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Biomedical subjects

Y Higashida

Publications and source records attributed to Y Higashida.

At least 19 recordsLinked to original sources
PubMed1998

Characterization of a second gene (ZSOD22) of Na+/H+ antiporter from salt-tolerant yeast Zygosaccharomyces rouxii and functional expression of ZSOD2 and ZSOD22 in Saccharomyces cerevisiae.

We reported in our previous paper on the characterization of the Na+/H(+)-antiporter gene (ZSOD2) closely related to the salt-tolerance of yeast Zygosaccharomyces rouxii. In the present paper, we have cloned a second gene (ZSOD22) of Na+/H+ antiporter from Z. rouxii. The deduced amino acid sequence of Zsod22p was highly homologous to that of Zsod2p, Sod2p from Schizosaccharomyces pombe, and Nhalp from Saccharomyces cerevisiae. The open reading frames (ORFs) from ZSOD2 or ZSOD22 were inserted into a yeast expression vector pYES2, and their constructs (pZSOD2 and pZSOD22) were used to transform the salt-sensitive S. cerevisiae. pZSOD2- or pZSOD22-harboring-recombinant S. cerevisiae cells showed increases in salt tolerance. However, the Z. rouxii disruptant of ZSOD22 did not show any phenotypes related to salt tolerance or osmotolerance, unlike that of ZSOD2. The transcriptional expression of ZSOD22 was not observed by Northern blot analysis even in Z. rouxii cells subjected to NaCl-shock. From these results we conclude that although Z. rouxii includes at least two copies of the Na+/H(+)-antiporter gene (ZSOD2 and ZSOD22), ZSOD2 encodes a functional product as an antiporter and ZSOD22 is poorly transcribed, if at all.

Amino Acid Sequence↗
PubMed1998

Three-dimensional FISP imaging in the evaluation of carotid cavernous fistula: comparison with contrast-enhanced CT and spin-echo MR.

PURPOSE: The purpose of this study was to assess the value of three-dimensional fast imaging with steady-state precession (FISP) MR sequences relative to contrast-enhanced CT and spin-echo MR imaging in the diagnosis of carotid cavernous fistula (CCF). METHODS: Seventeen patients with 19 angiographically proved CCFs had contrast-enhanced CT, spin-echo MR imaging, and 3-D FISP imaging. Three observers assessed these imaging studies as well as those of 43 control sides in a blinded manner for the presence or absence of CCF. Receiver operating characteristic analysis was used to assess the diagnostic utility of each imaging technique. In a nonblinded study, contrast-enhanced 3-D FISP images were also evaluated. RESULTS: Higher diagnostic accuracy was obtained with 3-D FISP sequences, as the shunt flow within the cavernous sinus was well seen. Sensitivity of 3-D FISP images was 83% and specificity was 100% in the blinded study. In the receiver operating characteristic analysis, the diagnostic performance of observers was found to be better with the 3-D FISP images than with the spin-echo MR images. Although there were no significant difference between 3-D FISP and contrast-enhanced CT, higher diagnostic performance was obtained with 3-D FISP images. In three CCFs without anterior drainage, a diagnosis was made only from the 3-D FISP images. The contrast-enhanced 3-D FISP images were not helpful, since the cavernous sinuses enhanced. CONCLUSION: Three-dimensional FISP imaging is superior to spin-echo MR imaging and contrast-enhanced CT in the diagnosis of CCF. Contrast-enhanced 3-D FISP images are not helpful for the evaluation of CCF.

Adolescent↗
PubMed1998

[Improvement of detectability of microcalcifications by magnification digital mammography].

