Biomedical subjects

K Doi

Publications and source records attributed to K Doi.

At least 523 records · Page 29Linked to original sources

PubMed1993

Comparison of bilateral-subtraction and single-image processing techniques in the computerized detection of mammographic masses.

RATIONALE AND OBJECTIVES: Identification of regions as possible masses on digitized screen film mammograms is an important initial step in the computerized detection of breast carcinomas. Possible masses may be initially extracted using criteria based on optical densities, geometric patterns, and asymmetries between corresponding locations in right and left mammograms. In this study, the usefulness of information arising from mammographic asymmetries for the identification of mass lesions is investigated. METHODS: Two techniques are investigated--a nonlinear bilateral-subtraction technique based on image pairs and a local gray-level thresholding technique based on single images. Detection performances obtained with the two techniques in combination with various feature-analysis techniques are evaluated using 154 pairs of mammograms and compared using free-response receiver operating characteristic (FROC) analysis. RESULTS: The nonlinear bilateral-subtraction technique performed better than the local gray-level thresholding technique. CONCLUSION: The incorporation of asymmetric information appears to be useful for computerized identification of possible masses on mammograms.

Female↗

PubMed1993

Computer-aided diagnosis in chest radiography. Preliminary experience.

RATIONALE AND OBJECTIVES: Computer-aided diagnosis (CAD) schemes for chest radiography are being developed with which to alert radiologists to possible lesions, and thus potentially improve diagnostic accuracy. However, CAD schemes have not been tested on a large number of clinical cases. The authors identify design parameters that would be required for development of an intelligent workstation. METHODS: Computer-aided diagnosis programs were applied for the automated detection of lung nodules, cardiomegaly, and interstitial infiltrates to 310 consecutive chest radiographs, and were analyzed for potential usefulness and limitations. Computer-aided diagnosis output was evaluated by radiologists and physicists for accuracy and technical problems, respectively. RESULTS: Approximately 70% of the results were judged to be potentially acceptable; however, the number of false-positive findings was relatively high. Technical problems included failure to detect subtle abnormalities and the occurrence of false-positive detections caused by normal anatomical structures. CONCLUSION: Computer-aided diagnosis has the potential to be a valuable aid to radiologists in clinical practice, if certain technical problems can be overcome and if optimal operating points can be defined for clinical use.

Adult↗

PubMed1993

Evaluation of an enhanced digital film-duplication system by receiver operating characteristic analysis.

RATIONALE AND OBJECTIVES: Over- or underexposure often results in poor quality radiographs. Using receiver operating characteristic analysis, the authors investigated the potential utility of a system that corrects densities in such images to improve the accuracy of lung nodule detection. METHODS: Chest radiographs were digitized by a laser film digitizer. Simulated nodules were superimposed on 36 improperly exposed chest radiographs. All images, with and without nodules, were then processed by a nonlinear density-correction technique. Hard-copy images were produced by a laser film printer. Eight radiologists evaluated the corrected and uncorrected images for the presence or absence of lung nodules using a continuous (0-100) confidence-rating scale. RESULT: The detectability of lung nodules improved significantly in the retrocardiac/retrodiaphragmatic regions of underexposed images and in the peripheral lung region of overexposed images. CONCLUSIONS: This system may increase diagnostic accuracy in detection of lung nodules in improperly exposed images.

Confidence Intervals↗

PubMed1993

Reinnervated free muscle transplantation for extremity reconstruction.

Reinnervated free muscle transplantation was used to rehabilitate severely impaired extremities in patients with brachial plexus palsy and for functional limb salvage in cases of traumatic muscle loss or radical excision of a malignant soft-tissue tumor. Fifty-eight reinnervated free muscle transplantations were implanted in 46 patients. Twenty-four patients had simultaneous reconstruction of two functions, such as finger and elbow flexion lost to brachial plexus palsy; 12 patients underwent double muscle transplantation; 15 patients received free muscle transplants for limb salvage after tumor excision in an extremity; 6 transplants replaced traumatic muscle loss; and 1 was used for reconstruction of finger flexion after poliomyelitis. Twenty-six latissimus dorsi, 25 gracilis, and 7 rectus femoris muscles were used as donors. All muscles survived. The postoperative follow-up ranged from 18 months to 4 years. The speed and extent of reinnervation of the transplanted muscle depended on the choice of recipient nerve, the patient's age, and the occurrence of postoperative vascular complications. Neurotization by the spinal accessory nerve or the posterior interosseous nerve resulted in the most rapid recovery. The administration of postoperative chemotherapy did not delay recovery of function. Free muscle transplantation is consistently successful and provides a functional extremity in severely handicapped patients.

