TY  - JOUR
A1  - Kosmala, Aleksander
A1  - Gruschwitz, Philipp
A1  - Veldhoen, Simon
A1  - Weng, Andreas Max
A1  - Krauss, Bernhard
A1  - Bley, Thorsten Alexander
A1  - Petritsch, Bernhard
T1  - Dual-energy CT angiography in suspected pulmonary embolism: influence of injection protocols on image quality and perfused blood volume
JF  - The International Journal of Cardiovascular Imaging
N2  - Abstract
To compare intravenous contrast material (CM) injection protocols for dual-energy CT pulmonary angiography (CTPA) in patients with suspected acute pulmonary embolism with regard to image quality and pulmonary perfused blood volume (PBV) values. A total of 198 studies performed with four CM injection protocols varying in CM volume and iodine delivery rates (IDR) were retrospectively included: (A) 60 ml at 5 ml/s (IDR = 1.75gI/s), (B) 50 ml at 5 ml/s (IDR = 1.75gI/s), (C) 50 ml at 4 ml/s (IDR = 1.40gI/s), (D) 40 ml at 3 ml/s (IDR = 1.05gI/s). Image quality and PBV values at different resolution settings were compared. Pulmonary arterial tract attenuation was highest for protocol A (397 ± 110 HU; p vs. B = 0.13; vs. C = 0.02; vs. D < 0.001). CTPA image quality of protocol A was rated superior compared to protocols B and D by reader 1 (p = 0.01; < 0.001), and superior to protocols B, C and D by reader 2 (p < 0.001; 0.02; < 0.001). Otherwise, there were no significant differences in CTPA quality ratings. Subjective iodine map ratings did not vary significantly between protocols A, B, and C. Both readers rated protocol D inferior to all other protocols (p < 0.05). PBV values did not vary significantly between protocols A and B at resolution settings of 1, 4 and 10 (p = 0.10; 0.10; 0.09), while otherwise PBV values displayed a decreasing trend from protocol A to D (p < 0.05). Higher CM volume and IDR are associated with superior CTPA and iodine map quality and higher absolute PBV values.
KW  - CT
KW  - dual-energy CT
KW  - pulmonary embolism
KW  - contrast media
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-314739
SN  - 1569-5794
SN  - 1573-0743
VL  - 36
IS  - 10
ER  - 
TY  - GEN
A1  - Kosmala, Aleksander
A1  - Gruschwitz, Philipp
A1  - Veldhoen, Simon
A1  - Weng, Andreas Max
A1  - Krauss, Bernhard
A1  - Bley, Thorsten Alexander
A1  - Petritsch, Bernhard
T1  - Correction to: Dual-energy CT angiography in suspected pulmonary embolism: infuence of injection protocols on image quality and perfused blood volume
T2  - The International Journal of Cardiovascular Imaging
N2  - No abstract available.
KW  - correction
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350830
VL  - 38
IS  - 3
SP  - 707
ER  - 
TY  - JOUR
A1  - Schreiber, Laura M.
A1  - Lohr, David
A1  - Baltes, Steffen
A1  - Vogel, Ulrich
A1  - Elabyad, Ibrahim A.
A1  - Bille, Maya
A1  - Reiter, Theresa
A1  - Kosmala, Aleksander
A1  - Gassenmaier, Tobias
A1  - Stefanescu, Maria R.
A1  - Kollmann, Alena
A1  - Aures, Julia
A1  - Schnitter, Florian
A1  - Pali, Mihaela
A1  - Ueda, Yuichiro
A1  - Williams, Tatiana
A1  - Christa, Martin
A1  - Hofmann, Ulrich
A1  - Bauer, Wolfgang
A1  - Gerull, Brenda
A1  - Zernecke, Alma
A1  - Ergün, Süleyman
A1  - Terekhov, Maxim
T1  - Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research
JF  - Frontiers in Cardiovascular Medicine
