@article{UeceylerHomolaGonzalezetal.2014, author = {{\"U}{\c{c}}eyler, Nurcan and Homola, Gy{\"o}rgy A. and Gonz{\´a}lez, Hans Guerrero and Kramer, Daniela and Wanner, Christoph and Weidemann, Frank and Solymosi, L{\´a}szl{\´o} and Sommer, Claudia}, title = {Increased Arterial Diameters in the Posterior Cerebral Circulation in Men with Fabry Disease}, doi = {10.1371/journal.pone.0087054}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-112614}, year = {2014}, abstract = {A high load of white matter lesions and enlarged basilar arteries have been shown in selected patients with Fabry disease, a disorder associated with an increased stroke risk. We studied a large cohort of patients with Fabry disease to differentially investigate white matter lesion load and cerebral artery diameters. We retrospectively analyzed cranial magnetic resonance imaging scans of 87 consecutive Fabry patients, 20 patients with ischemic stroke, and 36 controls. We determined the white matter lesion load applying the Fazekas score on fluid-attenuated inversion recovery sequences and measured the diameters of cerebral arteries on 3D-reconstructions of the time-of-flight-MR-angiography scans. Data of different Fabry patient subgroups (males - females; normal - impaired renal function) were compared with data of patients with stroke and controls. A history of stroke or transient ischemic attacks was present in 4/30 males (13\%) and 5/57 (9\%) females with Fabry disease, all in the anterior circulation. Only one man with Fabry disease showed confluent cerebral white matter lesions in the Fazekas score assessment (1\%). Male Fabry patients had a larger basilar artery (p<0.01) and posterior cerebral artery diameter (p<0.05) compared to male controls. This was independent of disease severity as measured by renal function and did not lead to changes in arterial blood flow properties. A basilar artery diameter of >3.2 mm distinguished between men with Fabry disease and controls (sensitivity: 87\%, specificity: 86\%, p<0.001), but not from stroke patients. Enlarged arterial diameters of the posterior circulation are present only in men with Fabry disease independent of disease severity.}, language = {en} } @article{TranGiaWechBleyetal.2015, author = {Tran-Gia, Johannes and Wech, Tobias and Bley, Thorsten and K{\"o}stler, Herbert}, title = {Model-Based Acceleration of Look-Locker T1 Mapping}, series = {PLoS One}, volume = {10}, journal = {PLoS One}, number = {4}, doi = {10.1371/journal.pone.0122611}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126436}, pages = {e0122611}, year = {2015}, abstract = {Mapping the longitudinal relaxation time \(T_1\) has widespread applications in clinical MRI as it promises a quantitative comparison of tissue properties across subjects and scanners. Due to the long scan times of conventional methods, however, the use of quantitative MRI in clinical routine is still very limited. In this work, an acceleration of Inversion-Recovery Look-Locker (IR-LL) \(T_1\) mapping is presented. A model-based algorithm is used to iteratively enforce an exponential relaxation model to a highly undersampled radially acquired IR-LL dataset obtained after the application of a single global inversion pulse. Using the proposed technique, a \(T_1\) map of a single slice with 1.6mm in-plane resolution and 4mm slice thickness can be reconstructed from data acquired in only 6s. A time-consuming segmented IR experiment was used as gold standard for \(T_1\) mapping in this work. In the subsequent validation study, the model-based reconstruction of a single-inversion IR-LL dataset exhibited a \(T_1\) difference of less than 2.6\% compared to the segmented IR-LL reference in a phantom consisting of vials with \(T_1\) values between 200ms and 3000ms. In vivo, the \(T_1\) difference was smaller than 5.5\% in WM and GM of seven healthy volunteers. Additionally, the \(T_1\) values are comparable to standard literature values. Despite the high acceleration, all model-based reconstructions were of a visual quality comparable to fully sampled references. Finally, the reproducibility of the \(T_1\) mapping method was demonstrated in repeated acquisitions. In conclusion, the presented approach represents a promising way for fast and accurate \(T_1\) mapping using radial IR-LL acquisitions without the need of any segmentation.