Abstract
Background
The consequences of poor insonation conditions on autoregulation parameters assessed
with transcranial Doppler (TCD) are unclear.
Methods
We present two new complementary methods to assess the quality of a TCD signal. Inserting
a thin aluminium foil between TCD probe and skin makes a simple model to artificially
worsen a good insonation window. Validation studies are presented. We assessed insonation
quality and cerebral autoregulation parameters with transfer function analysis and
cross correlation in 46 healthy volunteers with and without the aluminium foil model.
The same studies were operated on 45 patients with good insonation windows, naïve,
after worsening the bone window and during constant infusion of an ultrasound contrast
agent. For studying reproducibility, we assessed autoregulation twice in 30 patients
with poor bone windows, with and without constant contrast infusion.
Results
Both methods to measure insonation quality are valid and reproducible. The aluminium
foil model realistically simulates a natural poor bone window, reducing the signal
quality (e.g. energy of the signal spectrum from 33.4±3.5 to 26.2±2.5 dB, p<0.001). Thereby, the autoregulation parameters are systematically biased (e.g. phase
difference from 37.3±10.1° to 25.9±15.1°, p<0.001); while with the use of an ultrasound contrast agent this can be largely compensated
(phase difference 35.7±10.7°, p<0.001). The reproducibility is significantly improved (ICC from 0.76 to 0.90, p<0.05).
Conclusions
Poor bone windows can cause considerable bias in TCD autoregulation parameters. This
bias might be avoided by the use of ultrasound contrast agents, which may greatly
improve the credibility of TCD autoregulation assessment in elderly patients.
Keywords
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References
- Impaired dynamic cerebral autoregulation in carotid artery stenosis.Stroke. 1997; 28: 1340-1344
- Cerebral autoregulation testing after aneurysmal subarachnoid hemorrhage: the phase relationship between arterial blood pressure and cerebral blood flow velocity.Crit Care Med. 2001; 29: 158-163
- Dynamic cerebral autoregulation testing as a diagnostic tool in patients with carotid artery stenosis.Neurol Res. 2001; 23: 55-63
- Dynamic autoregulation testing in patients with middle cerebral artery stenosis.Stroke. 2003; 34: 1881-1885
- Dynamic cerebral autoregulation and collateral flow patterns in patients with severe carotid stenosis or occlusion.Ultrasound Med Biol. 2003; 29: 1105-1113
- Bilateral severe carotid artery stenosis or occlusion – cerebral autoregulation dynamics and collateral flow patterns.Acta Neurochir (Wien). 2003; 145: 1053-1060
- Impaired dynamic cerebral autoregulation in eclampsia.Ultrasound Obstet Gynecol. 2003; 22: 395-398
- M-wave analysis and passive tilt in patients with different degrees of carotid artery disease.Acta Neurol Scand. 2004; 109: 210-216
- Dynamic autoregulation testing in the posterior cerebral artery.Stroke. 2004; 35: 848-852
- Impaired cerebral autoregulation in patients with malignant hypertension.Circulation. 2004; 110: 2241-2245
- Impact of vertebral artery disease on dynamic cerebral autoregulation.Acta Neurol Scand. 2005; 112: 309-316
- Dynamic cerebral autoregulation in acute lacunar and middle cerebral artery territory ischemic stroke.Stroke. 2005; 36: 2595-2600
- Comparison of static and dynamic cerebral autoregulation measurements.Stroke. 1995; 26: 1014-1019
- Evaluation of impaired cerebral autoregulation by the Valsalva maneuver.Stroke. 1996; 27: 1177-1182
- Spontaneous blood pressure oscillations and cerebral autoregulation.Clin Auton Res. 1998; 8: 7-12
- Transfer function analysis of dynamic cerebral autoregulation in humans.Am J Physiol. 1998; 274: H233-241
- Assessment of the thigh cuff technique for measurement of dynamic cerebral autoregulation.Stroke. 2000; 31: 476-480
- Transfer function analysis for clinical evaluation of dynamic cerebral autoregulation – a comparison between spontaneous and respiratory-induced oscillations.Physiol Meas. 2003; 24: 27-43
- Cerebral vasomotor reactivity and cerebral white matter lesions in the elderly.Neurology. 1999; 52: 578-583
- Acetazolamide vasoreactivity in vascular dementia: a positron emission tomographic study.Eur Neurol. 1999; 41: 31-36
- Pravastatin improves cerebral vasomotor reactivity in patients with subcortical small-vessel disease.Stroke. 2001; 32: 2817-2820
- Acetazolamide vasoreactivity in persistent vegetative state and vascular dementia evaluated by transcranial harmonic perfusion imaging and Doppler sonography.Acta Neurochir Suppl. 2003; 87: 63-69
- Cerebral hemodynamics and silent cerebral white matter lesions in middle-aged essential hypertensive patients.Blood Press. 2004; 13: 304-309
- Relationship between cerebral vasomotor reactivity and white matter lesions in elderly subjects without large artery occlusive disease.J Neuroimaging. 2006; 16: 120-125
- Influence of galantamine on vasomotor reactivity in Alzheimer's disease and vascular dementia due to cerebral microangiopathy.Stroke. 2007; 38: 3186-3192
- Cerebrovascular reactivity in degenerative and vascular dementia: a transcranial Doppler study.Eur Neurol. 2007; 58: 84-89
- Periventricular white matter lucency and cerebral blood flow autoregulation in hypertensive patients.Hypertension. 1994; 23: 565-568
- Subcortical vascular dementia.Cerebrovasc Dis. 2002; 13: 58-60
- The thickness of the temporal squama and its implication for transcranial sonography.J Neuroimaging. 2004; 14: 139-142
- Funktionelle Dopplersonografie in der Neurologie.Springer-Verlag, Berlin Heidelberg1996 (ISBN 3540614192)
- Monitoring of cerebral autoregulation in head-injured patients.Stroke. 1996; 27: 1829-1834
- The continuous assessment of cerebrovascular reactivity: a validation of the method in healthy volunteers.Anesth Analg. 1999; 89: 944-949
- Cerebral autoregulation in carotid artery occlusive disease assessed from spontaneous blood pressure fluctuations by the correlation coefficient index.Stroke. 2003; 34: 2138-2144
Article info
Publication history
Published online: March 09, 2009
Identification
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© 2009 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
