Assessment Of Penumbra Research Articles

Artificial intelligence software for assessing brain ischemic penumbra/core infarction on computed tomography perfusion: A real-world accuracy study.

With the increasingly extensive application of artificial intelligence (AI) in medical systems, the accuracy of AI in medical diagnosis in the real world deserves attention and objective evaluation. To investigate the accuracy of AI diagnostic software (Shukun) in assessing ischemic penumbra/core infarction in acute ischemic stroke patients due to large vessel occlusion. From November 2021 to March 2022, consecutive acute stroke patients with large vessel occlusion who underwent mechanical thrombectomy (MT) post-Shukun AI penumbra assessment were included. Computed tomography angiography (CTA) and perfusion exams were analyzed by AI, reviewed by senior neurointerventional experts. In the case of divergences among the three experts, discussions were held to reach a final conclusion. When the results of AI were inconsistent with the neurointerventional experts' diagnosis, the diagnosis by AI was considered inaccurate. A total of 22 patients were included in the study. The vascular recanalization rate was 90.9%, and 63.6% of patients had modified Rankin scale scores of 0-2 at the 3-month follow-up. The computed tomography (CT) perfusion diagnosis by Shukun (AI) was confirmed to be invalid in 3 patients (inaccuracy rate: 13.6%). AI (Shukun) has limits in assessing ischemic penumbra. Integrating clinical and imaging data (CT, CTA, and even magnetic resonance imaging) is crucial for MT decision-making.

Assessment of computed tomography perfusion software in predicting spatial location and volume of infarct in acute ischemic stroke patients: a comparison of Sphere, Vitrea, and RAPID

BackgroundCT perfusion (CTP) infarct and penumbra estimations determine the eligibility of patients with acute ischemic stroke (AIS) for endovascular intervention. This study aimed to determine volumetric and spatial agreement of...

Penumbra pattern assessment in acute stroke patients: comparison of quantitative and non-quantitative methods in whole brain CT perfusion.

Background And PurposeWhile penumbra assessment has become an important part of the clinical decision making for acute stroke patients, there is a lack of studies measuring the reliability and reproducibility of defined assessment techniques in the clinical setting. Our aim was to determine reliability and reproducibility of different types of three-dimensional penumbra assessment methods in stroke patients who underwent whole brain CT perfusion imaging (WB-CTP).Materials And MethodsWe included 29 patients with a confirmed MCA infarction who underwent initial WB-CTP with a scan coverage of 100 mm in the z-axis. Two blinded and experienced readers assessed the flow-volume-mismatch twice and in two quantitative ways: Performing a volumetric mismatch analysis using OsiriX imaging software (MMVOL) and visual estimation of mismatch (MMEST). Complementarily, the semiquantitative Alberta Stroke Programme Early CT Score for CT perfusion was used to define mismatch (MMASPECTS). A favorable penumbral pattern was defined by a mismatch of ≥30% in combination with a cerebral blood flow deficit of ≤90 ml and an MMASPECTS score of ≥1, respectively. Inter- and intrareader agreement was determined by Kappa-values and ICCs.ResultsOverall, MMVOL showed considerably higher inter-/intrareader agreement (ICCs: 0.751/0.843) compared to MMEST (0.292/0.749). In the subgroup of large (≥50 mL) perfusion deficits, inter- and intrareader agreement of MMVOL was excellent (ICCs: 0.961/0.942), while MMEST interreader agreement was poor (0.415) and intrareader agreement was good (0.919). With respect to penumbra classification, MMVOL showed the highest agreement (interreader agreement: 25 agreements/4 non-agreements/κ: 0.595; intrareader agreement 27/2/0.833), followed by MMEST (22/7/0.471; 23/6/0.577), and MMASPECTS (18/11/0.133; 21/8/0.340).ConclusionThe evaluated approach of volumetric mismatch assessment is superior to pure visual and ASPECTS penumbra pattern assessment in WB-CTP and helps to precisely judge the extent of 3-dimensional mismatch in acute stroke patients.

Detection of ischemic penumbra using combined perfusion and T2* oxygen challenge imaging.

