Ultra High-Field Functional and Anatomical MRI*

Outline of the module
Magnets with field strength greater than 3 Tesla have been at the forefront of basic imaging research for the past decade. The increased signal to noise ratio, resulting in increased resolution, and better contrast to noise make them appealing to clinical practice. However, the technical challenges associated with high magnetic field imaging require expert knowledge and advanced user skills.
This course aims to detail the advantages of high field imaging, highlight its technical challenges and provide information about state-of-the-art solutions to them.

Learning objectives
At the end of the module, students will have expert knowledge about the following topics:

  • Anatomical contrast at 7 Tesla (T1, PD, T2*, SWI).
  • Inhomogeneity Correction in Anatomical Imaging at 7 Tesla (Acquisition strategies and post processing).
  • Functional contrast at 7 Tesla (T2* and T2 weighted).
  • Challenges in functional Imaging at high fields (SAR, B1 and B0 inhomogeneities) and how to control them.
  • Acquisition strategies for high resolution functional imaging (parallel imaging, simultaneous multi slice, 3D-GRASE)

Content
At high magnetic fields, increases in the signal to noise ratio (SNR) and the susceptibility contrast of, for example, the blood oxygenation level-dependent (BOLD) signal result in supra-linear gains in the contrast to noise (CNR) ratio of anatomical and functional MRI. However, to date, the limitations of high magnetic fields (i.e. short T2*, increased physiological noise, susceptibility effects, B1 inhomogeneities, SAR, etc.) have restricted the impressive gains in CNR, SNR and spatial resolution at high fields, e.g. in fMRI to portions of the cortex and with reduced field of views (FOV), severely limiting its general application. However, with the advent of parallel imaging (PI), as well as continued sequence design and improvements in gradient and RF hardware, the restrictions of high fields and thus high resolution MRI continue to be alleviated, limiting the need for trade-offs between spatial specificity and contrast, resolution, or volume coverage. This module will introduce anatomical and functional imaging at high fields. Contrast mechanisms will be discussed and the field strength dependency of fMRI signals are and how to optimize MRI scanning approaches to get the most SNR and spatial specificity at UHF.  Further, optimized post processing strategies for high spatial resolution data will be discussed (e.g. inhomogeneity correction, cortical depth sampling).

Overview of tasks and lectures
There will be 8 lectures over 5 days.
• Introduction into Ultra High-Field (UHF) MRI
• Anatomical imaging at UHF I (anatomical contrast, Susceptibility, T1, T2*)
• Anatomical imaging at UHF II (acquisition)
• Anatomical imaging at UHF III (post processing)
• Functional MRI at UHF I (functional contrast, T2*, T2)
• Functional MRI at UHF II (acquisition strategies, 2D-EPI, 3D-EPI, 3D-GRASE)
• Functional MRI at UHF III (post processing)
• Applications

Position within the programme
This module is related to most of the modules of the executive master, e.g. MRI physics module, Clinical applications. To follow the content of the module only the module MRI physics is mandatory. Ultra High Field MRI scanners are relatively novel and pose various novel challenges and advantages. So, this module will introduce scientist-practitioners to the novel field which will become increasingly important in the near future.

Teaching format
Structure
The module is a one week-long residential module consisting of 8 lectures. Each day, the students will in addition perform data acquisition on the UHF scanners located at Scannexus (7 and 9.4 Tesla), subsequent data analysis and/or implementation of computer algorithms relevant to one the lecture topics guided by tutors.

Grading
Passing the module requires an 85% attendance to the lectures and practical sessions, and a satisfactory completion of the practical sessions and the module assignments. The module assignments will be summarised by the students in a written form which will be evaluated by the module coordinator(s).


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