Sebastian Kozerke

Last Name

Kozerke

First Name

Sebastian

ORCID

0000-0003-3725-8884

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09548 - Kozerke, Sebastian / Kozerke, Sebastian

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Publications 1 - 10 of 23

Localized FNO for Spatiotemporal Hemodynamic Upsampling in Aneurysm MRI
Flouris, Kyriakos; Halter, Moritz; Lee, Yolanne Y.R.; et al. (2026)
Lecture Notes in Computer Science ~ Reconstruction and Imaging Motion Estimation, and Graphs in Biomedical Image Analysis
Hemodynamic analysis is essential for predicting aneurysm rupture and guiding treatment. While magnetic resonance flow imaging enables time-resolved volumetric blood velocity measurements, its low spatiotemporal resolution and signal-to-noise ratio limit its diagnostic utility. To address this, we propose the Localized Fourier Neural Operator (LoFNO), a novel 3D architecture that enhances both spatial and temporal resolution with the ability to predict wall shear stress (WSS) directly from clinical imaging data. LoFNO integrates Laplacian eigenvectors as geometric priors for improved structural awareness on irregular, unseen geometries and employs an Enhanced Deep Super-Resolution Network (EDSR) layer for robust upsampling. By combining geometric priors with neural operator frameworks, LoFNO de-noises and spatiotemporally upsamples flow data, achieving superior velocity and WSS predictions compared to interpolation and alternative deep learning methods, enabling more precise cerebrovascular diagnostics. The code, ablations and hyperparameters are available at: https://github.com/moritz-halter/deepflow.
Clinical Quantitative Coronary Artery Stenosis and Coronary Atherosclerosis Imaging: A Consensus Statement from the Quantitative Cardiovascular Imaging Study Group
Vázquez Mézquita, Aldo J.; Biavati, Federico; Falk, Volkmar; et al. (2024)
Quantification of Biophysical Parameters in Medical Imaging
The detection and characterization of coronary artery stenosis and atherosclerosis using imaging tools are key for clinical decision-making in patients with known or suspected coronary artery disease (CAD). In this regard, imaging-based quantification can be improved by choosing the most appropriate imaging modality for diagnosis, treatment and procedural planning. In this consensus statement, we provide clinical consensus recommendations on the optimal use of different imaging techniques in various patient populations and describe the advances in imaging technology. Clinical consensus recommendations on the appropriateness of each imaging technique for direct coronary artery visualization were derived through a three-step, real-time Delphi process that took place before, during and after the Second International Quantitative Cardiovascular Imaging Meeting in September 2022. According to the Delphi survey answers, CT is the method of choice to rule out obstructive stenosis in patients with an intermediate pre-test probability of coronary artery disease and enables quantitative assessment of coronary plaque with respect to dimensions, composition, location and related risk of future cardiovascular events, whereas MRI facilitates the visualization of coronary plaque and can be used in experienced centres as a radiation-free, second-line option for noninvasive coronary angiography. PET has the greatest potential for quantifying inflammation in coronary plaque, but SPECT presently has a limited role in clinical coronary artery stenosis and atherosclerosis imaging. Invasive coronary angiography (ICA) is the reference standard for stenosis assessment but cannot characterize coronary plaques. Finally, intravascular ultrasonography (IVUS) and optical coherence tomography are the most important invasive imaging modalities for the identification of plaques at high risk of rupture. The recommendations made in this consensus statement will help clinicians to choose the most appropriate imaging modality on the basis of the specific clinical scenario, individual patient characteristics and the availability of each imaging modality.
T1 Mapping Detects Myocardial Oedema in a Rat Model of Myocardial Ischaemia
Oh-Ici, Darach; Jeuthe, Sarah; Kozerke, Sebastian; et al. (2013)
Irish Journal of Medical Science
Consensus recommendations for hyperpolarized [1-¹³C]pyruvate MRI multi-center human studies
Punwani, Shonit; Larson, Peder E.Z.; Laustsen, Christoffer; et al. (2025)
Magnetic Resonance in Medicine