Our aim in this study was to evaluate the potential utility of magnification mammography with a CR system by investigating the basic imaging parameters and detectability of microcalcifications in comparison with those of conventional screen-film systems. The basic imaging parameters were evaluated by measuring scatter fraction, modulation transfer function (MTF), Wiener spectrum, and incident dose for the various magnification factors. The detection of simulated microcalcifications in radiographs of a mammographic phantom and breast specimens were evaluated subjectively and quantitatively for screen-film and CR techniques with various magnification factors. The scatter fraction of digital magnification mammography decreased with increasing magnification factor. MTF of magnification digital mammography improved with increasing magnification factor. The detectability of microcalcifications with the CR system was significantly improved by magnification technique. From the above results, it is expected that the use of magnification mammography with a CR system will improve the detectability of microcalcification.

Breast Diseases↗
PubMed1996

Physical and clinical evaluation of a 2,048 x 2,048-matrix image intensifier TV digital imaging system in bone radiography.

RATIONALE AND OBJECTIVES: To evaluate the potential utility of a 2,048 x 2,048-matrix image intensifier television digital radiography (DR) system versus a conventional screen-film (S-F) system for bone radiography. METHODS: Basic imaging properties were evaluated including resolution properties, Wiener spectra, and detectabilities of low-contrast signals. DR images were obtained with the same exposure (iso-dose) or one-third the exposure (low-dose) used with the S-F system. The visibility of pathologic details of metastatic disease on bone radiographs of 27 patients was evaluated subjectively by six radiologists. RESULTS: Resolution properties of the DR system were slightly superior to those of the S-F system at low-frequency range, but the S-F system showed considerably higher resolution properties at the high-frequency range. The noise levels for iso-dose DR were slightly greater than those for S-F imaging at low spatial frequency; however, low-dose digital radiographs showed higher noise levels. Visibility of details of diagnostic features on bone radiographs was similar with both systems, but the low-dose digital radiographs were slightly inferior. CONCLUSION: High-resolution image intensifier television DR systems may be clinically useful for bone radiography.

Bone Neoplasms↗
PubMed1996

Basic imaging properties of a new screen-film system for chest radiography.

To evaluate the potential clinical usefulness of a new screen-film system (advanced screen-film system; AD system) for chest radiography, its fundamental imaging properties compared with a conventional screen-film system (HR-4/HR-S) were investigated. The basic imaging properties were evaluated by measuring characteristic (H&D) curves, relative speeds, MTFs (modulation transfer functions), WS (Wiener spectra), and x-ray attenuations of screens. The detail visibilities and pathological details of various diseases in chest radiographs of patients were evaluated subjectively. The film gradient of the AD system was slightly lower at low radiographic density, and higher at high density, as compared with a conventional screen-film system. The screen speed of the AD system was 212% greater than that of the conventional system, and the film speed was 53% that of the conventional film. As the result, the total speed of the AD system was slightly higher compared with the conventional system. The spatial resolution of the AD system was comparable to or slightly lower than that of the conventional system. The noise level of the AD system was considerably lower than that of the conventional system at low (D = 0.5) and middle (D = 1.0) radiographic density levels. However, it was high at high radiographic density (D = 1.8). The radiographic densities in the underpenetrated areas with the AD system were greater than those of the conventional system when the lung densities are matched comparable. Improvement in noise level with the AD system at low and middle density levels may be useful for detection of various diseases in chest radiographs.

Equipment Design↗
PubMed1996

Dynamic MR imaging of the temporomandibular joint in patients with arthrosis: relationship between contrast enhancement of the posterior disk attachment and joint pain.

