Thrombus size and Doppler embolic signal intensity.
BACKGROUND
Migration of thrombus through the cerebral arteries is a common cause of stroke. Thrombus emboli can be detected non-invasively using Doppler ultrasound, but even where the embolus composition is known, there is currently no method for estimating the size of an embolus based on the returned ultrasound signal. Here we report the results of in vitro experiments investigating the relationship between size and embolic signal intensity for fresh thrombus emboli with a view to estimating the sizes of thrombi detected following carotid surgery.


METHODS
Thrombi were formed from whole blood using the 'Chandler loop' method under flow conditions similar to those associated with arterial thrombus formation in vivo. A total of 390 Doppler embolic signals were then measured from 37 pieces of thrombus circulated in a pulsatile closed-flow circuit. The dimensions of each of the thrombi were measured before and after circulation using an optical microscope. Relationships between thrombus size and embolic signal properties were then investigated using standard statistical methods with a view to size estimation of thrombi during clinical monitoring.


RESULTS
Although embolic signals generally became more intense with increasing thrombus size, strong oscillations due to resonance effects were observed. Pearson tests revealed strong positive correlations between embolus diameter, signal intensity and duration (r > 0.8, p < or = 0.01).


CONCLUSIONS
This study provides experimental evidence supporting theoretical predictions relating Doppler embolic signal intensity to thrombus size. In our discussion, we tentatively suggest how this information might be used to size emboli in clinical practice.
Martin
Matthew J
MJ
University Hospitals of Leicester NHS Trust, Leicester, UK.
Chung
Emma M L
EM
Ramnarine
Kumar V
KV
Goodall
Alison H
AH
Naylor
A Ross
AR
Evans
David H
DH
D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D010316:Particle Size; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011673:Pulsatile Flow; D013927:Thrombosis / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D017585:Ultrasonography, Doppler, Transcranial / Q000295:instrumentation