Faculty Profiles - NAGANAWA, Shinji

Papers - NAGANAWA, Shinji

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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.

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.

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.

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

超高磁場磁気共鳴画像診断(MRI)について

長縄慎二

健康文化振興財団紀要 Vol. 38 page： 40-42 2002.4

Authorship：Lead author Language：Japanese

はじめに

　脳ドックや腰椎の椎間板ヘルニア、膝の半月板損傷などで磁気共鳴画像診断(MRI)を受けられた方も多いと思います。MRIは磁石と電波をつかって体の断層像を得る検査です。X線CTと異なり、電離放射線被爆のない安全な検査で、この15年ほどで国内でも急速に普及しました。

　従来までは1.5T(テスラ)という磁石の強さが国内ではもっとも強いものでしたが、この3年ほどで超高磁場とよばれる3Tの製品が実用化されてきました。１Tは１万ガウスで、3Tは３万ガウスという強力な磁石です。今回は、この超高磁場MRIについて、述べてみたいと思います。

Serial MR imaging studies in enlarged endolymphatic duct and sac syndrome.

Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Nakashima T

Eur Radiol Vol. 12 ( 3 ) page： 114-117 2002

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

Large vestibular aqueduct syndrome (LVAS) is a congenital disorder characterized by progressive or fluctuating sensorineural hearing loss of unknown etiology. Serial MR examinations were performed before and after the development of hearing loss in two patients with LVAS. The signal and volume of the enlarged endolymphatic sac (EES) vary even in ears with stable hearing. In ears with fluctuating hearing, changes in EES signals were observed in only one of two patients. The finding that the EES volume and signal intensity vary dynamically independently of hearing is important for future research into the pathophysiology of hearing loss in this syndrome.

Regional differences of fMR signal changes induced by hyperventilation: comparison between SE-EPI and GE-EPI at 3-T. Reviewed

Naganawa S, Norris DG, Zysset S, Mildner T

J Magn Reson Imaging Vol. 15 ( 1 ) page： 23-30 2002

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

PURPOSE: To evaluate whether reproducible signal change of brain tissues by hyperventilation (HV) can be seen on spin-echo (SE)-echo planar imaging (EPI) at 3-T and to examine the sensitivity of SE-EPI for measuring vascular reactivity in regions of the brain, such as the hippocampal formation, that are difficult to visualize with gradient-echo (GE)-EPI due to susceptibility artifacts. MATERIALS AND METHODS: Six healthy human subjects performed a voluntary HV task. The task design was as follows: two minutes normal breathing (rest) followed by two minutes HV, giving a basic four-minute block that was repeated three times for a total scan time of 12 minutes for one run. Each subject performed the run both for SE-EPI and GE-EPI. Statistical analysis was performed to detect the area with significant cerebrovascular reactivity. The percentage signal change was also obtained for each cerebral region. RESULTS: Both GE-EPI and SE-EPI showed globally significant signal decreases in the cerebral cortex. In GE-EPI, the frontal cortex showed a larger signal decrease than the other gray matter tissues (P < 0.05). In SE-EPI, the differences among gray matter tissues except for the hippocampal formation were not significant. The hippocampal formation showed the largest signal change (P < 0.05) in SE-EPI, but no significant signal change was observed in GE-EPI due to the presence of susceptibility artifacts. CONCLUSION: HV using SE-EPI at 3-T provides robust and reproducible signal decreases and may make the evaluation of the vascular reactivity in hippocampal formation feasible.

Fast recovery 3D fast spin-echo MR imaging of the inner ear at 3 T. Reviewed

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

AJNR Am J Neuroradiol Vol. 23 ( 2 ) page： 229-302 2002

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

High-resolution MR imaging of the inner ear with a heavily T2-weighted 3D fast spin-echo sequence has been performed successfully at 1.5 T. However, at 3 T, the longer T1 time of CSF necessitates a longer TR, resulting in significantly prolonged imaging times. In this study, the fast recovery 3D fast spin-echo sequence, which permits the TR to be reduced while maintaining T2 contrast, was optimized at 3 T for imaging of the inner ear. The optimized sequence parameters are as follows: 1500/294 (TR/TE); echo spacing, 18.1 ms; bandwidth, 38 kHz at 512 readout; and imaging time, 13 minutes.

