Biomedical subjects

Hiroyuki Yoshida

Publications and source records attributed to Hiroyuki Yoshida.

48 records · Page 3Linked to original sources

PubMed2002

Automated detection of polyps with CT colonography: evaluation of volumetric features for reduction of false-positive findings.

RATIONALE AND OBJECTIVES: To achieve high performance in computer-assisted diagnosis (CAD) of polyps with computed tomographic (CT) colonography, the authors (a) developed new gradient concentration and directional gradient concentration (DGC) features for differentiating between the true-positive and false-positive (FP) findings generated by the authors' CAD scheme, and (b) used receiver operating characteristic (ROC) analysis to quantify the differentiation performance of these and other volumetric features. MATERIALS AND METHODS: CT colonography was performed in 43 patients prone and supine with a helical CT scanner; there were 12 polyps in 11 patients. The polyp candidates generated by the authors' CAD scheme were characterized by nine statistics of six volumetric features, and the resulting 54 feature statistics were combined by a linear or quadratic discriminant classifier. The discrimination performance was measured with round-robin method by ROC analysis and the FP rate of the CAD scheme. RESULTS: The mean value of shape index (SI) yielded the highest individual ROC performance (area under the curve = 0.92). Among combinations, the mean values of SI and DGC and the variance of CT value yielded a high ROC performance (area under the curve = 0.95). With quadratic classifier, the sensitivity and FP rate of the case-based (data set-based) analysis was 100% (95%) with 2.4 FP findings per patient (1.7 FP findings per data set), respectively. CONCLUSION: Combination of the mean values of SI and DGC and the variance of CT value reduced the FP rate substantially without sacrificing sensitivity. These three features are potentially useful in improving the performance of the authors' CAD scheme for detecting polyps with CT colonography.

Colonic Polyps↗

PubMed2002

Computerized detection of pulmonary nodules in chest radiographs based on morphological features and wavelet snake model.

We have developed a new computer-aided diagnosis scheme for automated detection of lung nodules in digital chest radiographs based on a combination of morphological features and the wavelet snake. In our scheme, two processes were applied in parallel to reduce the false-positive detections after initial nodule candidates were selected. One process consisted of adaptive filtering for enhancement of nodules and suppression of normal lung structures, followed by extraction of conventional morphological features. The other process consisted of a novel approach for elimination of false positives called the edge-guided wavelet snake model. In the latter process, multiscale edges of the candidate nodules were extracted to yield parts of the nodule boundaries. A wavelet snake was then used for fitting of these multiscale edges for approximation of the true boundaries of nodules. A boundary feature called the weighted overlap between the snake and the multiscale edges was calculated and used for elimination of false positives. Finally, the weighted overlap and the morphological features were combined by use of an artificial neural network for efficient reduction of false positives. Our scheme was applied to a publicly available database of digital chest images for pulmonary nodules. Receiver operating characteristic analysis was employed for evaluation of the performance of each process in the scheme. The combined features yielded a large reduction of false positives, and thus achieved a high performance in discriminating between true and false positives. These results show that our new method, in particular the false-positive reduction method based on the wavelet snake, is effective in improving the performance of a computerized scheme for detection of pulmonary nodules in chest radiographs.

Adult↗

PubMed2002

Excision of transposable elements from the chalcone isomerase and dihydroflavonol 4-reductase genes may contribute to the variegation of the yellow-flowered carnation (Dianthus caryophyllus).

In the "Rhapsody" cultivar of the carnation, which bears white flowers variegated with red flecks and sectors, a transposable element, dTdic1, belonging to the Ac/Ds superfamily, was found within the dihydroflavonol 4-reductase (DFR) gene. The red flecks and sectors of "Rhapsody" may be attributable to a reversion to DFR activity after the excision of dTdic1. The yellow color of the carnation petals is attributed to the synthesis and accumulation of chalcone 2'-glucoside. In several of the carnation cultivars that bear yellow flowers variegated with white flecks and sectors, both the chalcone isomerase (CHI) and DFR genes are disrupted by dTdic1.

