Automated versus human in vivo segmentation of Carotid Plaque MRI C Oppenheim 1, R van 't Klooster 2, R Marsico 1, O Naggara 1, O Eker 1, RJ van der Geest 2, IM Adame 3, E Touzé 1, Meder JF Université Paris Descartes, INSERM U894 Sainte-Anne hospital, Paris, France 2. Division of Image Processing, Department o f Radiology, Leiden University Medical Center, Leiden, The Netherlands 3. Medis medical imaging systems bv, Leiden, The Netherlands

Introduction

Beyond the lumen … Initial MRAOne year follow-up  Fibrous Calcium Lipid core Hemorrhage Introduction

Oppenheim et al. Radiographics 2009

Stable Unstable

methods How to study atherosclerotic plaques in vivo ? Visual / ManualAutomatic Ex vivo and in vivo histological validation studies Little validation 1-7 ExpertiseNone Time consumingQuick Interobserver variability 8 Reproducible 1. Clarke, et al. Magn Reson Med Ronen, et al. Magn Reson Med Liu, et al. Magn Reson Med Binjian et al. Magn Reson Med Adame IM, et al. MAGMA Karmonik et al.. IEEE Trans Bio. Eng Kerwin et al. Top Magn Reson Imaging Touzé et al. Stroke 2007

Purpose To compare the detection and quantification of the main MR plaque components in vivo using 1.manual approach 2.automatic approach

Material and Methods 60 patients with carotid stenosis –Extracted from a multicentric prospective study (HIRISC) –Asymptomatic high grade stenosis or symptomatic moderate stenosis –With high quality MRI (at least ¾ sequences = excellent) Training set n=20 Study group n=40 No differences for age, sex, degree of stenosis, % symptomatic stenosis

Training set, n=20 Study group, n=40 Software Q Plaque (Medis medical imaging bv) Supervised classifier

Manual versus Automatic Study group : 40 patients, 344 sections  Qualitative Analysis: Kappa coefficient (IC 95%)  Quantitative Analysis: Intraclass coefficient correlation (IC 95%) Linear correlation between volumes Bland Altman plots méthodes

Qualitative analysis (per patient) ComponentsManual Automatic Agreement  [95% CI] AbsencePresence Calcium Absence %0,59 [0,36 - 0,82] Presence 513 Lipid core Absence 10 97%0,65 [0,03-1,27] Presence 138 Hemorrhage Absence %0,65 [0,42-0,88] Presence 318 Results

Quantitative analysis ComponentsICC (95% CI) Lipids0,65 (0,43 à 0,80) Hemorhage0,80 (0,54 à 0,92) Calcium0,10 (-0,45 à 0,60) Fibrous tissue0,80 (0,65 à 0,89) Results Lipids Hemorrhage Fibrous Calcium

LIPIDS: Bland Altman plots Results Mean Volume, mm 3 Volume (Manual – Automatic)

Discussion The automatic analysis of atherosclerotic components on MRI is possible Identification : –Kappa at least substantial for all components –Slightly better for hemorrhage (high contrast on all sequences) Quantification : –Best for hemorrhage, fibrous tissue, lipid core < 100 mm 3 –Poor for Calcium In patients without clear surgical indications using different MR plateforms

1)High quality images 2)Results could be improved with a larger training set 3)Fibrous cap ? 4)No reference (patients not scheduled for endarteriectomy) discussion Limites

A gain in time No variability Potentially interesting for –Large multicentric therapeutic trials –Longitudinal studies Could help the integration of HR MRI of atherosclerosis in clinical practice Conclusion : Automatic plaque analysis Day 0 1 year