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Biomedical subjects

T Kawazu

Publications and source records attributed to T Kawazu.

At least 19 recordsLinked to original sources
PubMed2005

Patency assessment of the internal jugular vein after neck dissection.

Twenty-seven patients with oral malignant tumours, who underwent neck dissection with preservation of the internal jugular vein (IJV), were studied retrospectively to evaluate patency of the IJV. Twenty-three patients underwent ablative surgery of the primary lesion with neck dissection and 4 underwent neck dissection alone. Three patients received simple closure and skin grafting of the primary lesion, and 20 received reconstruction surgery (4 platysma flaps, 3 radial forearm flaps, 3 lateral upper arm flaps, 2 pectoralis major myocutaneous flaps and 8 rectus abdominis myocutaneous flaps). The maximum and minimum diameters of the IJV as measured on computed tomographic (CT) scans were used to assess patency. The cross-sectional area of the IJV and the ratio of its long axis to short axis (L/S ratio) were calculated. The relation between the change in IJV status and the type of flap used for reconstruction was also examined. Occlusion of the IJV was present in 3.7% of the patients, and 'narrowing' was present in 63.6%. The size of the flap significantly correlated with 'narrowing' of the IJV, suggesting that 'narrowing' was caused mainly by compression due to the flap.

Carcinoma, Squamous Cell↗
PubMed2005

Correlation between diagnostic accuracy and perceptibility.

OBJECTIVES: To correlate diagnostic accuracy for proximal caries with perceptibility of low contrast image details using regression analysis. The other purpose was to determine the attenuation range required for proximal caries diagnosis. METHODS: The results of the two types of observer performance tests described above were retrieved from previous studies. Recording media included in those studies were the Compuray and the Dixel, direct digital radiographic systems, and Ektaspeed Plus film. The average numbers of perceptibility of image details from five observers were calculated for each step and for every combination of contiguous steps of the aluminium test phantom from the perceptibility test. The average diagnostic accuracy for proximal caries from the same five observers was correlated with the total number of perceptible details from the phantom using regression analysis. Finally, attenuation range required for proximal caries diagnosis was calculated from the attenuation range of the phantom where the maximum correlation coefficient was obtained. RESULTS: Maximum correlation (r=0.68) was obtained at the combination of five contiguous steps of the aluminium test phantom. Attenuation range required for proximal caries diagnosis corresponded to the 2 mm to 6 mm thickness of aluminium with acrylic block of 12 mm thickness. CONCLUSIONS: There is a correlation between perceptibility of low contrast image details and diagnostic accuracy for proximal caries. There may be a possibility to simplify observer performance tests for proximal caries diagnosis by using the standardized phantom simulating its attenuation range.

Adolescent↗
PubMed2005

Effects of the automatic exposure compensation on the proximal caries diagnosis.

OBJECTIVE: To elucidate the effect of automatic exposure compensation (AEC) on the diagnostic accuracy of proximal caries by comparing several digital intraoral imaging systems with a film. MATERIALS AND METHODS: Twenty-seven extracted teeth served as proximal caries samples. Three digital radiographic systems; the Compuray, the Dixel, and the Sens-A-Ray without scintillator layer, and Kodak Ekta-speed Plus films were used as recording media. Radiographs of the teeth samples were obtained with each recording medium under seven to eight different exposures including the optimum level. Six oral radiologists evaluated the possibility of proximal caries with the five-grade-confidence-scale. On digital radiographs, image manipulations were allowed after the initial assessment. Receiver operating characteristic (ROC) curves were obtained at each exposure in each recording medium. The area under the ROC curve (Az) was used as the representative value of diagnostic accuracy. Diagnostic accuracy (DA) curves were obtained by plotting averaged Az values from all observers as a function of incident exposure in each system. RESULTS: The effect of exposure variation on the DA was slight in the film while it was significantly larger in the digital systems without AEC. Among digital systems, the effect of exposure variation was smaller in the system with AEC than those without AEC. There was no significant effect on the diagnostic accuracy even if digital image manipulation was employed. CONCLUSION: AEC minimizes the decrease of DA due to inadequate exposures. Since it compensates for the narrow exposure range in the digital intraoral sensor systems, the system with AEC may be preferable for the clinical diagnostic tasks.

