Faculty Profiles - NAGANAWA, Shinji

Papers - NAGANAWA, Shinji

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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.

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.

Water fat separation using the single acquisition "sandwich" type 3-point Dixon method to optimize knee joint scans. Reviewed Open Access

Shibahara E, Fukatsu H, Naganawa S, Ito T, Iwayama E, Ishigaki T, Segawa T, Zhang W

Nagoya J Med Sci Vol. 63 ( 1-2 ) page： 41-49 2000

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

In this paper, we tried to evaluate the effect of water-fat separation on and to optimize the scan condition of the newly developed "Sandwiched" 3-point Dixon method at 0.35 Tesla (T), for knee joint imaging. Using a 0.35T superconductive open magnet system with a solenoid type knee coil, one male and two female normal volunteers (27-37 y.o.) underwent knee joint imaging. Each sequence provided good water-fat separated images. At 0.35T, the gradient echo provided a better contrast than the spin echo. Optimal cartilage-marrow and cartilage-fluid contrast could be obtained at a frip angle (FA) of 90 degrees. There was no significant correlation between cartilage-marrow, cartilage-fluid contrast and repetition time (TR) values within the tested range. Cartilage-fluid and cartilage-marrow contrast were both best at an FA of 90 degrees with the gradient echo sequence. TR from 350 ms to 650 ms did not cause any significant contrast difference in the fat suppressed images. This method is useful and could be the only practical choice for obtaining fat suppressed T1 weighted images for joint magnetic resonance (MR) imaging at 0.35T.

DOI： 10.18999/nagjms.63.1-2.41

Open Access

Stent-graft placement for pseudoaneurysm of the aorta. Reviewed

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

Radiat Med Vol. 18 ( 3 ) page： 177-185 2000

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

PURPOSE: To evaluate the use of endovascular stent-graft placement to repair pseudoaneurysm of the aorta. METHODS: Six patients were treated with stent-grafts for pseudoaneurysms located in the thoracic aorta (n=2), thoracoabdominal aorta (n=3), and abdominal aorta (n=1). Etiologies of the pseudoaneurysms included leakage from surgical graft, penetrating atherosclerotic ulcer, pneumonia, perforated esophageal ulcer, and mycotic aneurysm. All patients were clinically considered to be at high surgical risk. RESULTS: Stent-grafts were successfully placed in all patients. There was one death in the perioperative period due to massive hemoptysis before stent-grafting. Two patients died of persistent infection. One patient with persistent perigraft leak died of rupture. Two other patients needed no further therapy for pseudoaneurysm. CONCLUSION: Stent-graft placement for pseudoaneurysm of the aorta can play the role of a temporizing method prior to surgical repair in high-risk cases and be a therapeutic alternative in cases without infection or perigraft leakage.

Arachnoid granulations on high-resolution MR images and diffusion-weighted MR images: normal appearance and frequency. Reviewed

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

Radiat Med Vol. 18 ( 3 ) page： 187-191 2000

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

Arachnoid granulations (AGs), protrusions into the cerebral venous sinus lumen, have been reported on cerebral venography, contrast enhanced CT, and conventional MR imaging. Although thin-sliced high-resolution MR images and diffusion-weighted images are frequently obtained, there have been no detailed reports concerning AGs on these images. In this study, the frequency and positional distribution of AGs in the transverse sinus was investigated on thin-sliced high-resolution MR images, and their appearance on diffusion-weighted MR images was evaluated. At least one AG was found in 107 of 151 subjects (70.9%). No statistically significant differences were noticed between males and females or between the right and left sides. No significant correlations between age and size or between age and the number of AGs were noted. On diffusion-weighted images, all AGs showed iso-intensity to normal brain tissue, which was higher than the reported signal intensity of arachnoid cyst and lower than that of epidermoids. In conclusion, AGs are normal structures that are frequently found in the cerebral venous sinuses on high-resolution MR images. Knowledge regarding their frequency and normal appearance would be helpful to avoid confusion between pathological processes and AGs. It is also important to know that AGs are frequently found even in the younger population.

