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Dive into the research topics where Marc A. Brockmann is active.

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Featured researches published by Marc A. Brockmann.


Journal of NeuroInterventional Surgery | 2016

Initial experience with a new distal intermediate and aspiration catheter in the treatment of acute ischemic stroke: clinical safety and efficacy

S. Stampfl; Christoph Kabbasch; Marguerite Müller; Anastasios Mpotsaris; Marc A. Brockmann; Thomas Liebig; Martin Wiesmann; Martin Bendszus; Markus Möhlenbruch

Purpose To describe our initial experience with the novel 5u2005F SOFIA (Soft Torqueable catheter Optimized For Intracranial Access) intermediate and aspiration catheter for endovascular treatment of patients with acute ischemic stroke. Methods A retrospective review was performed in three centers of prospectively collected data of all stroke patients who underwent endovascular therapy using the SOFIA catheter. Patients were enrolled between November 2013 and December 2014. The primary endpoint of the study was accessibility of the thrombus with the SOFIA catheter. As a secondary endpoint, the study assessed recanalization success (Thrombolysis In Cerebral Infarction (TICI) ≥2b). Clinical presentation on admission and discharge was also documented. In addition, catheter- and procedure-related complications (particularly thromboembolic complications) were recorded. Results The SOFIA catheter was used in 115 acute stroke procedures. In 110 cases (96%) the catheter could be advanced to the occlusion site. After mechanical thrombectomy, successful recanalization (TICI ≥2b) was documented in 86.9%. There were no complications related to positioning of the catheter. Distal thrombus migration into a new vascular territory occurred in three patients following thrombectomy with a stent retriever (2.6%). The mean NIH Stroke Scale (NIHSS) score on admission was 16.8±6 and at discharge the mean NIHSS score was 8.2±7.7. Sixteen patients died. Conclusions The SOFIA catheter is a safe and efficient catheter for endovascular stroke therapy.


Journal of Neuroradiology | 2016

Radiation dose reduction in perfusion CT imaging of the brain: A review of the literature

Ahmed E. Othman; Saif Afat; Marc A. Brockmann; Omid Nikoubashman; Carolin Brockmann; Konstantin Nikolaou; Martin Wiesmann

Perfusion CT (PCT) of the brain is widely used in the settings of acute ischemic stroke and vasospasm monitoring. The high radiation dose associated with PCT is a central topic and has been a focus of interest for many researchers. Many studies have examined the effect of radiation dose reduction in PCT using different approaches. Reduction of tube current and tube voltage can be efficient and lead to a remarkable reduction of effective radiation dose while preserving acceptable image quality. The use of novel noise reduction techniques such as iterative reconstruction or spatiotemporal smoothing can produce sufficient image quality from low-dose perfusion protocols. Reduction of sampling frequency of perfusion images has only little potential to reduce radiation dose. In the present article we aimed to summarize the available data on radiation dose reduction in PCT imaging of the brain.


Academic Radiology | 2013

Comparison of Fenestra LC, ExiTron nano 6000, and ExiTron nano 12000 for micro-CT imaging of liver and spleen in mice.

Hanne Boll; Giovanna Figueiredo; Teresa Fiebig; Stefanie Nittka; Fabian Doyon; Hans U. Kerl; Ingo Nölte; Alex Förster; Martin Kramer; Marc A. Brockmann

RATIONALE AND OBJECTIVESnThe purpose of this study was to compare different contrast agents for longitudinal liver and spleen imaging in a mouse model of liver metastasis.nnnMATERIALS AND METHODSnMice developing liver metastases underwent longitudinal micro-computed tomography imaging after injection of Fenestra LC, ExiTron nano 6000, or ExiTron nano 12000. Elimination times and contrast enhancement of liver and spleen were compared.nnnRESULTSnFor all contrast agents, liver contrast peaked at approximately 4 hours and spleen contrast at 48 hours postinjection. A single dose of 100 μL of ExiTron nano 6000 or 12000 resulted in longstanding enhancement of liver and spleen tissue for longer than 3 weeks, whereas repeated injections of 400 μL of Fenestra LC were required to retain contrast at acceptable levels and allowed imaging of the liver/spleen for up to 2 and 9 days, respectively.nnnCONCLUSIONnBoth ExiTron nano agents provide longer and stronger contrast enhancement of liver and spleen compared to Fenestra LC, and they do so at a 75% lower injection volume in mice.


European Radiology | 2016

Impact of image denoising on image quality, quantitative parameters and sensitivity of ultra-low-dose volume perfusion CT imaging.

