Early Diagnosis of Intracranial Internal Carotid Artery Stenosis Using Extracranial Hemodynamic Indices from Carotid Doppler Ultrasound

Figure 1. Hemodynamic simulation model of the human cardiovascular system: (A) 1D model of the systemic artery tree; (B) 1D model of the Willis circle; (C) cross-section of the artery model; (D) prescribed flow rate curve at the inlet of the ascending aorta; (E) peripheral vessel model at the outlets of the artery networks; 1D, one-dimensional.

Figure 2. Schematic images of the measurement procedure: (A) schematic diagram of a stenosis location and the Doppler ultrasound measurement location; (B) magnetic resonance angiography image of a patient with IICAS; (C) original image of ICA flow waveforms and measurements of the PSV, EDV, and RI; (D) typical digitalized single-period flow velocity waveforms of a patient with IICAS and a patient without IICAS; (E) normalized harmonic amplitudes of waveforms in (D). ICA, internal carotid artery; IICAS, intracranial internal carotid artery stenosis; PSV, peak systolic velocity; EDV, end-diastolic velocity; RI, resistive index.

Figure 3. ICA flow waveforms of a patient: (A) original Doppler ultrasound data; (B) comparison of the measured data and simulated results from the hemodynamic model; (C) comparison of the simulated waveforms with and without stenoses; (D) comparison in the frequency domain. ICA, internal carotid artery; FHR, first harmonic ratio. The patient ID is 18 in the Supplementary Data.

Figure 4. Diagnosis of the patients with and without IICAS: (A) FHR data of both sides; (B) receiver operating characteristic curve of IICAS diagnosis using the maximum FHR of both sides. FHR, first harmonic ratio; IICAS, intracranial internal carotid artery stenosis; AUC, area under the receiver operating characteristic curve; CI, confidence interval.

Figure 5. Incorrectly labeled case in the CTA scan due to an insufficient contrast agent, with the FHR in the normal range: (A) CTA image of the intracranial arteries of the patient, with the misdiagnosed intracranial internal carotid artery stenosis indicated in the red circle; (B) gold standard intracranial digital subtraction angiography image of the same patient showing no stenosis in the arteries, which is consistent with the FHR-based diagnosis. CTA, computed tomography angiography; FHR, first harmonic ratio.