BackgroundAcute ischemic stroke is common and disabling, but there remains a paucity of acute treatment options and available treatment (thrombolysis) is underutilized. Advanced brain imaging, designed to identify viable hypoperfused tissue (penumbra), could target treatment to a wider population. Existing magnetic resonance imaging and computed tomography-based technologies are not widely used pending validation in ongoing clinical trials. T2* oxygen challenge magnetic resonance imaging, by providing a more direct readout of tissue viability, has the potential to identify more patients likely to benefit from thrombolysis – irrespective of time from stroke onset – and patients within and beyond the 4·5 h thrombolysis treatment window who are unlikely to benefit and are at an increased risk of hemorrhage.AimsThis study employs serial multimodal imaging and voxel-based analysis to develop optimal data processing for T2* oxygen challenge penumbra assessment. Tissue in the ischemic hemisphere is compartmentalized into penumbra, ischemic core, or normal using T2* oxygen challenge (single threshold) or T2* oxygen challenge plus cerebral blood flow (dual threshold) data. Penumbra defined by perfusion imaging/apparent diffusion coefficient mismatch (dual threshold) is included for comparison.MethodsPermanent middle cerebral artery occlusion was induced in male Sprague-Dawley rats (n = 6) prior to serial multimodal imaging: T2* oxygen challenge, diffusion-weighted and perfusion imaging (cerebral blood flow using arterial spin labeling).ResultsAcross the different methods evaluated, T2* oxygen challenge combined with perfusion imaging most closely predicted 24 h infarct volume. Penumbra volume declined from one to four-hours post-stroke: mean ± SD, 77 ± 44 to 49 ± 37 mm3 (single T2* oxygen challenge-based threshold); 55 ± 41 to 37 ± 12 mm3 (dual T2* oxygen challenge/cerebral blood flow); 84 ± 64 to 42 ± 18 mm3 (dual cerebral blood flow/apparent diffusion coefficient), as ischemic core grew: 155 ± 37 to 211 ± 36 mm3 (single apparent diffusion coefficient threshold); 178 ± 56 to 205 ± 33 mm3 (dual T2* oxygen challenge/cerebral blood flow); 139 ± 30 to 168 ± 38 mm3 (dual cerebral blood flow/apparent diffusion coefficient). There was evidence of further lesion growth beyond four-hours (T2-defined edema-corrected infarct, 231 ± 19 mm3).ConclusionsIn conclusion, T2* oxygen challenge combined with perfusion imaging has advantages over alternative magnetic resonance imaging techniques for penumbra detection by providing serial assessment of available penumbra based on tissue viability.

Asymmetrically hypointense veins on T2*w imaging and susceptibility-weighted imaging in ischemic stroke

To review the literature on the assessment of venous vessels to estimate the penumbra on T2*w imaging and susceptibility-weighted imaging (SWI). Literature that reported on the assessment of penumbra by T2*w imaging or SWI and used a validation method was included. PubMed and relevant stroke and magnetic resonance imaging (MRI) related conference abstracts were searched. Abstracts that had overlapping content with full text articles were excluded. The retrieved literature was scanned for further relevant references. Only clinical literature published in English was considered, patients with Moya-Moya syndrome were disregarded. Data is given as cumulative absolute and relative values, ranges are given where appropriate. Forty-three publications including 1145 patients could be identified. T2*w imaging was used in 16 publications (627 patients), SWI in 26 publications (453 patients). Only one publication used both (65 patients). The cumulative presence of hypointense vessel sign was 54% (range 32%-100%) for T2* (668 patients) and 81% (range 34%-100%) for SWI (334 patients). There was rare mentioning of interrater agreement (6 publications, 210 patients) and reliability (1 publication, 20 patients) but the numbers reported ranged from good to excellent. In most publications (n = 22) perfusion MRI was used as a validation method (617 patients). More patients were scanned in the subacute than in the acute phase (596 patients vs 320 patients). Clinical outcome was reported in 13 publications (521 patients) but was not consistent. The low presence of vessels signs on T2*w imaging makes SWI much more promising. More research is needed to obtain formal validation and quantification.

Using Pimonidazole Delineated Penumbra To Improve Translational Research on Acute Stroke Neuroprotection (SC02.005)

