Biomedical subjects

Norio Hirabuki

Publications and source records attributed to Norio Hirabuki.

8 recordsLinked to original sources

PubMed2002

Parallel distributed processing neuroimaging in the Stroop task using spatially filtered magnetoencephalography analysis.

Parallel distributed processing neuroimaging in the Stroop color word interference task in five healthy subjects was studied. The total reaction time was set at 650 ms with a time window of 200 ms in steps of 50 ms. Spatially filtered magnetoencephalography analysis, as used in synthetic aperture magnetometry, was used. Neural activation began in the left posterior parietal-occipital area (150-250 ms post-stimulus), followed by the right prefrontal polar area (250-350 ms), the left dorsolateral prefrontal cortex (250-400 ms), and the mid- to lower- primary motor area (350-400 ms). Successive and temporally overlapping activation of various cortical regions were successfully estimated within a short 200 ms time interval, contrary to previous positron emission tomography and fMRI studies.

Adult↗

PubMed2002

Primary solitary intracranial melanoma in the sylvian fissure: MR demonstration.

We present a rare case of a primary intracranial melanoma originating from leptomeningeal melanoblasts in the sylvian fissure. The mass appeared hyperintense on T1-weighted MR images and hypointense on T2-weighted MR images, reflecting the presence of abundant melanin granules in the tumor. Associated leptomeningeal enhancement suggested a dire prognosis.

Brain Neoplasms↗

PubMed2002

Frequency-dependent spatial distribution of human somatosensory evoked neuromagnetic fields.

Using synthetic aperture magnetometry (SAM), we examined the spatial distribution of frequency changes in magnetoencephalography signal rhythms on individual magnetic resonance images following somatosensory stimulation. SAM is a novel statistical spatial filtering method that uses an adaptive beamformer. Electrical stimulation of the right median nerve demonstrated high-frequency event-related synchronization (ERS) in the 50-200-Hz range, consistently localized in the contralateral primary sensorimotor area in all subjects (n=7). Event-related desynchronization (ERD) was demonstrated in the 8-13, 13-25 and 25-50-Hz ranges bilaterally in the area surrounding the central sulcus. The differences in the spatial distribution as well as the frequency bands between ERS and ERD suggest that ERS and ERD reflect the responses of different cell assemblies rather than a frequency shift of the same cell assembly.

Adult↗

PubMed2002

Evaluation of indexes of in vivo manganese status and the optimal intravenous dose for adult patients undergoing home parenteral nutrition.

BACKGROUND: There are no accurate indexes for determining the status of manganese in humans, and there is no clear recommended daily dose of this essential trace element to be administered in total parenteral nutrition solutions. OBJECTIVE: The objectives were to evaluate accurate indexes of manganese status and elucidate the optimal manganese dose to be administered to adult patients undergoing home parenteral nutrition. DESIGN: Patients were administered total parenteral nutrition solutions providing 0, 1, 2, or 20 micromol Mn/d according to an on-off design, after which manganese concentrations in whole blood and plasma were determined. Magnetic resonance imaging (MRI) was performed to determine the intensity on T(1)-weighted images (MRI intensity) and T(1) values in the globus pallidus. Hematologic and biochemistry tests were also performed. RESULTS: High degrees of correlation were found between whole-blood manganese concentrations and both MRI intensity (r = 0.7728) and T(1) values (r = -0.7519) in the globus pallidus. A strong negative correlation was found between MRI intensity and T(1) values (r = -0.8407). The dose of 1 micromol Mn/d caused no change in MRI intensity or T(1) values, and the whole-blood manganese concentration remained within the normal range in all patients. CONCLUSIONS: Whole-blood manganese concentrations and MRI intensity and T(1) values in the globus pallidus are useful indexes of the status of manganese in humans. The optimal dose of manganese may be 1 micromol/d for adult patients undergoing home parenteral nutrition.

Adolescent↗

PubMed2002

Evaluation of video capture equipment for secondary image acquisition in the PACS.

There are many cases in which picture archiving and communication systems (PACS) are built with old-type existing modalities with no DICOM output. One of the methods for interfacing them to the PACS is to implement video capture (/ frame grabber) equipment. This equipment takes analog video signal output from medical imaging modalities, and amplitude of the video signal is A/D converted and supplied to the PACS. In this report, we measured and evaluated the accuracy at which this video capture equipment could capture the image. From the physical evaluation, we found the pixel values of an original image and its captured image were almost equal in gray level from 20%-90%. The change in the pixel values of a captured image was +/-3 on average. The change of gray level concentration was acceptable and had an average standard deviation of around 0.63. As for resolution, the degradation was observed at the highest physical level. In a subjective evaluation, the evaluation value of the CT image had a grade of 2.81 on the average (the same quality for a reference image was set to a grade of 3.0). Abnormalities in heads, chests, and abdomens were judged not to influence diagnostic accuracy. Some small differences were seen when comparing captured and reference images, but they are recognized as having no influence on the diagnoses.

