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Hiroshi Natori

Publications and source records attributed to Hiroshi Natori.

6 recordsLinked to original sources
PubMed2006

Assessment of left ventricular ejection fraction using long-axis systolic function is independent of image quality: a study of tissue Doppler imaging and m-mode echocardiography.

BACKGROUND: Quantitative assessment of left ventricular ejection fraction (LVEF) is technically difficult in patients with poor image quality (IQ). Mitral annulus velocity assessed by pulsed tissue Doppler imaging (TDI) and mitral annulus motion assessed by M-mode echocardiography has been shown to correlate with LVEF. Furthermore, mitral annulus sites are easy to identify even in patients with poor IQ. The purpose of this study was to determine whether these methods are useful for estimating LVEF in patients with poor IQ. METHODS: One hundred ten patients underwent TDI and M-mode echocardiography simultaneously. Mitral annulus velocity and mitral annulus motion were obtained from each of the four mitral annulus sites. Mean mitral annular peak systolic velocities (Sm) and mean mitral annular motions (MAM) were calculated by averaging at each site. IQ was defined according to a previous report. RESULTS: Both Sm and MAM were successfully measured in all patients. Mean Sm and mean MAM correlated with LVEF. These correlations were observed not only in patients with good IQ (p < 0.001, r = 0.61 for mean Sm; p < 0.001, r = 0.61 for mean MAM) or fair IQ (p < 0.001, r = 0.58 for mean Sm; p < 0.001, r = 0.68 for mean MAM) but also in patients with poor IQ (p < 0.05, r = 0.42 for mean Sm, p < 0.001, r = 0.61 for mean MAM). Using optimal cutoff values of mean Sm and mean MAM in each IQ group, sensitivity and specificity for identifying LVEF < 50% were comparable among three IQ groups. CONCLUSIONS: Assessment of long-axis systolic function by TDI and M-mode echocardiography enables estimation of LVEF even in patients with poor IQ.

Aged↗
PubMed2006

A method for bronchoscope tracking by combining a position sensor and image registration.

This paper describes a method for tracking a bronchoscope by combining a position sensor and image registration. A bronchoscopy guidance system is a tool for providing real-time navigation information acquired from pre-operative CT images to a physician during a bronchoscopic examination. In this system, one of the fundamental functions is tracking a bronchoscope's camera motion. Recently, a very small electromagnetic position sensor has become available. It is possible to insert this sensor into a bronchoscope's working channel to obtain the bronchoscope's camera motion. However, the accuracy of its output is inadequate for bronchoscope tracking. The proposed combination of the sensor and image registration between real and virtual bronchoscopic images derived from CT images is quite useful for improving tracking accuracy. Furthermore, this combination has enabled us to achieve a real-time bronchoscope guidance system. We performed evaluation experiments for the proposed method using a rubber phantom model. The experimental results showed that the proposed system allowed the bronchoscope's camera motion to be tracked at 2.5 frames per second.

Artificial Intelligence↗
PubMed2005

Automated nomenclature of bronchial branches extracted from CT images and its application to biopsy path planning in virtual bronchoscopy.

We propose a novel anatomical labeling algorithm for bronchial branches extracted from CT images. This method utilizes multiple branching models for anatomical labeling. In the actual labeling process, the method selects the best candidate models at each branching point. Also a special labeling procedure is proposed for the right upper lobe. As an application of the automated nomenclature of bronchial branches, we utilized anatomical labeling results for assisting biopsy planning. When a user inputs a target point around suspicious regions on the display of a virtual bronchoscopy (VB) system, the path to the desired position is displayed as a sequence of anatomical names of branches. We applied the proposed method to 25 cases of CT images. The labeling accuracy was about 90%. Also the paths to desired positions were generated by using anatomical names in VB.

Algorithms↗
PubMed2005

Hybrid bronchoscope tracking using a magnetic tracking sensor and image registration.

In this paper, we propose a hybrid method for tracking a bronchoscope that uses a combination of magnetic sensor tracking and image registration. The position of a magnetic sensor placed in the working channel of the bronchoscope is provided by a magnetic tracking system. Because of respiratory motion, the magnetic sensor provides only the approximate position and orientation of the bronchoscope in the coordinate system of a CT image acquired before the examination. The sensor position and orientation is used as the starting point for an intensity-based registration between real bronchoscopic video images and virtual bronchoscopic images generated from the CT image. The output transformation of the image registration process is the position and orientation of the bronchoscope in the CT image. We tested the proposed method using a bronchial phantom model. Virtual breathing motion was generated to simulate respiratory motion. The proposed hybrid method successfully tracked the bronchoscope at a rate of approximately 1 Hz.

Algorithms↗
PubMed2002

A hematoma of the esophagus causing the trachea to stenose.

We report a case of spontaneous intramural hematoma of the esophagus (SIHE) with severe dyspnea due to compression of the trachea. SIHE is a rare hematoma that commonly presents with chest pain, epigastralgia, hematemesis, and dysphagia. Dyspnea is not a common symptom; it has been reported in only one patient, who underwent surgery. In our case, intubation of the compressed trachea prevented it from becoming more stenosed, and an operation was not needed. Another unusual feature of this case is the endoscopic findings. Endoscopic examination in SIHE has often revealed the presence of a dark red, bluish, or purplish bulge, suggesting the presence of a clot or blood in the esophageal wall. In our case, the bulge revealed by endoscopy in the esophageal lumen was white at first, before later turning dark red.

Journal Article↗