Ahmed E. Othman; Carolin Brockmann; Z Yang; Changwon Kim; Saif Afat; Rastislav Pjontek; Omid Nikoubashman; Marc A. Brockmann; Konstantin Nikolaou; Martin Wiesmann; Jong Hyo Kim

AbstractObjectivesTo examine the impact of denoising on ultra-low-dose volume perfusion CT (ULD-VPCT) imaging in acute stroke.MethodsSimulated ULD-VPCT data sets at 20xa0% dose rate were generated from perfusion data sets of 20 patients with suspected ischemic stroke acquired at 80xa0kVp/180xa0mAs. Four data sets were generated from each ULD-VPCT data set: not-denoised (ND); denoised using spatiotemporal filter (D1); denoised using quanta-stream diffusion technique (D2); combination of both methods (D1u2009+u2009D2). Signal-to-noise ratio (SNR) was measured in the resulting 100 data sets. Image quality, presence/absence of ischemic lesions, CBV and CBF scores according to a modified ASPECTS score were assessed by two blinded readers.ResultsSNR and qualitative scores were highest for D1u2009+u2009D2 and lowest for ND (all pu2009≤u20090.001). In 25xa0% of the patients, ND maps were not assessable and therefore excluded from further analyses. Compared to original data sets, in D2 and D1u2009+u2009D2, readers correctly identified all patients with ischemic lesions (sensitivity 1.0, kappa 1.0). Lesion size was most accurately estimated for D1u2009+u2009D2 with a sensitivity of 1.0 (CBV) and 0.94 (CBF) and an inter-rater agreement of 1.0 and 0.92, respectively.ConclusionAn appropriate combination of denoising techniques applied in ULD-VPCT produces diagnostically sufficient perfusion maps at substantially reduced dose rates as low as 20xa0% of the normal scan.Key Points• Perfusion-CT is an accurate tool for the detection of brain ischemias.n • The high associated radiation doses are a major drawback of brain perfusion CT.n • Decreasing tube current in perfusion CT increases image noise and deteriorates image quality.n • Combination of different image-denoising techniques produces sufficient image quality from ultra-low-dose perfusion CT.


European Radiology | 2015

Effects of radiation dose reduction in Volume Perfusion CT imaging of acute ischemic stroke

Ahmed E. Othman; Carolin Brockmann; Z Yang; Changwon Kim; Saif Afat; Rastislav Pjontek; Omid Nikobashman; Marc A. Brockmann; Jong Hyo Kim; Martin Wiesmann

AbstractPurposeTo examine the influence of radiation dose reduction on image quality and sensitivity of Volume Perfusion CT (VPCT) maps regarding the detection of ischemic brain lesions.Methods and materialsVPCT data of 20 patients with suspected ischemic stroke acquired at 80xa0kV and 180xa0mAs were included. Using realistic reduced-dose simulation, low-dose VPCT datasets with 144xa0mAs, 108xa0mAs, 72xa0mAs and 36xa0mAs (80xa0%, 60xa0%, 40xa0% and 20xa0% of the original levels) were generated, resulting in a total of 100 datasets. Perfusion maps were created and signal-to-noise-ratio (SNR) measurements were performed. Qualitative analyses were conducted by two blinded readers, who also assessed the presence/absence of ischemic lesions and scored CBV and CBF maps using a modified ASPECTS-score.ResultsSNR of all low-dose datasets were significantly lower than those of the original datasets (pu2009<u2009.05). All datasets down to 72xa0mAs (40xa0%) yielded sufficient image quality and high sensitivity with excellent inter-observer-agreements, whereas 36xa0mAs datasets (20xa0%) yielded poor image quality in 15xa0% of the cases with lower sensitivity and inter-observer-agreements.ConclusionLow-dose VPCT using decreased tube currents down to 72xa0mAs (40xa0% of original radiation dose) produces sufficient perfusion maps for the detection of ischemic brain lesions.Key Points• Perfusion CT is highly accurate for the detection of ischemic brain lesionsn • Perfusion CT results in high radiation exposure, therefore low-dose protocols are requiredn • Reduction of tube current down to 72xa0mAs produces sufficient perfusion maps


Neurosurgery | 2014

Implantation of Pipeline Flow-Diverting Stents Reduces Aneurysm Inflow Without Relevantly Affecting Static Intra-aneurysmal Pressure

Hans U. Kerl; Hanne Boll; Teresa Fiebig; Giovanna Figueiredo; Alex Förster; Ingo Nölte; Andrea Nonn; Christoph Groden; Marc A. Brockmann

