Instytut Podstawowych Problemów Techniki

Streszczenie:

Ignacy Malecki was born on November 18, 1912, at the family estate of Pokiewnia near Vilnius. After Poland regained its independence in 1918, the town was at the border of the Second Republic of Poland and Central Lithuania. The church and village were located in the Polish area, while the family estate on the Lithuanian side. It took some time before those parts could be reunited.
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Examination of the carotid artery stenosis is very important in the diag-nosis of cerebrovascular diseases. New possibilities in the diagnosis of stenotic lesions are provided by ultrasonic Doppler angiography. The aim of this paper is to present a Doppler imaging system developed by the authors for the exami¬nation of blood flowing in carotid arteries. The system is based upon a 5 MHz bi-directional c.tv. Doppler flowmeter with a separate output for anterograde and retrograde flows. A special bank of filters converts signals into various levels of the gray-scale display which correspond to the value of the blood flow velocity. The ultrasonic probe is held by the scanning arm. The position of the probe on the skin of the patient is electronically sensed by the position-sensing circuity which causes the bright spot on the image display to move according to the position of the probe. The Doppler image from the artery is stored in a digital memory system. The clinical results obtained by means of this system showed good agreement with X-ray arteriography for obstructions occluding more than 50 per cent of the arterial diameter.

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The authors applied two absolute methods for the determination of the intensity of ultrasonic focused beams of 2·5 MHz frequency used in ultrasonograph UG-4 for abdominal visualization: the electrodynamic and the capacitance methods. For the first method a special electrodynamic transducer was constructed which made it possible to measure the acoustic (particle) velocity in the focal point of the ultrasonic beam radiating into water. Hence the focal intensity could be determined.

The two methods gave almost the same intensity values equal to 23 Wcm−2 in peak, (∼ 23 mWcm−2 time average value) although the mean surface value near to the radiating transducer was equal only to 0·59Wcm−2 in peak (∼0·59 MWcm−2 time average value).

Next, the loss of the ultrasonic signal was measured in pregnant women in vivo using for this purpose steel balls as reflecting targets placed in the gravid uterus. The echo amplitudes obtained in the uterus were compared with echoes received from the same steel balls placed in (nonabsorbing) water in the same position relative to the radiating transducer.

In this manner it could be found that intensity levels inside of the uterus were 6–14 dB lower than at the body surface, depending on the anatomical characteristics of the patient.

Thus the maximum (focal) intensities which are to be expected in the gravid uterus in early pregnancy will be between 0·9 and 5·5 Wcm−2 in peak (0·9–5·5 mWcm−2 time average values) when applying the ultrasonograph UG-4.

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