Sizing Gaseous Emboli Using Doppler Embolic Signal Intensity

Abstract

Extension of transcranial Doppler embolus detection to estimation of bubble size has historically been hindered by difficulties in applying scattering theory to the interpretation of clinical data. This article presents a simplified approach to the sizing of air emboli based on analysis of Doppler embolic signal intensity, by using an approximation to the full scattering theory that can be solved to estimate embolus size. Tests using simulated emboli show that our algorithm is theoretically capable of sizing 90% of “emboli” to within 10% of their true radius. In vitro tests show that 69% of emboli can be sized to within 20% of their true value under ideal conditions, which reduces to 30% of emboli if the beam and vessel are severely misaligned. Our results demonstrate that estimation of bubble size during clinical monitoring could be used to distinguish benign microbubbles from potentially harmful macrobubbles during intraoperative clinical monitoring.

Size Distribution of Air Bubbles Entering the Brain during Cardiac Surgery

“…2012. [ 11 ] This is based on theoretical models describing backscattered ultrasound from a spherical embolus moving through a blood-filled vessel. [ 12 ] In tests, 91% of 10,000 randomly generated simulated emboli were correctly sized to within 10% of their true dimensions.…”

“…[ 12 ] In tests, 91% of 10,000 randomly generated simulated emboli were correctly sized to within 10% of their true dimensions. [ 11 ] The algorithm includes estimates for Doppler sample length (which varied between 8 and 12 mm), and Doppler angle (assumed to be 30°). As changes in haematocrit concentration can affect estimates of MEBR by up to 5 dB, backscattered intensities were adjusted for intra-operative haematocrit values based on the results of perfusionist blood sampling.…”

Visualisation du passage de micro-emboles cérébraux par ultrasonographie en mode B-Flow

“…Le diagnostic et la caractérisation des micro-embolies chez les patients à risque reposent essentiellement sur l'examen Doppler transcrânien et de nombreux procédés d'analyse du signal ont été proposés et évalués pour leur identification et leur dénombrement automatiques [23][24][25][26][27][28]. Le mode B-Flow apparaît capable de les visualiser de façon spectaculaire en montrant leur transit dans les principales artères cérébrales de façon non équivoque.…”

An In Vitro Comparison of Embolus Differentiation Techniques for Clinically Significant Macroemboli: Dual-Frequency Technique versus Frequency Modulation Method

“…Care was taken to inject very small volumes of BMF with the solid emboli to ensure the blood flow waveform was not altered and to minimize the risk of introducing artifactual bubbles and artifacts. Bubble sizes were estimated using a validated algorithm developed by Banahan et al. (2012) based on the analysis of backscattered signal intensity.…”