BACKGROUNDnFlow-diverting stent (FDS) implantation is an endovascular treatment option for intracranial aneurysms. However, little is known about the hemodynamic effects.nnnOBJECTIVEnTo assess the effect of stent compression on FDS porosity, to evaluate the influence of single and overlapping implantation of FDS on intra-aneurysmal flow profiles, and to correlate stent porosity with changes in static mean intra-aneurysmal pressure.nnnMETHODSnIntra-aneurysmal time-density curves were recorded in a pulsatile in vitro flow model before and after implantation of FDSs (Pipeline Embolization Device; ev3) in 7 different types of aneurysm models. Reductions in the maximum contrast inflow and time to maximum intra-aneurysmal contrast were calculated. Micro--computed tomography was performed, and compression-related FDS porosity was measured. The influence of FDS placement on mean static intra-aneurysmal pressure was measured.nnnRESULTSnFDS compression resulted in an almost linear reduction in stent porosity. Stent porosity (struts per 1 mm) correlated significantly with the reduction of aneurysm contrast inflow (R = 0.81, P < .001) and delay until maximum contrast (R = 0.34, P = .001). Circulating intra-aneurysmal high-velocity flow was terminated in all sidewall models after implantation of a single stent. Superimposition of 2 stents reduced maximum intra-aneurysmal contrast by 69.1 ± 3.1% (mean ± SD) in narrow-necked sidewall aneurysm models, whereas no substantial reduction in maximum intra-aneurysmal contrast was observed in wide-necked sidewall aneurysm models. Intra-aneurysmal mean static pressure did not correlate with FDS porosity or number of implanted stents.nnnCONCLUSIONnImplantation of FDS effectively reduces aneurysm inflow in a porosity-dependent way without relevantly affecting static mean intra-aneurysmal pressure.nnnABBREVIATIONSnFDS, flow-diverting stentMAP, mean arterial pressurePED, Pipeline Embolization Device.


Journal of NeuroInterventional Surgery | 2016

Metal artifact reduction for flat panel detector intravenous CT angiography in patients with intracranial metallic implants after endovascular and surgical treatment

Rastislav Pjontek; Belgin Önenköprülü; Bernhard Scholz; Yiannis Kyriakou; Gerrit Alexander Schubert; Omid Nikoubashman; Ahmed E. Othman; Martin Wiesmann; Marc A. Brockmann

Background Flat panel detector CT angiography with intravenous contrast agent injection (IV CTA) allows high-resolution imaging of cerebrovascular structures. Artifacts caused by metallic implants like platinum coils or clips lead to degradation of image quality and are a significant problem. Objective To evaluate the influence of a prototype metal artifact reduction (MAR) algorithm on image quality in patients with intracranial metallic implants. Methods Flat panel detector CT after intravenous application of 80u2005mL contrast agent was performed with an angiography system (Artis zee; Siemens, Forchheim, Germany) using a 20u2005s rotation protocol (200° rotation angle, 20u2005s acquisition time, 496 projections). The data before and after MAR of 26 patients with a total of 34 implants (coils, clips, stents) were independently evaluated by two blinded neuroradiologists. Results MAR improved the assessability of the brain parenchyma and small vessels (diameter <1u2005mm) in the neighborhood of metallic implants and at a distance of 6u2005cm (p<0.001 each, Wilcoxon test). Furthermore, MAR significantly improved the assessability of parent vessel patency and potential aneurysm remnants (p<0.005 each, McNemar test). MAR, however, did not improve assessability of stented vessels. Conclusions When an intravenous contrast protocol is used, MAR significantly ameliorates the assessability of brain parenchyma, vessels, and treated aneurysms in patients with intracranial coils or clips.


Neuroradiology | 2016

Volume perfusion CT imaging of cerebral vasospasm: diagnostic performance of different perfusion maps

Ahmed E. Othman; Saif Afat; Omid Nikoubashman; Marguerite Müller; Gerrit Alexander Schubert; Georg Bier; Marc A. Brockmann; Martin Wiesmann; Carolin Brockmann

IntroductionIn this study, we aimed to evaluate the diagnostic performance of different volume perfusion CT (VPCT) maps regarding the detection of cerebral vasospasm compared to angiographic findings.MethodsForty-one datasets of 26 patients (57.5u2009±u200910.8xa0years, 18xa0F) with subarachnoid hemorrhage and suspected cerebral vasospasm, who underwent VPCT and angiography within 6xa0h, were included. Two neuroradiologists independently evaluated the presence and severity of vasospasm on perfusion maps on a 3-point Likert scale (0—no vasospasm, 1—vasospasm affecting <50xa0%, 2—vasospasm affecting >50xa0% of vascular territory). A third neuroradiologist independently assessed angiography for the presence and severity of vasospasm on a 3-point Likert scale (0—no vasospasm, 1—vasospasm affectingu2009<u200950xa0%, 2—vasospasm affectingu2009>u200950xa0% of vessel diameter). Perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to drain (TTD) were evaluated regarding diagnostic accuracy for cerebral vasospasm with angiography as reference standard. Correlation analysis of vasospasm severity on perfusion maps and angiographic images was performed. Furthermore, inter-reader agreement was assessed regarding findings on perfusion maps.ResultsDiagnostic accuracy for TTD and MTT was significantly higher than for all other perfusion maps (TTD, AUCu2009=u20090.832; MTT, AUCu2009=u20090.791; pu2009<u20090.001). TTD revealed higher sensitivity than MTT (pu2009=u20090.007). The severity of vasospasm on TTD maps showed significantly higher correlation levels with angiography than all other perfusion maps (pu2009≤u20090.048). Inter-reader agreement was (almost) perfect for all perfusion maps (kappau2009≥u20090.927).ConclusionThe results of this study indicate that TTD maps have the highest sensitivity for the detection of cerebral vasospasm and highest correlation with angiography regarding the severity of vasospasm.


