Gray scale echography with simultaneous a mode presentation a new apparatus for high resolution ultrasonograms
A diagnostic ultrasonic system has been developed for simultaneous display of quantitative A mode and gray scale B mode presentations. An independent calibrator and preset amplification levels allow the apparatus to be calibrated for precise, repeatable examinations. A wide range of echo amplitude information is available to the clinician by the use of selective logarithmic signal compression. Distance measurements in the eye and the orbit are made to 0.1 mm precision and are displayed numerically on the control panel. The newer signal processing techniques provide high‐resolution imaging of ophthalmic structures over a wide system bandwidth. Sensitivity has been improved to image structures heretofore not observable with ultrasonic instruments. This technique is the basis for recently initiated clinical studies.
Linear array multiple transducer ultrasonic examination of the eye.
Dynamic ultrasonic imaging adds a time dimension to the clinical diagnosis of ocular pathology. A recent development in this area of ophthalmic sonography has been the introduction of an electronically scanned, multiple transducer system that provides improved real-time imaging of ocular tissue motion. This paper discusses clinical observations made in a variety of ophthalmic conditions with a high speed, linear array ultrasound system and discusses briefly the apparatus and special examination techniques needed to make these observations. Clinical subjects include vitreo-retinal adhesions: the clear cortical vitreous network; vitreous hemorrhage, opacities and membranes; shallow, fixed, and mobile retinal detachments; blood vessels within ocular tumors and the evaluation of intraocular foreign bodies.
ABOUT SELECTIVE ECHOGRAPHY IN SOME EYE DISEASES
In the course of the last six years several investigators ( 1 , 2-4, 5, 6-9, 10-12) have noted that ultrasonic examination of the eye has proved to be a very serviceable diagnostic method of research in numerous eye diseases. Such diseases are e. g. intraocular foreign bodies and tumours, detachment of the retina and vitreous opacities. Although differentiation between these diseases is usually easy on the basis of echograms, there are none the less cases in which the interpretation of echograms is very difficult. In addition, there are other eye diseases which present difficulties in the interpretation of echograms. During the last two years I have mainly concentrated on the clinical side of ultrasonic examinations of the eye, and by way of one of the results of this investigation I shall describe the following method which, in my experience, facilitates the analysis of echograms. By selective echography I mean a study in which some eye diseases are differentiated from each other on the basis of the amplitudes of the echograms obtained. In order to enhance the accuracy of determinations I have decreased the amplitudes up to the disappearance of the echoes from the screen, in such a way that the power of both the issuing and the returning impulse was reduced. The clinical study reported below shows that the echoes reflected in some pathological conditions can usually be clearly distinguished from each other on the basis of the amplitudes. A prerequisite of selective echography is that we have a sufficiently sensitive crystal at our disposal. The frequency of the crystal may not be so high