Vascular and Tissue Changes of Magnetic Susceptibility in the Mouse Brain After Transient Cerebral Ischemia

Abstract

Quantitative susceptibility mapping (QSM) has been recently introduced as a novel MRI post-processing technique of gradient recalled echo (GRE) data. QSM is useful in depicting both brain anatomy and for detecting abnormalities. Its utility in the context of ischemic stroke has, however, not been extensively characterized so far. In this study, we explored the potential of QSM to characterize vascular and tissue changes in the transient middle cerebral artery occlusion (tMCAO) mouse model of cerebral ischemia. We acquired GRE data of mice brains at different time points after tMCAO, from which we computed QSM and MR frequency maps, and compared these maps with diffusion imaging and multi-slice multi-echo imaging data acquired in the same animals. Prominent vessels with increased magnetic susceptibility were visible surrounding the lesion on both frequency and magnetic susceptibility maps at all time points (mostly visible at > 12 h after reperfusion). Immunohistochemistry revealed the presence of compressed capillaries and dilated larger vessels, suggesting that the appearance of prominent vessels after reestablishment of reperfusion may serve compensatory purposes. In addition, on both contrast maps, tissue regions of decreased magnetic susceptibility were observed at 24 and 48 h after reperfusion that were distinctly different from the lesions seen on maps of the apparent diffusion coefficient and T 2 relaxation time constant. Since QSM can be extracted as an add-on from GRE data and thus requires no additional acquisition time in the course of acute stroke MRI examination, it may provide unique and complementary information during the course of acute stroke MRI examinations.

Quantitative susceptibility mapping (QSM) with an extended physical model for MRI frequency contrast in the brain: a proof‐of‐concept of quantitative susceptibility and residual (QUASAR) mapping

“…Susceptibility map reconstruction issues similar to those observed in the present work with the traditional physical model (Figures and ) may be found also in published rodent work by other authors. For example, susceptibility contrast was absent from the frontal horn of the lateral ventricles on all in vivo images presented by O'Callaghan et al (Figures and therein), Ziser et al (Figures and therein) and Vaas et al (Figure therein), as well as studies to which we have contributed …”

SWI and phase imaging reveal intracranial calcifications in the P301L mouse model of human tauopathy

“…Quantitative susceptibility maps (QSM) represent an intrinsic tissue property and are independent of data acquisition parameters and should reflect the actual spatial extent of lesions. The feasibility of QSM for the depiction of the cerebral lesion has been shown in a number of studies [8,[34][35][36]. However, in contrast to QSM post-processing, procedures for SWI are established on clinical scanners and can be readily applied for the detection of calcifications and other brain lesions.…”

Rosiglitazone ameliorates tissue plasminogen activator‐induced brain hemorrhage after stroke

“…Early reestablishment of cerebral blood flow is crucial for the functional recovery of acute ischemic stroke patients. 28,29 The latest guideline of acute stroke treatment still recommends tPA as the first-line of effective thrombolytic treatment to achieve early reperfusion of the ischemic brain. 2,3,30 However, the current therapeutic window of 4.5 hours after the onset of stroke remarkably limits the clinical use of tPA thrombolysis.…”