Faculty Profiles - NAGANAWA, Shinji

Papers - NAGANAWA, Shinji

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

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.

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

MR hydrographyの臨床応用耳鼻科銭域

画像診断 Vol. 19 ( 7 ) page： 755-763 1999

Fetal sacrococcygesl terotoma visualized by ultrafast T₂ Wighted megnetic resonance imaging

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

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.

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.

Magnitude subtraction vs. complex subtraction in dynamic contrast-enhanced 3D-MR angiography: basic experiments and clinical evaluation. Reviewed

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

J Magn Reson Imaging Vol. 10 ( 5 ) page： 813-820 1999

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

Magnitude subtraction and complex subtraction in dynamic contrast-enhanced three-dimensional magnetic resonance (3D-MR) angiography were compared using a phantom and 23 human subjects. In phantom studies, complex subtraction showed far better performance than magnitude subtraction, especially for longer echo times, with thicker slices, and without fat suppression. With complex subtraction, non-fat-suppressed studies showed contrast-to-noise ratios comparable to those in fat-suppressed studies. In human subjects, complex subtraction was superior to magnitude subtraction in 9 subjects, but comparable to magnitude subtraction in 14 subjects. There were no cases in which magnitude subtraction was superior to complex subtraction. Although the differences observed in human studies when complex subtraction was applied with thinner slices, shorter echo times, and the fat-suppression technique were not as pronounced as those seen in phantom studies, complex subtraction should be performed in dynamic contrast-enhanced 3D-MR angiography because there are no drawbacks in complex subtraction. Further research is necessary to assess the feasibility of dynamic contrast-enhanced 3D-MR angiography without fat suppression in human subjects using complex subtraction, as suggested by the results of phantom studies. If it is found to be feasible, dynamic contrast-enhanced 3D-MR angiography without fat suppression using complex subtraction may prove to be a robust technique that eliminates the need for shimming and can reduce the acquisition time. J. Magn. Reson. Imaging 1999;10:813-820.

MR imaging of the cochlear modiolus: area measurement in healthy subjects and in patients with a large endolymphatic duct and sac. Reviewed

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

Radiology Vol. 213 ( 3 ) page： 819-823 1999

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

PURPOSE: To evaluate the cochlear modiolus with thin-section magnetic resonance (MR) imaging in healthy subjects and patients with a large endolymphatic duct and sac, and to assess whether the cochlea is normal or abnormal in patients with a large endolymphatic duct and sac. MATERIALS AND METHODS: MR images were obtained in 10 ears in five volunteers (group 1), 40 ears in 20 patients with bilateral sensory hearing loss (group 2), three ears in two patients with Mondini malformation (group 3), and 12 ears in seven patients with a large endolymphatic duct and sac (group 4). RESULTS: In groups 1 and 2, all modiolar areas were larger than 4.0 mm2. In group 3, each modiolus was smaller than 2.0 mm2. In group 4, modiolar areas were smaller than 2.0 mm2 in eight ears and were larger than 4.0 mm2 in four ears. CONCLUSION: Findings in this study confirm that a large endolymphatic duct and sac is frequently associated with modiolar deficiency, but the modiolar area is normal in some cases. This result does not support the recently proposed hypothesis that hearing loss with a large endolymphatic duct and sac is caused by the transmission of subarachnoid pressure forces into the labyrinth through a deficient modiolus.

MR cisternography of the cerebellopontine angle using a 3D fast spin echo sequence

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

Medical Imaging International Vol. 9 page： 16-18 1999

Inter observer agreement in sonographic diagnosis of breast tumors

European Journal of ultrasound Vol. 8 page： 25-31 1998

MR imaging of the inner ear

Radiology Vol. 208 page： 679-685 1998

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Papers - NAGANAWA, Shinji