TY  - JOUR
A1  - Fiedler, Thomas M.
A1  - Orzada, Stephan
A1  - Flöser, Martina
A1  - Rietsch, Stefan H. G.
A1  - Schmidt, Simon
A1  - Stelter, Jonathan K.
A1  - Wittrich, Marco
A1  - Quick, Harald H.
A1  - Bitz, Andreas
A1  - Ladd, Mark E.
T1  - Performance and safety assessment of an integrated transmitarray for body imaging at 7 T under consideration of specificabsorption rate, tissue temperature, and thermal dose
JF  - NMR in Biomedicine
N2  - In this study, the performance of an integrated body-imaging array for 7 T with 32 radiofrequency (RF) channels under consideration of local specific absorption rate (SAR), tissue temperature, and thermal dose limits was evaluated and the imaging performance was compared with a clinical 3 T body coil.

Thirty-two transmit elements were placed in three rings between the bore liner and RF shield of the gradient coil. Slice-selective RF pulse optimizations for B1 shimming and spokes were performed for differently oriented slices in the body under consideration of realistic constraints for power and local SAR. To improve the B1+ homogeneity, safety assessments based on temperature and thermal dose were performed to possibly allow for higher input power for the pulse optimization than permissible with SAR limits.

The results showed that using two spokes, the 7 T array outperformed the 3 T birdcage in all the considered regions of interest. However, a significantly higher SAR or lower duty cycle at 7 T is necessary in some cases to achieve similar B1+ homogeneity as at 3 T. The homogeneity in up to 50 cm-long coronal slices can particularly benefit from the high RF shim performance provided by the 32 RF channels. The thermal dose approach increases the allowable input power and the corresponding local SAR, in one example up to 100 W/kg, without limiting the exposure time necessary for an MR examination.