Adolescent↗
PubMed2003

Perceptibility curves for the Digora system.

OBJECTIVES: To construct perceptibility curves (PCs) for given calibration settings in order to define psychophysical properties of the Digora storage phosphor system and to evaluate the effects of automatic exposure correction (AEC) on the PCs. METHODS: The Digora system was calibrated at two exposures, 80 microC kg(-1) (high calibration) and 40 microC kg(-1) (low calibration). Since the grey levels displayed in the radiographs are adjusted by AEC, dose-response functions at high calibration were obtained using AEC on and off modes. The dose-response function at low calibration was obtained with AEC off. The PC at each experimental setting was calculated using known physical parameters of the system and the performance of the average observer used in a previous study. In addition, PCs were also constructed using transmitted radiation flux behind the test object calculated from the attenuation coefficient in order to study observer and system performance. PCs obtained under these conditions were compared. RESULTS: The PC using calculated transmitted radiation flux behind the test object showed a wide plateau at the peak owing to AEC, while the PC obtained by a modified approach showed a higher but narrower peak. There were no differences between the two PCs using AEC on and off modes when the PCs were constructed using a modified approach. There were no differences between the two PCs obtained at high and low calibration settings or between the three PCs obtained with AEC on except for the position along the exposure axis. CONCLUSIONS: Psychophysical properties of the Digora system may be determined if we employ registered exposures from a dose-response function with AEC off under a given calibration setting. Under these circumstances the shape and height of the PCs will be unchanged irrespective of the AEC mode.

Algorithms↗
PubMed2003

Extraction of total RNA from leaves of Eucalyptus and other woody and herbaceous plants using sodium isoascorbate.

Rapid extraction of total RNA from Eucalyptus leaves is difficult due to the high content of polyphenolics and polysaccharides. A rapid and simple method was developed by using an extraction buffer containing sodium isoascorbate at a concentration of 500 mM. This method consisted of one or two chloroform extractions, one acid guanidium-phenol-chloroform extraction, and isopropanol precipitation alone. The yields of the RNA fractions were 246-1750 micrograms/g fresh weight when leaves of Eucalyptus, five other woody plants, and four herbaceous plants were used as samples. The contamination of the RNA fractions by proteins and polysaccharides was very limited as judged spectrophotometrically. When the RNA fractions were subjected to agarose gel electrophoresis, intact rRNA bands were detected. The RNA fractions could be used for RT-PCR. These results indicate that our new method achieves a simple and rapid preparation of high-quality RNA from leaves of Eucalyptus and other plant species.

Ascorbic Acid↗
PubMed2001

Conventional and predicted perceptibility curves for contrast-enhanced direct digital intraoral radiographs.

OBJECTIVES: To construct Perceptibility Curves (PCs) for contrast-enhanced digital intraoral radiographs. METHODS: Radiographs of a test object having holes of increasing depths were exposed using three digital systems, the CDR (Schick Technologies, Long Island, NY, USA), the Dixel (J Morita MFG, Kyoto, Japan) and the Sens-A-Ray (Regam Medical Systems, Sundsvall, Sweden). The radiographs were contrast-enhanced and PCs constructed in the conventional way using 10 observers. Predicted PCs were calculated and compared with observer data. RESULTS: The PCs showed that contrast enhancement is effective for the perception of small contrast details, especially in the low exposure range. Predicted PCs demonstrated excellent agreement with observer data. CONCLUSIONS: Contrast enhancement should be advantageous in digital radiography. The effects of contrast enhancement on PCs may be predicted without previous knowledge of observer performance.

Algorithms↗
PubMed2001

The combined use of US and MR imaging for the diagnosis of masses in the parotid region.

PURPOSE: To evaluate the usefulness of the combination of the two non-invasive modalities US and MR imaging to diagnose masses in the parotid region. MATERIAL AND METHODS: The US and MR findings of 21 patients with parotid masses were analyzed retrospectively by two radiologists without any clinical or histopathological information. The specific points evaluated were location, shape, margin, internal architecture, and intensity level on both US and MR, posterior echo enhancement on US, and capsule-like lining of the tumor on MR. RESULTS: The findings concerning the shape and margin on US and MR were in fairly good agreement. Concerning the findings of the internal architecture, US could reveal the minute structures of the tumor while MR demonstrated differences in the signal intensities of histological tissue types of the various tumors. The posterior echo enhancement on US and the capsule-like lining on MR of the tumors were also useful for the diagnosis. CONCLUSION: Our results suggest that the combination of US and MR is useful for examining soft tissue masses in the parotid region to make a more accurate diagnosis, and not just differentiate malignant lesions from those which are benign.