MRI of hyperpolarized (HP) [1-¹³C]pyruvate allows in vivo assessment of metabolism and has translated into human studies across diseases at 15 centers worldwide. To determine consensus on best practice for multi-center studies for development of clinical applications. This paper presents the results of a two-round formal consensus building exercise carried out by experts with HP [1-¹³C]pyruvate human study experience. Twenty-nine participants from 13 sites brought together expertise in pharmacy methods, MR physics, translational imaging, and data analysis with the goal of providing recommendations and best practice statements on conduct of multi-center human studies of HP [1-¹³C]pyruvate MRI. Overall, the group reached consensus on approximately two-thirds of 246 statements in the questionnaire, covering HP ¹³C-pyruvate preparation; MRI system setup, calibration, and phantoms; acquisition and reconstruction; and data analysis and quantification. Consensus was present across categories. Examples include: (i) Different HP pyruvate preparation methods could be used in human studies, but the same release criteria have to be followed; (ii) site qualification and quality assurance must be performed with phantoms and the same field strength must be used, but the rest of the system setup and calibration methods could be determined by individual sites; (iii) the same pulse sequence and reconstruction methods were preferable, but the exact choice should be governed by the anatomical target; (iv) normalized metabolite area-under-curve values and metabolite area under curve were the preferred metabolism metrics. The consensus proces revealed that HP[1-¹³C] pyruvate MRI as a technology has progressed sufficiently to plan multi-center studies. The work confirmed areas of consensus for multi-center study conduct and identified where further research is required to ascertain best practice.
Splenic switch-off in three-dimensional adenosine stress cardiac magnetic resonance perfusion for differentiating true-negative from potentially false-negative studies identified by fractional flow reserve
Károlyi , Mihály; Fuetterer , Maximilian; Kolossváry , Márton; et al. (2025)
Journal of Cardiovascular Magnetic Resonance
Background False-negative cardiovascular magnetic resonance (CMR) perfusion results may arise from inadequate stress responses, even when patients exhibit an adequate clinical or heart-rate response to adenosine. This study aimed to explore the ability of qualitative and quantitative splenic switch-off (SSO) markers to differentiate true-negative from potentially false-negative adenosine stress-perfusion CMR findings in a cohort where fractional flow reserve (FFR) was used to adjudicate lesion significance. Methods Patients with known or suspected coronary artery disease (CAD) from five centers underwent three-dimensional (3D) adenosine stress perfusion CMR and coronary angiography with FFR. SSO was assessed qualitatively using both standard stress-to-rest (SSO) and a stress-only (SSOstress) approach. In addition, quantitative signal intensity (SI) ratios were assessed, including the splenic stress-to-rest SI-ratio (SIstress/rest) and the spleen-to-myocardium SI ratio at stress (SIspleen/myocarcium). The diagnostic accuracy of these measures was evaluated using cross-validated area under the curve (cvAUC) analysis. Results Among 179 patients (mean age 63 ± 10 years; 130 male), SSO prevalence was 73% (130/179) and was significantly more frequent in true-negative than false-negative CMR cases (80.6% [54/67] vs 36.8% [7/19], p < 0.001). SSOstress showed moderate agreement (κ = 0.60) and robust diagnostic performance (AUC 0.80), as compared to SSO. Splenic SIstress/rest and SIspleen/myocarcium at stress demonstrated high predictive accuracy for visual SSO, with cvAUCs of 0.94 (95% CI: 0.90–0.96) and 0.90 (95% CI: 0.86–0.95), respectively. The positive likelihood ratio of SSO for true-negative CMR was 1.70, while the negative likelihood ratio was 0.24. Qualitative and quantitative splenic-switch off metrics classified 77%–80% (66-69/86) of negative CMR cases correctly as true- or potentially false-negatives, with sensitivities ranging from 81.4% to 91.2%. Clinically applicable cut-offs for differentiating true- and false-negative studies with splenic SIstress/rest and SIspleen/myocarcium at stress were identified as ≤0.32 and ≤0.38, respectively. Conclusion In a multicenter cohort using FFR-adjudicated reference for lesion severity, qualitative SSO and quantitative SI metrics were associated with myocardial stress adequacy and these markers may improve the interpretation of negative stress-perfusion CMR studies.
