Lukas Wissmann


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Wissmann

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Lukas

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0000-0001-8849-1470

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2014 - 201942020 - 20231
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Publications 1 - 5 of 5
  • Diffuse myocardial fibrosis precedes subclinical functional myocardial impairment and provides prognostic information in systemic sclerosis
    Item type: Journal Article
    Gotschy, Alexander; Jordan, Suzana; Stoeck, Christian; et al. (2023)
    European Heart Journal. Cardiovascular Imaging
    Aims Myocardial involvement is common in patients with systemic sclerosis (SSc) and causes myocardial fibrosis and subtle ventricular dysfunction. However, the temporal onset of myocardial involvement during the progression of the disease and its prognostic value are yet unknown. We used cardiovascular magnetic resonance (CMR) to investigate subclinical functional impairment and diffuse myocardial fibrosis in patients with very early diagnosis of SSc (VEDOSS) and established SSc and examined whether this was associated with mortality. Methods and results One hundred and ten SSc patients (86 established SSc, 24 VEDOSS) and 15 healthy controls were prospectively recruited. The patients were followed-up for a median duration of 7.0 years (interquartile range 6.0-7.3 years). Study subjects underwent CMR including assessment of myocardial fibrosis [native T1 and extracellular volume (ECV)] and measurement of global longitudinal (GLS) and circumferential (GCS) myocardial strain. Native T1 values and ECV were elevated in VEDOSS and SSc patients compared with controls (P < 0.001). GLS was similar in VEDOSS and controls but significantly impaired in patients with established SSc (P < 0.001). GCS was similar over all groups (P = 0.88). There were 12 deaths during follow-up. Elevated native T1 [hazard ratio (HR) 5.8, 95% confidence interval (CI): 1.7-20.4; P = 0.006] and reduced GLS (HR 6.1, 95% CI: 1.3-29.9; P = 0.038) identified subjects with increased risk of death. Only native T1 was predictive for cardiovascular mortality (P < 0.001). Conclusion Subclinical myocardial involvement first manifests as diffuse myocardial fibrosis identified by the expansion of ECV and increased native T1 in VEDOSS patients while subtle functional impairment only occurs in established SSc. Native T1 and GLS have prognostic value for all-cause mortality in SSc patients.
  • Hyperpolarized metabolic imaging of myocardial ischemia-reperfusion in a small-animal model at 9.4T
    Item type: Other Conference Item
    H-Ici, Darach O.; Wespi, Patrick; Busch, Julia; et al. (2015)
    Journal of Cardiovascular Magnetic Resonance
  • Analysis of spatiotemporal fidelity in quantitative 3D first-pass perfusion cardiovascular magnetic resonance
    Item type: Journal Article
    Wissmann, Lukas; Gotschy, Alexander; Santelli, Claudio; et al. (2017)
    Journal of Cardiovascular Magnetic Resonance
    Background Whole-heart first-pass perfusion cardiovascular magnetic resonance (CMR) relies on highly accelerated image acquisition. The influence of undersampling on myocardial blood flow (MBF) quantification has not been systematically investigated yet. In the present work, the effect of spatiotemporal scan acceleration on image reconstruction accuracy and MBF error was studied using a numerical phantom and validated in-vivo. Methods Up to 10-fold scan acceleration using k-t PCA and k-t SPARSE-SENSE was simulated using the MRXCAT CMR numerical phantom framework. Image reconstruction results were compared to ground truth data in the k-f domain by means of modulation transfer function (MTF) analysis. In the x-t domain, errors pertaining to specific features of signal intensity-time curves and MBF values derived using Fermi model deconvolution were analysed. In-vivo first-pass CMR data were acquired in ten healthy volunteers using a dual-sequence approach assessing the arterial input function (AIF) and myocardial enhancement. 