Faculty Profiles - NAGANAWA, Shinji

Papers - NAGANAWA, Shinji

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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.

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.

Virtual endoscopy of the labyrinth, using a 3D-FastASE sequence. Reviewed

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

J Magn Reson Imaging Vol. 13 ( 5 ) page： 792-796 2001

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

Virtual endoscopy (VE) of the labyrinth was performed using three-dimensional (3D)-fast asymmetric spin-echo MR imaging. The spatial resolution requirements and the usefulness of zero-fill interpolation (ZIP) were evaluated, and VE was used to examine three patients. The (0.6-mm) voxel data with ZIP satisfies the minimum requirements for VE for evaluation of the complex 3D anatomy and pathology of the labyrinth. J. Magn. Reson. Imaging 2001;13:792-796.

Aortoiliac stenooculusive disease and aneurysms: screening with non-contrast enhanced two-dimensional cardiac gated cine phase contrast MR angiography with multiple velocity encoded values and cardiac gated two-dimensional time-of-flight MR angiography. Reviewed

Naganawa S, Koshikawa T, Kato K, Ishiguchi T, Ishigaki T, Sato K, Katagiri T, Kishimoto H, Mimura T, Takizawa O, Imura C

Radiat Med Vol. 19 ( 2 ) page： 99-105 2001

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

PURPOSE: To evaluate the performance of two-dimensional cine phase contrast MRA with multi-velocity encoded values (multi-VENC cine PC) and ECG-gated two-dimensional time-of-flight MRA (ECG-2D-TOF) for the detection of stenoocclusive lesions and aneurysms in the aortoiliac area, when each method was used individually and when the two methods were used together. METHODS: Forty-one patients were included in this study. Multi-VENC cine PC and ECG-2D-TOF were obtained first, then contrast enhanced three-dimensional magnetic resonance angiography (CE-3D-MRA) was performed as the standard of reference. Two observers reviewed the images separately without knowledge of patients' symptoms or histories. Sensitivities and specificities were obtained separately for stenooclusive lesions and aneurysms by two reviewers. RESULTS: When the two methods were applied together, high sensitivities (93.0 by observer 1 and 91.9% by observer 2) and adequate specificities (87.6 and 82.3%) were obtained for stenoocclusive lesions. For aneurysms, moderate to high sensitivities (91.1 and 71.1%) and high specificities (98.8 and 99.4%) were obtained. CONCLUSION: These results suggest that the performance of two non-contrast enhanced MRA techniques may be valuable as a screening tool when the two methods are applied together.

MR cisternography of the cerebellopontine angle: comparison of three-dimensional fast asymmetrical spin-echo and three-dimensional constructive interference in the steady-state sequences. Reviewed

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

AJNR Am J Neuroradiol Vol. 22 ( 6 ) page： 1179-1185 2001

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

BACKGROUND AND PURPOSE: MR cisternography has been used as the noninvasive screening tool of the cerebellopontine angle. The purpose of this study was to directly compare two currently dominant types of sequences for heavily T2-weighted MR cisternography. METHODS: Three-dimensional fast asymmetric spin-echo (3D-FASE) sequences, which are 3D half-Fourier rapid acquisition with relaxation enhancement and 3D constructive interference in the steady-state (3D-CISS) sequences, were compared on a clinical 1.5-T MR unit using the same scan times. In five healthy volunteers, the contrast-to-noise ratio (C/N) between CSF and the cerebellum was measured at three locations. Then, for qualitative analysis, the quality of the labyrinth was scored on the original source multiplanar reformatted images, the virtual endoscopic images, and the maximum intensity projection (MIP) images. In 20 consecutive patients with suspected cerebellopontine angle tumors, visualization of the tumors was evaluated using 3D contrast-enhanced spoiled gradient-echo imaging as the standard of reference. RESULTS: Both sequences showed comparable mean C/N values; however, in qualitative analysis, the scores for 3D-CISS on the source, virtual endoscopic, and MIP images were significantly lower than those on the images obtained with 3D-FASE, owing to more prominent flow and magnetic susceptibility artifacts on the 3D-CISS sequences. In all subjects, discontinuity of the semicircular canals was seen on the virtual endoscopic and MIP images obtained with 3D-CISS, owing to susceptibility artifacts, but not on those obtained with 3D-FASE. All 12 tumors were detected by both sequences, but 3D-CISS gave one false-positive result. CONCLUSION: 3D-FASE is considered the method of choice because artifacts are reduced and specificity is increased.