Turbulent Shear Stress Quantification using Phase Contrast MRI
Binter, Christian; Knobloch, Verena; Sigfridsson, Andreas B.J.; et al. (2012)
Magnetic Resonance Materials in Physics, Biology, and Medicine
P459: Inflammatory reactions of the pericardium as measured with parametric mapping CMR
Gastl, Mareike; Sokolska, Justyna Maria; Polacin, Malgorzata; et al. (2019)
European Heart Journal. Cardiovascular Imaging ~ Abstract Book
Background: Despite the improved spectrum of diagnostic tools and technical developments, diagnosis of pericardial inflammation can remain challenging. Cardiovascular magnetic resonance (CMR) is increasingly used to diagnose pericardial inflammation through the visualization of thickened pericardium, pericardial edema and contrast agent uptake. Unlike T1- and T2-weighted imaging, parametric mapping (T1 and T2 mapping) has emerged as an alternative to visualize and quantify focal and global changes of the myocardium. Purpose: To investigate the role of parametric mapping for the diagnosis of pericardial inflammation. Methods: Twelve patients with suspected or known pericardial inflammation underwent CMR at a 1.5T system including T1/T2 black blood imaging with fat suppression (SPIR), T1/T2 mapping and a 3D gradient-spoiled fast-field-echo sequence for late gadolinium enhancement (LGE). T1/T2 mapping was performed in end-diastole covering 3 short axis slices (T1: TR shortest, TE shortest, 11 images; T2-GraSE: TR 1 heartbeat, TE shortest, 9 echoes). The diagnosis of pericardial inflammation was made according to recent guidelines using LGE imaging and T1/T2 black blood. T1 and T2 measurements were pursued by manually drawing a region of interest (ROI) in the pericardium of all slices avoiding contamination by other cardiac structures, e.g. epicardial fat. Results: T1 mapping could be performed in all subjects, T2 maps could only be analysed in 5 patients. In addition to pericardial inflammation, 3 patients displayed myocardial involvement. On average, the pericardium displayed a thickness of 6.7 ± 2.0 mm. T1 values were 1394.7 ± 318.8 ms and T2 values were 149.4 ± 24.6 ms, which was above local reference and patients" myocardial values (Myocardial T1: 1031.5 ± 42.1 ms, p = 0.003; T2: 50.2 ± 1.2 ms, p = 0.001). Both, T1 and T2, did not show a correlation to the extent of the thickened pericardium. There was no correlation of T1/T2 to blood markers of inflammation and myocardial injury (CRP, troponin, CK). Conclusions: Parametric T1 and T2 mapping was able to support the diagnosis of pericardial inflammation by T1/T2-weighted and LGE imaging. Because of partial volume effects of the healthy, thin pericardium, the implementation of normal values can be hampered.
Controlled synthesis and characterization of porous silicon nanoparticles for dynamic nuclear polarization
von Witte, Gevin Christoph; Himmler, Aaron; Hyppönen, Viivi; et al. (2024)
Nanoscale
Si nanoparticles (NPs) have been actively developed as a hyperpolarized magnetic resonance imaging (MRI) contrast agent with an imaging window close to one hour. However, the progress in the development of NPs has been hampered by the incomplete understanding of their structural properties that correspond to efficient hyperpolarization buildup and long polarization decays. In this work we study dynamic nuclear polarization (DNP) of single crystal porous Si (PSi) NPs with defined doping densities ranging from nominally undoped to highly doped with boron or phosphorus. To develop such PSi NPs we perform low-load metal-assisted catalytic etching for electronic grade Si powder followed by thermal oxidation to form the dangling bonds in the Si/SiO2 interface, the Pb centers. Pb centers are the endogenous source of the unpaired electron spins necessary for DNP. The controlled fabrication and oxidation procedures allow us to thoroughly investigate the impact of the magnetic field, temperature and doping on the DNP process. We argue that the buildup and decay rate constants are independent of size of Si crystals between approximately 10 and 60 nm. Instead, the rates are limited by the polarization transfer across the nuclear spin diffusion barrier determined by the large hyperfine shift of the central 29Si nuclei of the Pb centers. The size-independent rates are then weakly affected by the doping degree for low and moderately doped Si although slight doping is required to achieve the highest polarization. Thus, we find the room temperature relaxation of low boron doped PSi NPs reaching 75 +/- 3 minutes and nuclear polarization levels exceeding similar to 6% when polarized at 6.7 T and 1.4 K. Our study thus establishes solid grounds for further development of Si NPs as hyperpolarized contrast agents.