Adolescent↗

PubMed1993

Analysis of serotype-specific antibodies to Trichosporon cutaneum types I and II in patients with summer-type hypersensitivity pneumonitis with monoclonal antibodies to serotype-related polysaccharide antigens.

Summer-type hypersensitivity pneumonitis is the most prevalent type of hypersensitivity pneumonitis in Japan. We constructed a sandwich enzyme-linked immunosorbent assay system for diagnosis of summer-type hypersensitivity pneumonitis in which monoclonal antibodies were used to bind serotype-related polysaccharides to plastic plates, and this system was proven to have sufficient sensitivity and specificity.

Adolescent↗

PubMed1993

Clinical experience with an advanced laser digitizer for cost-effective digital radiography.

Film digitization has not been widely pursued in clinical settings mainly because of perceived limitations involving film latitude and image quality. However, a high-quality laser digitizer can be combined with wide-latitude film and specially developed digital processing techniques to achieve image quality comparable or superior to that of storage phosphor computed radiography (SPR) over a wide range of exposure. This film digitization system provides the operational advantages of digital radiography, such as consistent image density, high-quality inexpensive duplicates, and digital storage and retrieval capability. The reliability and monetary costs of the system also compare favorably with those of SPR. In the long term, technologies that employ reusable plates and do not require chemical processing to produce diagnostic images may well replace screen-film systems. Presently, however, film digitization remains a practical and cost-effective approach to digital radiography.

Cost-Benefit Analysis↗

PubMed1993

An "intelligent" workstation for computer-aided diagnosis.

Computer-aided diagnosis (CAD) involves a computerized analysis of radiographs that is used as a "second opinion" by the radiologist. The approach presented incorporates computer vision and artificial intelligence techniques and includes schemes for the analysis of lung nodules, interstitial infiltrates, and cardiomegaly seen on chest radiographs; masses and clustered microcalcifications on mammograms; and stenoses and blood flow on angiograms. The demonstration of various CAD schemes in chest radiography and mammography on a six-monitor workstation simulates one possible clinical implementation of CAD in radiology. Whether soft- or hard-copy display media are used, the radiologist can refer to the CAD results and still use the original radiograph for the final diagnosis. Although initial impressions of this simulated "intelligent" workstation are encouraging, CAD is still in a preliminary stage of development. Various methods for effectively and efficiently integrating CAD into a clinical radiology department are being investigated.

Angiography↗

PubMed1993

Computerized radiographic analysis of osteoporosis: preliminary evaluation.

Measurement of bone mass is important in determining the risk for fracture and in following the course of patients undergoing therapy for osteoporosis. Bone mineral densitometry (BMD) is a good predictor of fracture risk, but there is considerable overlap in BMD measurements between individuals with fracture risk and those without. In this study, computerized texture analysis of the trabecular pattern on conventional spine radiographs was used to evaluate bone structure as a determinant of fracture risk. Standard lumbar spine radiographs of 43 individuals were analyzed and compared with BMD measurements obtained with dual-photon absorptiometry. This method was more effective than BMD in differentiation of patients with fractures elsewhere in the spine from those with no fracture. These preliminary results suggest that this method of bone structure analysis, combined with BMD, may lead to a more sensitive and specific predictor of osteoporosis and risk of fracture.

Adult↗

PubMed1993

Artificial neural networks in mammography: application to decision making in the diagnosis of breast cancer.

The authors investigated the potential utility of artificial neural networks as a decision-making aid to radiologists in the analysis of mammographic data. Three-layer, feed-forward neural networks with a back-propagation algorithm were trained for the interpretation of mammograms on the basis of features extracted from mammograms by experienced radiologists. A network that used 43 image features performed well in distinguishing between benign and malignant lesions, yielding a value of 0.95 for the area under the receiver operating characteristic curve for textbook cases in a test with the round-robin method. With clinical cases, the performance of a neural network in merging 14 radiologist-extracted features of lesions to distinguish between benign and malignant lesions was found to be higher than the average performance of attending and resident radiologists alone (without the aid of a neural network). The authors conclude that such networks may provide a potentially useful tool in the mammographic decision-making task of distinguishing between benign and malignant lesions.

