Experimental and Clinical Observations on the Echograms in Vitreous Haemorrhages.

IN previous communications (Oksala and Lehtinen, 1959; Oksala 1960a, b), I noted that vitreous haemorrhages reflected echoes on the screen of an ultrasound equipment, and that these echoes were clearer if a fresh haemorrhage was involved. I also found that old haemorrhages, on account of the destruction of the vitreous, do not always become visible in ultrasonic examinations (Oksala and Lehtinen, 1959). Baum and Greenwood (1958), who have also noted clear echoes in vitreous haemorrhages, stated that it was possible to differentiate between them and the echoes obtained from a foreign body. During these last 2 years I have been better able to visualize echoes from vitreous haemorrhages by using a more sensitive crystal, which has also made possible so-called "selective echography". In the present paper I propose to describe my observations on vitreous haemorrhages with the new instruments , which show an improvement in the possibilities of diagnosis by ultrasound. Krautkramer, Mode. Usip. 9. At my request this same factory manufactured a specially sensitive barium titanate crystal with a slight damping, a frequency of 6 MHz and a diameter of 10 mm. Resolution in depth was about 0-6 mm. in the eye. With this crystal echoes could be obtained even from slight vitreous haemorrhages. Another ultrasonic instrument was constructed$ using a barium titanate crystal with a frequency of 10 MHz which also proved to have a very " broad spectrum". The sensitive "broad spectrum" crystal enabled me to use the Krautkramer ultrasonic equipment for the selective echography which I have used for about 2 years in differential diagnosis. By reducing the power of the issuing impulse (IP) as well as the amplification of the returning impulse, it is possible to differentiate between various intra-ocular pathological changes because they produce acoustic reactions of different density. These results have been described elsewhere (Oksala, 1962). The IP values indicated do not represent fixed measuring units, as the IP can be regulated gradually from 1 to 5 and the amplification without gradation from 1 to 10.