Contrast-enhanced MR imaging of the endolymphatic sac in patients with sudden hearing loss. Reviewed

Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Nakashima T, Ichinose N

Eur Radiol Vol. 12 ( 5 ) page： 1121-1126 2002

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

Our objective was to evaluate the frequency of contrast enhancement of the endolymphatic sac in patients with sudden hearing loss. Forty consecutive patients with sudden sensorineural hearing loss (20 males and 20 females; age range 11-82 years), 40 age-matched control subjects, and 5 patients with Meniere's disease were examined using the same imaging protocol on a 1.5-T MR system. Pre- and post-contrast-enhanced T1-weighted 3D spoiled gradient-echo sequence (3D SPGR; TR/TE=23/10 ms, no. of excitations=1, flip angle=30 degrees) images were obtained using a voxel size of 0.6 x 0.7 x 0.8 mm(3). Contrast enhancement in the area of the endolymphatic sac was assessed by two radiologists, and the frequency of contrast enhancement was compared between the three study groups. Enhancement of the ipsilateral endolymphatic sac was observed in 30 of the 40 patients with sudden hearing loss (75%). Twenty of these 30 patients also showed enhancement on the contralateral side, and 1 patient showed enhancement only on the contralateral side. Only 1 of the 5 patients with Meniere's disease showed enhancement. Nine of the 40 control subjects (22.5%) showed enhancement (bilateral enhancement in 5 subjects, unilateral in 4). The frequency of enhancement in patients with sudden hearing loss was significantly higher than that in control subjects ( P<0.0001) or patients with Meniere's disease ( P<0.05). The frequency of contrast enhancement of the endolymphatic sac is significantly increased in patients with sudden hearing loss, but further study is necessary to clarify the relationship between this finding and the pathophysiology of sudden hearing loss.

The role of contrast-enhanced MR mammography for determining candidates for breast conservation surgery. Reviewed

Zhang Y, Fukatsu H, Naganawa S, Satake H, Sato Y, Ohiwa M, Endo T, Ichihara S, Ishigaki T

Breast Cancer Vol. 9 ( 3 ) page： 231-239 2002

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

PURPOSE: The aim of this study was to assess the impact of preoperative magnetic resonance mammography (MRM) on the surgical determination of breast conservation treatment for breast cancer patients. METHODS: From September 1997 to March 2000, 57 consecutive breast conservation treatment candidates were prospectively evaluated with conventional imaging studies (mammography and ultrasonography) and preoperative MRM. RESULTS: In 47 of 54 (87% ) breast cancer patients breast conservation surgery (BCS) was indicated on the basis of mammography (MMG) and ultrasonography (US). However in 40 of the 54 (74% ) patients BCS was indicated on the basis of MRM. Thirty-eight of the 40 patients ultimately underwent BCS and only 1 showed a positive margin. There were 7 patients whose MRM findings suggested that more aggressive treatment than BCS was needed but for whom US/MMG suggested that BCS was appropriate. Five of the 7 patients underwent mastectomy rather than BCS based on the MRM findings, which were justified by post-surgical histological findings. Of the 2 remaining patients who underwent BCS, one had a positive histological margin and one had recurrence, both of which resulted in salvage mastectomy. CONCLUSION: Our study suggests that high resolution preoperative MRM provides more accurate information compared with US and MMG for selecting candidates for BCS. Using MRM as a routine staging tool may reduce unnecessary repeated excisions. A larger study will be required to confirm these findings and to define the patients most likely to benefit from breast MR imaging.

