John A. Myers

Ultrasonic Imaging, a Potential Tool for Sex Determination of Live Fish

Abstract Using two conventional, medical, ultrasound imaging systems, we studied 15 juvenile and 5 mature coho salmon (Oncorhynchus kisutch) to determine if their sex could be ascertained from ultrasound images. Although liver, gut, and skeletal structures were discernible, we found the ovary and testes of the juvenile salmon difficult to identify. In mature salmon (less than 1 month from spawning), the eggs, testes, and even the male gonadal duct were clearly visible. The present study provides the first report of a technique for rapid, less-than-60-second, non-invasive identification of the sex of salmon. Our findings indicate that rapid sex determination of live fish with ultrasound is feasible.

An optical fiber transducer for single myofibril force measurement

A force transducer has been developed for use in force measurement of skeletal muscle myofibrils. The transducer is suitable for measurement of passive and contractile forces in a range up to 200 mu g, with 1 mu g resolution. It is based upon the operating principle of the deflection of an optical fiber of known compliance, sensed by the differential illumination of two phototransistors. Attractive features include ease of operation and specimen mounting, high bandwidth, adaptability for different force ranges, and simple and inexpensive construction.<<ETX>>

An endoscopic Doppler probe for assessing intestinal vasculature

Flexible fiberoptic endoscopes permit the physician to inspect the mucosal surface of the upper gastrointestinal tract and colon. However, this visual inspection provides little information about the underlying vascular supply to the intestinal wall. We tested the hypothesis that a Doppler probe could be constructed small enough to pass through the biopsy channel of a fiber endoscope and be used with it while performing endoscopy. The purpose would be to determine the location of patent arteries or veins, determine the magnitude and waveforms of the velocity in them, and estimate their contribution or potential contribution to intestinal bleeding. For this purpose, a miniature catheter probe (1.8 mm O.D. and 2 m in length) and an electronic range limited pulsed Doppler unit were developed. This probe and unit were studied in a series of 13 dogs to determine efficacy of detecting arterial and venous flow and to test the safety of the device. The duodenum was surgically exposed and opened in the region of the common bile duct (CBD). Arteries and veins surrounding the CBD were studied. Particular attention was directed to arterial structures which clinically pose a risk of bleeding when performing endoscopic papillotomy, a therapeutic technique in which the papilla of Vater is cut to release bile duct stones. The results of the study revealed that the probe could indeed detect arterial and venous structures accurately. There was no evidence that the probe produced any injury to the common bile duct or pancreas by histological or serum amylase studies and the device was determined safe and suitable for clinical evaluation.

Stepwise shortening of muscle fibre segments.

SummaryShortening dynamics were measured in single fibres of frog skeletal muscle using a system that could track the spacing between hairs mounted on the fibre surface. Segment length changes were predominantly stepwise. The objective of the study was to identify potential artifacts and check their relevance. Several possible causes of artifactual steps were evaluated quantitatively and ruled out. In addition, the surface marker method and an independent length-detection method based on light diffraction were used simultaneously. The concurrence of results confirmed that it is highly unlikely that stepwise shortening could arise out of instrument artifact. Possible mechanisms underlying the phenomenon are considered.

Measurement of the ultrasonic attenuation of fat at high frequency

RATIONALE AND OBJECTIVES High-frequency ultrasound devices are often limited by a decreased depth of acoustic imaging caused by the increased attenuation of tissue at high frequencies. We investigated the role of adipose tissue in this phenomenon. METHODS A substitution technique was used to calculate the ultrasonic attenuation (decibels per centimeter) of fresh samples of sheep rumen, omental fat, and back fat and swine back fat and various concentrations of bovine milk fat at 22 degrees C and 37 degrees C for frequencies of 15 and 20 MHz. RESULTS The attenuation was significantly higher for sheep adipose tissue than for the intestinal wall, in descending order, omental fat, back fat, and rumen wall (P < 0.01). A correlation was found between bovine milk fat concentrations and attenuation at both frequencies (R2 > 0.9). The attenuation of adipose tissues decreased significantly with an increase in temperature (P < 0.01), whereas the attenuation of sheep rumen showed no significant change (P > 0.1). CONCLUSIONS The ultrasonic attenuation of fat may contribute to limitations on the use of high-frequency ultrasound in clinical situations in which adipose tissue is present.

