymphatic hydrops and presbycusis are suspected of being related to alterations in cochlear blood flow. However, the human cochlea is not easily accessible for investigation because this delicate sensory organ is hidden deep in the temporal bone. In patients with sensorineural hearing loss, magnetic resonance imaging, laser-Doppler flowmetry and ultrasonography have been used to investigate the status of cochlear blood flow. There have been many reports of hearing loss that were considered to be caused by blood flow disturbance in the cochlea. However, direct evidence of blood flow disturbance in the cochlea is still lacking in most of the cases.

Pseudostenosis of the internal carotid artery in 3D time-of-flight MR angiography: effects of a magnetization transfer contrast pulse and metallic material.

Naganawa S, Koshikawa T, Sato K, Katagiri T, Mimura T, Ishigaki T, Aoki I

Eur Radiol Vol. 13 ( 10 ) page： 2298-2303 2003

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Pseudostenosis or pseudoocclusion of the internal carotid artery in 3D time-of-flight MR angiography has been reported to be caused by susceptibility artifacts due to the presence of a metallic foreign body in the subject's neck. We experimentally demonstrate that the use of a non-slice-selective magnetization transfer contrast (MTC) pulse increases the degree of pseudostenosis, whereas slice-selective MTC does not. Selective MR angiography demonstrating this phenomenon was also performed. We then report a case that exhibited this phenomenon. We conclude that the magnetic field inhomogeneity induced by metallic material causes the non-slice-selective MTC pulse to act as a local presaturation pulse. Selective MR angiography using this phenomenon can be applied on varieties of MR scanners from different vendors.

Regional ADC values of the normal brain: differences due to age, gender, and laterality. Reviewed

Naganawa S, Sato K, Katagiri T, Mimura T, Ishigaki T

Eur Radiol Vol. 13 ( 1 ) page： 6-11 2003

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The purpose of this study was to evaluate the stability of measurement for apparent diffusion coefficient (ADC) values in normal brain, to clarify the effect of aging on ADC values, to compare ADC values between men and women, and to compare ADC values between right and left sides of the brain. To evaluate the stability of measurements, five normal volunteers (four men and one woman) were examined five times on different days. Then, 294 subjects with normal MR imaging (147 men and 147 women; age range 20-89 years) were measured. The ADC measurement in normal volunteers was stable. The ADC values stayed within the 5% deviation of average values in all volunteers (mean+/-standard deviation 2.3+/-1.2%). The ADC values gradually increased by aging in all regions. In thalamus, no significant difference was seen between right and left in the subjects under 60 years; however, right side showed higher values in the subjects over 60 years (p<0.01). In the subjects under 60 years, women showed higher values in right frontal, bilateral thalamus, and temporal (p<0.01); however, in the subjects over 60 years, no region showed difference between men and women. The knowledge obtained in this study may be helpful to understand the developmental and aging mechanisms of normal brain and may be useful for the future quantitative study as a reference.

Imaging of a congenital perilymphatic fistula. Reviewed

Nakashima T, Sone M, Teranishi MA, Tominaga M, Sugiura M, Naganawa S

Int J Pediatr Otorhinolaryngol Vol. 67 ( 4 ) page： 421-425 2003

Language：English Publishing type：Research paper (scientific journal)

A 7-year-old boy with a history of purulent meningitis and watery rhinorrhea was studied using computed tomography (CT) and magnetic resonance imaging (MRI). He had a common cavity in the left inner ear. With high-resolution heavily T2-weighted MRI, leakage of the inner ear fluid into the middle ear at the oval window area through a congenital perilymphatic fistula could be visualized. Surgery to close the fistula showed a perforation in the stapes footplate.

Determination of cerebrovascular reactivity by means of FMRI signal changes in cerebral microangiopathy: a correlation with morphological abnormalities.

Hund-Georgiadis M, Zysset S, Naganawa S, Norris DG, Von Cramon DY.

Cerebrovasc Dis Vol. 16 ( 2 ) page： 158-165 2003

　 PREV - NEXT 　

<NAGANAWA, Shinji>

Papers - NAGANAWA, Shinji