ORGANIZERS: Anke Henning, Ph.D. & Roland Kreis, Ph.D.
Saturday, 22 April 2017
||08:15 - 12:05
||Thomas Ernst, Harald Möller
Skill Level: Basic to Intermediate
Slack Channel: #e_cancer_mol_mrs
Session Number: WE07
This course provides a comprehensive introduction into in vivo MR spectroscopy and is dedicated for people who enter this field or want to refresh their knowledge. It reviews basic principles, pre-scan calibrations, state-of-the-art sequences and data analysis pipelines. It also introduces advanced methods that enable to detect a broad neurochemical profile.
Imaging scientists/MR physicists/engineers, physicians, technologists and neuroscientists who are interested in performing MR spectroscopy studies or starting to develop related methodology.
Upon completion of this course, participants should be able to:
-Recall the basic physical principles behind MR spectroscopy;
-Recognize state-of-the-art MR spectroscopy sequences;
-Recognize artefacts and their sources;
-Describe the data analysis pipeline; and
-Be able to set up and conduct MRS studies.
|Basic Principles of MRS (Chemical Shift, J-coupling, Spectral Resolution, Field Strength Effects)
Robin de Graaf
The basic principles of NMR are discussed based on classical concepts like compass needles, bar magnets, precession and electromagnetic induction. More advanced topics such as chemical shift, scalar coupling, T1 and T2 relaxation and basic MR sequences are also covered.
|Localization (Sequences: semiLASER, PRESS, STEAM, Chemical Shift Displacement)
Accurate localization is key for MR spectra quality and metabolites quantification. Metabolites low concentration and multiple frequencies pose more challenges in-vivo MRS than MRI, due to B0 inhomogeneity, insufficient B1, chemical shift displacement, and artifacts from lipids. Volume selection methods based on overlapping slices improves MRS quality by limiting the region of interest to areas where B0 and B1 can be better controlled. Spatial coverage can be improved by more modern approaches where arbitrary volumes can be shaped with parallel transmit, multiple volumes disentangled by parallel imaged, and different contributions to the MRS signal can be modeled in the reconstruction
|Water & Lipid Suppression - VAPOR, WET, OVS, IR, Novel Approaches (MC, Crushers)
In this presentation, the need for water and lipid suppression, as well as the most widely used approaches to achieve this are explained.
|Pre-Scan Adjustments (B0 Shimming, F0, PO, Water Suppression)
Jullie Pan, Hoby Hetherington, Nikolai Avdievich
The pre-scan adjustments, while nearly invisible to many practitioners, are very important for the successful acquisition of many spectroscopic and imaging sequences. In this talk, approaches and constructs specific to B0 and B1 optimization are discussed with examples of methods and results.
|Break & Meet the Teachers
|MRSI (Basic Sequences & Acceleration) - permission withheld
|Editing, 2D & UHF - Detection a Comprehensive Neurochemical Profile
While the vast majority of MRS applications focus on the strong resonances of NAA, Cr, Cho and sometimes mIns and Glu+Gln, resonances from at least 15 neurochemicals, i.e., a comprehensive neurochemical profile are present in the spectrum. For detecting the small, weakly represented neurochemical resonances that underlie the typically detected large resonances such as NAA, Cr, Cho and mIns, options are: 1) to de-convolve all of the signals that are present or 2) to edit, i.e., to set the signal of interest apart (at least partially) from the others. Of course, there are advantages and disadvantages to each approach.
|Postprocessing & Quality Assurance
In-vivo MRS data is unavoidably degraded by experimental imperfections such as subject motion, scanner drift, and eddy currents. Spectral preprocessing improves spectral quality and quantification reliability, and is an indispensable part of any in-vivo MRS experiment. MRS preprocessing is usually organized as a sequence, or ‘pipeline’ of individual processing routines, each designed to address a specific issue with the data. This talk covers some of the most common experimental issues affecting MRS data, and the processing routines and pipelines that can address these issues.
|Spectral Fitting & Absolute Quantification
MRS quantification is complicated due to the metabolic resonance overlap and complex line shapes. The modern methods for the spectral fitting increasingly relies on the linear combination (LC) modeling algorithms. The absolute quantification can be carried out using internal or external concentration references. The challenges remain in the following areas: the generation of the accurate prior knowledge, creating proper model/constraints for data fitting algorithms and choice of more robust concentration references.