Air-bone gap and resonant frequency in large vestibular aqueduct syndrome. Reviewed

Nakashima T, Ueda H, Furuhashi A, Sato E, Asahi K, Naganawa S, Beppu R

Am J Otol Vol. 21 ( 5 ) page： 671-674 2000

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

BACKGROUND: Conductive hearing loss is occasionally recognized in large vestibular aqueduct (LVA) syndrome; however, the incidence rate and the cause are not known. OBJECTIVE: To compare air and bone conduction levels between patients with LVA syndrome and those with idiopathic sudden sensorineural hearing loss, and to investigate the cause of the air-bone gap. STUDY DESIGN: Retrospective study. SETTING: The patients were treated at a tertiary referral center. PATIENTS: Twenty-eight ears of 15 patients with LVA syndrome and 28 ears of patients with idiopathic sudden sensorineural hearing loss were examined. The latter patients were selected from a computerized database to match the former patients in air conduction levels. MAIN OUTCOME MEASURES: Pure-tone audiometry, multiple frequency tympanometry, acoustic reflex, otoacoustic emission, vestibular evoked myogenic response. RESULTS: The air-bone gap in patients with LVA syndrome was always larger than that in patients with idiopathic sudden sensorineural hearing loss with the same air conduction level. The resonant frequency in patients with LVA syndrome was rather low compared with that in normal control subjects, in contrast to the finding that resonant frequency was significantly high in patients with otosclerosis. CONCLUSIONS: An air-bone gap exists to some degree in almost all patients with LVA syndrome. The air-bone gap may not be associated with the movement restriction of the stapes as it is with otosclerosis.

内耳MRIの現状と展望

長縄慎二　越川都紀子　深津博　石垣武男

映像情報メディカル臨時増刊号ビジュアルブックシリーズ Vol. 32 page： 46-52 2000

MR hydrographyの臨床応用, 耳鼻科領域

長縄慎二、伊藤都紀子

画像診断 Vol. 19 ( 7 ) page： 755-763 1999.7

MR imaging of the cerebollo pontine argle using a 3D fast spin echo sequence

Medical Imaging International Vol. 9 ( 2 ) page： 16-19 1999

High-resolution MR cisternography of the cerefellopintine angle, of tired in a 0.35-T Open MR unit

American Journal of Neuro radiology(AJNR) Vol. 20 ( 6 ) page： 1143-1147 1999

Fetal sacrococcygesl terotoma visualized by ultrafast T₂ Wighted megnetic resonance imaging

International Journal of gynecology and obstetrics Vol. 65 page： 191-193 1999

MR hydrographyの臨床応用耳鼻科銭域

画像診断 Vol. 19 ( 7 ) page： 755-763 1999

High-resolution MR images of inner ear internal anatomy using a local gradient coil at 1.5 Tesla: correlation with histological specimen. Reviewed

Ito T, Naganawa S, Fukatsu H, Ishiguchi T, Ishigaki T, Kobayashi M, Kobayashi K, Ichinose N, Miyazaki M, Kassai Y

Radiat Med Vol. 17 ( 5 ) page： 343-347 1999

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

PURPOSE: To obtain high-resolution MR images of the inner ear at 1.5 Tesla with a local gradient coil and to correlate these images with the histological specimen. MATERIALS AND METHODS: All studies were performed on a 1.5 Tesla MR unit with a local gradient coil (23 mT/m, slew rate of 107 mT/m/ms). The cranio-facial region of a cadaver was examined using 3D-fast spin echo (FSE) imaging with the voxel size of 0.27 mm x 0.27 mm x 0.5 mm in 9 h 37 min. Two normal volunteers were examined with the same system using 3D-FSE imaging with the voxel size of 0.20 mm x 0.26 mm x 1.0 mm in 57 min. These images were correlated with the cadaver images and histological specimens. RESULTS: On cadaver images, internal structures such as the macula utriculi, macula sacculi, crista ampullaris, lamina spiralis ossea, ligamentum spirale cochleae, modiolus, scala tympani, scala vestibuli, and cochlear aqueduct were visualized. On the images of both volunteers, the same structures were visualized as on the cadaver images. CONCLUSIONS: This study confirmed that high-resolution MR images obtained at 1.5 Tesla can visualize inner ear internal anatomy. Knowledge obtained in this study may be of significant value for the diagnosis of pathology in the area of the inner ear.

