Aim: Pre-surgical evaluation of the extent of internal carotid artery stenosis (ICA) according to NASCT criteria using digital 3D ultrasound methods.
Material/methods: In a prospective study, 25 patients (54-88 years, mean 75) with neurological deficits and the diagnosis of ICA stenosis underwent pre-surgical ultrasound examination using Color Coded Duplex Sonography (CCDS), 3D CCDS, 3D power Doppler, 3D B-flow, contrast enhanced 3D B-flow, and CTA/MRA. Ultrasound was performed by an experienced examiner with a multifrequency linear transducer (6-9 MHz, Logiq 9, GE). After bolus injection of 2.4 ml Sonovue i.v., low mechanical index technique (MI<0.16) was used for contrast enhanced 3D B-flow. As reference method for evaluation of the extent of ICA stenosis each patient underwent CTA (multislice CT, Sensation 16, Siemens) and/or MRA (1.5 T, Symphony Siemens). Indications for surgery (carotid EEA) followed the NASCET criteria. All images were interpreted and evaluated independently by two observers with three measurements of the degree of the ICA stenosis. For assessment of the extent of stenosis a 10%-scale from 50% to 99% was used. Statistical analysis was performed using Spearman Correlation and Wilcoxon Signed Rank Test with a significance threshold of p<0.05.
Results: Assessment of the extent of ICA stenosis during surgery and in CTA/MRA displayed a range from 60% to 99% (mean 80%). Non significant differences were found with paired Wilcoxon test only for 3D B-flow with and without contrast medium (p<0.05). Correlation with surgical evaluation regarding the extent of ICA stenosis using Spearman correlation teat was 0.77 for B-scan, 0.90 for 3D CCDS, 0.84 for 3D Power Doppler, 0.91 for B-flow and 0.93 for contrast enhanced 3D B-flow. When circular calcifications were present, contrast enhanced flow detection of 3D B-flow proved to be useful. Visualisation of intrastenotic variances of severe and profound stenosis (70-99%) without blooming and reverberation artefacts was possible only with 3D B-flow. This facilitates the detection of the morphology of plaques ulcers as an embolic source.
Conclusion: In correlation with surgery and CTA/MRA, a valid evaluation of the extent and morphology of ICA stenosis using 3D B-flow, with and without contrast medium, is feasible.