}, language = {en} } @phdthesis{Portmann2023, author = {Portmann, Johannes}, title = {Accelerated inversion recovery MRI of the myocardium using spiral acquisition}, doi = {10.25972/OPUS-30282}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-302822}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {This work deals with the acceleration of cardiovascular MRI for the assessment of functional information in steady-state contrast and for viability assessment during the inversion recovery of the magnetization. Two approaches are introduced and discussed in detail. MOCO-MAP uses an exponential model to recover dynamic image data, IR-CRISPI, with its low-rank plus sparse reconstruction, is related to compressed sensing. MOCO-MAP is a successor to model-based acceleration of parametermapping (MAP) for the application in the myocardial region. To this end, it was augmented with a motion correction (MOCO) step to allow exponential fitting the signal of a still object in temporal direction. Iteratively, this introduction of prior physical knowledge together with the enforcement of consistency with the measured data can be used to reconstruct an image series from distinctly shorter sampling time than the standard exam (< 3 s opposed to about 10 s). Results show feasibility of the method as well as detectability of delayed enhancement in the myocardium, but also significant discrepancies when imaging cardiac function and artifacts caused already by minor inaccuracy of the motion correction. IR-CRISPI was developed from CRISPI, which is a real-time protocol specifically designed for functional evaluation of image data in steady-state contrast. With a reconstruction based on the separate calculation of low-rank and sparse part, it employs a softer constraint than the strict exponential model, which was possible due to sufficient temporal sampling density via spiral acquisition. The low-rank plus sparse reconstruction is fit for the use on dynamic and on inversion recovery data. Thus, motion correction is rendered unnecessary with it. IR-CRISPI was equipped with noise suppression via spatial wavelet filtering. A study comprising 10 patients with cardiac disease show medical applicability. A comparison with performed traditional reference exams offer insight into diagnostic benefits. Especially regarding patients with difficulty to hold their breath, the real-time manner of the IR-CRISPI acquisition provides a valuable alternative and an increase in robustness. In conclusion, especially with IR-CRISPI in free breathing, a major acceleration of the cardiovascular MR exam could be realized. In an acquisition of less than 100 s, it not only includes the information of two traditional protocols (cine and LGE), which take up more than 9.6 min, but also allows adjustment of TI in retrospect and yields lower artifact level with similar image quality.}, subject = {Kernspintomografie}, language = {en} } @article{PetritschKoestlerGassenmaieretal.2016, author = {Petritsch, Bernhard and K{\"o}stler, Herbert and Gassenmaier, Tobias and Kunz, Andreas S and Bley, Thorsten A and Horn, Michael}, title = {An investigation into potential gender-specific differences in myocardial triglyceride content assessed by \(^{1}\)H-Magnetic Resonance Spectroscopy at 3Tesla}, series = {Journal of International Medical Research}, volume = {44}, journal = {Journal of International Medical Research}, number = {3}, doi = {10.1177/0300060515603884}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168808}, pages = {585-591}, year = {2016}, abstract = {Objective: Over the past decade, myocardial triglyceride content has become an accepted biomarker for chronic metabolic and cardiac disease. The purpose of this study was to use proton (hydrogen 1)-magnetic resonance spectroscopy (\(^{1}\)H-MRS) at 3Tesla (3 T) field strength to assess potential gender-related differences in myocardial triglyceride content in healthy individuals. Methods: Cardiac MR imaging was performed to enable accurate voxel placement and obtain functional and morphological information. Double triggered (i.e., ECG and respiratory motion gating) \(^{1}\)H-MRS was used to quantify myocardial triglyceride levels for each gender. Two-sample t-test and Mann-Whitney U-test were used for statistical analyses. Results: In total, 40 healthy volunteers (22 male, 18 female; aged >18 years and age matched) were included in the study. Median myocardial triglyceride content was 0.28\% (interquartile range [IQR] 0.17-0.42\%) in male and 0.24\% (IQR 0.14-0.45\%) in female participants, and no statistically significant difference was observed between the genders. Furthermore, no gender-specific difference in ejection fraction was observed, although on average, male participants presented with a higher mean ± SD left ventricular mass (136.3 ± 25.2 g) than female participants (103.9 ± 16.1 g). Conclusions: The study showed that \(^{1}\)H-MRS is a capable, noninvasive tool for acquisition of myocardial triglyceride metabolites. Myocardial triglyceride concentration was shown to be unrelated to gender in this group of healthy volunteers.