10x accelerated 3D k-t PCA and k-t SPARSE-SENSE were compared and related to non-accelerated 2D reference images. Results MTF analysis revealed good recovery of data upon k-t PCA reconstruction at 10x undersampling with some attenuation of higher temporal frequencies. For 10x k-t SPARSE-SENSE the MTF was found to decrease to zero at high spatial frequencies for all temporal frequencies indicating a loss in spatial resolution. Signal intensity-time curve errors were most prominent in AIFs from 10x k-t PCA, thereby emphasizing the need for separate AIF acquisition using a dual-sequence approach. These findings were confirmed by MBF estimation based on AIFs from fully sampled and undersampled simulations. Average in-vivo MBF estimates were in good agreement between both accelerated and the fully sampled methods. Intra-volunteer MBF variation for fully sampled 2D scans was lower compared to 10x k-t PCA and k-t SPARSE-SENSE data. Conclusion Quantification of highly undersampled 3D first-pass perfusion CMR yields accurate MBF estimates provided the AIF is obtained using fully sampled or moderately undersampled scans as part of a dual-sequence approach. However, relative to fully sampled 2D perfusion imaging, intra-volunteer variation is increased using 3D approaches prompting for further developments.
  • Quantitative three-dimensional myocardial perfusion cardiovascular magnetic resonance with accurate two-dimensional arterial input function assessment
    Item type: Journal Article
    Wissmann, Lukas; Niemann, Markus; Gotschy, Alexander; et al. (2015)
    Journal of Cardiovascular Magnetic Resonance
    Background Quantification of myocardial perfusion from first-pass cardiovascular magnetic resonance (CMR) images at high contrast agent (CA) dose requires separate acquisition of blood pool and myocardial tissue enhancement. In this study, a dual-sequence approach interleaving 2D imaging of the arterial input function with high-resolution 3D imaging for myocardial perfusion assessment is presented and validated for low and high CA dose. Methods A dual-sequence approach interleaving 2D imaging of the aortic root and 3D imaging of the whole left ventricle using highly accelerated k-t PCA was implemented. Rest perfusion imaging was performed in ten healthy volunteers after administration of a Gadolinium-based CA at low (0.025 mmol/kg b.w.) and high dose (0.1 mmol/kg b.w.). Arterial input functions extracted from the 2D and 3D images were analysed for both doses. Myocardial contrast-to-noise ratios (CNR) were compared across volunteers and doses. Variations of myocardial perfusion estimates between volunteers and across myocardial territories were studied. Results High CA dose imaging resulted in strong non-linearity of the arterial input function in the 3D images at peak CA concentration, which was avoided when the input function was derived from the 2D images. Myocardial CNR was significantly increased at high dose compared to low dose, with a 2.6-fold mean CNR gain. Most robust myocardial blood flow estimation was achieved using the arterial input function extracted from the 2D image at high CA dose. In this case, myocardial blood flow estimates varied by 24 % between volunteers and by 20 % between myocardial territories when analysed on a per-volunteer basis. Conclusion Interleaving 2D imaging for arterial input function assessment enables robust quantitative 3D myocardial perfusion imaging at high CA dose.
  • MRXCAT: Realistic numerical phantoms forcardiovascular magnetic resonance
    Item type: Journal Article
    Wissmann, Lukas; Santelli, Claudio; Segars, William P.; et al. (2014)
    Journal of Cardiovascular Magnetic Resonance
    Background Computer simulations are important for validating novel image acquisition and reconstruction strategies. In cardiovascular magnetic resonance (CMR), numerical simulations need to combine anatomical information and the effects of cardiac and/or respiratory motion. To this end, a framework for realistic CMR simulations is proposed and its use for image reconstruction from undersampled data is demonstrated. Methods The extended Cardiac-Torso (XCAT) anatomical phantom framework with various motion options was used as a basis for the numerical phantoms. Different tissue, dynamic contrast and signal models, multiple receiver coils and noise are simulated. Arbitrary trajectories and undersampled acquisition can be selected. The utility of the framework is demonstrated for accelerated cine and first-pass myocardial perfusion imaging using k-t PCA and k-t SPARSE. Results MRXCAT phantoms allow for realistic simulation of CMR including optional cardiac and respiratory motion. Example reconstructions from simulated undersampled k-t parallel imaging demonstrate the feasibility of simulated acquisition and reconstruction using the presented framework. Myocardial blood flow assessment from simulated myocardial perfusion images highlights the suitability of MRXCAT for quantitative post-processing simulation. Conclusion The proposed MRXCAT phantom framework enables versatile and realistic simulations of CMR including breathhold and free-breathing acquisitions.
Publications 1 - 5 of 5