Thomas Lindner

Comparison of Perfusion CT Software to Predict the Final Infarct Volume After Thrombectomy

Background and Purpose— Computed tomographic perfusion represents an interesting physiological imaging modality to select patients for reperfusion therapy in acute ischemic stroke. The purpose of our study was to determine the accuracy of different commercial perfusion CT software packages (Philips (A), Siemens (B), and RAPID (C)) to predict the final infarct volume (FIV) after mechanical thrombectomy. Methods— Single-institutional computed tomographic perfusion data from 147 mechanically recanalized acute ischemic stroke patients were postprocessed. Ischemic core and FIV were compared about thrombolysis in cerebral infarction (TICI) score and time interval to reperfusion. FIV was measured at follow-up imaging between days 1 and 8 after stroke. Results— In 118 successfully recanalized patients (TICI 2b/3), a moderately to strongly positive correlation was observed between ischemic core and FIV. The highest accuracy and best correlation are shown in early and fully recanalized patients (Pearson r for A=0.42, B=0.64, and C=0.83; P<0.001). Bland–Altman plots and boxplots demonstrate smaller ranges in package C than in A and B. Significant differences were found between the packages about over- and underestimation of the ischemic core. Package A, compared with B and C, estimated more than twice as many patients with a malignant stroke profile (P<0.001). Package C best predicted hypoperfusion volume in nonsuccessfully recanalized patients. Conclusions— Our study demonstrates best accuracy and approximation between the results of a fully automated software (RAPID) and FIV, especially in early and fully recanalized patients. Furthermore, this software package overestimated the FIV to a significantly lower degree and estimated a malignant mismatch profile less often than other software.

Superselective pseudo-continuous arterial spin labeling angiography

PURPOSE To evaluate the utility of a novel non-contrast enhanced, vessel-selective magnetic resonance angiography (MRA) approach based on superselective pseudo-continuous arterial spin labeling (ASL) for the morphologic assessment of intracranial arteries when compared to a clinically used time-of-flight (TOF) MRA. MATERIALS AND METHODS Three sets of selective ASL angiographies (right and left internal carotid artery, basilar artery) as well as one TOF data set were obtained from each of the five volunteers included in this study on a clinical 1.5T system. The depiction of arterial segments as well as their delineation was evaluated and independently analyzed by two radiologists. Additionally, the ASL angiography approach was performed in two patients suffering from arterio-venous malformations (AVM) in order to illustrate potential applications in a clinical setting. RESULTS In both angiography techniques, intracranial arteries and their segments (distal branches up to A5 segments of the anterior cerebral arteries, M8 segments of the middle cerebral arteries, and P5 segments of the posterior cerebral arteries) were continuously depicted with excellent inter-reader agreement (κ>0.81). In AVM patients, reconstructed images of the TOF angiography presented similar information about the size and shape of the AVM as did superselective ASL angiography. In addition, the acquired ASL angiograms of selected vessels allowed assessing the blood supply of individually labeled arteries to the AVM which could also be confirmed by digital subtraction angiography. CONCLUSION Superselective ASL angiography makes it possible to visualize arterial trees of selected vessels, thereby, providing information about the macrovascular blood supply and flow territories of intracranial arteries. Similar image quality is achieved when compared to clinically used TOF angiography with respect to the identification and delineation of arterial segments. Initial application of superselective ASL angiography in two patients with AVMs demonstrates the ability to gather additional important information about feeding vessels and blood supply.

3D time-resolved vessel-selective angiography based on pseudo-continuous arterial spin labeling.

Angiographic imaging is an important diagnostic tool for the assessment of the intracranial arterial status. Using arterial spin labeling (ASL) techniques, it is possible to visualize the arteries without the administration of exogenous contrast agents. Moreover, modifications of the labeling method allow for the visualization of single arterial trees. In this study, an approach is presented for time-resolved MR angiography based on superselective ASL and keyhole accelerated image acquisition in order to selectively visualize individual cerebral arteries in a clinically acceptable scan time. Keyhole percentage as well as the flip angle of the acquisition sequence was optimized in numerical simulations. Subsequently, the method was validated in healthy volunteers. As a result, image acquisition in 5 minutes with a temporal resolution of 100 ms and spatial resolution below 1 mm was achieved.