Adolescent↗
PubMed2000

A new, simple method of making a spacer in interstitial brachytherapy for mobile tongue cancer.

OBJECTIVES: This article demonstrates a new method of making a spacer that increases the distance between the mandible and implanted radioactive sources in interstitial brachytherapy for patients with mobile tongue cancer. STUDY DESIGN: Fifty-three patients with mobile tongue cancer underwent interstitial brachytherapy with spacers made by this new technique. RESULTS: Our spacer is not difficult to create or to use. The spacer was made from a plastic splint by using thermoforming techniques and quick self-curing resin, which did not need waxing, wiring, or casting. The surface of the spacer, which comes in contact with the tongue, is smooth because it is covered with tissue-conditioning material. There were no complaints of pain from the patients. Osteoradionecrosis of the mandible developed in only 1 (1.9%) of these patients. CONCLUSIONS: This spacer is simple to make and prevented osteoradionecrosis.

Brachytherapy↗
PubMed2000

Computed tomography and ultrasonography of metastatic cervical lymph nodes in oral squamous cell carcinoma.

OBJECTIVES: To define criteria for CT and US in differentiating cervical lymph node metastases in oral squamous cell carcinoma (SCC). MATERIALS AND METHODS: CT and/or US of 230 metastatic lymph nodes and 228 benign lymph nodes in 147 patients with oral SCC were retrospectively evaluated. The CT and US findings of each lymph node were compared with the histopathological findings. A metastasis was defined on CT as a lymph node with rim or heterogeneous enhancement, or measuring 10 mm or more in the short axis, regardless of enhancement pattern, and on US as having definite internal echoes, regardless of size, or without definite internal or hilar echoes, but measuring 10 mm or more in the short axis. A lymph node with hilar echoes or a ratio of the long to short axis (L/S ratio) of 3.5 or more was considered benign. A lymph node failing to comform to any of these categories was termed questionable. RESULTS: The positive predictive value (PPV) for CT was 90.8% and the negative predictive value (NPV) was 70.4%. However, 65.7% of all lymph nodes could not be classified as either metastastic or benign. PPV for US was 96.5% and NPV was 88.1%. 25.5% of all lymph nodes could not be classified as either metastatic or benign. CONCLUSIONS: Despite limitations in detecting metastases, by including a third category 'questionable' our criteria appear clinically more useful than other current methods based on two groups only.

Adult↗
PubMed2000

Evaluation of filtration leucocytapheresis for use in the treatment of patients with rheumatoid arthritis.

OBJECTIVES: To evaluate the efficacy of filtration leucocytapheresis (LCP) for rheumatoid arthritis (RA). METHODS: LCP was carried out three times, with 1 week separating each session, in 25 drug-resistant RA patients. RESULTS: During each session, 96, 98, 61, 84 and 8% of the granulocytes, monocytes, lymphocytes, platelets and erythrocytes, respectively, that entered the LCP filter were removed. The number of granulocytes, monocytes and lymphocytes in the peripheral blood significantly decreased during each session of LCP. However, there was no significant decrease in the number of circulating blood cells during the study period. On average, 110 x 10(8) granulocytes, 5.23 x 10(8) monocytes, and 20.5 x 10(8) lymphocytes were removed during LCP therapy. Assessment of RA before and after LCP showed a substantial and rapid improvement in the tender joints counts, swollen joint counts, and patient's and physician's assessments. No adverse reactions or complications were noted. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels decreased following LCP, although the change in the latter parameter was statistically insignificant. The concentrations of serum albumin, gamma-globulin, IgG, IgM, CH50 and rheumatoid factor titres did not change during or after LCP. Careful analysis indicated that 16 of 25 patients with RA showed > or =20% improvement following LCP therapy. CONCLUSIONS: Our results suggest that filtration LCP to remove leucocytes from the peripheral blood exerts an immunomodulatory effect in patients with RA.

