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Variations in acoustical beam properties of intracoronary Doppler catheters
12nd Medical Clinic, Johannes Gutenberg University, Mainz, Germany.
Insights
Intraluminal Doppler sonography provides functional insights into coronary blood flow velocity. However, variations in Doppler catheter beam characteristics can lead to inaccurate blood flow velocity measurements, potentially underestimating critical values.
Area of Science:
- Cardiovascular Ultrasound
- Medical Imaging
- Biomedical Engineering
Background:
- Coronary angiography has limitations in assessing the functional significance of coronary obstructions.
- Intraluminal Doppler sonography offers functional information on coronary blood flow velocity, a critical but hard-to-measure variable.
Purpose of the Study:
- To investigate the transmitter-receiver characteristics and ultrasound beam topology of commonly used Doppler catheters.
- To evaluate the impact of beam inhomogeneities on the accuracy of blood flow velocity measurements.
Main Methods:
- Experimental setup to characterize the transmitter-receiver properties of five Doppler catheters.
- Analysis of lateral beam spread at a penetration depth of 3.0 mm, measuring beam shape variations.
Main Results:
- Significant inhomogeneities were found in the lateral beam spread of the investigated Doppler transducers.
- Beam shape varied from 1.25 mm to 3.5 mm at 3.0 mm penetration depth (mean 2.25 mm).
- These beam profile differences introduce errors, leading to underestimation of blood flow velocity, particularly with increasing vessel diameter and flow velocity.
Conclusions:
- Inhomogeneities in Doppler catheter beam characteristics compromise the accuracy of blood flow velocity measurements.
- For spectral analysis of Doppler signals, a broader beam illuminating the entire vessel lumen is advantageous, contrary to imaging transducer design.
Abstract:
The limitations of coronary angiography in assessing the functional significance of coronary obstructions is well known. While the critical variable of coronary blood flow cannot be readily measured, intraluminal Doppler sonography offers useful related functional information on blood flow velocity. In order to fully evaluate Doppler signals it is essential to have exact knowledge of the transducer transmission characteristics and of the ultrasound beam topology. In an experimental set-up, the transmitter-receiver characteristics of five commonly used Doppler catheters were investigated. In comparing the beam characteristics we found inhomogeneities in the lateral beam spread. At a penetration depth of 3.0 mm the beam shape varied from a minimum of 1.25 mm up to a maximum of 3.5 mm. The mean was 2.25 mm. The different beam profiles of the investigated Doppler transducers cause an error in measuring the blood flow velocity. The blood flow velocity tends to be underestimated the more the vessel diameter and the blood flow velocity increase. Contrary to transducer design optimized for imaging, for spectral analysis of the Doppler signal it would be advantageous to have as broad a beam as possible in order to illuminate the entire vessel lumen.