Spatiotemporal Dynamic Simulation of Acute Perfusion/Diffusion Ischemic Stroke Lesions Evolution: A Pilot Study Derived from Longitudinal MR Patient Data

Islem Rekik,Stéphanie Allassonnière,Trevor Carpenter,Joanna Wardlaw,Stanley Durrleman

doi:10.1155/2013/283593

Abstract

The spatiotemporal evolution of stroke lesions, from acute injury to final tissue damage, is complex. Diffusion-weighted (DWI) and perfusion-weighted (PWI) imaging is commonly used to detect early ischemic changes and attempts to distinguish between permanently damaged and salvageable tissues. To date, 2D and 3D measures of diffusion/perfusion regions at individual timepoints have been widely used but may underestimate the true lesion spatio-temporal dynamics. Currently there is no spatio-temporal 4D dynamic model that simulates the continuous evolution of ischemic stroke from MR images. We determined whether a 4D current-based diffeomorphic model, developed in the field of statistical modeling for measuring the variability of anatomical surfaces, could estimate patient-specific spatio-temporal continuous evolution for MR PWI (measured as mean transit time, (MTT)) and DWI lesions. In our representative pilot sample, the model fitted the data well. Our dynamic analysis of lesion evolution showed different patterns; for example, some DWI/PWI dynamic changes corresponded with DWI lesion expansion into PWI lesions, but other patterns were much more complex and diverse. There was wide variation in the time when the final tissue damage was reached after stroke for DWI and MTT.

Highlights

Stroke is the third leading cause of death in industrialized countries [1], the second commonest cause of death worldwide [2], and a major social and inancial burden. 80% of stroke is ischemic, and so far the only efective treatment is with thrombolytic drugs to dissolve the occluding thrombus
For the initial application of the model we required that (i) the mean transit time (MTT) and DWI lesions should both be visible at, at least, 3 timepoints, (ii) the MTT/DWI mismatch should be larger than 3 cm3, and (iii) the lesion consisted of one solitary lesion only and this did not vary between timepoints
We evaluated the accuracy of our estimation of DWI and MTT lesion evolution by computing the mean and standard deviation (SD) values of the dice index between the estimated and the true lesion volumes at the second and third timepoints for the 8 patients

Summary

Introduction

Stroke is the third leading cause of death in industrialized countries [1], the second commonest cause of death worldwide [2], and a major social and inancial burden. 80% of stroke is ischemic, and so far the only efective treatment is with thrombolytic drugs to dissolve the occluding thrombus. Many have suggested that their use could be focused on patients who are most likely to beneit by using techniques such as Magnetic Resonance (MR) imaging to identify the location and spatial extent of ischemic tissue and diferentiate salvageable from nonsalvageable tissues [ , 5]. Numerous medical image analysis approaches have been applied to DWI and/or PWI data using 2D or 3D approaches to determine how the ischemic stroke lesions evolve and what factors inluence this. Most of these studies evaluated MR (or CT) images of ischemic stroke as static “snapshots” to predict tissue prognosis and its association with clinical outcome [5, 7]. Many studies to date suggest that some patients conform to the expected growth of the DWI into the PWI lesion [1 –16], others did not. his might be due to insensitivity of visually assessed 2D

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Conclusion