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Biomedical subjects

Shinichi Tamura

Publications and source records attributed to Shinichi Tamura.

42 records · Page 3Linked to original sources
PubMed2002

Intrabody three-dimensional position sensor for an ultrasound endoscope.

To avoid or reduce the X-ray exposure in endoscopic examinations and therapy, as an alternative to the conventional two-dimensional X-ray fluoroscopy we are developing an intrabody navigation system that can directly measure and visualize the three-dimensional (3-D) position of the tip and the trace of an ultrasound endoscope. The proposed system can identify the 3-D location and direction of the endoscope probe inserted into the body to furnish endoscopic images. A marker transducer(s) placed on the surface of the body transmits ultrasound pulses, which are visualized as a marker synchronized to the scanning of the endoscope. The position (direction and distance of the marker transducer(s) outside the body relative to the scanning probe inside the body) of the marker is detected and measured in the scanned image of the ultrasound endoscope. Further, an optical localizer locates the marker transducer(s) with six degrees of freedom. Thus, the proposed method performs inside-body 3-D localization by utilizing the inherent image reconstruction function of the ultrasound endoscope, and is able to be used with currently available commercial ultrasound image scanners. The system may be envisaged as a kind of global positioning system for intrabody navigation.

Algorithms↗
PubMed2002

Reconstruction of time-varying 3-D left-ventricular shape from multiview X-ray cineangiocardiograms.

This paper reports on the clinical application of a system for recovering the time-varying three-dimensional (3-D) left-ventricular (LV) shape from multiview X-ray cineangiocardiograms. Considering that X-ray cineangiocardiography is still commonly employed in clinical cardiology and computational costs for 3-D recovery and visualization are rapidly decreasing, it is meaningful to develop a clinically applicable system for 3-D LV shape recovery from X-ray cineangiocardiograms. The system is based on a previously reported closed-surface method of shape recovery from two-dimensional occluding contours with multiple views. To apply the method to "real" LV cineangiocardiograms, user-interactive systems were implemented for preprocessing, including detection of LV contours, calibration of the imaging geometry, and setting of the LV model coordinate system. The results for three real LV angiographic image sequences are presented, two with fixed multiple views (using supplementary angiography) and one with rotating views. 3-D reconstructions utilizing different numbers of views were compared and evaluated in terms of contours manually traced by an experienced radiologist. The performance of the preprocesses was also evaluated, and the effects of variations in user-specified parameters on the final 3-D reconstruction results were shown to be sufficiently small. These experimental results demonstrate the potential usefulness of combining multiple views for 3-D recovery from "real" LV cineangiocardiograms.

Algorithms↗
PubMed2001

Landau-Kleffner Syndrome: Localization of Epileptogenic Lesion Using Wavelet- Cross-Correlation Analysis.

Magnetoencephalographic findings in a 6-year-old patient suffering from acquired aphasia with convulsive disorder (Landau-Kleffner Syndrome, LKS) are presented. The data were analyzed using wavelet-cross-correlation analysis, a nonstationary analysis method developed to analyze the localization of an epileptogenic lesion and the propagation of epileptiform discharges. The results indicate that LKS might be a disorder of the primary temporal cortex, and that the auditory neural network may function as the circuit for the epileptic discharge propagation.

Journal Article↗
PubMedDate not supplied

In vivo elbow biomechanical analysis during flexion: three-dimensional motion analysis using magnetic resonance imaging.

The purpose of this article is to evaluate in vivo 3-dimensional kinematics of the elbow joint during elbow flexion. We studied the ulnohumeral and radiohumeral joint noninvasively in 3 elbows in healthy volunteers using a markerless bone registration algorithm. Magnetic resonance images were acquired in 6 positions of elbow flexion. The inferred contact areas on the ulna against the trochlea tended to occur only on the medial facet of the trochlear notch in all of the elbow positions we tested. The inferred contact areas on the radial head against the capitellum occurred on the central depression of the radial head in all of the tested elbow positions except for 135 degrees flexion, where the anterior rim of the radial head articulates with the capitellum.

Adult↗
PubMedDate not supplied

Preoperative evaluation of residual tumor extent by three-dimensional magnetic resonance imaging in breast cancer patients treated with neoadjuvant chemotherapy.

The purpose of this study was to evaluate the usefulness of three-dimensional magnetic resonance imaging (3D MRI) for the preoperative assessment of residual tumor extent in breast cancer patients treated with neoadjuvant chemotherapy (NAC). Thirty-eight breast cancer patients treated with NAC containing taxane and/or anthracycline for 3-6 months were enrolled in this study. Tumor size was measured by means of calipers, ultrasonography, and dynamic MRI before and after NAC. Three-dimensional maximum intensity projection MRIs to measure the tumor size were created for every case. The tumor size determined by calipers, ultrasonography, and 3D MRI after NAC was compared with that determined by pathologic examination. The tumor size determined by 3D MRI showed a strong correlation with that determined by pathologic examination (r = 0.896). Moderate, but significant correlations were found between measurements obtained with calipers and pathology (r = 0.554), and between ultrasonography and pathology (r = 0.484). The response rates to NAC were estimated at 84.2% with calipers, 58.0% with ultrasonography, and 44.7% with 3D MRI. Calipers and ultrasonography thus tended to overestimate the response to NAC compared to 3D MRI (p < 0.001 and 0.240, respectively). Three-dimensional MRI can visualize residual tumor extent after NAC more accurately than calipers and ultrasonography, and seems to be more reliable than other modalities for estimating response to NAC. It should also help surgeons with decision making for breast-conserving surgery after NAC.

Antineoplastic Combined Chemotherapy Protocols↗