Alcohol Oxidoreductases↗

PubMed2002

Diagnosis of symptomatic disc by magnetic resonance imaging: T2-weighted and gadolinium-DTPA-enhanced T1-weighted magnetic resonance imaging.

Although radial tear of the annulus fibrosus can be detected on T2-weighted and Gd-DTPA-enhanced magnetic resonance (MR) images, the association between the annular tear on MR images and the symptomatic discs is unclear. The purpose of this study was to investigate the relationship between T2-weighted, gadolinium-DTPA-enhanced MR images and pain response through discography in patients with chronic low back pain. A total of 56 lumbar discs from 23 patients with chronic low back pain (13 to 47 years old) underwent MR imaging (T2-weighted, gadolinium-DTPA-enhanced MR images) followed by provocative discography. The sensitivity, specificity, positive predictive value, and negative predictive value of T2-weighted and gadolinium-DTPA-enhanced MR images in detecting the symptomatic discs were calculated. The sensitivity, specificity, positive predictive value, and negative predictive value of T2-weighted images in detecting the symptomatic disc were 94%, 71%, 59%, and 97%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of gadolinium-DTPA-enhanced images were 71%, 75%, 56%, and 86%, respectively. The high sensitivity and the high negative predictive value of T2-weighted MR imaging in detecting the symptomatic disc indicated that MR imaging can be a useful screening tool in avoiding unnecessary discography in patients with chronic low back pain.

Adolescent↗

PubMed2002

Computerized detection of colonic polyps at CT colonography on the basis of volumetric features: pilot study.

PURPOSE: To develop a computer-aided diagnosis (CAD) scheme for automated detection of colonic polyps on the basis of volumetric features and to assess its accuracy on the basis of colonoscopy, the standard. MATERIALS AND METHODS: Computed tomographic (CT) colonography was performed in patients with use of standard bowel cleansing, air insufflation, and helical scanning in supine and prone positions. The colon was extracted from volumetric data sets generated from transverse CT sections. Volumetric features characterizing polyps were computed at each point in the extracted colon. Polyps were detected by means of hysteresis thresholding and fuzzy clustering followed by a rule-based test on the basis of feature values. Locations of the detected polyps were compared with those detected at conventional colonoscopy. RESULTS: Forty-one cases were analyzed: nine cases with polyps and 32 without polyps. Each case with polyps had one polyp of clinically important size (six were 5-9 mm; three, 10 mm). Thus, there were 82 volumetric data sets, 18 included polyps. Eighty-nine percent (16 of 18) of the polyps were detected. Each of the two false-negative findings was detected in the other position; thus, 100% of polyp cases were detected, with 2.5 false-positive findings per patient. The false-positive findings were similar to those due to common perceptual errors. Most of the false-positive findings were easily distinguishable from true polyps by experienced radiologists. CONCLUSION: The CAD scheme has the potential to depict polyps with high sensitivity and an acceptable false-positive rate.

Adult↗

PubMedDate not supplied

Adsorption of cadmium ion and gallium ion to immobilized metallothionein fusion protein.

A fusion protein made from maltose binding protein (pmal) and human metallothionein (MT) was expressed using E. coli. The purified recombinant protein (pmal-MT) was immobilized on Chitopearl resin, and characteristics of pmal-MT for metal binding were evaluated. As expected from the tertiary structure of metallothionein, the pmal-MT ligand adsorbed 12.1 cadmium molecules per one molecule of the ligand at pH 5.2. The pmal-MT ligand also bound 26.6 gallium molecules per one molecule of the ligand at pH 6.5. Neither cadmium ion nor gallium ion bound to a control protein bovine serum albumin (BSA). Adsorption isotherms for both ions were correlated by Langmuir-type equations. Two types of binding sites have been elucidated on the basis of HSAB (hard and soft acid and base) theory. It was suggested that gallium ion specifically binds to amino acid residues containing oxygen and nitrogen atoms, while cadmium ion binds to specific binding sites formed by multiple cysteine residues. The pmal-MT ligand bound these metals in the concentration range of 0.2-1.0 mM, and the bound metal ions could be eluted under relatively mild conditions (pH 2.0). The pmal-MT Chitopearl resin was stable and could be used repeatedly without loss of binding activity. Thus, this new ligand would be useful for recovery of toxic heavy metals and/or valuable metal ions from various aqueous solutions.