Phase-Locked Loop Measurement of Sarcomere Length with High Time Resolution

A method for making high-speed measurements of sarcomere length directly from the muscle striation image is presented. A phase-locked loop is used with a self-scanned photodiode array to measure the spatial frequency of the striation pattern. Computation circuitry converts frequency to sarcomere length. The sarcomere length output has a resolution better than 2 nm at a sample rate of once every 250¿s.

Prototype scanning fiber endoscope

Commercial optical endoscopes rely on image transfer and acquisition based on an array of photon detectors, such as a coherent fiberoptic bundle, a video camera, and/or the human retina. An alternative approach uses a resonantly vibrating optical fiber that scans laser illumination. However, the limitation of laser-scanning endoscopic development has been the technological challenge of fabricating a small diameter, opto-mechanical scanner. A proof-of-concept micro-optical scanner has been built using a 2.3 mm diameter piezoelectric actuator and 4 mm diameter lenses. Images are generated using resonant spiral scanning of the fiber, projecting monochromatic laser light to an illumination plane. A single photodetector is used to acquire grayscale images one pixel at a time. In vitro, the acquired images of test targets have 10 to 20 micrometers maximum spatial resolution and a field-of-view that can be electronically varied.

A low-cost fiber-optic instrument to colorimetrically detect patients with Barrett's esophagus for early detection of esophageal adenocarcinoma

In Barretts esophagus, the precursor to esophageal adenocarcinoma, the squamocolumnar junction (SCJ) between the normal esophagus and the stomach like mucosa is proximally displaced. Currently it can be detected only by an expensive upper GI endoscopic procedure. The authors have developed a minimally invasive and easy to operate colorimetric instrument for the low-cost detection of Barretts esophagus. The instrument is based on a flexible, narrow diameter, fiber-optic probe that performs a colorimetric scan of the esophageal lumen. The instrument was clinically evaluated in 50 subjects. The instrument could identify both symmetric and asymmetric SCJs. The SCJ locations determined by the colorimetric instrument correlated strongly (R/sup 2/=0.89) with those determined by endoscopy. The instrument identified the SCJ locations accurately (Mean of difference /spl plusmn/SEM: 0.97/spl plusmn/1.72 cm) and reproducibly (mean of absolute difference /spl plusmn/SEM: 1.33/spl plusmn/1.40 cm). The instrument has a 90% sensitivity of identifying patients with Barretts esophagus, based on the clinical algorithm that if the SCJ is located at a distance less than 37 cm from the teeth, then the subject has Barretts esophagus, otherwise the subject does not have Barretts esophagus. In conclusion, the colorimetric instrument has the potential of being a cost-effective way of determining patients likely to have Barretts esophagus in the population.

Novel low-cost fiber optic colorimetric instrument to rapidly screen premalignant esophageal tissue

A cost-efficient screening device is needed to detect patients who have Barretts esophagus, a precursor to esophageal adenocarcinoma -- the most rapidly increasing cancer in the US. We have developed a prototype instrument based on colorimetric assessment of esophageal lumen. The system consists of a small diameter fiber-optic probe, interfacing electronics, a probe-head position sensor and a computer for display and analysis. The probe has a central plastic optical fiber through which white light is incident on the collapsed esophageal lumen via c conical mirror in the probe-head. A parabolic mirror in the probe-head focuses the reflected light is applied to a linear 520 X 3 RGB photo-diode array to generate proportional electrical signals. A position sensor tracks probe-head location as it is retracted, allowing generation of a 2D colormap of esophageal lumen. A color change from white to red indicates Barretts esophagus. The system performed accurately in tests using models of esophageal lumen which simulate patterns observed in Barretts esophagus.