Metabolic Counterpart of Decreased Apparent Diffusion Coefficient During Hyperacute Ischemic Stroke

Zhou

J Cereb Blood Flow Metab

et al. 2006

301

342

The classic definition of the ischemic penumbra is a hypoperfused region in which metabolism is impaired, but still sufficient to maintain cellular polarization. Perfusion-and diffusion-weighted MRI (PWI, DWI) can identify regions of reduced perfusion and cellular depolarization, respectively, but it often remains unclear whether a PWI-DWI mismatch corresponds to benign oligemia or a true penumbra. We hypothesized that pH-weighted MRI (pHWI) can subdivide the PWI-DWI mismatch into these regions. Twenty-one rats underwent permanent middle cerebral artery occlusion and ischemic evolution over the first 3.5 h post-occlusion was studied using multiparametric MRI. End point was the stroke area defined by T 2 -hyperintensity at 24 h. In the acute phase, areas of reduced pH were always larger than or equal to DWI deficits and smaller than or equal to PWI deficits. Group analysis showed that pHWI deficits during this phase coincided with the resulting infarct area at endpoint. Final infarcts were smaller than PWI deficits (range 65% to 90%, depending on the severity of the occlusion) and much larger than acute DWI deficits. These data suggest that the outer boundary of the hypoperfused area showing a decrease in pH without DWI abnormality may correspond to the outer boundary of the ischemic penumbra, while the hypoperfused region at normal pH may correspond to benign oligemia. These first results show that pHWI can provide information complementary to PWI and DWI in the delineation of ischemic tissue.

Section: Discussionmentioning

confidence: 88%

Detection of the Ischemic Penumbra Using pH-Weighted MRI

Zhou

J Cereb Blood Flow Metab

et al. 2006

301

342

“…All personal identifiers were removed from the data spreadsheets such that there were no links between the study sequence folders and the individual patients as shown in Figure 1. Each radiologist documented his results into positive or negative restricted diffusion for infarction via analysis of restricted DWI & ADC mapping, blooming artifact seen on gradient sequencing, perfusion deficit as determined by analysis of cerebral blood flow, cerebral blood volume, and mean transit time [38][39][40][41][42][43]. In addition, other CNS pathologic etiologies were assayed including: intracranial hemorrhage, spinal cord compression, fracture, spinal canal stenosis, neural foraminal stenoses, disk herniation, and annular fissuring [24,[44][45][46][47].…”

Section: Methodsmentioning

confidence: 99%

Intra and Inter-Observer Reliability of Mobile Tablet PACS Viewer System vs. Standard PACS Viewing Station-Diagnosis of Acute Central Nervous System Events

Bhatia¹,

Patel²,

Pantol³

et al. 2013

OJRad

Background and Purpose: The display resolution of the Apple iPad® is 1024 × 768 pixels, which is greater than that required for generating the typical CT or MRI images. The purpose of this study is to determine if specific CT and MR sequences can be interpreted accurately on mobile device/PACS software platforms when compared to a traditional stationary high resolution monitor/PACS radiological workstation. If so, this allows radiologists to provide comparable interpretation as if they were onsite at an imaging center or hospital. Materials and Methods: This study is an investigator initiated, single site, retrospective, nonrandomized, IRB approved study. Five radiologists were included in this study. Each independently interpreted specific CT and MR sequences on traditional high-resolution LCD monitors via eFilm® software as well as an iPad® mobile device using Osirix® software program. Repeat interpretations were performed, with 4 weeks minimum interval between interpretations of each patient. This investigation included: 50 patients with CTA perfusion imaging, 50 patients with MRI of the brain, and 50 patients with MRI of the spine, which were image study orders generated through emergency room requests. Subsequently, interpretive results of each radiologist for each patient were statistically compared to evaluate for intra-observer and inter-observer reliability. Results: The parameters set within the CTA perfusion brain studies demonstrated excellent intra-observer variability. All of the parameters within the MRI brain studies demonstrated excellent intra-observer variability with a Cohen's kappa value > 0.75. The Cohen's kappa values for the board certified neuroradiologist demonstrated excellent variability for all parameters; the resident radiologists had good variability, with a majority of kappa values near 0.75. Conclusions: The data and statistical analysis demonstrated that portable mobile devices such as the Apple iPad® can display adequate resolution of CT and MRI sequences to accurately diagnose acute central nervous system injuries and other non-acute pathology.

“…In clinical cases of proximal MCA occlusion, Nicoli reported that within 7 hours from onset, MRSI could indicate a large heterogeneity in NAA concentration in ischemic areas showing even the lowest ADC values. 79 Moreover, some reports suggest a wide range of NAA concentrations, from 40 to more than 100% of the normal range, in acute-stage ischemic lesions having an unperturbed DWI. 59,80 Although it is difficult at present to ascribe a threshold NAA concentration for making an accurate tissue prognosis, i.e., whether it will infarct or be salvageable, during the acute stages of ischemia, it has been suggested that salvageable areas might be characterized by the presence of lactate with no or only subtle NAA attenuation.…”

Section: Association and Dissociation Between Naa Attenuation And Dwimentioning

confidence: 99%

N-acetylaspartate Decrease in Acute Stage of Ischemic Stroke:A Perspective from Experimental and Clinical Studies

et al. 2015

N-acetylaspartate (NAA) appears in a prominent peak in proton magnetic resonance spectroscopy ( 1 H-MRS) of the brain. Exhibition by NAA of time-dependent attenuation that reflects energy metabolism during the acute stage of cerebral ischemia makes this metabolite a unique biomarker for assessing ischemic stroke. Although magnetic resonance (MR) imaging is a powerful technique for inspecting the pathological changes that occur during ischemic stroke, biomarkers that directly reflect the drastic metabolic changes associated with acute-stage ischemia are strongly warranted for appropriate therapeutic decision-making in daily clinical settings. In this review, we provide a brief overview of NAA metabolism and focus on the use of attenuation in NAA as a means for assessing the pathophysiological changes that occur during the acute stage of ischemic stroke.