In conclusion, the integrated antenna array at 7 T enables a clinical workflow for body imaging and comparable imaging performance to a conventional 3 T clinical body coil.
KW  - body imaging at 7 T MRI
KW  - thermal dose
KW  - tissue temperature
KW  - transmit antenna arrays
Y1  - 2022
U6  - http://dx.doi.org/10.1002/nbm.4656
SN  - 0952-3480 (Print)
SN  - 1099-1492 (Online)
VL  - 35
IS  - 5
SP  - 1
EP  - 17
PB  - Wiley
ER  - 
TY  - JOUR
A1  - Rietsch, Stefan H. G.
A1  - Brunheim, Sascha
A1  - Orzada, Stephan
A1  - Voelker, Maximilian N.
A1  - Maderwald, Stefan
A1  - Bitz, Andreas
A1  - Gratz, Marcel
A1  - Ladd, Mark E.
A1  - Quick, Harald H.
T1  - Development and evaluation of a 16-channel receive-only RF coil to improve 7T ultra-high field body MRI with focus on the spine
JF  - Magnetic Resonance in Medicine
Y1  - 2019
U6  - http://dx.doi.org/10.1002/mrm.27731
SN  - 1522-2594
IS  - Early view
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Rietsch, Stefan H. G.
A1  - Pfaffenrot, Viktor
A1  - Bitz, Andreas
A1  - Orzada, Stephan
A1  - Brunheim, Sascha
A1  - Lazik-Palm, Andrea
A1  - Theysohn, Jens M.
A1  - Ladd, Mark E.
A1  - Quick, Harald H.
A1  - Kraff, Oliver
T1  - An 8-channel transceiver 7-channel receive RF coil setup for high SNR ultrahigh-field MRI of the shoulder at 7T
JF  - Medical Physics
Y1  - 2017
U6  - http://dx.doi.org/10.1002/mp.12612
SN  - 0094-2405
IS  - Article in press
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Bank, Bart L. van de
A1  - Orzada, Stephan
A1  - Smits, Frits
A1  - Lagemaat, Miriam W.
A1  - Rodgers, Christopher T.
A1  - Bitz, Andreas
A1  - Scheenen, Tom W. J.
T1  - Optimized (31) P MRS in the human brain at 7 T with a dedicated RF coil setup
JF  - NMR in Biomedicine
Y1  - 2015
U6  - http://dx.doi.org/10.1002/nbm.3422
SN  - 1099-1492
VL  - 28
IS  - 11
SP  - 1570
EP  - 1578
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lagemaat, Miriam W.
A1  - Maas, Marnix C.
A1  - Vos, Eline K.
A1  - Bitz, Andreas
A1  - Orzada, Stephan
A1  - Weiland, Elisabeth
A1  - Uden, Mark J. van
A1  - Kobus, Thiele
A1  - Heerschap, Arend
A1  - Scheenen, Tom W. J.
T1  - (31) P MR spectroscopic imaging of the human prostate at 7 T: T1 relaxation times, Nuclear Overhauser Effect, and spectral characterization
JF  - Magnetic Resonance in Medicine
Y1  - 2015
U6  - http://dx.doi.org/10.1002/mrm.25209
SN  - 1522-2594
VL  - 73
IS  - 3
SP  - 909
EP  - 920
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kraff, Oliver
A1  - Wrede, Karsten H.
A1  - Schoemberg, Tobias
A1  - Dammann, Philipp
A1  - Noureddine, Yacine
A1  - Orzada, Stephan
A1  - Ladd, Mark E.
A1  - Bitz, Andreas
T1  - MR safety assessment of potential RF heating from cranial fixation plates at 7 T
JF  - Medical Physics
Y1  - 2013
U6  - http://dx.doi.org/10.1118/1.4795347
SN  - 2473-4209
VL  - 40
IS  - 4
SP  - 042302-1
EP  - 042302-10
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Orzada, Stephan
A1  - Johst, Sören
A1  - Maderwald, Stefan
A1  - Bitz, Andreas
A1  - Solbach, Klaus
A1  - Ladd, Mark E.
T1  - Mitigation of B1(+) inhomogeneity on single-channel transmit systems with TIAMO
JF  - Magnetic Resonance in Medicine
Y1  - 2013
U6  - http://dx.doi.org/10.1002/mrm.24453
SN  - 1522-2594
VL  - 70
IS  - 1
SP  - 290
EP  - 294
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Orzada, Stephan
A1  - Bitz, Andreas
A1  - Schäfer, Lena C.
A1  - Ladd, Susanne C.
A1  - Ladd, Mark E.
A1  - Maderwald, Stefan
T1  - Open design eight-channel transmit/receive coil for high-resolution and real-time ankle imaging at 7 T
JF  - Medical Physics
N2  - Purpose:
At 1.5 T, real-time MRI of joint movement has been shown to be feasible. However, 7 T, provides higher SNR and thus an improved potential for parallel imaging acceleration. The purpose of this work was to build an open, U-shaped eight-channel transmit/receive microstrip coil for 7 T MRI to enable high-resolution and real-time imaging of the moving ankle joint.

Methods:
A U-shaped eight-channel transmit/receive array for the human ankle was built.urn:x-wiley:00942405:mp3399:equation:mp3399-math-0001-parameters and urn:x-wiley:00942405:mp3399:equation:mp3399-math-0002-factor were measured. SAR calculations of different ankle postures were performed to ensure patient safety. Inhomogeneities in the transmit field consequent to the open design were compensated for by the use of static RF shimming. High-resolution and real-time imaging was performed in human volunteers.

Results:
The presented array showed good performance with regard to patient comfort and image quality. High acceleration factors of up to 4 are feasible without visible acceleration artifacts. Reasonable image homogeneity was achieved with RF shimming.

Conclusions:
Open, noncylindrical designs for transmit/receive coils are practical at 7 T and real-time imaging of the moving joint is feasible with the presented coil design.
Y1  - 2011
U6  - http://dx.doi.org/10.1118/1.3553399
SN  - 2473-4209
VL  - 38
IS  - 3
SP  - 1162
EP  - 1167
PB  - Wiley
CY  - Hoboken
ER  -