Improved characterization of cerebral infarction using combined tissue T2 and high b-value diffusion MRI in post-thrombectomy patients: a feasibility study.

BACKGROUND: The utility of incorporating both diffusion information and T2 relaxation times in the imaging work-up of stroke patients is being investigated in a number of clinical trials and scientific studies. However, these tissue characteristics are often determined both qualitatively and independent of each other.

PURPOSE: To investigate the feasibility of varying T2- (multi echo time [TE]) and diffusion- (multi b-value) weighting within a single series to detect differences in infarcted tissue in post-thrombectomy patients.

MATERIAL AND METHODS: An experimental magnetic resonance imaging (MRI) diffusion series consisting of multiple b-values (0, 500, 1000, and 4000 s/mm2 ) and multiple TEs (85, 103, and 120 ms) was implemented. In order to model the signal intensity, an extension of the bi-exponential model to include unique T2 values for each component was formulated. As proof of concept, four stroke patients were imaged the day after thrombectomy. Non-linear optimization tools were used to estimate model parameters in manually drawn regions of interest.

RESULTS: Simulations of signal intensity demonstrated that clinically standard ADC maps acquired solely using b = 1000 s/mm2 data may ignore changes in underlying tissue compartment properties. Analysis of normal-appearing and infarcted tissue in stroke patients demonstrated shifts in T2 relaxation times in both the slow (158 ms [95% confidence interval = 79-236 ms] to 214 ms [86-342 ms]) and fast (82 ms [71-92 ms] to 171 ms [40-303 ms]) diffusion components.

CONCLUSIONS: Although results are shown in only a few patients, multi-b-value, multi-echo parameters could provide clinicians and researchers with a more complete understanding of the effective T2 properties of infarcted tissue.