Adsorption↗

PubMedDate not supplied

Hydrogen production from glucose by anaerobes.

Various anaerobes were cultivated in media containing glucose. When 100 mL of thioglycollate medium containing 2.0% (w/v) glucose was used, Clostridium butyricum ATCC 859, NBRC 3315, and NBRC 13949 evolved 227-243 mL of biogas containing about 180 mL of hydrogen in 1 day. Although some strains had some resistance against oxygen, C. butyricum ATCC 859 and 860 did not have it. C. butyricum NBRC 3315 and Enterobacter aerogenes NBRC 13534 produced hydrogen in the presence of glucose or pyruvic acid, and E. aerogenes NBRC 13534 produced hydrogen by not only glucose and pyruvic acid but also dextrin, sucrose, maltose, galactose, fructose, mannose, and mannitol. When a medium containing 0.5% (w/v) yeast extract and 2.0% (w/v) glucose was used, E. aerogenes NBRC 13534 evolved more biogas and hydrogen than C. butyricum NBRC 3315 in the absence of reducing agent.

Bacteria, Anaerobic↗

PubMedDate not supplied

Automated knowledge-guided segmentation of colonic walls for computerized detection of polyps in CT colonography.

PURPOSE: We have developed a novel automated technique for segmenting colonic walls for the application of computer-aided polyp detection in CT colonography. In particular, the technique was designed to minimize the presence of extracolonic components, such as small bowel, in the segmented colon. METHODS: The segmentation technique combines an improved version of our previously reported anatomy-oriented colon segmentation technique with a colon-based analysis step that performs self-adjusting volume-growing within the colonic lumen. Extracolonic components are eliminated by intersecting of the resulting two segmentations, so that the colonic walls remain in the intersection. The technique was evaluated on 88 CT colonography datasets. The colon segmentations were evaluated subjectively by four radiologists, as well as objectively by performance of an automated polyp detection on the segmentation. For comparison, the tests were also performed for the anatomy-oriented colon segmentation technique. RESULTS: On average, the technique covered 98% of the visible colonic walls. Approximately 50% of the extracolonic components remaining in the anatomy-oriented segmentation were removed, but 10-15% of the segmentation still contained extracolonic components. The dataset-based false-positive rate of the automated polyp detection was improved by 10% without compromising the 100% case-based sensitivity, and the case-based false-positive rate was improved by 15% over the previous false-positive rate. CONCLUSIONS: The technique segments practically all of the colonic walls in the region of diagnostic quality with a large reduction in the amount of extracolonic components over our previously used technique. The new segmentation improves the specificity of our computer-aided polyp detection scheme significantly without any degradation in detection sensitivity.

Artificial Intelligence↗

PubMedDate not supplied

Computer-aided diagnosis scheme for detection of polyps at CT colonography.

Colon cancer is one of the leading causes of cancer deaths in the United States. However, most colon cancers can be prevented if precursor colonic polyps are detected and removed. An advanced computer-aided diagnosis (CAD) scheme was developed for the automated detection of polyps at computed tomographic (CT) colonography. A region encompassing the colonic wall is extracted from an isotropic volume data set obtained by interpolating CT colonographic scans along the axial direction. Polyp candidates are detected with computation of three-dimensional (3D) geometric features that characterize polyps, followed by extraction of polyps with hysteresis thresholding and fuzzy clustering using these geometric features. The number of false-positive findings is reduced by extracting 3D texture features from polyp candidates and applying quadratic discriminant analysis to the candidates. This CAD scheme was applied in 71 patients who underwent CT colonography, 14 of whom had colonoscopically confirmed polyps (n = 21). At by-patient analysis, sensitivity was 100%, with an average false-positive rate of 2.0 per patient. At by-polyp analysis, the scheme detected 90% of the polyps at the same false-positive rate. This CAD scheme permits accurate detection of suspicious lesions and thus has the potential to reduce radiologists' interpretation time and improve their diagnostic accuracy in the detection of polyps at CT colonography.

