Direct Comparison of T2 and T2&[rho] Image Contrast in a Rat Model of Acute Cerebral Ischemia

Introduction: Metabolic and structural changes occur in brain tissue within minutes of ischemia. Changes in the relative concentration of oxyand deoxy-hemoglobin, blood volume, and cell microstructure within ischemic tissue may also initiate specific metabolic processes and lead to changes in tissue magnetic susceptibility. The Localization by Adiabatic Selective Refocusing (LASER) MR localization sequence (1), has shown promise in detecting tissue H2O changes within the first few minutes of ischemia (2,3). This sequence is sensitive to the diffusion of spins through tissue regions with different magnetic susceptibility (3), and has demonstrated novel image contrast by combining sensitivity to T2, T2ρ and diffusion (T2 , 3,4). LASER can also be used to create high resolution, reduced field of view images. The purpose of this study was to make a direct in-vivo comparison of T2, T2ρ and diffusion image contrast during acute ischemia. It was hypothesized that T2ρ weighted images acquired using LASER would show enhanced contrast in ischemic tissue, compared to T2 weighted images acquired with a Carr-Purcell Meiboom Gill (CPMG) sequence and diffusion-weighted images. Acute ischemia by electrocoagulation of the left Middle Cerebral Artery (MCA).