}, language = {en} } @phdthesis{Kleineisel2024, author = {Kleineisel, Jonas}, title = {Variational networks in magnetic resonance imaging - Application to spiral cardiac MRI and investigations on image quality}, doi = {10.25972/OPUS-34737}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-347370}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {Acceleration is a central aim of clinical and technical research in magnetic resonance imaging (MRI) today, with the potential to increase robustness, accessibility and patient comfort, reduce cost, and enable entirely new kinds of examinations. A key component in this endeavor is image reconstruction, as most modern approaches build on advanced signal and image processing. Here, deep learning (DL)-based methods have recently shown considerable potential, with numerous publications demonstrating benefits for MRI reconstruction. However, these methods often come at the cost of an increased risk for subtle yet critical errors. Therefore, the aim of this thesis is to advance DL-based MRI reconstruction, while ensuring high quality and fidelity with measured data. A network architecture specifically suited for this purpose is the variational network (VN). To investigate the benefits these can bring to non-Cartesian cardiac imaging, the first part presents an application of VNs, which were specifically adapted to the reconstruction of accelerated spiral acquisitions. The proposed method is compared to a segmented exam, a U-Net and a compressed sensing (CS) model using qualitative and quantitative measures. While the U-Net performed poorly, the VN as well as the CS reconstruction showed good output quality. In functional cardiac imaging, the proposed real-time method with VN reconstruction substantially accelerates examinations over the gold-standard, from over 10 to just 1 minute. Clinical parameters agreed on average. Generally in MRI reconstruction, the assessment of image quality is complex, in particular for modern non-linear methods. Therefore, advanced techniques for precise evaluation of quality were subsequently demonstrated. With two distinct methods, resolution and amplification or suppression of noise are quantified locally in each pixel of a reconstruction. Using these, local maps of resolution and noise in parallel imaging (GRAPPA), CS, U-Net and VN reconstructions were determined for MR images of the brain. In the tested images, GRAPPA delivers uniform and ideal resolution, but amplifies noise noticeably. The other methods adapt their behavior to image structure, where different levels of local blurring were observed at edges compared to homogeneous areas, and noise was suppressed except at edges. Overall, VNs were found to combine a number of advantageous properties, including a good trade-off between resolution and noise, fast reconstruction times, and high overall image quality and fidelity of the produced output. Therefore, this network architecture seems highly promising for MRI reconstruction.}, subject = {Kernspintomografie}, language = {en} } @article{HuflageKarstenKunzetal.2021, author = {Huflage, Henner and Karsten, Sebastian and Kunz, Andreas Steven and Conrads, Nora and Jakubietz, Rafael Gregor and Jakubietz, Michael Georg and Pennig, Lenhard and Goertz, Lukas and Bley, Thorsten Alexander and Schmitt, Rainer and Grunz, Jan-Peter}, title = {Improved diagnostic accuracy for ulnar-sided TFCC lesions with radial reformation of 3D sequences in wrist MR arthrography}, series = {European Radiology}, volume = {31}, journal = {European Radiology}, number = {12}, issn = {1432-1084}, doi = {10.1007/s00330-021-08024-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-266512}, pages = {9399-9407}, year = {2021}, abstract = {Objectives Triangular fibrocartilage complex (TFCC) injuries frequently cause ulnar-sided wrist pain and can induce distal radioulnar joint instability. With its complex three-dimensional structure, diagnosis of TFCC lesions remains a challenging task even in MR arthrograms. The aim of this study was to assess the added diagnostic value of radial reformatting of isotropic 3D MRI datasets compared to standard planes after direct arthrography of the wrist. Methods Ninety-three patients underwent wrist MRI after fluoroscopy-guided multi-compartment arthrography. Two radiologists collectively analyzed two datasets of each MR arthrogram for TFCC injuries, with one set containing standard reconstructions of a 3D thin-slice sequence in axial, coronal and sagittal orientation, while the other set comprised an additional radial plane view with the rotating center positioned at the ulnar styloid. Surgical reports (whenever available) or radiological reports combined with clinical follow-up served as a standard of reference. In addition, diagnostic confidence and assessability of the central disc and ulnar-sided insertions were subjectively evaluated. Results Injuries of the articular disc, styloid and foveal ulnar attachment were present in 20 (23.7\%), 10 (10.8\%) and 9 (9.7\%) patients. Additional radial planes increased diagnostic accuracy for lesions of the styloid (0.83 vs. 0.90; p = 0.016) and foveal (0.86 vs. 0.94; p = 0.039) insertion, whereas no improvement was identified for alterations of the central cartilage disc. Readers' confidence (p < 0.001) and assessability of the ulnar-sided insertions (p < 0.001) were superior with ancillary radial reformatting. Conclusions Access to the radial plane view of isotropic 3D sequences in MR arthrography improves diagnostic accuracy and confidence for ulnar-sided TFCC lesions.