"In some cases, follow-up was early and fell during a period when temporary reversal is now recognized to be common (Chalela et al, 2004). Other studies used delayed follow-up without accounting for infarct atrophy (Ritzl et al, 2004; Rivers et al, 2006). The imaging modality used for follow-up is also critical as ADC normalizes after a few days and infarct volume using T2 images varies depending on the windowing employed. "
[Show abstract][Hide abstract] ABSTRACT: Diffusion-weighted imaging (DWI) is commonly used to assess irreversibly infarcted tissue but its accuracy is challenged by reports of diffusion lesion reversal (DLR). We investigated the frequency and implications for mismatch classification of DLR using imaging from the EPITHET (Echoplanar Imaging Thrombolytic Evaluation Trial) and DEFUSE (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution) studies. In 119 patients (83 treated with IV tissue plasminogen activator), follow-up images were coregistered to acute diffusion images and the lesions manually outlined to their maximal visual extent in diffusion space. Diffusion lesion reversal was defined as voxels of acute diffusion lesion that corresponded to normal brain at follow-up (i.e., final infarct, leukoaraiosis, and cerebrospinal fluid (CSF) voxels were excluded from consideration). The appearance of DLR was visually checked for artifacts, the volume calculated, and the impact of adjusting baseline diffusion lesion volume for DLR volume on perfusion-diffusion mismatch analyzed. Median DLR volume reduced from 4.4 to 1.5 mL after excluding CSF/leukoaraiosis. Visual inspection verified 8/119 (6.7%) with true DLR, median volume 2.33 mL. Subtracting DLR from acute diffusion volume altered perfusion-diffusion mismatch (T(max)>6 seconds, ratio>1.2) in 3/119 (2.5%) patients. Diffusion lesion reversal between baseline and 3 to 6 hours DWI was also uncommon (7/65, 11%) and often transient. Clinically relevant DLR is uncommon and rarely alters perfusion-diffusion mismatch. The acute diffusion lesion is generally a reliable signature of the infarct core.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 07/2011; 32(1):50-6. DOI:10.1038/jcbfm.2011.102 · 5.41 Impact Factor
"This reversible oedema can be either due to tumour compression that was present before resection, similar to peritumoral oedema as observed in some meningiomas for instance, or due to surgical manipulation of the tissue surrounding the resection cavity. Furthermore, the diffusion restricted areas may evolve in ischaemic (non-tumoral) tissue with volume involution over weeks to months similar to spontaneous infarction . "
[Show abstract][Hide abstract] ABSTRACT: Standards for residual tumour measurement after resection of gliomas with no or minimal enhancement have not yet been established. In this study residual volumes on early and late postoperative T2-/FLAIR-weighted MRI are compared.
A retrospective cohort included 58 consecutive glioma patients with no or minimal preoperative gadolinium enhancement. Inclusion criteria were first-time resection between 2007 and 2009 with a T2-/FLAIR-based target volume and availability of preoperative, early (<48 h) and late (1-7 months) postoperative MRI. The volumes of non-enhancing T2/FLAIR tissue and diffusion restriction areas were measured.
Residual tumour volumes were 22% smaller on late postoperative compared with early postoperative T2-weighted MRI and 49% smaller for FLAIR-weighted imaging. Postoperative restricted diffusion volume correlated with the difference between early and late postoperative FLAIR volumes and with the difference between T2 and FLAIR volumes on early postoperative MRI.
We observed a systematic and substantial overestimation of residual non-enhancing volume on MRI within 48 h of resection compared with months postoperatively, in particular for FLAIR imaging. Resection-induced ischaemia contributes to this overestimation, as may other operative effects. This indicates that early postoperative MRI is less reliable to determine the extent of non-enhancing residual glioma and restricted diffusion volumes are imperative.
European Radiology 02/2011; 21(7):1526-34. DOI:10.1007/s00330-011-2081-y · 4.01 Impact Factor
"Using not only morphologic, but also functional MRI tools, it is possible to verify successful induction of stroke by DWI (van Everdingen et al, 1998) at an early time point. Brain MR imaging of sheep indicated diffusion disturbances, which in their extent, localization, and time-dependency during a 42-day-timecourse are comparable to those observed in human patients (Förschler et al, 2007, who for comparison referred to Ritzl et al, 2004). Magnetic resonance imaging is, furthermore, able to depict infarct size and associated vessel occlusion type in vivo (Higashida et al, 2003). "
[Show abstract][Hide abstract] ABSTRACT: As effective stroke treatment by thrombolysis is bound to a narrow time window excluding most patients, numerous experimental treatment strategies have been developed to gain new options for stroke treatment. However, all approaches using neuroprotective agents that have been successfully evaluated in rodents have subsequently failed in clinical trials. Existing large animal models are of significant scientific value, but sometimes limited by ethical drawbacks and mostly do not allow for long-term observation. In this study, we are introducing a simple, but reliable stroke model using permanent middle cerebral artery occlusion in sheep. This model allows for control of ischemic lesion size and subsequent neurofunctional impact, and it is monitored by behavioral phenotyping, magnetic resonance imaging, and positron emission tomography. Neuropathologic and (immuno)histologic investigations showed typical ischemic lesion patterns whereas commercially available antibodies against vascular, neuronal, astroglial, and microglial antigens were feasible for ovine brain specimens. Based on absent mortality in this study and uncomplicated species-appropriate housing, long-term studies can be realized with comparatively low expenditures. This model could be used as an alternative to existing large animal models, especially for longitudinal analyses of the safety and therapeutic impact of novel therapies in the field of translational stroke research.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 08/2008; 28(12):1951-64. DOI:10.1038/jcbfm.2008.89 · 5.41 Impact Factor
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