Age- and sex-specific differences in myocardial sympathetic tone and left ventricular remodeling following myocardial injury
Haider, Achi; Bengs, Susan; Portmann, Angela; et al. (2025)
Biology of Sex Differences
Background Presentations and outcomes of acute myocardial infarction (MI) differ between women and men, with the worst outcomes being reported in younger women. Mental stress induced ischemia and sympathetic activation have been suggested to play a prominent role in the pathogenesis of MI in younger women, however, the impact of sex hormones on these parameters remains unknown. Methods The effect of sex hormones and age on myocardial infarct size and myocardial sympathetic activity (MSA) was assessed in male and female, as well as young (4-6 months) and aged (20-22 months) FVB/N mice (n = 106, 60 gonadectomized and 46 sham-operated animals) who underwent in vivo [C-11]meta-hydroxyephedrine ([C-11]mHED) positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging 24 h after a 30 min myocardial ischemic injury. Results MSA and catecholamine levels following myocardial injury were highest in young males (p = 0.008 and p = 0.043 vs. young females, respectively) and were reduced by orchiectomy. Accordingly, testosterone serum levels correlated positively with MSA (r = 0.66, p < 0.001). Males had a larger average infarct size and lower left ventricular contractility following myocardial injury than females (p < 0.05 vs. females). These sex differences were no longer evident in gonadectomized animals (p = NS vs. females). In female animals, estrogen depletion did not affect MSA (ovariectomy effect, p = 0.892). Female animals showed an age-dependent increase in MSA (p = 0.011), which was absent in males. Conclusion Testosterone associates with an increase in sympathetic tone, contributing to adverse cardiac remodeling following MI. Conversely, females maintain sympathetic integrity, independent of sex hormones. Our results suggest a biological advantage of female sex in post MI recovery. Further research is warranted to confirm these findings in humans.
Closed-chest small animal model to study myocardial infarction in an MRI environment in real time
Oh-Ici, Darach; Jeuthe, Sarah; Dietrich, Thore; et al. (2015)
The International Journal of Cardiovascular Imaging
Current models for real time study of the effects of myocardial ischemia/reperfusion have major limitations and confounders. Confounders include the surgical stresses of a thoracotomy and abnormal physiology of an open chest. The need to reposition the animal interferes with the study of the early changes associated with ischemia. Direct comparison of pre-ischemia and post-ischemia images is then difficult. We developed a novel “closed chest” model of ischemia/reperfusion to overcome these issues. Following thoracotomy, we sutured a balloon occluder to the left coronary artery of male Sprague–Dawley rats. We used both visual inspection and ECG to assess for successful occlusion and reperfusion of the coronary artery at the time of operation by brief inflation and deflation of the balloon. The tubing was then placed under the skin and the incision closed. Following a recovery period (5–10 days), the animals underwent MRI. We performed baseline assessment of left ventricle function, and repeated LV measurement during a 15-min coronary occlusion and again during a 60-min reperfusion period following reopening of the coronary artery. The occluder was successfully placed in 40 of 44 animals. Four developed intraoperative complications; two large myocardial infarction, two terminal bleeding. Six died in the week following surgery, [four sudden deaths (presumed arrhythmic), one anterior infarction, one sepsis]. Cine-MRI demonstrated localised hypokinesia in 31 of the remaining 34 animals. LV ejection fraction (EF) was reduced from 63 ± 7 % at baseline, to 49 ± 9 % during coronary occlusion. LV EF recovered to 61 ± 2 %. The area at risk on staining of the heart was 41.9 ± 15.8 %. This method allows the effects of ischemia/reperfusion to be studied before, during, and after coronary occlusion. Ischemia can be caused while the animal is in the MRI. This new and clinically relevant small animal model is a valuable tool to study the effects of single or repeated coronary occlusion/reperfusion in real-time.

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