MR Imaging of Individual Perfusion Reorganization Using Superselective Pseudocontinuous Arterial Spin-Labeling in Patients with Complex Extracranial Steno-Occlusive Disease

Super selective pseudocontinuous arterial spin-labeling with a circular labeling spot enabling selective vessel labeling was added to routine imaging in a prospective pilot study in 50 patients with extracranial steno-occlusive disease. The detected vessel occlusions/stenoses and perfusion patterns corresponded between cerebral DSA and super selective pseudocontinuous ASL maps in all cases. Perfusion deficits on DSC-CBF maps significantly correlated with those on super selective pseudocontinuous ASL maps. The authors conclude that superselectivepseudocontinuousASL is a robust technique for regional brain perfusion imaging, suitable for the noninvasive diagnostics of individual patient perfusion patterns. BACKGROUND AND PURPOSE: Patients with multiple stenoses or occlusions of the extracranial arteries require an individualized diagnostic approach. We evaluated the feasibility and clinical utility of a novel MR imaging technique for regional perfusion imaging in this patient group. MATERIALS AND METHODS: Superselective pseudocontinuous arterial spin-labeling with a circular labeling spot enabling selective vessel labeling was added to routine imaging in a prospective pilot study in 50 patients (10 women, 70.05 ± 10.55 years of age) with extracranial steno-occlusive disease. Thirty-three had infarct lesions. DSC-MR imaging was performed in 16/50 (32%), and cerebral DSA, in 12/50 patients (24%). Vascular anatomy and the distribution of vessel stenoses and occlusions were defined on sonography and TOF-MRA. Stenoses were classified according to the NASCET criteria. Infarct lesions and perfusion deficits were defined on FLAIR and DSC-MR imaging, respectively. Individual perfusion patterns were defined on the superselective pseudocontinuous arterial spin-labeling maps and were correlated with vascular anatomy and infarct lesion localization. RESULTS: The superselective pseudocontinuous arterial spin-labeling imaging sequence could be readily applied by trained technicians, and the additional scan time of 12.7 minutes was well-tolerated by patients. The detected vessel occlusions/stenoses and perfusion patterns corresponded between cerebral DSA and superselective pseudocontinuous arterial spin-labeling maps in all cases. Perfusion deficits on DSC-CBF maps significantly correlated with those on superselective pseudocontinuous arterial spin-labeling maps (Pearson r = 0.9593, P < .01). Individual collateral recruitment patterns were not predictable from the vascular anatomy in 71% of our patients. CONCLUSIONS: Superselective pseudocontinuous arterial spin-labeling is a robust technique for regional brain perfusion imaging, suitable for the noninvasive diagnostics of individual perfusion patterns in patients with complex cerebrovascular disease.

Accelerated visualization of selected intracranial arteries by cycled super-selective arterial spin labeling

ObjectiveTo accelerate super-selective arterial spin labeling (ASL) angiography by using a single control condition denoted as cycled super-selective arterial spin labeling.Materials and methodsA single non-selective control image is acquired that is shared by selective label images. Artery-selective imaging is possible by geometrically changing the position of the labeling focus to more than one artery of interest during measurement. The presented approach is compared to conventional super-selective imaging in terms of its labeling efficiency inside and outside the labeling focus using numerical simulations and in vivo measurements. Additionally, the signal-to-noise ratios of the images are compared to non-selective ASL angiography and analyzed using a two-way ANOVA test and calculating the Pearson’s correlation coefficients.ResultsThe results indicate that the labeling efficiency is not reduced within the labeled artery, but can increase as a function of distance to the artery of interest when compared to conventional super-selective ASL. In the final images, no statistically significant difference of image quality can be observed while the acquisition duration could be reduced when the major brain feeding arteries are being tagged.ConclusionUsing super-selective arterial spin labeling, a single non-selective control acquisition suffices for reconstructing selective angiograms of the cerebral vasculature, thereby accelerating image acquisition of the major intracranial arteries without notable loss of information.

Changes in intracranial venous hemodynamics in a patient with idiopathic intracranial hypertension after lumbar puncture precedes therapeutic success

Idiopathic intracranial hypertension (IIH), also denoted as pseudotumor cerebri (PTC), is a syndrome of raised intracranial pressure of unknown etiology. Clinical symptoms include headache, visual impairment, and nausea. Its incidence is reported as 0.9–1.6 per 100,000 persons. The patient profile is quite characteristic, as most often obese females of childbearing age are affected, thereby raising the incidence in this group to 11.9/100,000. The diagnosis is based on clinical assessment with ophthalmoscopy revealing bilateral papilledema and lumbar puncture (LP). IIH is characterized by normal cerebrospinal fluid (CSF) composition and an elevated opening pressure at LP (>250 mm H20). Cranial magnetic resonance imaging (MRI) is used to exclude mass lesions, hydrocephalus, and venous sinus thrombosis and often depicts signs of increased CSF pressure such as an empty sella and optic nerve sheath hydrops. Bilateral transverse sinus narrowing is seen in 90% of patients and associated changes in intracranial venous blood pressure and blood flow have been reported. The etiology of these narrowings and their impact on the disease is not fully understood. However, it is known that sinus narrowings normalize after CSF diversion in some patients, but often persist with conservative treatment. Therefore, MRI including MR venography is well suited to help diagnose IIH, but not to exactly predict clinical response to treatment. MR measurements of intracranial blood flow, in particular venous pulsatility and resistance index (PI and RI) might be more sensitive in predicting response to treatment in patients with IIH.

