18.10.15

You are invited to attend a lecture

By:

Dr. Rita Schmidt

Leiden University Medical Center

High dielectric materials in 7 T human MRI: New dielectric resonator designs, shaped materials (e.g. pre-fractal) for improved transmit field homogeneity, and imaging of electrical properties of tissue

Abstract

Magnetic resonance Imaging  and spectroscopy (MRI and MRS) are important diagnostically as well as being contemporary research tools for the study of biological tissue. Human MRI at ultra-high fields (>4 T) is a new fascinating direction in research, with  advantages  including higher signal-to-noise ratio (SNR), increased spectral resolution, and much greater magnetic susceptibility induced tissue contrast. However, one of the main challenges for MRI at these very high magnetic fields is the significant inhomogeneity of the transmit radio frequency (RF) magnetic field. This is due to constructive and destructive wavelength effects, as the wavelength is comparable to the dimensions of the object being imaged.

My research explores methods to overcome these challenges through the use of high permittivity dielectric materials; turning the wave like interference “weakness” into  strength. Exploring the effects of these materials in the vicinity of regions of interest has shown both local increase and severe decrease in RF field intensity. Shaping the materials with holes (e.g. pre-fractal arrangement) can manipulate the magnetic and electric fields and improve the local and global RF field intensity. Also, new dielectric resonators having high Q factor values with the required electromagnetic modes can be built; for example using just water. Combining these new resonators with traveling wave antenna enables a new simple implementation for dual-nuclei imaging (protons and phosphorous nucleus, for example). Finally, by changing the magnetic and electric field using these dielectric materials, one can solve an inverse problem, using the Maxwell equations in their integral representations, and so reconstruct the electrical properties fingerprint of biological tissue, which is a new MRI contrast containing important physiological information.

Bio

Rita Schmidt received her B.Sc. in Physics at the Tel-Aviv University in 2000 and her M.Sc. in Medical Physics from the Tel-Aviv University in 2005. During her M.Sc. research and until 2010 she worked in the industry. Her positions included Research Physicist and Lead System Engineer in a company developing Focused Ultrasound devices with MRI guidance for non-invasive therapy. In 2014 she received a PhD from the Weizmann Institute, where she developed new methods for rapid imaging methods. She is currently a postdoctoral fellow in the Department of Radiology at the Leiden University Medical Center, and her research focuses on a deeper understanding of electromagnetic radiation in biological tissue in the presence of ultra-high magnetic field.

Sunday, October 18, 2015, at 14:00

Room 011, Kitot building