Zusammenfassung
Das Auge ist als echographisches Untersuchungsobjekt besonders geeignet. Nach Anpassung
der Geräte und Schallköpfe an die relativ kleinen Abmessungen gelangen daher schon
sehr früh vielfältige, zuverlässige differentialdiagnostische Entscheidungen. Bald
wurde erkannt, daß die diagnostischen Kriterien in den Echogrammen durch gerätetechnische
Parameter verfälscht werden können. Zur Aufdeckung solcher Fehlerquellen und zur Sicherstellung
optimaler, reproduzierbarer Untersuchungsbedingungen wurden Meßtechniken zur Prüfung
und Kalibrierung der Geräte und Schallköpfe entwickelt - lange bevor ähnliche meßtechnische
Vorschläge von der International Electrotechnical Commission veröffentlicht wurden.
Heute werden für die echographische Darstellung des Auges und der Orbita schnell abtastende,
elektromechanische B-Bild-Verfahren in Kombination mit A-Bild-Verfahren benutzt. Mit
meßtechnisch überprüften Geräten und Schallköpfen (Gesamtempfindlichkeit, Arbeitsfrequenz
und Frequenzspektrum, Schallfeldgeometrie usw.) können vielfältige diagnostische Entscheidungen
zuverlässig getroffen werden.
Längen- und Distanzmessungen hoher Genauigkeit sind hilfreich zur Beurteilung des
axialen Linsendurchmessers bei linsenbedingtem Glaukom. Die Messung der Achsenlänge
des Auges ergibt ein zusätzliches Kriterium zur Verlaufsbeurteilung der Hydrophthalmie;
in Verbindung mit der Messung anderer Durchmesser erlaubt sie die genaue Lokalisation
von Fremdkörpern. Die Ultraschall-Exophthalmometrie dient der exakten Differenzierung
von Pseudoprotrusio und echter Protrusio bulbi.
Innerhalb des Bulbus kann man unter Berücksichtigung von Arbeitsfrequenz, Gesamtempfindlichkeit
und resultierenden Echoamplituden Glaskörpertrübungen, Fibrinmembranen, Fremdkörper,
primäre (exsudative) Netzund Aderhautablösungen und Tumoren erkennen und voneinander
differenzieren. Hierzu werden auch die Lokalisationsbeziehungen der pathologischen
Strukturen und ihre Ortsveränderungen nach Bulbusbewegungen herangezogen.
Abstract
The eye and orbit offer particularly suitable conditions for diagnostic ultrasonography.
Hence, versatile and successful differential diagnoses were obtained early, after
the apparatus and transducer probes had been adapted to the eyes relatively small
dimensions. It was soon evident that the diagnostic criteria could be falsified by
technical parameters of the equipment used. Measurement techniques for the control
and calibration of apparatus and transducer probes were developed in order to discover
such sources of error and to ensure optimum, reproducible conditions of examination.
This was long before similar suggestions of measurement technique had been published
by the International Electrotechnical Commission.
Today, electro-mechanic real-time scanner are preferred for B-scanning of the eye
and orbit, in combination with A-scanning. Equipement and transducer probes which
had been subjected to checking and control procedures (especially in respect of sensitivity,
working frequency and frequency spectrum as well as beam shape) will enable a multitude
of reliable diagnostic decisions. High-accuracy length and distance measurements prove
helpful to determine the axialdiameter of the lens in lens-induced glaucoma. Measurement
of the axial length of the eye yields an additional criterion to assess the course
of buphthalmos cases; in combination with measurements of other diameters, foreignbody
localisation can be performed more accurately. Ultrasound exophthalmometry (a combination
of Hertel's opticexophthalmometry and ultrasound axial length measurements) can help
in arriving at a reliable differentiation of pseudo-protrusion and genuine Protrusion
of the eye.
Within the eye itself (in respect of working frequency, sensitivity and resulting
echo amplitudes) it is possible to detect vitreous opacities, fibrin membranes, foreígn
bodíes, primary retinal and choroidal detachments and tumours, which can then be differentiated
from one another. Location of the pathologic structures and their movements after
changing the direction of glance, are also taken into consideration in differential
diagnosis.
Circumscribed and diffuse space-occupying lesions can be identified in the orbit.
Cysts are reliably differentiated from tumours; in certain tumour types, further differentiation
can be achieved, e.g. in cavernous haemangioma. Penetration of the orbital wall by
a tumour can be recognized. Sound attenuation in the lesion area, the echo amplitude
of structures behind the lesion, movements of the lesion area as the direction of
glance changes, will yield further information; this also applies to echogram changes
during compression of the lesion area by the transducer probe or following Valsalva's
manoeuvre or jugular vein compression. Further developments will concentrate on properly
calibrated equipment and computerized echo Signal evaluation. The technical Parameters
which offer best possibilities of arriving at a reliable diagnosis in a particular
disease will be worked out. The manufacturers are facing an increasing demand for
calibrated and correctly declared apparatus and transducer probes, For evaluating
more of the information contents of echo Signals, e.g. phase shifts and frequency
spectrum alterations, computer-assisted echogram analyses are in the course of being
developed; in certain cases they can already be applied in clinical diagnosis.
X-ray computerized tomography is additionally applied in many cases. The different
information obtained by means of both these methods, especially when their evaluation
is combined, will yield more relevant diagnostic information than if one of these
techniques is used alone.
