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B J Arnolds

Publications and source records attributed to B J Arnolds.

5 recordsLinked to original sources
PubMed1989

Spatial resolution of transcranial pulsed Doppler technique in vitro evaluation of the sensitivity distribution of the sample volume.

The spatial resolution of pulsed Doppler sonography is determined by the size of the sample volume. It is known that the axial length is dependent upon the duration of the range gate interval and the lateral extension upon the beam width. In addition, the working size is also a function of the sensitivity distribution within the sample volume. All of these parameters determine the working size of the sample volume. Especially for the transcranial Doppler evaluation of the basal cerebral arteries, the site and the working size of the sample volume are essential diagnostic criteria. To measure the working size of the sample volume a flow rig with a thin tube target has been developed and used. The highest sensitivity (100% level) was registered only in a relatively small area and only if the center of the sample volume hit the target. At the 10% level the size of the sample volume increased 5 to 10 times in the lateral and axial dimension in comparison with the 90% level. Therefore, the Doppler signal from a strong reflector distant from the center of the sample volume may mask the signal of a weak reflector located within the center. This lack of spatial resolution due to sensitivity effects may result in clinical misinterpretation. The manufacturers should be urged to supply more precise information relative to the sample volume size.

Blood Flow Velocity↗
PubMed1986

Transcranial Doppler sonography. Examination technique and normal reference values.

The main application of ultrasound in neurology is the examination of extracranial arteries. Recently the Doppler sonographic measurement of flow velocity in the basal cerebral arteries through the intact skull was developed using a pulsed Doppler technique and 2 MHz emitting frequency. Doppler frequencies in systole and diastole were recorded in 51 healthy subjects at 0.5 cm steps along the middle (MCA), anterior (ACA) and posterior cerebral artery (PCA) as well as the basilar artery (BA). The averaged Doppler shift in the MCA was 2.3 +/- 0.4 kHz in systole and 1.15 +/- 0.25 kHz in diastole, in the ACA 1.8 +/- 0.35 kHz and 0.85 +/- 0.22 kHz, in the PCA 1.5 +/- 0.29 kHz and 0.74 +/- 0.18 kHz, in the BA 1.45 +/- 0.31 kHz and 0.72 +/- 0.22 kHz. Separation in four age groups showed a decrease of Doppler shift in the MCA of 20% from a mean age of 17 to 67 years. Static and dynamic compression tests were evaluated to assign transcranial Doppler signals to the MCA, ACA and PCA. No compression test was necessary for the identification of the BA insonated through the occipital foramen.

Adolescent↗
PubMed1984

[Simulation of arterial pulse curves in elastic tubes and a carotid preparation].

Results of Doppler sonographic examination of the arteries in the neck are not completely comparable to angiographical findings, because the application of the Doppler probe is not standardised and angiography does not demonstrate the exact vascular morphology. To experimentally correlate the Doppler-findings with morphology, a flow rig was constructed that generated within elastic tubes as well as human carotid artery specimens all types of human arterial pulse curves (e.g. subclavian or internal carotid artery). This was achieved by taking into account the principles of pulse wave propagation and reflection in vivo. A degassed aqueous suspension of amylum maidis was used as circulating medium. This flow rig allows the evaluation of the diagnostic criteria of Doppler spectrum analysis, such as peak frequencies and spectral broadening. Testing the characteristics of Doppler equipment is another useful application.

Blood Pressure↗