Zeitschrift Fur Medizinische Physik | 2015

Review of potential improvements using MRI in the radiotherapy workflow

Alberto Torresin; Maria Grazia Brambilla; Angelo Filippo Monti; Alessio Moscato; Marc A. Brockmann; Lothar R. Schad; Ulrike I. Attenberger; Frank Lohr

The goal of modern radiotherapy is to deliver a lethal amount of dose to tissue volumes that contain a significant amount of tumour cells while sparing surrounding unaffected or healthy tissue. Online image guided radiotherapy with stereotactic ultrasound, fiducial-based planar X-ray imaging or helical/conebeam CT has dramatically improved the precision of radiotherapy, with moving targets still posing some methodical problems regarding positioning. Therefore, requirements for precise target delineation and identification of functional body structures to be spared by high doses become more evident. The identification of areas of relatively radioresistant cells or areas of high tumor cell density is currently under development. This review outlines the state of the art of MRI integration into treatment planning and its importance in follow up and the quantification of biological effects. Finally the current state of the art of online imaging for patient positioning will be outlined and indications will be given what the potential of integrated radiotherapy/online MRI systems is.


Journal of Neuro-oncology | 2015

In vivo micro-CT imaging of untreated and irradiated orthotopic glioblastoma xenografts in mice: capabilities, limitations and a comparison with bioluminescence imaging

Stefanie Kirschner; Manuela Felix; Linda Hartmann; Miriam Bierbaum; Máté E. Maros; Hans U. Kerl; Frederik Wenz; Gerhard Glatting; Martin Kramer; Frank A. Giordano; Marc A. Brockmann

Small animal imaging is of increasing relevance in biomedical research. Studies systematically assessing the diagnostic accuracy of contrast-enhanced in vivo micro-CT of orthotopic glioma xenografts in mice do notxa0exist. NOD/SCID/γc−/− mice (nxa0=xa027) underwent intracerebral implantation of 2.5xa0×xa0106 GFP-Luciferase-transduced U87MG cells. Mice underwent bioluminescence imaging (BLI) to detect tumor growth and afterwards repeated contrast-enhanced (300xa0µl Iomeprol i.v.) micro-CT imaging (80xa0kV, 75xa0µAs, 360° rotation, 1,000 projections, 33xa0s scan time, resolution 40xa0×xa040xa0×xa053xa0µm, 0.5xa0Gy/scan). Presence of tumors, tumor diameter and tumor volume in micro-CT were rated by two independent readers. Results were compared with histological analyses. Six mice with tumors confirmed by micro-CT received fractionated irradiation (3xa0×xa05xa0Gy every other day) using the micro-CT (5xa0mm pencil beam geometry). Repeated micro-CT scans were tolerated well. Tumor engraftment rate was 74xa0% (nxa0=xa020). In micro-CT, mean tumor volume was 30xa0±xa033xa0mm3, and the smallest detectable tumor measured 360xa0×xa0620xa0µm. The inter-rater agreement (nxa0=xa051 micro-CT scans) for the item tumor yes/no was excellent (Spearman-Rhoxa0=xa00.862, pxa0<xa00.001). Sensitivity and specificity of micro-CT were 0.95 and 0.71, respectively (PPVxa0=xa00.91, NPVxa0=xa00.83). BLI on day 21 after tumor implantation had a sensitivity and specificity of 0.90 and 1.0, respectively (PPVxa0=xa01.0, NPVxa0=xa00.5). Maximum tumor diameter and volume in micro-CT and histology correlated excellently (tumor diameter: 0.929, pxa0<xa00.001; tumor volume: 0.969, pxa0<xa00.001, nxa0=xa017). Irradiated animals showed a large central tumor necrosis. Longitudinal contrast enhanced micro-CT imaging of brain tumor growth in live mice is feasible at high sensitivity levels and with excellent inter-rater agreement and allows visualization of radiation effects.

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Saif Afat

RWTH Aachen University

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