P.46 Assessment of Intraplaque Hemorrhage by Photoacoustics Imaging (PAI): First in-vivo Human Validation Study

Abstract

Aim

To validate a photoacoustic imaging (PAI) system, for the identification of intraplaque hemorrhage, comparing it with MRI and histology (gold standard).

Methods

25 patients with carotid stenosis>70% and clinical indication to tromboendoarterectomy were recruited. Angio-MRI for intraplaque hemorrhage assessment (Cube sequence) was performed. PAI clips (5 seconds, Frame rate 1000/sec, 3 to 15 per patient) were acquired. Each clip was scored for the presence of PAI signal by means of an integrated scoring system (semiquantitative, from 0 to 12). Semiquantitative grading scales were used to assess plaque histological features of hemorrhage and vulnerability.

Results

18 patients had no missing MRI, PAI and histology data and were included in this analysis. Mean age was 73 ± 8 years, 60% men, 80% Caucasians, 92% hypertensives, 60% with a previous stroke. At histology, only 3 plaques out of 21 showed no signs of intraplaque hemorrhage, 4 showed small hemorrhage, while 14 (67%) showed large hemorrhages. PAI score (best cut-off ≥ 4) correctly classified 14 out of 18 patients (Sensitivity = 73.3%, specificity = 100%, AUC = 0.867). MRI performance was substantially similar, with 12 patients correctly classified (sensitivity = 60%, specificity = 100%, AUC = 0.800), with a non-significant difference in AUC compared to PAI (p = 0.420).

Conclusions

In this first in-vivo human study, PAI is able to identify histological intraplaque hemorrhage with an excellent specificity and acceptable sensitivity, equivalent to MRI. The very high specificity, with a low number of false positives, make PAI a good candidate for evaluation of plaques prior to surgery to i.e. reinforce the decision to perform surgery.