OBJECTIVE: The purpose of this study was to determine the relationship between joint pain, disk position, and the degree of contrast enhancement of the posterior disk attachment in patients with temporomandibular joint arthrosis using dynamic contrast-enhanced MR imaging. SUBJECTS AND METHODS: T1- and T2-weighted spin-echo and spoiled gradient-recalled acquisition in the steady state MR imaging was performed in 36 healthy volunteers and 105 patients who were asymptomatic or who had joint pain, muscular pain, or both. On T1-weighted images, the position of the disk was classified as normal and anteriorly displaced. Next, on sagittal spoiled gradient-recalled acquisition in the steady state MR images, signal intensity from teh posterior disk attachment was measured. Time-intensity curves of the signal-intensity ratio versus the time after contrast administration were obtained in each case. Diagnostic accuracy of enhancement among the clinical symptoms was assessed using receiver operating characteristic curves. Imaging findings of contrast enhancement were correlated with pain and disk position. RESULTS: In quantitative measurement, a rapid enhancement pattern was seen most frequently in patients with joint-pain, whereas relatively gradual enhancement was seen in the healthy subjects and in patients who were asymptomatic or who had muscular pain. The mean peak-signal-intensity ratio of the group with joint pain was significantly higher than that of the other groups (p < .001). In the group with joint pain, anterior disk displacement without reduction was strongly associated with the mean signal-intensity ratio (p < .01). With regard to receiver operating characteristic analysis, the group with joint pain showed significantly greater accuracy than did the other groups (p < .001). CONCLUSION: Our results suggest that prominent contrast enhancement of the posterior disk attachment on spoiled gradient-recalled acquisition in the steady state MR images may help differentiate intraarticular from extraarticular causes of pain in and around the temporomandibular joint. In the group with joint pain, anterior disk displacement without reduction was closely associated with prominent enhancement.

Adolescent↗
PubMed1995

Gastrointestinal examinations with a 2,048- x 2,048-pixel image intensifier television digital radiography system.

The clinical usefulness of a 2,048- x 2,048-pixel matrix image intensifier television digital radiography system was evaluated. Screen-film and digital images (with and without postprocessing) of the upper and lower gastrointestinal (GI) tract were used for clinical evaluation. For the upper GI tract, digital images processed with unsharp mask techniques were comparable in quality to screen-film images before and after upgrading the system. For the lower GI tract, screen-film images were better than digital images, except for those processed with a 2,048- x 2,048-line monitor was comparable to a screen-film system.

Data Display↗
PubMed1995

Adnexal masses: accuracy of characterization with transvaginal US and precontrast and postcontrast MR imaging.

PURPOSE: To determine the accuracy of transvaginal ultrasound (TVUS) and of precontrast and contrast material-enhanced magnetic resonance (MR) imaging in the differentiation of adnexal masses. MATERIALS AND METHODS: Five blinded readers analyzed images of 80 masses in 72 patients. MR and TVUS images were interpreted in separate sessions. Findings were confirmed at surgery or laparoscopy. RESULTS: Higher diagnostic accuracy was attained with MR imaging in mature cystic teratomas and endometriomas. However, better accuracy was achieved with contrast-enhanced MR imaging and TVUS in simple cysts, cystadenomas, and malignant tumors because internal details could be visualized. Receiver operating characteristic study indicated that observer confidence was significantly higher with contrast-enhanced MR imaging than with precontrast MR imaging (P = .011) or TVUS (P = .002) in the differentiation of benign and malignant masses. CONCLUSION: Contrast-enhanced MR imaging is superior to precontrast MR and TVUS imaging in the characterization and differentiation of adnexal masses.

Adnexal Diseases↗
PubMed1995

Hepatocellular carcinoma in cirrhotic livers: detection with unenhanced and iron oxide-enhanced MR imaging.

PURPOSE: To evaluate diagnostic accuracy with unenhanced and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection of hepatocellular carcinoma (HCC) in cirrhotic livers. MATERIALS AND METHODS: Fifteen patients with 26 histologically proved HCCs associated with liver cirrhosis underwent imaging with T1-, T2-, and proton-density-weighted spin-echo (SE) and fast low-angle shot (FLASH) sequences. Lesion-to-liver contrast-to-noise ratios were measured in all sequences. Diagnostic performance of the imaging techniques was assessed by using receiver operating characteristic analysis. RESULTS: Enhanced SE and FLASH sequences were significantly more accurate (P < .005) for the detection of small HCCs. Among the unenhanced pulse sequences, the accuracy of tumor localization was highest with the T2-weighted SE sequences; however, 25% of the lesions were located incorrectly. Compared with unenhanced images, lesions were correctly located more often when SPIO-enhanced SE and FLASH sequences were used. CONCLUSION: SPIO-enhanced MR imaging with proton-density-weighted or FLASH sequences was more accurate in the detection of small HCCs in cirrhotic livers.