Objective: To improve the translation of animal model findings on stroke neuroprotection into clinical practice, we used pimonidazole (HypoxyProbe) to delineate the penumbra to study its associated biomarkers. In addition we focused on markers within 6 hours of stroke onset as this time period may represent the best window to protect the penumbra from evolving into irreversible damage of ischemic core. Background Translation of animal stroke research has not been successful. For most of the published reports, the outcome measures have been infarct volume or behavioral measures. Perhaps an outcome reflecting biomarkers of penumbra would be more relevant. In addition, there is increased use of penumbra assessment in clinical settings; we need a better understanding of penumbra. Design/Methods: We used twenty Sprague-Dawley rats ages 5 to 24 months for our study. All animal procedures were approved by the Purdue Animal Care and Use Committee. We used an intraluminal middle cerebral artery occlusion (MCAo) model for stroke induction. Occlusion was maintained without reperfusion for 5 hours. Results: Immunostained formalin-fixed sections with antibodies against adducts of reduced pimonidazole demonstrated the location of penumbra with clear border in each animal. The location, morphology, and size of penumbra of each animal varied significantly even with identical MCAo procedures. This variability is similar to what we have observed in clinical stroke research. Pimonidazole stained mostly cytoplasm of neurons and glia with neuropil staining more towards the boundaries of the penumbra. Within the penumbra, we noted peri-nuclear condensation of hypoxia-inducible factor 1 and increase in methionine sulfoxide expression; with q-PCR, we noted a significant increase in heat-shock protein 70 gene expression but not that of methionine sulfoxide reductase. Conclusions: Pimonidazole delineation of penumbra offers a method to study molecular events within the penumbra precisely and to assess early response to putative therapeutic agents in a more clinically relevant fashion. Supported by: Lutheran Foundation. Disclosure: Dr. Chang has nothing to disclose. Dr. Hong-Goka has nothing to disclose.

Novel MRI detection of the ischemic penumbra: direct assessment of metabolic integrity

We describe a novel magnetic resonance imaging technique to directly assess the metabolic integrity of penumbral tissue following stroke. For ischemically stressed tissue to be salvageable, it has to be capable of recovering aerobic metabolism (in place of anaerobic metabolism) on reperfusion. We probed ischemic brain tissue by altering the rate of oxygen delivery using a challenge of 100% oxygen ventilation. Any change from anaerobic to aerobic metabolism should alter the rate of lactate production and hence, levels of tissue lactate. Stroke was induced by permanent middle cerebral artery occlusion in rats. In Series 1 (n = 6), changes in tissue lactate during and following 100% oxygen challenge were monitored using (1)H magnetic resonance spectroscopy (MRS). Diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) were used to locate MRS voxels within the ischemic core, the homotopic contralateral striatum and within PWI/DWI mismatch (i.e. presumed penumbra). After 20 min of oxygen, lactate signal change was -16.1 ± 8.8% (mean ± SD) in PWI/DWI mismatch, +2.8 ± 5.1% in the ischemic core, and -0.6 ± 7.6% in the contralateral striatum. Return to air ventilation for 20 min resulted in a reversal, with lactate increasing by 46 ± 25.3% in the PWI/DWI mismatch, 6.6 ± 6.2% in the ischemic core, and -5 ± 11.4% in the contralateral striatum. In Series 2 (n = 6), a novel form of spectroscopic imaging was used to acquire lactate change maps to spatially identify regions of lactate change within the ischemic brain. This technique has potential clinical utility by identifying tissue that displays anaerobic metabolism capable of recovering aerobic metabolism when oxygen delivery is increased, which could provide a more precise assessment of penumbra.

Potential use of Oxygen as a Metabolic Biosensor in Combination with T2*-Weighted MRI to Define the Ischemic Penumbra

We describe a novel magnetic resonance imaging technique for detecting metabolism indirectly through changes in oxyhemoglobin:deoxyhemoglobin ratios and T2(*) signal change during 'oxygen challenge' (OC, 5 mins 100% O(2)). During OC, T2(*) increase reflects O(2) binding to deoxyhemoglobin, which is formed when metabolizing tissues take up oxygen. Here OC has been applied to identify tissue metabolism within the ischemic brain. Permanent middle cerebral artery occlusion was induced in rats. In series 1 scanning (n=5), diffusion-weighted imaging (DWI) was performed, followed by echo-planar T2(*) acquired during OC and perfusion-weighted imaging (PWI, arterial spin labeling). Oxygen challenge induced a T2(*) signal increase of 1.8%, 3.7%, and 0.24% in the contralateral cortex, ipsilateral cortex within the PWI/DWI mismatch zone, and ischemic core, respectively. T2(*) and apparent diffusion coefficient (ADC) map coregistration revealed that the T2(*) signal increase extended into the ADC lesion (3.4%). In series 2 (n=5), FLASH T2(*) and ADC maps coregistered with histology revealed a T2(*) signal increase of 4.9% in the histologically defined border zone (55% normal neuronal morphology, located within the ADC lesion boundary) compared with a 0.7% increase in the cortical ischemic core (92% neuronal ischemic cell change, core ADC lesion). Oxygen challenge has potential clinical utility and, by distinguishing metabolically active and inactive tissues within hypoperfused regions, could provide a more precise assessment of penumbra.