1. Distinguishing air from solid emboli using ultrasound: in-vitro study of the effect of Doppler carrier frequency.
- Author
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Rodriguez RA, Rodriguez CD, Mesana T, and Nathan HJ
- Subjects
- Analysis of Variance, Embolism, Air diagnostic imaging, Gels, Humans, Intracranial Embolism diagnostic imaging, Microspheres, Phantoms, Imaging, ROC Curve, Reproducibility of Results, Sensitivity and Specificity, Statistics, Nonparametric, Transducers, Air, Ultrasonography, Doppler, Transcranial methods
- Abstract
Objective: To compare the ability of the signal relative-intensity and sample-volume-length (SVL) to discriminate air bubbles from solid spheres in an in-vitro model using two different carrier frequencies of the Doppler transducer., Methods: A gel ultrasound phantom was connected to a circuit in which blood-mimicking fluid circulated. Air bubbles (100-140 microm) and latex spheres (125 +/- 10 microm) were injected into the circuit and interrogated using 1- and 2-MHz transducers. High-intensity-transient-signals (HITS) were recorded with a dual-gated transcranial Doppler (TCD) system. Receiver-Operating-Characteristic curves determined the best cut-off points that would distinguish between embolic materials., Results: HITS from air bubbles had higher intensities and longer SVL than solid spheres with either transducer (P < .0001). Air bubbles (P < .0001) and microspheres (P= .049) showed higher intensities with the 1-MHz relative to the 2-MHz transducer. The intensity increase with the 1-MHz transducer was greater for air bubbles than microspheres (P < .0001). The discriminating efficacy of both the relative-intensity and SVL was similar between transducers (intensity, P= .201; SVL, P= .98)., Conclusions: The relative-intensity and SVL are equally effective to distinguish solid from air emboli using 1- and 2-MHz transducers. Our study indicates that using a lower carrier frequency does not improve the discrimination of air from solid emboli.
- Published
- 2007
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