High-spatial-resolution MR cisternography of the cerebellopontine angle in 90 seconds with a zero-fill interpolated fast recovery 3D fast asymmetric spin-echo sequence. Reviewed

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

AJNR Am J Neuroradiol Vol. 23 ( 8 ) page： 1407-1412 2002

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

BACKGROUND AND PURPOSE: Although the 12-minute 3D fast asymmetric spin-echo (FASE) protocol for imaging the inner ear has been satisfactory, reducing imaging time to minimize patient discomfort and maximize system throughput is desirable. We therefore evaluated the performance of a zero-fill interpolated (ZIP) fast recovery 3D FASE sequence in screening for cerebellopontine (CP) angle lesions in 90 seconds. METHODS: Thirty consecutive patients known or suspected to have CP angle lesions underwent MR imaging at 1.5 T with use of bilateral quadrature phased-array coils designed for examination of the CP angle. Conventional 3D FASE images (4000/240/1 [TR/TE/NEX]) were obtained in 11 minutes 48 seconds with a field of view (FOV) of 16 cm, matrix of 512 x 512 x 40, section thickness of 0.8 mm, and echo train length of 80. Then, ZIP fast recovery 3D FASE images (2000/240/1) were obtained in 90 seconds by using the same FOV. Contrast-enhanced T1-weighted 3D spoiled gradient-echo (SPGR) images were obtained as the reference standard. Three radiologists evaluated the images independently. Conventional 3D FASE and ZIP fast recovery 3D FASE images were reviewed at separate sessions. RESULTS: On 3D SPGR images, 10 tumors were detected in 10 of the 30 patients. All lesions were depicted with both 3D FASE protocols. There were no false-positive results with either 3D FASE protocol. Both protocols showed 100% sensitivity and 100% specificity for all three reviewers. CONCLUSION: High-spatial-resolution MR cisternography with the ZIP fast recovery 3D FASE protocol in 90 seconds results in a substantial reduction (by a factor of about eight) in the time required for screening for CP angle lesions compared with the previously reported conventional 3D FASE protocol, while maintaining high sensitivity and specificity.

Tympanometric findings in patients with enlarged vestibular aqueducts. Reviewed

Sato E, Nakashima T, Lilly DJ, Fausti SA, Ueda H, Misawa H, Uchida Y, Furuhashi A, Asahi K, Naganawa S

Laryngoscope Vol. 112 ( 9 ) page： 1642-1646 2002

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

OBJECTIVES: The purpose of this study was to study systematically some relationships between the resonance frequency of the middle-ear transmission system and the volume of the endolymphatic duct and sac in patients with an enlarged vestibular aqueduct (EVA). STUDY DESIGN: Prospective study. METHODS: Thirteen patients (24 ears) with EVA, 17 subjects (29 ears) with normal hearing, and 17 patients (21 ears) with sensorineural hearing loss without EVA served as experimental subjects. Standard pure-tone audiometry, standard clinical tympanometry (using a 226-Hz probe tone), and multifrequency tympanometry were performed on each ear. Magnetic resonance imaging was used to determine the area of the cochlear modiolus and the volume of the endolymphatic duct and sac. RESULTS: The audiometric configurations for most patients sloped downward from the low to the high frequencies. A significant air-bone gap was computed at each of these test frequencies. Multifrequency tympanometry yielded resonance frequencies for the patients with EVA that was significantly lower than those measured for the control subjects. In general, for patients with EVA, the resonance frequency of the middle ear system decreased as the volume of the endolymphatic duct and sac increased. This inverse relation was significant (correlation coefficient = -0.483, P =.0157). However, there was no correlation between resonance frequency and the degree of cochlea modiolar deficiency. CONCLUSIONS: Clinically, our findings suggest that EVA probably should be included in the differential diagnosis for a patient who presents with a moderate to severe mixed hearing loss, a normal tympanogram at 226 Hz, and a resonance frequency that is abnormally low.

脳の機能的MRI画像

長縄慎二

現代医学 Vol. 49 ( 3 ) page： 363-368 2002

CT and MR imaging of pancreatic cancer.

Ishiguchi T, Ota T, Naganawa S, Fukatsu H, Itoh S, Ishigaki T.