N2  - A key step in translational cardiovascular research is the use of large animal models to better understand normal and abnormal physiology, to test drugs or interventions, or to perform studies which would be considered unethical in human subjects. Ultrahigh field magnetic resonance imaging (UHF-MRI) at 7 T field strength is becoming increasingly available for imaging of the heart and, when compared to clinically established field strengths, promises better image quality and image information content, more precise functional analysis, potentially new image contrasts, and as all in-vivo imaging techniques, a reduction of the number of animals per study because of the possibility to scan every animal repeatedly. We present here a solution to the dual use problem of whole-body UHF-MRI systems, which are typically installed in clinical environments, to both UHF-MRI in large animals and humans. Moreover, we provide evidence that in such a research infrastructure UHF-MRI, and ideally combined with a standard small-bore UHF-MRI system, can contribute to a variety of spatial scales in translational cardiovascular research: from cardiac organoids, Zebra fish and rodent hearts to large animal models such as pigs and humans. We present pilot data from serial CINE, late gadolinium enhancement, and susceptibility weighted UHF-MRI in a myocardial infarction model over eight weeks. In 14 pigs which were delivered from a breeding facility in a national SARS-CoV-2 hotspot, we found no infection in the incoming pigs. Human scanning using CINE and phase contrast flow measurements provided good image quality of the left and right ventricle. Agreement of functional analysis between CINE and phase contrast MRI was excellent. MRI in arrested hearts or excised vascular tissue for MRI-based histologic imaging, structural imaging of myofiber and vascular smooth muscle cell architecture using high-resolution diffusion tensor imaging, and UHF-MRI for monitoring free radicals as a surrogate for MRI of reactive oxygen species in studies of oxidative stress are demonstrated. We conclude that UHF-MRI has the potential to become an important precision imaging modality in translational cardiovascular research.
KW  - ultrahigh-field MRI
KW  - large animal models
KW  - translational research
KW  - research infrastructure
KW  - heart
KW  - organoid
KW  - pig
KW  - cardiovascular MRI
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-317398
SN  - 2297-055X
VL  - 10
ER  - 
TY  - JOUR
A1  - Herz, Stefan
A1  - Stefanescu, Maria R.
A1  - Lohr, David
A1  - Vogel, Patrick
A1  - Kosmala, Aleksander
A1  - Terekhov, Maxim
A1  - Weng, Andreas M.
A1  - Grunz, Jan-Peter
A1  - Bley, Thorsten A.
A1  - Schreiber, Laura M.
T1  - Effects of image homogeneity on stenosis visualization at 7 T in a coronary artery phantom study: With and without B1-shimming and parallel transmission
JF  - PloS One
N2  - 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.
KW  - stenosis
KW  - magnetic resonance imaging
KW  - thorax
KW  - in vivo imaging
KW  - coronary arteries
KW  - image processing
KW  - 3D printing
KW  - signal to noise ratio
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300129
VL  - 17
IS  - 6
ER  - 
TY  - JOUR
A1  - Hock, Michael
A1  - Terekhov, Maxim
A1  - Stefanescu, Maria Roxana
A1  - Lohr, David
A1  - Herz, Stefan
A1  - Reiter, Theresa
A1  - Ankenbrand, Markus
A1  - Kosmala, Aleksander
A1  - Gassenmaier, Tobias
A1  - Juchem, Christoph
A1  - Schreiber, Laura Maria
T1  - B\(_{0}\) shimming of the human heart at 7T
JF  - Magnetic Resonance in Medicine
N2  - Purpose
Inhomogeneities of the static magnetic B\(_{0}\) field are a major limiting factor in cardiac MRI at ultrahigh field (≥ 7T), as they result in signal loss and image distortions. Different magnetic susceptibilities of the myocardium and surrounding tissue in combination with cardiac motion lead to strong spatio‐temporal B\(_{0}\)‐field inhomogeneities, and their homogenization (B0 shimming) is a prerequisite. Limitations of state‐of‐the‐art shimming are described, regional B\(_{0}\) variations are measured, and a methodology for spherical harmonics shimming of the B\(_{0}\) field within the human myocardium is proposed.