Biopsy↗
PubMed1995

Hemifacial spasm: three-dimensional MR images in the evaluation of neurovascular compression.

PURPOSE: To assess the diagnostic accuracy of three-dimensional (3D) magnetic resonance (MR) images in the preoperative evaluation of hemifacial spasm. MATERIALS AND METHODS: In 27 patients with surgically confirmed hemifacial spasm, the axial source images from 3D time-of-flight MR angiography were evaluated for 27 symptomatic sides and 26 asymptomatic sides by three observers in a blinded manner for neurovascular compression and identification of compressive vessels. RESULTS: Sensitivity was 95% and specificity was 77%. Vascular compression on the symptomatic sides could be identified retrospectively in all 27 patients. On the asymptomatic sides, vascular compression could be excluded retrospectively in all but one patient. In the blinded study, as the mean value of three observers, the vertebral artery and posterior inferior cerebellar artery could be identified correctly in seven and 7.7 of seven and nine patients, respectively, whereas the compressive anterior inferior cerebellar artery was identified correctly in 7.7 of 16 patients. CONCLUSION: Three-dimensional MR images have a high diagnostic accuracy and are useful in the preoperative evaluation of hemifacial spasm.

Adult↗
PubMed1994

[Preliminary clinical applications of asymmetric screen-film systems in chest radiography].

The physical imaging properties of asymmetric systems and a conventional system were evaluated by measuring characteristic curves, resolution properties and noise Wiener spectra. The potential clinical application of asymmetric screen-film systems was studied by evaluating the visibility of the anatomical structures and various types of abnormalities in comparison with those of a conventional screen-film system. The asymmetric systems showed a wider dynamic range than the conventional system. The resolution properties of asymmetric systems depend on the combination of front and back screens used. Chest radiographs obtained with asymmetric systems improved the visibility of the mediastinal area. The visibility of the lung field in the asymmetric systems was slightly inferior to that with the conventional system when the same tube potential was used. However, the image quality and visibility of various abnormalities showed greater improvement with the asymmetric systems when a lower tube potential was applied. We conclude that the selection of radiographic techniques and combination of screens are important for the clinical use of asymmetric systems.

Humans↗
PubMed1992

Development of a 2,048 x 2,048-pixel image intensifier-TV digital radiography system. Basic imaging properties and clinical application.

RATIONALE AND OBJECTIVES: A 2,048 x 2,048-pixel matrix image intensifier (II)-TV digital radiography system has been developed. Potential clinical applications of this new II-TV system were investigated. METHODS: Basic imaging properties were assessed with clinical applications to gastrointestinal (GI) tract and chest examinations. RESULTS: Basic imaging properties showed improvement of modulation transfer functions (MTFs) from the 1,024 x 1,024- to the 2,048 x 2,048-pixel matrix and approximated the screen-film system at low spatial frequencies. Receiver operating characteristic (ROC) curves of simulated linear shadows improved similarly. Clinical applications showed that the image quality of the 2,048 x 2,048-pixel matrix was comparable with that of the screen-film system for upper GI and chest radiography, but the image quality of the screen-film system was better for the lower GI tract. CONCLUSIONS: The authors' II-TV digital radiography system is clinically applicable to gastrointestinal and chest examinations.

Digestive System↗
PubMed1992

Gastrointestinal examinations with digital radiography.