Humans↗

PubMedDate not supplied

Origin of high signal intensity in the cavernous sinus in MR angiographic source images: correlation between MR and conventional angiography.

OBJECTIVE: To investigate the origin of a high signal intensity in a cavernous sinus on magnetic resonance (MR) angiography. METHODS: Time-of-flight MR angiography was performed in 20 patients scheduled for conventional angiography for disease not related to carotid cavernous fistula. Venous drainage pattern was assessed, and flow rate to a cavernous sinus was semiquantitatively evaluated on conventional angiography. RESULTS: Two sinuses showed high signal intensity in the anterior portion. These were associated with direct venous drainage to the anterosuperior aspect of the cavernous sinus from the superficial middle cerebral vein, and their flow rates were among the 10% of the sides with the highest flow rates. Two other sinuses showed high signal intensity in the posterior portion. Their flow rates from the superficial petrosal sinus were also among the 10% of the sides with the highest flow rates. CONCLUSION: High signal intensity in the anterior or posterior portions of the cavernous sinus is probably a result of inflow from the superficial middle cerebral vein and the superior petrosal sinus, respectively.

Adult↗

PubMedDate not supplied

Operating data and unsolved problems of the DICOM modality worklist: an indispensable tool in an electronic archiving environment.

PURPOSE: We evaluated the efficacy of DICOM worklist software for radiological modalities from the viewpoint of risk management, to reduce mislabeled image data in an electronic archiving environment. We focused on the following five points: 1) the effectiveness of the DICOM modality worklist, 2) problems involving incorrect patient and image data, 3) the presence of incorrect profiles despite the transfer of patient profiles online via the DICOM worklist, 4) ways to eliminate entry failure, and 5) further examination even if data entry were correct. MATERIALS AND METHODS: Retrospective data of patient profiles with image data were evaluated both before and after installation of DICOM modality worklist management software at Sakai Municipal Hospital. All radiology modalities were connected to RIS terminals in which DICOM modality worklist software was installed. Patient profiles were transferred online from RIS terminals to the modalities. It was not necessary for technologists to type patient profiles in usual examinations. RESULTS: Before installing the DICOM modality worklist software, the number of data entry errors was 31 and the rate was 6.4% of 487 examinations. After installation, manual data entry occurred in 80 of 1,994 examinations. The number of data entry errors for patient profiles was two, and the rate was 0.1% of the total examinations (p < 0.0001). Before installing the DICOM modality worklist, two wrong patient IDs that corresponded to other existing patient IDs were typed into the modality. No patient IDs were mixed up after installation of the DICOM modality worklist (p = 0.0385). CONCLUSION: The DICOM worklist was indispensable to electronic archiving because it decreased incorrect patient profiles that corresponded to image data loss. This was effective in decreasing patient mix-ups that could lead to serious malpractice. Despite the DICOM worklist, however, some incorrect patient profiles remained as a result of manual typing errors. The reasons for manual typing included emergency examinations, paper-based operations, and system shutdown. Furthermore, the risk of patient mix-ups remained even if the patient profile was correct. To eliminate or decrease medical accidents, determining why accidents happen and ensuring better data confirmation are necessary.

Archives↗

PubMedDate not supplied

Effect of stage 1 sleep on auditory cortex during pure tone stimulation: evaluation by functional magnetic resonance imaging with simultaneous EEG monitoring.

BACKGROUND AND PURPOSE: Responses of the auditory cortex to sound during sleep have been explored with somewhat discrepant results. The purpose of this study was to investigate the effect of stage 1 sleep on signal intensity changes in the auditory cortex in response to pure tone stimulus measured by functional MR imaging. METHODS: Six sleep-deprived subjects were exposed to a series of echo-planar images for 30-40 minutes. No medication was used to help the subjects go to sleep. A long repetition time of 12 seconds and a 1.9-second clustered multisection acquisition were used to minimize the effect of imager acoustic noise from the preceding acquisition and to make it possible to obtain electroencephalographs between image acquisitions. A pure tone stimulus (beep, 1,000-Hz sine waves, 30-millisecond duration, five beeps per second) was alternated with the baseline every 36 seconds. RESULTS: All subjects fell asleep. The effect of habituation evaluated by comparing the percentage of signal intensity change between the first and second half was not significant. The percentage of signal intensity changes in the right and left transverse temporal gyri were 0.49% and 0.43% during wakefulness and 0.05% and 0.07% during stage 1 sleep. The differences between wakefulness and stage 1 sleep were significant. CONCLUSION: Transition to stage 1 sleep coincides with a decrease in functional MR imaging-determined signal intensity changes in the auditory cortex in response to pure tone stimulus. The limited response of the brain at this stage may protect the brain from sound and facilitate deepening of the sleep stage.

Acoustic Stimulation↗