Sonic detection of intracranial aneurysm and AVM.

Abstract

SUMMARY This paper describes a method of detecting intracranial aneurysm and arteriovenous malformation (AVM) by analysing weak sounds produced by the blood circulation at the affected part. There is thought to be no turbulence in the normal cerebrovascular system, whereas abnormalities such as aneurysm and AVM sometimes cause turbulence in the blood flow. Thus, a small fraction of the flow energy might be converted into an acoustically detectable noise.For the detection of the sound, sensitive detectors must be applied close to the head since the sound is very weak, and, as in cerebrovascular diseases, the origin of the sound is usually concealed deep inside the hard shelter of the skull. The detection system we used had a gain of 40 to 50 dB greater than that of an ordinary stethoscope. The detection points were the teeth or forehead. Usually the sound started about 160 msec after the ventricular contraction and lasted for 100 to 400 msec. Its frequency component mostly ranged from 400 to 2000 Hz, but the spectrum profile changed according to the position and degree of abnormalities. The uttered sound was very random, which facilitated detection of the position of the sound origin by means of cross correlation methods using a pair of detectors.This method is completely noninvasive, causes no pain to the patient, and might be used even in mass examinations.

Blood flow noise transducer for detecting intracranial vascular deformations

“…However, evaluation of sensitivity and capacitance is considered to be helpful for the comparison. The pressure sensitivity of an accelerometer, with a sensitivity of 100 mV/g for instance [5], with load was represented to be −105 dB, under the assumption that the diameter of the contact area was 20 mm which was the same as that of the PVDF-film transducer. Its capacitance was several times higher than that of the PVDF-film transducer, i.e., less noise was expected, but the sensitivity was lower by about 30 dB.…”

“…The upper limit of the bruit frequency range has been reported to be below about 2 kHz and mainly up to 1 kHz [3,5]. Hence, the bruit transducer was regarded as a device for the low audio frequency range.…”

“…Sekhar and Wasserman (1984) [4] also used a horn-coupled probe microphone. Kosugi et al (1983) [5] developed a detector using an accelerometer that was pressed onto the skull. Taylor et al (1983) [6] described digital signal processing of bruits for the detection of aneurysms and pointed out the necessity of further improvement of the transducer they used.…”

Urophonographic studies of the lower urinary tract. A new approach to urodynamics.

“…Spectrum analysis and cross-correlation analysis were carried out by 7T08 program packages #39 and #100A, where averaging was taken over 32 or 64 beats. The resulting data was displayed on a CRT screen and hard copies were plotted on an XY-recorder (Ferguson 1970;Kosugi et al 1983). Prior to sound recording the patients were asked to urinate completely.…”

Modeling and simulation of flow in cerebral aneurysms

“…In such flow conditions, diseased vessels support flows with rapid fluctuations, which could be detected via non-invasive techniques. These so-called brain 'bruits' can be recorded and the spectrum of frequencies can give some characterization of the shape and size of the aneurysm, as well as of the dominant flow regime [45,49].…”