Arthritis, Rheumatoid↗
PubMed1999

Isokinetic strength of elbow extensor muscles correlates with race time in wheelchair half marathon racers.

It has been reported that grasping power and isometric muscle strength of elbow extensors in fine wheelchair racers were greater than the poor racers in the wheelchair full marathon. The purpose of the present study was to investigate the relationship between muscle strength of elbow extensors and flexors and the race time in wheelchair half marathon race. Four wheelchair half marathon racers who completed the half marathon division of the 16th Oita International Wheelchair Marathon (OIWM) in 1996 participated in the present study. The day before the race, all subjects reported to the training room and the isokinetic muscle strength of elbow extensor and flexor muscle groups was measured at angular speeds of 60 degrees, 120 degrees and 240 degrees/sec using the isokinetic dynamometer. There was a significant correlation between race time and isokinetic muscle strength of the elbow extensors at 60 degrees, 120 degrees and 240 degrees/sec, but not flexor muscles. Our findings suggest that increased muscle strength of elbow extensors may improve the race time in wheelchair half marathon race.

Adult↗
PubMed1999

A pair of invertedly repeated genes in Chlamydomonas reinhardtii encodes a zygote-specific protein whose expression is UV-sensitive.

Uniparental inheritance of the chloroplast genome has been observed in a wide variety of green plants. In Chlamydomonas this phenomenon, which can be selectively inhibited by UV irradiation of mt(+) gametes, has been shown cytologically to be due to the preferential degradation of mt(-)-derived chloroplast nucleoids in young zygotes. The zygote-specific pair of zys1 genes, zys1A and zys1B, is expressed earliest among five genes isolated from a "10-min" zygote library. We report here that the ZYS1 protein, which is encoded by the invertedly duplicated zys1 gene, accumulates in zygotes and is localized in nuclei. In addition, when mt(+) gametes (but not mt(-) gametes) are UV-irradiated before mating, only very limited accumulation of ZYS1 protein can be detected in the resulting zygotes.

Algal Proteins↗
PubMed1999

Value of contrast-enhanced magnetic resonance imaging in differentiation of hemangiomas from lymphangiomas in the oral and maxillofacial region.

OBJECTIVE: The purpose of this study was to investigate the ability of contrast-enhanced magnetic resonance imaging to differentiate hemangioma from lymphangioma in the oral and maxillofacial region. STUDY DESIGN: Contrast-enhanced magnetic resonance imaging was performed in 20 patients (21 masses: 17 hemangiomas and 4 lymphangiomas) through use of either a 0.2-T permanent system or a 0. 5-T superconductive system and spin-echo pulse sequences. RESULTS: After intravenous administration of contrast medium, enhancement was observed in all hemangiomas in areas corresponding to those with high signal on T(2)-weighted images. Unequivocally increased signal was observed in 10 masses, and slightly increased signal was observed in 7 masses. On the other hand, none of the lymphangiomas showed an enhancing mass on contrast-enhanced T(1)-weighted images. CONCLUSIONS: Although contrast-enhanced T(1)-weighted imaging may not improve delineation of masses in all cases, it can be used to differentiate between deep hemangiomas and lymphangiomas.

Adolescent↗
PubMed1999

Assessment of image quality in dental radiography, part 1: phantom validity.

OBJECTIVE: The purpose of this study was to describe and validate an image-quality phantom to be used in dental radiography for comparison of film and digitally acquired images. STUDY DESIGN: An aluminum block of 12 steps, with 7 holes in each step, was covered by acrylic blocks. This phantom was radiographed with Kodak Ultra-speed and Ektaspeed Plus films at 70, 65, and 60 kVp with the whole exposure range available. All together, 50 dental films were randomly sequenced and presented to 7 observers. The average number of perceptible holes from all steps was plotted against exposure for each tube voltage and film type, generating a modified perceptibility curve. The tentative optimum exposure level was determined from perceptibility curves in each experimental condition and compared with that determined by means of the standard aluminum stepwedge and the preset time of the x-ray machine. The density range of this phantom at the optimum exposure was compared with that of clinical dental radiographs. Validity of the phantom was evaluated according to the optimum exposure level from the modified perceptibility curves and the overall density range. Finally, the average maximum numbers of perceptible holes at the tentative optimum exposure level were compared for each tube voltage and film type. The statistical test used was a 2-way factorial analysis of variance. RESULTS: The exposure at the perceptibility curve peak approximated that obtained by means of the standard aluminum step-wedge and the time preset by the manufacturer. The overall density range at the perceptibility curve peak covered the clinical density range for each tube voltage and film type. There were no statistically significant differences between film types or among tube voltages. CONCLUSIONS: The x-ray attenuation range for this phantom seemed to approximate clinical conditions. In addition, differences in image quality could be quantitatively evaluated by means of the number of the holes seen in the phantom.