Basic imaging properties and clinical usefulness of an upgraded digital radiography system were evaluated. The system, which has 1,024 x 1,024 and 2,048 x 2,048 matrices, was upgraded with smaller focal spots (0.3 and 0.8 mm) and reduced thickness of the photoconductive layer of the video camera. Screen-film and digital images (with and without postprocessing) of the upper and lower gastrointestinal (GI) tract were used in the clinical evaluation. Overall modulation transfer functions of the upgraded digital system were comparable to those of the screen-film system, especially at the lower spatial frequency. Threshold contrasts of the two systems were similar despite a 50% reduction in incident exposure for the digital system. For the upper GI tract, digital images processed with unsharp masking techniques were comparable in quality to screen-film images before and after upgrade of the system. For the lower GI tract, screen-film images were better than digital images, except for those produced with a 2,048 x 2,048 matrix with unsharp masking. Further evaluation of the system for examination of other parts of the body seems warranted.

Digestive System↗
PubMed1992

Detection of subtle microcalcifications: comparison of computed radiography and screen-film mammography.

Observer performance tests were conducted to compare the effects of image-processing technique (unsharp mask filtering) on the diagnostic accuracy of computed radiography (CR) with storage phosphors in the detection of microcalcifications. Comparison of detectability of microcalcifications with CR and with screen-film mammography was also performed. Clusters of microcalcifications (125-250 microns in diameter) were randomly superimposed on human breast specimens. Observer performance tests were carried out with receiver operating characteristic (ROC) analysis. The area under the ROC curve and the cumulative true-positive-localization fraction were both used as indexes of performance. Observer performance experiments with nine observers indicated that the two types of screen-film images used provided higher detectability than the CR images. The detectability of microcalcifications on the CR images improved slightly with use of the unsharp masking technique. However, no statistically significant difference was found between processed and unprocessed CR images, and detectability still did not reach the level achieved with the screen-film images.

Breast Diseases↗
PubMed1989

[Investigation of low-contrast signal detection in computed radiography (CR)].

Threshold contrasts of low-contrast objects were compared between screen-film and computed radiography (CR) systems. Effects of incident exposure to the imaging plate (IP) and contrast enhancement on the detectability of low-contrast objects were also studied. We employed 18-alternative forced-choice (18AFC) experiments to study the dependence of the threshold contrasts of the test objects on the incident exposure, object size, and contrast enhancement. The results indicated that the threshold contrasts of CR system were comparable to that of the medium-speed screen-film system and increased by decreasing x-ray exposures. Although threshold contrasts decreased by contrast enhancement, the magnitude of improvement depended on the object size and incident exposure.

Radiographic Image Enhancement↗
PubMed1989

[Constructions of compensating screen of chest radiography and its clinical applications--evaluation of normal anatomical structures].

We have constructed compensating screens which have different sensitivities for the pulmonary hilum and mediastinum in contrast to the lung. With these screens the regions of the mediastinal and retrocardiac areas are simultaneously displayed with optimal contrast on postero-anterior (PA) chest radiographs. The potential clinical use of compensating screens was evaluated in 67 patients for visibility of the anatomical structures in comparison with conventional screens. Confidence test was used to compare the detectability of the various anatomical structures of the chest. The chest radiographs obtained with compensating screens improved visibility of the anatomical structures including the tracheal bifurcation, right and left main bronchus, and paraesophageal line.

Evaluation Studies as Topic↗
PubMed1988

Depth determination on stereoscopic digital subtraction angiograms.

The determination of depth on stereoscopic digital subtraction angiographic (DSA) images was evaluated. A "plus" phantom that contained simulated blood vessels of various sizes with various concentrations of contrast medium was used for the study. The vessels ranged in diameter from 0.46 to 1.35 mm, with concentrations of contrast material of 1.6%-25%. The images were evaluated by seven radiologists and six radiologic technologists. The detectability of depth separation increased as the iodine concentration and the vessel size increased. With stereoscopic DSA, correct identification of depth is possible more than 80% of the time for vessels approximately 1 mm in diameter and containing 3.1% contrast medium when the vessels are separated by more than 2.8 mm.

Angiography↗