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Student work

Investigation of different effects on RF field maps using the Actual Flip Angle Imaging (AFI) method
Published on
Reference number
Master Thesis


In our research group, we are developing new methods for magnetic resonance imaging (MRI) at ultrahigh magnetic fields (e.g., B0=7T). Our main goal is to be able to use the higher signal-to-noise ratio for in vivo human applications. However, a problem here is the spatially inhomogeneous distribution of the radio frequency (RF) field necessary to excite the nuclear spins that result in spatial variations of the image signal intensity. RF field maps are measured to quantify and compensate for the inhomogeneities of the RF fields, where the precision and accuracy of these maps is critical for imaging. We recently found that field maps acquired using the Actual Flip Angle Imaging method (AFI) (Yarnykh, 2007) in combination with polyvinylpyrrolidone (PVP) phantoms that are typically used for field validations are biased by acquisition parameters and unclear physical effects. Here, these effects need to be investigated in more detail.


The aim of the work is to perform simulations to quantify the influence of different effects such as diffusion on the results of the AFI for different materials. For this purpose, the Bloch equations will be simulated and extended for different effects. To achieve efficient simulations, the implementation shall be done on GPUs. In a later step, the code will be published under an open-source license. Measurements shall then be performed on the 3T or 7T scanner, which will be compared with the simulations.

Effekte wie z.B. Diffusion auf die Ergebnisse der AFI für unterschiedliche Materialien zu quantifizieren. Hierfür sollen die Bloch-Gleichungen simuliert werden und für die verschiedenen Effekte erweitert werden. Um eine möglichst effiziente Simulation zu erreichen, soll die Implementation auf GPUs erfolgen. Der Code soll in einem späteren Schritt unter einer Open-Source-Lizenz veröffentlicht werden. Es sollen dann Messungen am 3T oder 7T Scanner durchgeführt werden, welche mit den Simulationen verglichen werden.


Job Requirements
  • Study of physics, electrical engineering, computer science, biomedical engineering or a comparable course of study
  • good programming skills (Python/MATLAB, experience with CUDA/PyCUDA is advantageous)
  • interest in MR physics
Place of employment
Organisational unit
Div. 8 "Medical Physics and Metrological Information Technology"
Are you interested?

Dr. Sebastian Schmitter
E-Mail: sebastian.schmitterptb.de
Tel.: (+49) 030 3481-7767

Max Lutz
E-Mail: max.lutz(at)ptb.de
Tel.: (+49) 030 3481-7020