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Session: Arteries
Session starts: Thursday 24 January, 10:30
Presentation starts: 11:00
Room: Lecture room 536

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Hendrik Hansen ()
Inge van den Munckhof ()
Eveline van der Kolk ()
Anton Meijer ()
Marinette van der Graaf ()
Joost Rutten ()
Chris de Korte ()

Abstract:
The rupture of vulnerable plaques in the carotid artery is a main cause of transient ischemic attacks and stroke. To detect atherosclerotic plaques with a rupture prone composition, dedicated ultrasound strain imaging techniques have been developed to accurately and noninvasively measure deformations/strains of the carotid artery wall induced by the pulsating blood flow. Multiple studies have confirmed the relation between strain and plaque composition. However, most studies applied strain imaging methods that only allow imaging in longitudinal cross-sections, implying that they only allow imaging of plaques in the top or bottom part of the wall. This study for the first time investigates if strains obtained with a strain imaging technique designed for transverse planes correlate with MRI–based plaque composition in an asymptomatic population. Ultrasound radiofrequency (RF) data of 51 carotid plaques from 31 asymptomatic participants with an increased cardiovascular risk profile were recorded by an experienced sonographer in a dedicated three-angle (0°, +20° and -20°) focused acquisition mode using a Samsung Medison Accuvix V10 ultrasound system equipped with an L5-13IS transducer. Additionally, MR angiography and high resolution MR vessel wall data were obtained using a Siemens 3.0 T MAGNETOM Skyra MRI scanner (Erlangen, Germany) with a dedicated 4-channel Machnet Phased Array Carotid Coil (Eelde, the Netherlands). Principal radially-oriented strains were derived from the ultrasound RF data using our previously published compound strain imaging approach and cumulated over the diastolic phase. The resulting strain map was normalized with respect to pulse pressure measured with a sphygmomanometer. Two strain parameters were calculated from the strain map values in those parts of the circumference where the wall was at least 2 mm thick: 1) the median value, and 2) the percentage of strain values exceeding 0.5% strain. We studied the performance of both strain parameters for differentiating plaques classified as fatty, haemorrhagic, calcified, or aspecific/fibrous by an experienced neuroradiologist based on the MRI data and blinded to the ultrasound data. Strain parameters of the plaques with a composition associated with vulnerability, i.e. fatty (n=9) and haemorrhagic plaques (n=5), were significantly higher than the strain parameters of plaques with stable composition, i.e. calcified (n=14) and aspecific/fibrous plaques (n=23) (Mann-Whitney test, P<0.05). Overall, both strain parameters were highest for fatty plaques compared to the other plaques, although no significant differences between the individual groups were detected (Kruskall-Wallis test P<0.05). Median strain and percentage strain >0.5% for the vulnerable plaques were 0.95% and 53.4% versus -0.02% and 47.1% for the stable plaques, respectively. Thus, even in this small asymptomatic population, compound strain imaging discriminated between plaques with vulnerable and stable features.