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Perfusion Imaging at Ultra-High Field with Multi-Channel RF Transmission
Perfusion is the physiological process of nutritive delivery of arterial blood to a capillary bed in the biological tissue by means of blood flow. Adequate blood flow is survival for the tissues as the supply of oxygen and nutrients and the removal of waste products. Abnormalities of perfusion accou
Keywords: MRI, perfusion, arterial spin labeling
In recent years, the developments in magnetic resonance imaging (MRI) enabled the non-invasive measurement of the local tissue perfusion based on arterial spin labeling (ASL). ASL uses the magnetically labeled proton spins of arterial water as an endogenous diffusible tracer. ‘Labeling’ refers to an alternation in the magnetic state of the spins in the blood by either saturation or inversion. Implementation of ASL at ultra-high fields (7T) benefits from the increased signal to noise ratio (SNR) and prolonged longitudinal relaxation times.
In recent years, the developments in magnetic resonance imaging (MRI) enabled the non-invasive measurement of the local tissue perfusion based on arterial spin labeling (ASL). ASL uses the magnetically labeled proton spins of arterial water as an endogenous diffusible tracer. ‘Labeling’ refers to an alternation in the magnetic state of the spins in the blood by either saturation or inversion. Implementation of ASL at ultra-high fields (7T) benefits from the increased signal to noise ratio (SNR) and prolonged longitudinal relaxation times.
The limitations of the ultra-high fields have to be handled mainly including the inhomogeneity and specific absorption ratio (SAR). Parallel transmission describes the use of multiple RF transmit coils and can be applied to improve multidimensional, spatially selective RF excitation, to shorten the duration of RF pulses in two or three dimensions, or to minimize the occurring SAR. Project includes the following tasks:
• Develop a MATLAB based GUI for processing the ASL data obtained at 3T Philips scanner. The GUI will take the control and tag images and corresponding imaging parameters to produce a quantitative CBF map. The same GUI will serve for further ASL work at 7T.
• Obtain ASL images by using pseudo-continuous ASL scheme with estimation and correction for off-resonance effects at the tagging location using a pre-scan. Pre-developed tools will be used to overcome B1 and B0 issues.
• Implement multiple-channel RF labeling and slice excitation
• individual 3rd-order B0 shimming for the labeling slab and each imaging slice, relying on fast shim settling through available digital pre-emphasis
The limitations of the ultra-high fields have to be handled mainly including the inhomogeneity and specific absorption ratio (SAR). Parallel transmission describes the use of multiple RF transmit coils and can be applied to improve multidimensional, spatially selective RF excitation, to shorten the duration of RF pulses in two or three dimensions, or to minimize the occurring SAR. Project includes the following tasks:
• Develop a MATLAB based GUI for processing the ASL data obtained at 3T Philips scanner. The GUI will take the control and tag images and corresponding imaging parameters to produce a quantitative CBF map. The same GUI will serve for further ASL work at 7T. • Obtain ASL images by using pseudo-continuous ASL scheme with estimation and correction for off-resonance effects at the tagging location using a pre-scan. Pre-developed tools will be used to overcome B1 and B0 issues. • Implement multiple-channel RF labeling and slice excitation • individual 3rd-order B0 shimming for the labeling slab and each imaging slice, relying on fast shim settling through available digital pre-emphasis
Type of Work: Master Project: 10% Theory, 40% Software, 50% Experiments
Requirements: Basic skills in MATLAB and interest in electromagnetics, Medical Imaging.
Supervisor: Dr.Mustafa Cavusoglu, cavusoglu@biomed.ee.ethz.ch, ETZ F 64.1, Tel. 44 632 45 63
Professor: Klaas Prüssmann, pruessmann@biomed.ee.ethz.ch, ETZ F61.1, Tel. 44 632 66 96
Type of Work: Master Project: 10% Theory, 40% Software, 50% Experiments Requirements: Basic skills in MATLAB and interest in electromagnetics, Medical Imaging. Supervisor: Dr.Mustafa Cavusoglu, cavusoglu@biomed.ee.ethz.ch, ETZ F 64.1, Tel. 44 632 45 63 Professor: Klaas Prüssmann, pruessmann@biomed.ee.ethz.ch, ETZ F61.1, Tel. 44 632 66 96