TY  - JOUR
A1  - Orzada, Stephan
A1  - Ladd, Mark E.
A1  - Bitz, Andreas
T1  - A method to approximate maximum local SAR in multichannel transmit MR systems without transmit phase information
JF  - Magnetic Resonance in Medicine
N2  - Purpose
To calculate local specific absorption rate (SAR) correctly, both the amplitude and phase of the signal in each transmit channel have to be known. In this work, we propose a method to derive a conservative upper bound for the local SAR, with a reasonable safety margin without knowledge of the transmit phases of the channels.

Methods
The proposed method uses virtual observation points (VOPs). Correction factors are calculated for each set of VOPs that prevent underestimation of local SAR when the VOPs are applied with the correct amplitudes but fixed phases.

Results
The proposed method proved to be superior to the worst-case calculation based on the maximum eigenvalue of the VOPs. The mean overestimation for six coil setups could be reduced, whereas no underestimation of the maximum local SAR occurred. In the best investigated case, the overestimation could be reduced from a factor of 3.3 to a factor of 1.7.

Conclusion
The upper bound for the local SAR calculated with the proposed method allows a fast estimation of the local SAR based on power measurements in the transmit channels and facilitates SAR monitoring in systems that do not have the capability to monitor transmit phases
Y1  - 2016
U6  - http://dx.doi.org/10.1002/mrm.26398
SN  - 1522-2594
VL  - 78
IS  - 2
SP  - 805
EP  - 811
PB  - International Society for Magnetic Resonance in Medicine
ER  - 
TY  - JOUR
A1  - Orzada, Stephan
A1  - Solbach, Klaus
A1  - Gratz, Marcel
A1  - Brunheim, Sascha
A1  - Fiedler, Thomas M.
A1  - Johst, Sören
A1  - Bitz, Andreas
A1  - Shooshtary, Samaneh
A1  - Abuelhaija, Asjraf
A1  - Voelker, Maximilian N.
A1  - Rietsch, Stefan H. G.
A1  - Kraff, Oliver
A1  - Maderwald, Stefan
A1  - Flöser, Martina
A1  - Oehmingen, Mark
A1  - Quick, Harald H.
A1  - Ladd, Mark E.
T1  - A 32-channel parallel transmit system add-on for 7T MRI
JF  - Plos one
Y1  - 2019
U6  - http://dx.doi.org/10.1371/journal.pone.0222452
ER  - 
TY  - JOUR
A1  - Fagan, Andrew J.
A1  - Bitz, Andreas
A1  - Björkman-Burtscher, Isabella M.
A1  - Collins, Christopher M.
A1  - Kimbrell, Vera
A1  - Raaijmakers, Alexander J. E.
T1  - 7T MR Safety
JF  - Journal of Magnetic Resonance Imaging (JMRI)
Y1  - 2021
U6  - http://dx.doi.org/10.1002/jmri.27319
SN  - 1522-2586
VL  - 53
IS  - 2
SP  - 333
EP  - 346
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Sukhotina, Irina
A1  - Streckert, Joachim R.
A1  - Bitz, Andreas
A1  - Hansen, Volkert W.
A1  - Lerchl, Alexander
T1  - 1800 MHz electromagnetic field effects on melatonin release from isolated pineal glands
JF  - Journal of Pineal Research
Y1  - 2006
U6  - http://dx.doi.org/10.1111/j.1600-079X.2005.00284.x
SN  - 1600-079X
VL  - 40
IS  - 1
SP  - 86
EP  - 91
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  -