Biomedical subjects

Takayuki Ishida

Publications and source records attributed to Takayuki Ishida.

23 records · Page 2Linked to original sources

PubMed2003

[Detection of acute cerebral infarction by dual echo subtraction technique in MR imaging].

The purpose of this study was to develop an image enhancement technique to detect acute cerebral infarct regions in brain MR images. Transverse relaxation times for abnormal changes tend to be longer than those for normal tissues. In order to obtain MR images with two different echo times, we employed the fast spin echo sequence. We then employed the image subtraction technique using two T(2)-weighted images to enhance acute cerebral infarct regions. As a result, the areas of acute cerebral infarct regions were enhanced as regions of higher signal than normal regions of brain tissue. Further, high signal areas in dual echo subtraction images corresponded to cerebral infarct regions of high signal areas in diffusion weighted images (DWI). We found that the image subtraction technique is useful to enhance very subtle regions of acute cerebral infarction in MR images. Because we employ the difference between transverse relaxation times for normal and abnormal tissues, which does not depend on the strength of the magnetic field, the dual echo subtraction method can be used in many hospitals.

Aged↗

PubMed2002

Development of a computerized method for identifying the posteroanterior and lateral views of chest radiographs by use of a template matching technique.

In picture archiving and communications systems (PACS) or digital archiving systems, the information on the posteroanterior (PA) and lateral views for chest radiographs is often not recorded or is recorded incorrectly. However, it is necessary to identify the PA or lateral view correctly and automatically for quantitative analysis of chest images for computer-aided diagnosis. Our purpose in this study was to develop a computerized method for correctly identifying either PA or lateral views of chest radiographs. Our approach is to examine the similarity of a chest image with templates that represent the average chest images of the PA or lateral view for various types of patients. By use of a template matching technique with nine template images for patients of different size in two steps, correlation values were obtained for determining whether a chest image is either a PA or a lateral view. The templates for PA and lateral views were prepared from 447 PA and 200 lateral chest images. For a validation test, this scheme was applied to 1,000 test images consisting of 500 PA and 500 lateral chest radiographs, which are different from training cases. In the first step, 924 (92.4%) of the cases were correctly identified by comparison of the correlation values obtained with the three templates for medium-size patients. In the second step, the correlation values with the six templates for small and large patients were compared, and all of the remaining unidentifiable cases were identified correctly.

Databases as Topic↗

PubMed2002

[Development of a computerized method for identifying view position and orientation for chest radiographs by using a template matching technique].

For implementation of computer-aided diagnostic systems for chest radiographs in the clinical environment, it is necessary to correctly identify two view positions [posteroanterior (PA) and lateral views] and four orientations (upward, downward, leftward, and rightward) for chest radiographs. In picture archiving and communication system (PACS), the information on the view position and orientation for chest radiographs is often not recorded or is recorded incorrectly. The purpose of this study was to develop a computerized method for correctly identifying view position and orientation for chest radiographs by using a template matching technique. Our basic approach is to find the most similar template to an unknown chest image by examining the similarity of the unknown chest image with a number of templates for PA and lateral views at the four image orientations, and to determine simultaneously the view position and orientation for the unknown chest image. All upward templates were produced from the PA or lateral images for upward orientation for various patient sizes. By rotating the upward templates, we produced the templates for downward, leftward, and rightward orientations. To evaluate the similarity of a test image with all templates, the cross-correlation values of the test image with all templates were obtained. The view position and image orientation for the unknown image was considered to be identical to those for the template with which the largest cross-correlation value was obtained. Our results indicated that all cases of 200 PA and 200 lateral views were correctly identified in terms of the view position and image orientation.

Diagnosis, Computer-Assisted↗

PubMed2002

[Overview of computer-aided diagnosis].

Computer-aided diagnosis (CAD) systems have been developed in many institutions. CAD is able assist radiologists and physicians in detecting lesions and in differentiating benign from malignant lesions on medical images. The output from CAD can be used as a "second opinion" to assist radiologists in their interpretations and improve diagnostic accuracy. It is important to note that CAD is not designed for the automated diagnostic system. A few commercial CAD systems have recently been developed by venture companies, with pre-marketing approval having been obtained from the U.S. Food and Drug Administration (FDA). It is clear that CAD has practical value in radiologic diagnosis. In this paper, the background of CAD research and important topics, including the usage of an image database and methods of evaluating the performance of typical CAD schemes, are discussed. The number of CAD researchers in Japan is not yet sufficient. Radiological technologists who have a strong interest in CAD research will be good partners for radiologists in developing CAD schemes.

Database Management Systems↗

PubMedDate not supplied

Computer-aided diagnosis in chest radiography: results of large-scale observer tests at the 1996-2001 RSNA scientific assemblies.

Since 1996, computer-aided diagnosis (CAD) schemes have been presented as interactive demonstrations on computer workstations at each scientific assembly of the Radiological Society of North America. The schemes involved (a) detection of pulmonary nodules, (b) temporal subtraction, (c) detection of interstitial lung disease, (d) differential diagnosis of interstitial lung disease, and (e) distinction between benign and malignant pulmonary nodules on chest radiographs. Large-scale observer tests were carried out to examine how radiologists can benefit from CAD systems. Observer performance was evaluated by analysis of receiver operating characteristic (ROC) curves. The statistical significance of the difference between the areas under the ROC curves without and with CAD was analyzed with the Student t test. In all of the tests, the diagnostic accuracy of the radiologists in total improved significantly when CAD was used. This result provides additional evidence that CAD has the potential to improve the performance of radiologists in their decision-making process in interpreting chest radiographs.

Diagnosis, Computer-Assisted↗