}, language = {en} } @article{HerzStefanescuLohretal.2022, author = {Herz, Stefan and Stefanescu, Maria R. and Lohr, David and Vogel, Patrick and Kosmala, Aleksander and Terekhov, Maxim and Weng, Andreas M. and Grunz, Jan-Peter and Bley, Thorsten A. and Schreiber, Laura M.}, title = {Effects of image homogeneity on stenosis visualization at 7 T in a coronary artery phantom study: With and without B1-shimming and parallel transmission}, series = {PloS One}, volume = {17}, journal = {PloS One}, number = {6}, doi = {10.1371/journal.pone.0270689}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300129}, year = {2022}, abstract = {Background To investigate the effects of B\(_1\)-shimming and radiofrequency (RF) parallel transmission (pTX) on the visualization and quantification of the degree of stenosis in a coronary artery phantom using 7 Tesla (7 T) magnetic resonance imaging (MRI). Methods Stenosis phantoms with different grades of stenosis (0\%, 20\%, 40\%, 60\%, 80\%, and 100\%; 5 mm inner vessel diameter) were produced using 3D printing (clear resin). Phantoms were imaged with four different concentrations of diluted Gd-DOTA representing established arterial concentrations after intravenous injection in humans. Samples were centrally positioned in a thorax phantom of 30 cm diameter filled with a custom-made liquid featuring dielectric properties of muscle tissue. MRI was performed on a 7 T whole-body system. 2D-gradient-echo sequences were acquired with an 8-channel transmit 16-channel receive (8 Tx / 16 Rx) cardiac array prototype coil with and without pTX mode. Measurements were compared to those obtained with identical scan parameters using a commercially available 1 Tx / 16 Rx single transmit coil (sTX). To assess reproducibility, measurements (n = 15) were repeated at different horizontal angles with respect to the B0-field. Results B\(_1\)-shimming and pTX markedly improved flip angle homogeneity across the thorax phantom yielding a distinctly increased signal-to-noise ratio (SNR) averaged over a whole slice relative to non-manipulated RF fields. Images without B\(_1\)-shimming showed shading artifacts due to local B\(_1\)\(^+\)-field inhomogeneities, which hampered stenosis quantification in severe cases. In contrast, B\(_1\)-shimming and pTX provided superior image homogeneity. Compared with a conventional sTX coil higher grade stenoses (60\% and 80\%) were graded significantly (p<0.01) more precise. Mild to moderate grade stenoses did not show significant differences. Overall, SNR was distinctly higher with B\(_1\)-shimming and pTX than with the conventional sTX coil (inside the stenosis phantoms 14\%, outside the phantoms 32\%). Both full and half concentration (10.2 mM and 5.1 mM) of a conventional Gd-DOTA dose for humans were equally suitable for stenosis evaluation in this phantom study. Conclusions B\(_1\)-shimming and pTX at 7 T can distinctly improve image homogeneity and therefore provide considerably more accurate MR image analysis, which is beneficial for imaging of small vessel structures.}, language = {en} } @article{GuggenbergerVogtSongetal.2023, author = {Guggenberger, Konstanze V. and Vogt, Marius L. and Song, Jae W. and Weng, Andreas M. and Fr{\"o}hlich, Matthias and Schmalzing, Marc and Venhoff, Nils and Hillenkamp, Jost and Pham, Mirko and Meckel, Stephan and Bley, Thorsten A.}, title = {Intraorbital findings in giant cell arteritis on black blood MRI}, series = {European Radiology}, volume = {33}, journal = {European Radiology}, number = {4}, doi = {10.1007/s00330-022-09256-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324978}, pages = {2529-2535}, year = {2023}, abstract = {Objective Blindness is a feared complication of giant cell arteritis (GCA). However, the spectrum of pathologic orbital imaging findings on magnetic resonance imaging (MRI) in GCA is not well understood. In this study, we assess inflammatory changes of intraorbital structures on black blood MRI (BB-MRI) in patients with GCA compared to age-matched controls. Methods In this multicenter case-control study, 106 subjects underwent BB-MRI. Fifty-six patients with clinically or histologically diagnosed GCA and 50 age-matched controls without clinical or laboratory evidence of vasculitis were included. All individuals were imaged on a 3-T MR scanner with a post-contrast compressed-sensing (CS) T1-weighted sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) BB-MRI sequence. Imaging results were correlated with available clinical symptoms. Results Eighteen of 56 GCA patients (32\%) showed inflammatory changes of at least one of the intraorbital structures. The most common finding was enhancement of at least one of the optic nerve sheaths (N = 13, 72\%). Vessel wall enhancement of the ophthalmic artery was unilateral in 8 and bilateral in 3 patients. Enhancement of the optic nerve was observed in one patient. There was no significant correlation between imaging features of inflammation and clinically reported orbital symptoms (p = 0.10). None of the age-matched control patients showed any inflammatory changes of intraorbital structures. Conclusions BB-MRI revealed inflammatory findings in the orbits in up to 32\% of patients with GCA. Optic nerve sheath enhancement was the most common intraorbital inflammatory change on BB-MRI. MRI findings were independent of clinically reported orbital symptoms. Key Points • Up to 32\% of GCA patients shows signs of inflammation of intraorbital structures on BB-MRI. • Enhancement of the optic nerve sheath is the most common intraorbital finding in GCA patients on BB-MRI. • Features of inflammation of intraorbital structures are independent of clinically reported symptoms.