Quantitative T2′-Mapping in Acute Ischemic Stroke

Abstract

Background and Purpose-Quantitative T2′-mapping detects regional changes in the relation of oxygenated and deoxygenated haemoglobine and might reflect areas with increased oxygen extraction. T2′-mapping in conjunction with an elaborate algorithm for motion correction was performed in patients with acute large-vessel stroke, and quantitative T2′-values were determined within the diffusion-weighted imaging lesion and perfusion-restricted tissue. Methods-Eleven patients (median age, 71 years) with acute middle cerebral or internal carotid artery occlusion underwent MRI before scheduled endovascular treatment. MR-examination included diffusion-and perfusion-weighted imaging and quantitative, motion-corrected mapping of T2′. Time-to-peak maps were thresholded for different degrees of perfusion delays (eg, ≥0 s, ≥ 2s) when compared with a reference time-to-peak value from healthy contralateral tissue.

T2’-Imaging to Assess Cerebral Oxygen Extraction Fraction in Carotid Occlusive Disease: Influence of Cerebral Autoregulation and Cerebral Blood Volume

“…[6, 10, 12] In brief, MR imaging data were acquired on a 3-T whole-body scanner (Trio, Magnetom Series; Siemens, Erlangen/Germany) equipped with a body transmit coil and an 8-channel phased array head receive coil. T2-maps were acquired using a turbo spin echo (TSE) sequence with the following imaging parameters: 50 axial slices with 2-mm slice thickness, no interslice gap, TR: 10 seconds, bandwidth: 100 Hz/pixel, 180° refocusing pulses, matrix size 192×132 (readout×phase encoding), field of view (FOV) 240×165 mm 2 , isotropic in-plane resolution 1.25 mm, turbo factor (number of spin echoes per excitation): 11, delay between subsequent echoes: 17.1 ms. For quantitative T2-mapping, five TSE data sets were acquired with identical parameters but different TE values (17, 86, 103, 120, 188 ms).…”

“…T2’ has been shown to be decreased in perfusion-restricted brain regions in chronic cerebral hypoperfusion [10] as well as in acute ischemic stroke [11, 12] which was interpreted as a sign of increased OEF. However, a decrease of T2’, suggesting a shift in the relation between oxygenated and deoxygenated Hb in favor of deoxygenated Hb, can be the consequence of a decreased O 2 supply at constant O 2 demand, or can result from an increased O 2 consumption and constant supply in case of neuronal activation.…”

Mapping of cerebral metabolic rate of oxygen using dynamic susceptibility contrast and blood oxygen level dependent MR imaging in acute ischemic stroke

“…In both tissue areas, impaired perfusion causes not only reduced supply of oxygenated hemoglobin but also slowed removal of deoxyhemoglobin [7]. Therefore, since OEF is increased within tissue at risk of infarction as demonstrated with PET [19], the accumulation of deoxyhemoglobin is expected to increase accordingly, as detected in previous studies [7,12].…”

“…In both tissue areas, impaired perfusion causes not only reduced supply of oxygenated hemoglobin but also slowed removal of deoxyhemoglobin [7]. Therefore, since OEF is increased within tissue at risk of infarction as demonstrated with PET [19], the accumulation of deoxyhemoglobin is expected to increase accordingly, as detected in previous studies [7,12]. Bauer et al showed significant differences in T2′ values between perfusion-impaired, diffusion-restricted, and healthy tissue in a smaller sample size; yet, T2′-measurements demonstrated the highest values within the infarct core, which is not expected to contain tissue with the highest oxygen extraction fraction in acute stroke, as proven by PET previously [7].…”

“…Area with apparent diffusion coefficient restriction (area with reduced ADC values after setting a threshold of <550×10 −6 mm 2 /s) as described previously [7]. 2.…”