Methods
The spatial B\(_{0}\)‐field distribution in the heart was analyzed as well as temporal B\(_{0}\)‐field variations in the myocardium over the cardiac cycle. Different shim region‐of‐interest selections were compared, and hardware limitations of spherical harmonics B\(_{0}\) shimming were evaluated by calibration‐based B0‐field modeling. The role of third‐order spherical harmonics terms was analyzed as well as potential benefits from cardiac phase–specific shimming.

Results
The strongest B\(_{0}\)‐field inhomogeneities were observed in localized spots within the left‐ventricular and right‐ventricular myocardium and varied between systolic and diastolic cardiac phases. An anatomy‐driven shim region‐of‐interest selection allowed for improved B\(_{0}\)‐field homogeneity compared with a standard shim region‐of‐interest cuboid. Third‐order spherical harmonics terms were demonstrated to be beneficial for shimming of these myocardial B\(_{0}\)‐field inhomogeneities. Initial results from the in vivo implementation of a potential shim strategy were obtained. Simulated cardiac phase–specific shimming was performed, and a shim term‐by‐term analysis revealed periodic variations of required currents.

Conclusion
Challenges in state‐of‐the‐art B\(_{0}\) shimming of the human heart at 7 T were described. Cardiac phase–specific shimming strategies were found to be superior to vendor‐supplied shimming.
KW  - 7 T
KW  - B
KW  - cardiac MRI
KW  - shimming
KW  - ultrahigh field
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218096
VL  - 85
IS  - 1
SP  - 182
EP  - 196
ER  - 
TY  - JOUR
A1  - Grunz, Jan-Peter
A1  - Pennig, Lenhard
A1  - Fieber, Tabea
A1  - Gietzen, Carsten Herbert
A1  - Heidenreich, Julius Frederik
A1  - Huflage, Henner
A1  - Gruschwitz, Philipp
A1  - Kuhl, Philipp Josef
A1  - Petritsch, Bernhard
A1  - Kosmala, Aleksander
A1  - Bley, Thorsten Alexander
A1  - Gassenmaier, Tobias
T1  - Twin robotic x-ray system in small bone and joint trauma: Impact of cone-beam computed tomography on treatment decisions
JF  - European Radiology
N2  - Objectives
Trauma evaluation of extremities can be challenging in conventional radiography. A multi-use x-ray system with cone-beam CT (CBCT) option facilitates ancillary 3-D imaging without repositioning. We assessed the clinical value of CBCT scans by analyzing the influence of additional findings on therapy.

Methods
Ninety-two patients underwent radiography and subsequent CBCT imaging with the twin robotic scanner (76 wrist/hand/finger and 16 ankle/foot/toe trauma scans). Reports by on-call radiologists before and after CBCT were compared regarding fracture detection, joint affliction, comminuted injuries, and diagnostic confidence. An orthopedic surgeon recommended therapy based on reported findings. Surgical reports (N = 52) and clinical follow-up (N = 85) were used as reference standard.

Results
CBCT detected more fractures (83/64 of 85), joint involvements (69/53 of 71), and multi-fragment situations (68/50 of 70) than radiography (all p < 0.001). Six fractures suspected in radiographs were ruled out by CBCT. Treatment changes based on additional information from CBCT were recommended in 29 patients (31.5%). While agreement between advised therapy before CBCT and actual treatment was moderate (κ = 0.41 [95% confidence interval 0.35–0.47]; p < 0.001), agreement after CBCT was almost perfect (κ = 0.88 [0.83–0.93]; p < 0.001). Diagnostic confidence increased considerably for CBCT studies (p < 0.001). Median effective dose for CBCT was 4.3 μSv [3.3–5.3 μSv] compared to 0.2 μSv [0.1–0.2 μSv] for radiography.

Conclusions
CBCT provides advantages for the evaluation of acute small bone and joint trauma by detecting and excluding extremity fractures and fracture-related findings more reliably than radiographs. Additional findings induced therapy change in one third of patients, suggesting substantial clinical impact.
KW  - cone-beamcomputed tomography
KW  - extremities
KW  - fractures, bone
KW  - radiography
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-235233
SN  - 0938-7994
VL  - 31
ER  - 
TY  - JOUR
A1  - Petritsch, Bernhard
A1  - Pannbecker, Pauline
A1  - Weng, Andreas M.
A1  - Grunz, Jan-Peter
A1  - Veldhoen, Simon
A1  - Bley, Thorsten A.
A1  - Kosmala, Aleksander
T1  - Split-filter dual-energy CT pulmonary angiography for the diagnosis of acute pulmonary embolism: a study on image quality and radiation dose
JF  - Quantitative Imaging in Medicine and Surgery
N2  - Background: Computed tomography (CT) pulmonary angiography is the diagnostic reference standard in suspected pulmonary embolism (PE). Favorable results for dual-energy CT (DECT) images have been reported for this condition. Nowadays, dual-energy data acquisition is feasible with different technical options, including a single-source split-filter approach. Therefore, the aim of this retrospective study was to investigate image quality and radiation dose of thoracic split-filter DECT in comparison to conventional single-energy CT in patients with suspected PE.