Hepatogastroenterology Vol. 48 ( 40 ) page： 923-927 2001.7

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

Recent improvements in imaging techniques have made it possible to improve the diagnostic accuracy for detection, staging, and indicating surgical resectability of pancreatic cancer. The latest advance in the computed tomography technique, is the introduction of subsecond multislice helical scanning that improves z-axis resolution in the reformatted images and three-dimensional rendering with a large volume data. Magnetic resonance imaging provides versatile information including magnetic resonance cholangiopancreatography that allows noninvasive delineation of the pancreatic and biliary duct systems. The presence of pancreatic cancer may best be evaluated by dynamic computed tomography or dynamic magnetic resonance imaging with administration of intravenous contrast material. Both computed tomography and magnetic resonance imaging are valuable for the preoperative assessment of local invasion and vascular involvement. Multislice helical computed tomography is currently considered as the best single modality for the diagnosis of pancreatic cancer as it provides excellent image quality. When advanced magnetic resonance imaging equipment is used as a primary modality, in the future, it may have a possibility to replace other imaging modalities.

Phenotypes associated with replacement of His by Arg in the Pendred syndrome gene.

Sato E, Nakashima T, Miura Y, Furuhashi A, Nakayama A, Mori N, Murakami H, Naganawa S, Tadokoro M

Eur J Endocrinol Vol. 145 ( 6 ) page： 697-703 2001

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

BACKGROUND: Pendred syndrome is often associated with inner ear malformations, especially enlarged vestibular aqueduct (EVA). Recently, mutations in the Pendred syndrome gene (PDS) have been reported in patients with EVA, in addition to those with classical Pendred syndrome. OBJECTIVE: The aim of this study was to investigate the genotype-phenotype correlations of PDS. METHODS: Each of the 21 exons and flanking splice regions of PDS was analysed by direct DNA sequencing in nine patients with EVA; allele-specific amplification was performed to confirm the mutation. Genetic analyses were compared with thyroid function tests, perchlorate discharge tests, thyroid volume and pure-tone audiogram. Magnetic resonance imaging was used to determine the volume of the endolymphatic duct and sac of each patient. RESULTS: A missense mutation, H723R, was identified in the homozygous state in three patients and in the heterozygous state in another three. Although none of the patients had goitre, increased serum thyroglobulin and an abnormal degree of iodide release were correlated with the number of mutant alleles identified. However, there was no relationship between the degree of hearing loss and the number of mutant alleles. CONCLUSION: The present study reveals that the number of mutant alleles correlates with the degree of subclinical thyroid abnormality, but not with the degree of hearing loss in Japanese patients with the PDS missense mutation H723R.

MR labyrinthographyとMR cisternography

長縄慎二

日本医学放射線学会雑誌付録 Vol. 61 page： 2-6 2001

Accuracy of plastic replica of aortic aneurysm using 3D-CT data for transluminal stent-grafting: experimental and clinical evaluation. Reviewed

Kato K, Ishiguchi T, Maruyama K, Naganawa S, Ishigaki T

J Comput Assist Tomogr Vol. 25 ( 2 ) page： 300-304 2001

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

PURPOSE: To plan stent-grafting for aortic aneurysms with complicated morphology, we prepared life-sized aortic replicas by laser stereolithography using helical 3D--CT data. The accuracy of the replica was evaluated by measurement of vessel phantoms and clinical 3D--CT data. METHOD: An imaginary aortic wall was created from helical CT images of the aorta, and a hollow plastic replica was produced by laser stereolithography. The accuracy of the replica was evaluated in five abdominal aortic aneurysms by experimental phantom studies and measurements of the replicas. RESULTS: The mean difference in measurements between 3D--CT images and model vessels and between 3D--CT images and aortic replicas was 0.2 mm each. Therefore, the difference in measurements between real aortic aneurysms and the replicas was at most 0.4 mm. CONCLUSION: The accuracy of the replica is satisfactory, making it useful for preoperative evaluation and simulation for stent-grafting.

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Papers - NAGANAWA, Shinji