Adult↗

PubMedDate not supplied

Expression of survivin and matrix metalloproteinases in adenocarcinoma and squamous cell carcinoma of the uterine cervix.

Cervical cancer can be classified into two histological types: squamous cell carcinoma (SCA) and adenocarcinoma (ACA). Reportedly ACA has poorer prognoses, metastasizes more easily to lymph nodes, and is more resistant to radiotherapy than SCA. To clarify the cause of characteristic differences between these histological types, we examined the expressions of apoptosis inhibiting and tumor-invasion related factors in both histological types. We reviewed the 34 cases of cervical cancer (17 ACA, 17 SCA) that had surgery as their initial treatment at Osaka City University Medical School Hospital between 1996 and 2001. The differences of survivin, and matrix metalloproteinase (MMP-2, and MMP-7) expressions between both histological types were immunohistochemically assayed, and the correlation between the expression of each protein and clinicopathological characteristics was analyzed. Survivin was expressed significantly stronger in ACA cases (p=0.035). The number of patients who expressed MMP-2 and MMP-7 simultaneously was significantly higher in SCA cases (p=0.039). MMP-2 and MMP-7 had tendencies to be expressed stronger in SCA (p=0.057 and p=0.084, respectively). These results suggest that the differences of the expression of survivin (an apoptosis inhibiting factor), MMP-2, and MMP-7 (tumor-invasion related factors) between ACA and SCA were causes of the characteristic differences between the two histological types.

Adenocarcinoma↗

PubMedDate not supplied

Expression of matrix metalloproteinases in human transitional cell carcinoma of the urinary bladder.

Matrix metalloproteinases (MMPs) are associated with invasion and metastasis of several human malignant tumors. Especially so MMP-7, as it is mainly produced by the actual cancer cells. However, the expression of MMP-7 in transitional cell carcinoma (TCC) of the urinary bladder has not been previously investigated. We examined expressions of MMP-7 and MMP-2 in TCC, and compared them with clinicopathological characteristics in TCCs. Tumor samples from 20 patients with TCC of the urinary bladder who had surgery performed at the Osaka City University Medical School Hospital were immunohistochemically stained. Expression of MMP-2 was significantly stronger in advanced stage and high grade tumors than in low stage and low grade tumors. MMP-7 was also expressed in TCC, having a tendency to be more strongly expressed in high than in low grade tumors. However, there was no significant difference of MMP-7 expression between advanced and low stages. This increased expression of MMP-7 in high grade TCC of the urinary bladder may be associated with tumor invasion and metastasis.

Aged↗

PubMedDate not supplied

Expression of matrix metalloproteinases 7 and 2 in human renal cell carcinoma.

Matrix metalloproteinases (MMPs) are associated with invasion and metastasis of several malignant tumors in human. Especially so MMP-7, as it is mainly produced by the cancer cell itself. However, the expression of MMP-7 in renal cell carcinoma (RCC) has not been investigated. We examined expressions of MMP-7 and MMP-2 in RCC, and compared them with the clinicopathological characteristics in RCC. Tumor samples from 20 patients with RCC, who had surgery performed at Osaka City University Medical School Hospital, were immunohistochemically stained. Expression of MMP-2 was significantly stronger in advanced stage and in high grade tumors than in low stage and low grade tumors. MMP-7 was also expressed in RCCs, with its expression especially and significantly stronger in high grade than in low grade tumors (p=0.004). However, there was no significant difference of MMP-7 expression between advanced and low stages (p=0.1859). This increased expression of MMP-7 in high grade RCC might be associated with tumor invasion and metastasis.

Adenocarcinoma, Clear Cell↗