Advanced CT for diagnosis of seizure-related stroke mimics

Background and purposeIt is assumed that up to 30 % of clinically diagnosed acute ischaemic strokes (AIS) are actually stroke mimics (SM). Our aim was to evaluate the usefulness of advanced CT including CT angiography (CTA) and CT perfusion (CTP) findings when distinguishing AIS from seizure-related SM.MethodsOver a 22-month period data were gathered of patients who presented to our stroke centre with AIS-like symptoms and were examined immediately with an advanced CT, analysed and evaluated by two experienced neuroradiologists who preferred SM rather than AIS. All these patients additionally received electroencephalography and follow-up imaging. CTA was the important feature to exclude vessel occlusion or haemodynamic relevant stenosis. Perfusion patterns were retrospectively analysed qualitatively.ResultsThe most common perfusion abnormality was cortical hyperperfusion (22/37 [59.5 %] patients) followed by a hypoperfusion pattern with a cortical-subcortical involvement (15/37 [40.5 %] patients) without evidence of vessel occlusion or stenosis. Seizure-related hyper- and hypoperfusion patterns typically crossed the normal anatomical vascular territories boundaries.ConclusionBeyond its use in core and penumbra estimation, advanced CT provides important information to emergency physicians in the difficult clinical diagnosis when differentiating between AIS and seizure-related symptoms with an important impact on therapeutic decision-making.Key points• Advanced CT helps to differentiate between ischaemic strokes and stroke mimics.• Seizure-related perfusion patterns are distinct from ischaemia hypoperfusion.• Advanced CT could improve rapid adequate treatment for AIS and seizure events.

Intraoperative resection control using arterial spin labeling — Proof of concept, reproducibility of data and initial results

Objectives Intraoperative magnetic resonance imaging is a unique tool for visualizing structures during resection and/or for updating any kind of neuronavigation that might be hampered as a result of brain shift during surgery. Advanced MRI techniques such as perfusion-weighted imaging have already proven to be important in the initial diagnosis preoperatively, but can also help to differentiate between tumor and surgically induced changes intraoperatively. Commonly used methods to visualize brain perfusion include contrast agent administration and are therefore somewhat limited. One method that uses blood as an internal contrast medium is arterial spin labeling (ASL), which might represent an attractive alternative. Materials and methods Ten healthy volunteers were examined using three different scanners and coils within 1 h (3T Achieva MRI using 32-channel head coil, 1.5T Achieva MRI using a 6-channel head coil, 1.5 Intera Scanner using 2 surface coils, Philips, Best, The Netherlands) and quantitative CBF values were calculated and compared between the different setups. Additionally, in eight patients with glioblastoma multiforme, ASL was used pre-, intra-, and postoperatively to define tumor tissue and the extent of resection in comparison to structural imaging. Results A high correlation (r = 0.91–0.96) was found between MRI scanners and coils used. ASL was as reliable as conventional MR imaging if complete resection was already achieved, but additionally provided valuable information regarding residual tumor tissue in one patient. Conclusions Intraoperative arterial spin-labeling is a feasible, reproducible, and reliable tool to map CBF in brain tumors and seems to give beneficial information compared to conventional intraoperative MR imaging in partial resection.

A comparison of arterial spin labeling and dynamic susceptibility perfusion imaging for resection control in glioblastoma surgery

Resection control using magnetic resonance imaging during neurosurgical interventions increases confidence regarding the extent of tumor removal already during the procedure. In addition to morphological imaging, functional information such as perfusion might become an important marker of the presence and extent of residual tumor mass. The aim of this study was to implement arterial spin labeling (ASL) perfusion imaging as a noninvasive alternative to dynamic susceptibility contrast (DSC) perfusion imaging in patients suffering from intra-axial tumors for resection control already during surgery. The study included 15 patients suffering from glioblastoma multiforme in whom perfusion imaging using DSC and ASL was performed before, during, and after surgery. The data obtained from intraoperative scanning were analyzed by two readers blinded to any clinical information, and the presence of residual tumor mass was evaluated using a ranking scale. Similarity of results was analyzed using the intraclass correlation coefficient and Pearsons correlation coefficient. The results show that intraoperative ASL is as reliable as DSC when performing intraoperative perfusion imaging. According to the results of this study, intraoperative imaging using ASL represents an attractive alternative to contrast agent-based perfusion imaging.

Should you stop wearing neckties?—wearing a tight necktie reduces cerebral blood flow

PurposeNegative cerebrovascular effects can be expected by compressing jugular veins and carotids by a necktie. It was already demonstrated that a necktie increases intraocular pressure. In many professions, a special dress code including a necktie and a collared shirt is mandatory although little is known about the effect of this “socially desirable strangulation.”MethodsIn this study, the effect of wearing a necktie concerning cerebral blood flow and jugular venous flow by magnetic resonance imaging. Thirty volunteers were divided in two groups. One underwent MRI with necktie, the other without.ResultsThe examination resulted in a statistically significant decrease of CBF after tightening the necktie (p < 0.001) while the venous flow did not show any significant changes.ConclusionIt appears that wearing a necktie leads to a reduction in CBF.