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Biomedical subjects

Hans Larsson

Publications and source records attributed to Hans Larsson.

4 recordsLinked to original sources

Left ventricular involvement in arrhythmogenic right ventricular cardiomyopathy - a scintigraphic and echocardiographic study.

BACKGROUND: Left ventricular involvement in arrhythmogenic right ventricular cardiomyopathy (ARVC) is a common finding in autopsy studies. In clinical studies using myocardial scintigraphy, MRI and echocardiography, contradictory results have been reported. In this study, we therefore investigated a group of 15 patients with ARVC using thallium-201 (Tl) single-photon emission tomography (SPECT) and echocardiography including assessment of mitral annular motion with M-mode and pulsed tissue Doppler. METHODS: Exercise and rest Tl-201 SPECT were performed in 15 patients with ARVC. The time from diagnosis of the disease varied from less than 1-16 years. All patients fulfilled the established diagnostic criteria for ARVC. An echocardiographic examination, including assessment of left and right ventricular motion and measurements of the mitral annulus motion with M-mode and pulsed tissue Doppler was performed in the patients and in 25 normal subjects. RESULTS: Tl-201 uptake defects in the left ventricular myocardium were present in all except one patient (93%). The uptake defects were predominantly located to the anteroseptal and basal posterior segments. Wall motion abnormalities were seen in the same segments, and in addition to this, in the septal area. In line with this, the total amplitude and the peak systolic velocity of mitral annular motion at the septal point were significantly decreased in the patients compared with the control group. CONCLUSIONS: Our data show that left ventricular involvement is common in ARVC. Tl-201 SPECT and echocardiographic abnormalities were seen not only in patients with long-lasting symptoms but also in asymptomatic patients and in those with short duration of symptoms.

Adult↗

Calibration of high-speed imaging by laser triangulation.

A method was developed for absolute calibration of endoscopic vocal fold images using laser triangulation. The laser is attached to a rigid endoscope with 8-degrees angle in relation to the optical axis of the endoscope. A special software is used for calibration and measurements from high-speed images. The equipment can provide measurements both in horizontal and vertical planes, and can be used for calibrated measurements of vocal fold length, amplitude of vocal fold vibrations and vertical movements.

Calibration↗

Simultaneous analysis of vocal fold vibration and transglottal airflow: exploring a new experimental setup.

The purpose of this study was to develop an analysis system for studying the relationship between vocal fold vibration and the associated transglottal airflow. Recordings of airflow, electroglottography (EGG), oral air pressure, and acoustic signals were performed simultaneously with high-speed imaging at a rate of approximately 1900 frames/s. Inverse filtered airflow is compared with the simultaneous glottal area extracted from the high-speed image sequence. The accuracy of the synchronization between the camera images and the foot pedal synchronization pulse was examined, showing that potential synchronization errors increase with time distance to the synchronization pulse. Therefore, analysis was limited to material near the synchronization pulse. Results corroborate previous predictions that air flow lags behind area, but also they reveal that relationships between these two entities may be complex and apparently varying with phonation mode.

Acoustics↗

High-speed imaging: applications and development.

This article shows some examples of applications of digital high-speed imaging in phoniatrics. Advantages and disadvantages of digital high-speed imaging as compared to the current world-wide standard, videostroboscopy, are discussed as well as possible future developments in this area. Parts of this paper were presented by the authors at the Pan European Voice Conference in Stockholm in 2001 (Pevoc IV).

Biophysical Phenomena↗