High-resolution MR cisternography of the cerebellopontine angle: 2D versus 3D fast spin-echo sequences. Reviewed

Iwayama E, Naganawa S, Ito T, Fukatsu H, Ikeda M, Ishigaki T, Ichinose N

AJNR Am J Neuroradiol Vol. 20 ( 5 ) page： 889-895 1999

Clinical evaluation of three-dimensional MR-cholangiopancreatography using three-dimensional Fourier transform fast asymmetric spin echo method (3DFT-FASE): usefulness of observation by multi-planar reconstruction. Reviewed

Yamakawa K, Naganawa S, Maruyama K, Kato T, Fukatsu H, Ishigaki T

Radiat Med Vol. 17 ( 1 ) page： 15-19 1999

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

MR-cholangiopancreatography (MRCP) is a new method that is non-invasive and permits volume data collection and three-dimensional expression. With the three-dimensional Fourier transform fast asymmetric spin echo (3DFT-FASE) method, a higher spatial resolution can be obtained both in-pain and in slice selecting direction. In this paper, the usefulness of this new technique is investigated in the clinical diagnosis of MIP images and MPR. The study was performed in 10 normal volunteers and 21 patients with abnormalities in the pancreas or bile-duct sustem. The study was done using a 1.5 Tesla super-conductive machine. The MRCP images were interpreted by three radiologists. In most cases good images were obtained. The additional clinical information provided by MPR was remarkably useful in cystic lesions, especially in mucinous cystic neoplasm of the pancreas. Even when the intestine overlapped the pancreas, it was possible to evaluate the pancreatic duct by MPR. Three-dimensional observation and clinically useful diagnosis were possible by utilizing the advantageds of the 3DFT-FASE method appears quite useful in clinical application.

Fetal sacrococcygeal teratoma visualized by ultra-fast T2 weighted magnetic resonance imaging. Reviewed

Okamura M, Kurauchi O, Itakura A, Naganawa S, Watanabe Y, Mizutani S

Int J Gynaecol Obstet Vol. 65 ( 2 ) page： 191-193 1999

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

We report here a fetal sacrococcygeal teratoma found at 26 weeks of gestation. An ultra-fast T2 weighted imaging method enables the clear visualization of morphological details of the fetus without motion artifacts. Complete surgical resection was performed immediately after cesarean birth, and no evidence of tumor recurrence was confirmed at 1 year of age.

DOI： 10.1016/S0020-7292(98)00248-3

High-resolution MR cisternography of the cerebellopontine angle, obtained with a three-dimensional fast asymmetric spin-echo sequence in a 0.35-T open MR imaging unit. Reviewed

Naganawa S, Ito T, Iwayama E, Fukatsu H, Ishigaki T

AJNR Am J Neuroradiol Vol. 20 ( 6 ) page： 1143-1147 1999

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

High-resolution MR cisternography performed with 3D fast asymmetric spin-echo imaging (3D fast spin-echo with an ultra-long echo train length and asymmetric Fourier imaging) was optimized in a 0.35-T open MR imaging unit. The 0.35- and 1.5-T images of the two volunteers and three patients with acoustic schwannomas were then compared. The optimal parameters for images obtained by 3D fast asymmetric spin-echo imaging at 0.35 T were as follows: field of view, 15 cm; matrix, 256 x 256 x 40; section thickness, 1 mm; echo train length, 76; and imaging time, 10 minutes 44 seconds. Scans obtained from both normal volunteers showed the facial, cochlear, and superior and inferior vestibular nerves separately in the internal auditory canal on both 0.35- and 1.5-T images. All three acoustic schwannomas were depicted on both 0.35- and 1.5-T images. Screening for disease at the cerebellopontine angle and in the internal auditory canal, without the administration of contrast material on a low-field open MR imaging unit and within a clinically acceptable imaging time, may be possible. Further controlled prospective studies are required, however, before implementation on a wide basis. If proved effective, this may be of particular value for reducing healthcare costs and for imaging claustrophobic and pediatric patients in an open system.

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Papers - NAGANAWA, Shinji