title: An in vitro comparison of embolus differentiation techniques for clinically significant macroemboli: dual-frequency technique versus frequency modulation method.
abstract: The ability to distinguish harmful solid cerebral emboli from gas bubbles intra-operatively has potential to direct interventions to reduce the risk of brain injury. In this in vitro study, two embolus discrimination techniques, dual-frequency (DF) and frequency modulation (FM) methods, are simultaneously compared to assess discrimination of potentially harmful large pieces of carotid plaque debris (0.5-1.55 mm) and thrombus-mimicking material (0.5-2 mm) from gas bubbles (0.01-2.5 mm). Detection of plaque and thrombus-mimic using the DF technique yielded disappointing results, with four out of five particles being misclassified (sensitivity: 18%; specificity: 89%). Although the FM method offered improved sensitivity, a higher number of false positives were observed (sensitivity: 72%; specificity: 50%). Optimum differentiation was achieved using the difference between peak embolus/blood ratio and mean embolus/blood ratio (sensitivity: 77%; specificity: 81%). We conclude that existing DF and FM techniques are unable to confidently distinguish large solid emboli from small gas bubbles (<50 μm).
authors.affiliation: Medical Physics Department, University Hospitals of Leicester NHS Trust, Leicester, UK. Electronic address: caroline.banahan@uhl-tr.nhs.uk.
authors.forename: Caroline
authors.initials: C
authors.lastname: Banahan
authors.affiliation: Department of Physics, University of Leicester, Leicester, UK.
authors.forename: Zach
authors.initials: Z
authors.lastname: Rogerson
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: Clément
authors.initials: C
authors.lastname: Rousseau
authors.affiliation: Department of Physics, University of Leicester, Leicester, UK.
authors.forename: Kumar V
authors.initials: KV
authors.lastname: Ramnarine
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: David H
authors.initials: DH
authors.lastname: Evans
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: Emma M L
authors.initials: EM
authors.lastname: Chung
mesh_terms: D006801:Humans; D066298:In Vitro Techniques / Q000379:methods; D020766:Intracranial Embolism / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000000981:diagnostic imaging; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
keywords: Discrimination; Emboli; Embolus detection; Transcranial Doppler ultrasound