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Magnetic resonance perfusion (MRP) and computed tomographic perfusion (CTP) are being increasingly applied in acute stroke trials and clinical practice, yet the comparability of their perfusion values is not well validated. The aim of this study was to validate the comparability of CTP and MRP measures.

Arterial spin labeling (ASL) is a perfusion magnetic resonance imaging (MRI) technique that does not require contrast administration and thus may be more practical in hyperacute stroke than susceptibility-weighted bolus-tracking perfusion-weighted imaging (PWI). However, a threshold for ASL measurement of the ischemic penumbra needs to be determined.

Intracerebral hemorrhage is a serious potential complication of stroke thrombolysis. We investigated the optimal computed tomography perfusion (CTP) parameter to predict cerebral parenchymal hematoma (PH) in acute ischemic stroke.

Background:Electromagnetic imaging (EMI) is an emerging technology that transmits low energy electromagnetic waves from a ring of transceivers around the head, modified as they pass through abnormal tissue, providing unique signatures for brain pathology. It promises to provide portable, non-ionizing, rapid neuroimaging for prehospital and bedside evaluation of stroke, based on the dielectric properties of the tissue. We aimed to assess the clinical utility of EMI in stroke diagnosis in a pilot study.Methods:In a prospective, observational, open, non-interventional pilot study, patients with imaging-proven ischemic (IS) or haemorrhagic stroke (ICH) within the preceding 48 hours were recruited. Using the EMVision scanner, EMI was performed within 1-24 hours of diagnostic CT or MRI. Images were obtained by processing signals from encircling transceiver antennae contained in an instrumented 18 kg helmet which emit and detect low energy non-ionising signals in the microwave frequency spectrum (0.5-2.0 GHz). Localisation was assessed by determining whether fusion images resulted in target detection in the same quadrant as comparable CT or MRI. Electromagnetic (EM) images were reconstructed by creating maps of the EM wave scattering arising from contrast in electrical parameters between IS or ICH lesions and normal brain. A blinded clinician assessed agreement between regional abnormalities on EMI and CT or MRI scans. Algorithms for distinction between IS and ICH were based on differences in EM transmission, reflection and scattering through brain tissue.Results:Thirty patients were studied, 21 IS and 9 ICH. Mean age was 66.7 years (range 37-87), 57% were female. Mean NIHSS at presentation was 5. Mean time to routine imaging was 5.5 hrs (range 1-48) and to EMI 24 hrs (range 6-60). Nineteen patients (63%) had only CT performed; 11 (37%) had both CT and MRI. EMI differentiated ICH from IS with 93% accuracy and localised the stroke to the correct brain quadrant with 87% accuracy.Conclusion:In this early validation pilot study we show the ability to distinguish between IS and ICH and stroke location within a given brain quadrant. Further developments may produce a valuable imaging tool to assist in prehospital and bedside stroke diagnosis and management.

Introduction:Patients with stroke in rural and remote areas have limited access to time-critical stroke care and have worse outcomes. Mobile stroke units (MSUs) are increasingly used worldwide to deliver prehospital stroke care, improving treatment times. However, current brain scanners are too large, heavy, and costly to be used in standard ambulances to access rural regions. The Micro-X solution is a fixed gantry computed tomography (CT) device, using unique cold-cathode technology, in which microscopic carbon nanotubes emit electrons instantaneously when voltage is applied, without heat production, instead of the heated tungsten filament used in conventional CT. This novel technology reduces size and weight, enabling development of a novel CT scanner weighing under 50 kg, a ten-fold reduction compared to the scanner currently used in most MSUs.Methods:In partnership with the Australian Stroke Alliance, Micro-X is developing a novel lightweight brain scanner for use in ambulances. Based on data from an early prototype cadaver study, we are undertaking further validation studies, including a two-part preclinical study: (1) phantom study using 4 phantoms (CATphan, anthropomorphic, Jaszczak SPECT, and Nuclear Medicine); and (2) subsequent cadaver study, scanning cadavers within 24h of death, compared to standard CT.Results:The early prototype cadaver study demonstrated feasibility, including identification of lateral and third ventricles when compared to concurrent CT. Through technical improvements in hardware and software, including improved scanner geometry and algorithm development, the planned phantom study will provide data on contrast resolution, quantitative spatial resolution, identification of anatomical structures, and haemorrhage detection compared with conventional CT. The subsequent cadaver study will provide further validation on anatomy identification and artifact reduction and ensure whole-brain coverage.Conclusion:Preclinical evaluation of this novel lightweight technology compared with conventional CT will provide technical assessment and image validation. This will provide diagnostic confidence to perform pilot in-vivo studies, with the potential to revolutionise prehospital stroke care.

Background:The efficacy of endovascular thrombectomy (EVT) in M2 occlusions is uncertain.Methods:In a pooled patient level analysis of the prospective multicenter cohort study of imaging selection (SELECT) and the INternationalStroke Perfusion ImagingREgistry(INSPIRE) EVT outcomes were compared to medical management (MM) in M2 occlusions. Further, we assessed for potential treatment benefit in patients with higher stroke severity (NIHSS). The primary outcome was excellent outcome (mRS 0-1).Results:387 patients with isolated M2 occlusion (EVT 112, MM 275) met the inclusion criteria. Baseline NIHSS median (IQR) (EVT: 13 (9-19), MM: 10 (6-15), p<0.001) and infarct volume rCBF<30% (EVT 11 (4-24) vs MM: 8 (3-16), P=0.11). EVT was associated with a trend towards higher rates of excellent outcomes (48% vs 44%, aOR:2.80, 95% CI=0.95-8.25, p=0.061) with a shift towards better mRS outcomes (adj cOR: 2.57, 95% CI=1.11-5.94, p=0.028), and a reduction of neurological worsening (27% vs 47%, p<0.001) and numerically lower rates of sICH (4.5% vs 6.5%, p=0.43), and mortality (4.5% vs 9.5%, p=0.10). Assessing outcomes in NIHSS strata; there was no significant difference in excellent outcomes rates in patients with NIHSS ≤10 (EVT 62% vs MM 57%, aOR=2.18, 95% CI=0.30-15.73, p=0.44). In contrast, patients with NIHSS>10 had a trend towards higher excellent outcome rates outcomes with EVT (43%) vs MM (27%), aOR=3.11, 95% CI=0.81-11.95, p=0.098) as shown in figure 1.Conclusion:EVT may result in better rates of excellent outcomes in isolated M2 occlusions, especially those with more severe strokes who are more likely to have worse outcomes without emergent reperfusion.