Female↗

PubMed1993

Transmissibility of the D variant of encephalomyocarditis virus (EMC-D) in mice.

Transmissibility of the D variant of encephalomyocarditis virus (EMC-D) was examined. Eight-week-old ICR:CD-1 male mice inoculated with 10(5) plaque forming units (PFU)/animal of EMC-D intranasally, orally or intraperitoneally showed marked viraemia and prominent pancreatic lesions at 2 days after inoculation (2 DAI), and excreted virus in faeces from 2 to 8 DAI (virus titre: 10(3)-10(5) PFU/g). Only a small proportion of control mice housed with EMC-D-inoculated mice for 10 days developed viraemia and pancreatic lesions.

Animals↗

PubMed1993

The inheritance and breeding results of hairless descendants of Mexican hairless dogs.

The inheritance and breeding results of hairless descendants of Mexican hairless dogs (MHDs) were investigated. When the male hairless dogs were bred to female beagles, the birth ratio of hairless and haired dogs was 1:1. Mating between MHDs gave both hairless and haired pups. The results indicated that an autosomal dominant monogenic gene was responsible for their hairless characteristics. We propose the symbol Hm for this gene (hairless, Mexican type). The survival rate of hairless pups was markedly lower than that of haired ones. It was elevated to 50-90% by warming their cages to a minimum of 25 degrees C.

Animals↗

PubMed1993

Sporulation-inhibitory gene in pock-forming plasmid pSA1.1 of Streptomyces azureus.

A plasmid, pSA1.1, of Streptomyces azureus elicited conjugative pocks and inhibited the sporulation of its host mycelia. pSA1.1 was studied with a kanamycin resistance gene derived from S. kanamyceticus as a selective marker. The deletion analysis and sequencing of the derivative plasmid found an open reading frame (ORF909b) that was involved in the sporulation-inhibitory function of pSA1.1 and in pock formation. The nucleotide sequences of ORF909b were compared with those of the genes registered in GenBank, but no similarity was found. However, the predicted amino acid sequence of ORF909b showed a significantly high similarity with that of the spoIIIE gene of Bacillus subtilis. This detected gene might be a new sporulation-regulatory gene in streptomycetes.

Amino Acid Sequence↗

PubMed1993

The disturbance of water-maze task performance in mice with EMC-D virus infection.

The present study was performed to examine the influence of EMC-D virus on water-maze task performance in DBA/2 mice inoculated with 10(3) PFU/ml and BALB/c mice inoculated with 10(5) PFU/ml of EMC-D virus. In both strains, the latency to accomplish the task was shortened during successive 8 days of testing. However, the shortening of latency in the inoculated group was significantly smaller than that in the control group. Pathological studies showed that in both studies St. pyramidale hippocampi was commonly degenerated, but the degeneration of the spinal cord was shown only in DBA/2 mice. Therefore, the disturbance of water-maze task performance in mice infected with EMC-D virus might be partially due to the dysfunction of memory for working process or cognition of orientation other than underlying decreased ability in locomotion.

Animals↗

PubMed1993

Role of the extracellular Ca2+ on the intracellular Ca2+ changes in fertilized and activated mouse oocytes.

Changes in intracellular calcium concentration ([Ca2+]i) in fertilized mouse oocytes were measured using the calcium-sensitive dye, fura-2. After fertilization, an initial long-lasting [Ca2+]i increase was followed by a periodic [Ca2+]i increase. The periodic increase in [Ca2+]i persisted for 1 to 3 h and all fertilized oocytes extruded the second polar body within 4 h. The mean interval of periodic [Ca2+]i increase was 470 +/- 180 s (mean +/- SD). The frequency of the periodic [Ca2+]i increase depended on the extracellular calcium concentration. Verapamil and nifedipine inhibited the periodic [Ca2+]i increase. Sixty-five per cent of tested cells extruded the second polar body within 90 min of exposure to 7% ethanol. In these activated oocytes, the long-lasting [Ca2+]i increase was observed. However, no cells showed a repetitive increase in [Ca2+]i. Both release of calcium from intracellular stores and influx of extracellular calcium contribute to the increase in [Ca2+]i induced by ethanol. We conclude that the extrusion of the second polar body requires an increase in [Ca2+]i above a certain threshold level and the mobilization of calcium of both the intracellular and extracellular space in mouse oocytes.

Animals↗

PubMed1993

Effects of cardioplegic reperfusion on ATP recovery of rod-shaped myocytes isolated from rat ventricles.