}, language = {en} } @article{ElsnerKunzWagneretal.2023, author = {Elsner, Clara and Kunz, Andreas Steven and Wagner, Nicole and Huflage, Henner and H{\"u}bner, Stefan and Luetkens, Karsten Sebastian and Bley, Thorsten Alexander and Schmitt, Rainer and Erg{\"u}n, S{\"u}leyman and Grunz, Jan-Peter}, title = {MRI-based evaluation of the flexor digitorum superficialis anatomy: investigating the prevalence and morphometry of the "chiasma antebrachii"}, series = {Diagnostics}, volume = {13}, journal = {Diagnostics}, number = {14}, issn = {2075-4418}, doi = {10.3390/diagnostics13142406}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-362631}, year = {2023}, abstract = {Recent dissection studies resulted in the introduction of the term "chiasma antebrachii", which represents an intersection of the flexor digitorum superficialis (FDS) tendons for digits 2 and 3 in the distal third of the forearm. This retrospective investigation aimed to provide an MRI-based morphologic analysis of the chiasma antebrachii. In 89 patients (41 women, 39.3 ± 21.3 years), MRI examinations of the forearm (2010-2021) were reviewed by two radiologists, who evaluated all studies for the presence and length of the chiasma as well as its distance from the distal radioulnar and elbow joint. The chiasma antebrachii was identified in the distal third of the forearm in 88 patients (98.9\%), while one intersection was located more proximally in the middle part. The chiasma had a median length of 28 mm (interquartile range: 24-35 mm). Its distances to the distal radioulnar and elbow joint were 16 mm (8-25 mm) and 215 mm (187-227 mm), respectively. T1-weighted post-contrast sequences were found to be superior to T2- or proton-density-weighted sequences in 71 cases (79.8\%). To conclude, the chiasma antebrachii is part of the standard FDS anatomy. Knowledge of its morphology is important, e.g., in targeted injections of therapeutics or reconstructive surgery.}, language = {en} } @article{BiedererMirsadraeeBeeretal.2012, author = {Biederer, J{\"u}rgen and Mirsadraee, S. and Beer, M. and Molinari, F. and Hintze, C. and Bauman, G. and Both, M. and Van Beek, E. J. R. and Wild, J. and Puderbach, M.}, title = {MRI of the lung (3/3)—current applications and future perspectives}, series = {Insights into Imaging}, volume = {3}, journal = {Insights into Imaging}, number = {4}, doi = {10.1007/s13244-011-0142-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-124348}, pages = {373-386}, year = {2012}, abstract = {Background MRI of the lung is recommended in a number of clinical indications. Having a non-radiation alternative is particularly attractive in children and young subjects, or pregnant women. Methods Provided there is sufficient expertise, magnetic resonance imaging (MRI) may be considered as the preferential modality in specific clinical conditions such as cystic fibrosis and acute pulmonary embolism, since additional functional information on respiratory mechanics and regional lung perfusion is provided. In other cases, such as tumours and pneumonia in children, lung MRI may be considered an alternative or adjunct to other modalities with at least similar diagnostic value. Results In interstitial lung disease, the clinical utility of MRI remains to be proven, but it could provide additional information that will be beneficial in research, or at some stage in clinical practice. Customised protocols for chest imaging combine fast breath-hold acquisitions from a "buffet" of sequences. Having introduced details of imaging protocols in previous articles, the aim of this manuscript is to discuss the advantages and limitations of lung MRI in current clinical practice. Conclusion New developments and future perspectives such as motion-compensated imaging with self-navigated sequences or fast Fourier decomposition MRI for non-contrast enhanced ventilation- and perfusion-weighted imaging of the lung are discussed. Main Messages • MRI evolves as a third lung imaging modality, combining morphological and functional information. • It may be considered first choice in cystic fibrosis and pulmonary embolism of young and pregnant patients. • In other cases (tumours, pneumonia in children), it is an alternative or adjunct to X-ray and CT. • In interstitial lung disease, it serves for research, but the clinical value remains to be proven. • New users are advised to make themselves familiar with the particular advantages and limitations.}, language = {en} }