Contrast-enhanced MR angiography of the carotid artery using 3D time-resolved imaging of contrast kinetics: comparison with real-time fluoroscopic triggered 3D-elliptical centric view ordering. Reviewed

Naganawa S, Koshikawa T, Fukatsu H, Sakurai Y, Ichinose N, Ishiguchi T, Ishigaki T

Radiat Med Vol. 19 ( 4 ) page： 185-192 2001

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

PURPOSE: To evaluate contrast-enhanced MR angiography using the 3D time-resolved imaging of contrast kinetics technique (3D-TRICKS) by direct comparison with the fluoroscopic triggered 3D-elliptical centric view ordering (3D-ELLIP) technique. METHODS: 3D-TRICKS and 3D-ELLIP were directly compared on a 1.5-Tesla MR unit using the same spatial resolution and matrix. In 3D-TRICKS, the central part of the k-space is updated more frequently than the peripheral part of the k-space, which is divided in the slice-encoding direction. The carotid arteries were imaged using 3D-TRICKS and 3D-ELLIP sequentially in 14 patients. Temporal resolution was 12 sec for 3D-ELLIP and 6 sec for 3D-TRICKS. The signal-to-noise ratio (S/N) of the common carotid artery was measured, and the quality of MIP images was then scored in terms of venous overlap and blurring of vessel contours. RESULTS: No significant difference in mean S/N was seen between the two methods. Significant venous overlap was not seen in any of the patients examined. Moderate blurring of vessel contours was noted on 3D-TRICKS in five patients and on 3D-ELLIP in four patients. Blurring in the slice-encoding direction was slightly more pronounced in 3D-TRICKS. However, qualitative analysis scores showed no significant differences. CONCLUSION: When the spatial resolution of the two methods was identical, the performance of 3D-TRICKS was found to be comparable in static visualization of the carotid arteries with 3D-ELLIP, although blurring in the slice-encoding direction was slightly more pronounced in 3D-TRICKS. 3D-TRICKS is a more robust technique than 3D-ELLIP, because 3D-ELLIP requires operator-dependent fluoroscopic triggering. Furthermore, 3D-TRICKS can achieve higher temporal resolution. For the spatial resolution employed in this study, 3D-TRICKS may be the method of choice.

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

ECR2001印象記

長縄慎二

映像情報メディカル Vol. 33 page： 516-519 2000.5

MR imaging of the enlarged endolymphatic duct and sac syndrome by use of a 3D fast asymmetric spin-echo sequence: volume and signal-intensity measurement of the endolymphatic duct and sac and area measurement of the cochlear modiolus. Reviewed

Naganawa S, Koshikawa T, Iwayama E, Fukatsu H, Ishiguchi T, Ishigaki T, Ikeda M, Nakashima T, Ichinose N

AJNR Am J Neuroradiol Vol. 21 ( 9 ) page： 1664-1669 2000

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

BACKGROUND AND PURPOSE: In enlarged endolymphatic duct (EED) and sac (EES) syndrome, deformity of the EED and EES is congenital; however, hearing loss is acquired. To investigate the pathophysiology of progressive sensorineural hearing loss in EED and EES syndrome, we measured the volume of the EED and EES, the diameter of the EED and EES, the area of the cochlear modiolus, and the signal intensity of the EES and compared our findings against degree of hearing loss. METHODS: Thin-section MR images of 33 ears in 17 patients with EED and EES syndrome were studied. All studies were obtained on a 1.5-T MR unit using a quadrature surface phased-array coil. Heavily T2-weighted 3D fast asymmetric spin-echo images were obtained with a voxel size of 0.3 x 0.3 x 0.8 mm without zero-fill interpolation. Two radiologists traced the areas of the EED and EES manually, and the volume was calculated. The area of the cochlear modiolus, diameter of the EED and EES, and signal intensity of the EES were also measured by drawing regions of interest manually. The signal intensity ratio of EES/CSF was calculated. These measured values were compared against audiographic data, and the degree of linear correlation was determined. RESULTS: The volume of the EED and EES, the area of the modiolus, the diameter of the EED and EES, and the signal intensity of the EES did not show significant correlation with degree of hearing loss. CONCLUSION: These findings suggest that there is a microscopic area of damage or fragility in the inner ear not visible even with thin-section heavily T2-weighted MR imaging.

Real-time interactive MR imaging system: sequence optimization, and basic and clinical evaluations. Reviewed

Naganawa S, Ishiguchi T, Ishigaki T, Sato K, Katagiri T, Kishimoto H, Mimura T, Takizawa O, Imura C

Radiat Med Vol. 18 ( 1 ) page： 71-79 2000

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

A real-time interactive MR imaging system (real-time MRI) is an MR scanner which has a fast image updating cycle and the ability to freely change slice orientation, just like an ultrasound imaging system. Recently, such a system has been developed and installed on a clinical 1.5-Tesla system. The purpose of this study was to optimize the pulse sequences for clinical use and to evaluate the clinical usefulness and basic functionality of real-time MRI. For T1-weighted imaging, FLASH (fast low angle shot) can be selected, and up to 5 frames per second can be acquired depending on the matrix size. For T2-weighted imaging, true FISP (fast imaging with steady-state precession) can be selected, and up to 4 frames per second can be acquired. Maximum C/N between liver and spleen was obtained at a flip angle of 20 degrees on FLASH. Maximum C/N between cardiac cavity and wall was obtained at a flip angle of 60 degrees on true FISP. Localization of the right and left coronary arteries could be performed within 30 seconds in three volunteers. Although the present real-time MRI system has drawbacks such as low spatial resolution and relatively low contrast resolution, we expect real-time MRI to be one of the most important tools for future clinical MRI.

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