Absorptiometry, Photon↗
PubMed1999

Assessment of image quality in dental radiography, part 2: optimum exposure conditions for detection of small mass changes in 6 intraoral radiography systems.

OBJECTIVE: The purpose of this study was to compare 2 film systems and several digital intraoral systems with regard to visual image quality through use of a test phantom developed for this purpose. STUDY DESIGN: The detectors used for digital imaging were as follows: Computed Dental Radiography (CDR), Digora, Dixel, and Sens-A-Ray without scintillator layer. Two types of digital images were prepared for the observer performance test: one with original gray scales and another with contrast enhancement. Images with and without enhancement from the 4 systems were displayed to 7 observers. The change in the average number of perceptible holes was plotted against exposure, and modified perceptibility curves were created and compared with curves for the film systems. The exposure level at which the maximum number of holes was perceived was defined to be optimum. The optimum exposure levels were determined for each digital system and compared with that of the film systems. At the optimum exposure, the average maximum numbers of perceptible holes in each digital system with and without contrast enhancement were compared with the maximum numbers for the film systems. The minimum exposure levels were determined to be those at which the number of perceptible holes exceeded the number for film, and the possibility of exposure reduction was evaluated. RESULTS: All digital systems except the Digora system showed lower optimum exposures than E-speed film. In all digital images without enhancement, however, the maximum number of perceptible holes was significantly lower than that for the film systems at that exposure. With contrast enhancement, all digital systems except the Sens-A-Ray system showed visibility superior to that of the film systems. With the CDR, Digora, and Dixel systems, exposures could be further reduced by a considerable amount, with greater retention of information than was associated with film. CONCLUSIONS: Our results strongly suggest that digital systems, if properly used, can exceed film systems in the detection of small mass changes.

Contrast Media↗
PubMed1999

Expression of a bacterial endoglucanase gene in tobacco increases digestibility of its cell wall fibers.

Transgenic tobacco plants exhibiting exogenous cellulase activity were produced by introduction of a truncated cellulase (t-EgI) gene from Ruminococcus albus. They accumulated about 0.1-0.5% t-EgI of the total soluble proteins in the cytoplasm. They were normal in morphology and growth. t-EgI expressed in the transgenic plants degraded their own cell wall materials after the cells were disrupted. The plants expressing the t-egI gene could be used as "cellulase-encapsulating plants" for livestock and food industries.

Journal Article↗
PubMed1999

Kinetic factors determining wheelchair propulsion in marathon racers with paraplegia.

OBJECTIVE: To assess the different factors that determine the propulsion of wheelchair in long distance racers with spinal cord injuries. DESIGN AND METHODS: Nine highly handicapped men who competed at the Oita International Wheelchair Marathon in 1995, participated in this study. Subjects performed steady and exhaustive wheelchair propulsion at their optimal speed on wheelchair rollers in a laboratory setting during a 5-min period. Movements of the trunk and arms were filmed by a video camera then analyzed kinetically using a two-dimensional analysis system. In order to determine the actual pushing time and angle of wheelchair, we measured the duration between hand contact and hand release from handrim. SETTING: Department of Rehabilitation Medicine University of Occupational and Environmental Health, Japan. RESULTS: The push time, cycle time, total push time, and angular velocity did not relate with the race time or wheelchair velocity. However, the total push angle correlated significantly (P<0.01) with the race time and wheelchair velocity. Improvement of the pushing angular velocity and pushing duration did not contribute to the race time. CONCLUSION: The skilful wheelchair propulsion in long distance racing depends on the total push angle. Improvement of the total push angle should be achieved by both prolongation of the total push time and increased pushing angular velocity.

Adult↗