Methods: A total of 110 CT pulmonary angiographies were accomplished either as standard single-energy CT with automatic tube voltage selection (ATVS) (n=58), or as split-filter DECT (n=52). Objective [pulmonary artery CT attenuation, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR)] and subjective image quality [four-point Likert scale; three readers (R)] were compared among the two study groups. Size-specific dose estimates (SSDE), dose-length-product (DLP) and volume CT dose index (CTDIvol) were assessed for radiation dose analysis.

Results: Split-filter DECT images yielded 67.7% higher SNR (27.0 vs. 16.1; P<0.001) and 61.9% higher CNR (22.5 vs. 13.9; P<0.001) over conventional single-energy images, whereas CT attenuation was significantly lower (344.5 vs. 428.2 HU; P=0.013). Subjective image quality was rated good or excellent in 93.0%/98.3%/77.6% (R1/R2/R3) of the single-energy CT scans, and 84.6%/82.7%/80.8% (R1/R2/R3) of the split-filter DECT scans. SSDE, DLP and CTDIvol were significantly lower for conventional single-energy CT compared to split-filter DECT (all P<0.05), which was associated with 26.7% higher SSDE.

Conclusions: In the diagnostic workup of acute PE, the split-filter allows for dual-energy data acquisition from single-source single-layer CT scanners. The existing opportunity to assess pulmonary “perfusion” based on analysis of iodine distribution maps is associated with higher radiation dose in terms of increased SSDE than conventional single-energy CT with ATVS. Moreover, a proportion of up to 3.8% non-diagnostic examinations in the current reference standard test for PE is not negligible.
KW  - dual-energy
KW  - CT-angiography
KW  - vascular
KW  - pulmonary arteries
KW  - embolism/thrombosis
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-231456
VL  - 11
IS  - 5
ER  - 
TY  - JOUR
A1  - Petritsch, Berhard
A1  - Kosmala, Aleksander
A1  - Weng, Andreas Max
A1  - Bley, Thorsten Alexander
T1  - Tin-filtered 100kV ultra-low-dose CT of the paranasal sinus: initial clinical results
JF  - PLoS ONE
N2  - Objectives
To investigate the feasibility, diagnostic image quality and radiation dose of 3\(^{rd}\) generation dual-source computed tomography (CT) using a tin-filtered 100 kV protocol in patients with suspected acute inflammatory sinus disease.

Methods
We retrospectively evaluated 109 consecutive patients who underwent CT (Siemens SOMATOM Force, Erlangen, Germany) of the paranasal sinus with a new tin-filtered scanprotocol (Sn100 kV; tube current 35 mAs) using iterative reconstruction. Two readers independently assessed subjective image quality using a five-point Likert scale (1 = excellent, 5 = non-diagnostic). Inter-observer agreement was calculated and expressed as percentage of agreement. Noise was determined for calculation of signal-to-noise-ratio (SNR). Effective radiation dose (ED) was calculated from the dose-length-product (DLP).

Results
All examinations showed diagnostic image quality regarding evaluation of inflammatory sinus disease. On average, subjective general image quality was rated moderate (= 3) with a percentage of agreement between the observers of 81%. The mean image noise was 14.3 HU. The calculated median SNR was 6.0 for intraorbital fat, and 3.6 for the vitreous body, respectively. The median DLP was 2.1 mGy*cm, resulting in a median ED of 0.012 mSv.

Conclusions
Taking the study limitations into account, ultra-low-dose tin-filtered CT of the paranasal sinus at a tube voltage of 100 kV utilizing an iterative reconstruction algorithm provides for reliable exclusion of suspected acute inflammatory sinus disease in 100% of the cases.
KW  - Computed axial tomography
KW  - Inflammatory diseases
KW  - Radiation exposure
KW  - Diagnostic medicine
KW  - Fats
KW  - Mastoid process
KW  - X-ray radiography
KW  - Soft tissues
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204127
VL  - 14
IS  - 5
ER  -