ATP content [ATP] and fraction of rod-shaped myocytes (Rrod) were measured in ventricular myocytes isolated from the rat heart. [ATP] (nmol (10(6) cells)-1) and Rrod (%) were 72.0 and 60.5, respectively, and significantly reduced to 18.8 and 41.8 by no-flow ischemia for 30 min. Reperfusion for 15 min with cardioplegic solutions restored [ATP] of rod-shaped myocytes to the control level.

Adenosine Triphosphate↗

PubMed1993

Destabilization of the respiratory control by hypoxic ventilatory depressions: a model analysis.

Hypoxia induces unstable breathing such as Cheyne-Stokes breathing primarily through the increase in the peripheral chemoreceptor gain to CO2. Another consequence of hypoxia may be the direct depression of the respiratory center known as hypoxic ventilatory depression (HVD). The present study was undertaken to predict the effect of HVD on the generation of unstable breathing during hypoxia by way of a computer simulation. To represent HVD, the present respiratory control model includes the control of cerebral blood flow and a mechanism which reduces ventilation in proportion to the brain tissue PO2. Analyses conducted both in the frequency domain and the time domain demonstrated that incorporating the HVD mechanisms into the model considerably increased the open-loop gain and thereby destabilized the respiratory control system. Increase in the peripheral CO2 gain due to relative hypoxia (caused by ventilatory depression) accounted for only half of the increase in the overall loop gain found in the presence of HVD. Considerable portion of the increase in the open-loop gain could be explained by the relative hypercapnia due to ventilatory depression.

Adult↗

PubMed1993

Effects of adenylate cyclase activation on electrical resistance of scala media.

Electrical resistance of scala media at the second turn of the guinea pig cochlea was measured while cochlear adenylate cyclase was activated by perilymphatic perfusion with 2 x 10(-4) M forskolin. The electrical resistance decreased from the pre-forskolin value (6.36 +/- 0.27 k omega to 5.22 +/- 0.33 k omega, n = 5), while the endocochlear potential (EP) increased from the pre-forskolin value (70.2 +/- 2.1 mV to 81.2 +/- 2.8 mV, n = 5). The time course of the electrical resistance change was more rapid than that of the EP change but almost identical to the time course of the change in the Cl- activity of the endolymph. The results suggest that the forskolin-induced decrease in the electrical resistance of the perilymph-endolymph barrier (presumably Reissner's membrane), and the consequent increase in Cl- flux into the endolymph may trigger EP elevation.

Adenylyl Cyclases↗

PubMed1993

[Changes in coagulation and fibrinolytic factors observed during heparin-urokinase-pulse combined therapy for nephritis resistant to conventional treatment in children].

Coagulation and fibrinolytic factors in the blood were measured during heparin-urokinase (UK)-pulse combined therapy in order to investigate the background for the availability of the therapy. Five patients with nephritis resistant to conventional treatment were treated with this combined therapy (heparin: 350-450 U/kg day, continuously i.v. during the therapy; UK: 5000 IU/kg/2 hrs, i.v., two times a day, for 3 days = 1 Kur; methylprednisolone 20 mg/kg/2hrs, d.i.v., for 3 days = 1 Kur; 3 Kurs of UK and 3 Kurs of pulse were alternately administered). 1) Blood levels of alpha 2-plasmin inhibitor (alpha 2-PI) antigen were decreased and those of alpha 2-plasmin inhibitor.plasmin complex (alpha 2-PI. PmC) were elevated during 3 Kurs of UK administration. Accordingly, activation of the fibrinolytic system was confirmed during the combined therapy, suggesting that both alpha 2-PI and alpha 2-PI.PmC were relevant in monitoring the fibrinolytic state in blood. 2) Both tissue-plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) levels were sustained continuously in the elevated levels in the blood during both UK administration and pulse therapy. This movement of t-PA and PAI-1 was independent of that of the other fibrinolytic factors, such as alpha 2-PI,alpha 2-PI.PmC and plasminogen. 3) Inflammatory reactants such as fibrinogen, alpha 2-PI,alpha 2-macroglobulin and alpha 1-antitrypsin decreased more significantly during this heparin-urokinase-pulse combined therapy than during our previous combined therapy consisting of only heparin and urokinase. Therefore, we conclude that the anti-inflammatory effect was reinforced by adding the pulse therapy and that the combined therapy had some effect on the release of t-PA from vascular endothelial cells.

Adolescent↗