Ultra-High Field Magnetic Resonance Imaging: Towards an Imaging Based Healthcare
We would like to warmly thank Prof. Alayar Kangarlu, Director of the physics and engineering group at NYSPI MRI research center at Columbia University, for his visit to the ISTP and his interesting talk on ultra-high field magnetic resonance imaging and their importance in medicinal research and diagnostics.
by Gian Luca Gehwolf
Prof. Kangarlu started his talk on ultra-high field magnetic resonance imaging (MRI) by showing the periodic table, and highlighting the importance of the element Hydrogen as the reason, which made MRI possible in the first place. “The element Hydrogen is a gift from nature”, he stated. The human body mostly comprises of water, which consists of the elements Hydrogen and Oxygen. Additionally, Hydrogen atoms do not have neutrons in their nucleus (they only consist of one proton and one electron). These two reasons enabled obtaining images of the human tissue by using MRI.
Each Hydrogen atom has a magnetic spin that is randomly orientated in the absence of a magnetic field. If a magnetic field is applied, the spins will either align according to the direction of the magnetic field, a state termed “up-spin”, or they will align in the opposite way, which is termed “down-spin”. Therefore, there will be a population of spins in the up-spin position and a population of spins in the down-spin position if a strong external magnetic field is applied. There are slightly more spins in the up-spin position than in the down-spin position. Additionally, there is an energy difference between the up-spin population and the down-spin population. If the applied magnetic field is equal to the energy difference of the populations, the spins will “flip” meaning that the orientation of the spin changes, e.g. from up to down or vice versa. If the spins “unflip” again, they release the energy in form of electromagnetic waves, and this can be measured as a signal. The measured signals can then be computed to create an image of the examined sample. The stronger the applied external magnetic field is, the bigger the energy gap between the population states will be and as a result, the corresponding images will have a higher resolution.
The use of magnetic resonance imaging has become an indispensable tool in medicine as it provides high-resolution images of anatomy, physiology and biochemistry of the human body. Unlike cameras for photography, ultra-high magnetic field MRI allows taking different types of images. By fine-tuning the magnetic field, certain classes of tissues can be ignored, e.g. grey matter, white matter, blood, etc., and only the tissue of interest can remain visible. BOLD (Blood-oxygen-level-dependent) imaging can differentiate between oxygenated and deoxygenated blood. For certain areas of the brain to work, i.e. they are active, they need to be supplied with nutrients and oxygen, which is delivered by the blood. Therefore, BOLD imaging can be used to study which brain regions have to work together to perform certain tasks, e.g trying to visualize the capital letter A.
Chemical composition mapping can be also achieved with MRI. It allows a non-invasive blood test in the brain. With this method, the chemical composition in the brain can be studied. MRI can also detect haemorrhages. Another application is called volumetric measurement. It constitutes a method, which can measure the volume of grey and white matter in certain parts of the brain. Thus, the pattern of losses of grey matter over time can be studied. This is important because the brain structure is not very sensitive to small losses of brain matter whereas the brain function is highly sensitive to any losses.
Prof. Kangarlu’s team performed a series of MRI experiments on a pregnant monkey over a certain period of time. With this experiment, they were able to investigate how the brain of a fetus develops from the very beginning until after birth.
Furthermore, patients with psychiatric disorders (e.g. depression), who fail to respond to conventional medication treatment, can become candidates for electroconvulsive therapy (ECT). This kind of therapy is very invasive and may have side effects such as memory losses. A MRI technique called “function of connectivity” can predict whether a patient will respond to ECT. This means that patients who will not respond can be spared from the risk of doing an ECT in a non-invasive and safe fashion.
Prof. Kangarlu also elaborated on the importance of MRI in terms of the economic aspect. He stated that the number of invasive prostate biopsies can be reduced by almost half if MRI is used. Just in the US, this would save around USD 2 billion. Similar cost reductions can be obtained from the diagnosis of breast cancer or other organs. “If put altogether”, he stated, “you could save USD 100 billion just in the US by using non-invasive technology instead of surgery procedures”. Consequently, the number of MRI machines used worldwide has increased significantly. There is a trend of using stronger and stronger magnets in order to have better insights into the human body and to find new ways of diagnostics, which can circumvent the need to use invasive and expensive surgery procedures.
In the discussion which followed his talk, the difference of the US and the European healthcare system, regarding the use of MRI, was analysed. Prof. Kangarlu explained that the American system is much more entrepreneurship-orientated compared to the European, which has a more socialist approach with lower costs for the patients to bear. Finally, there was also some interesting discussion about the difficulty to explain the concept of hope from a psychological point of view.
The ISTP would like to thank Prof. Kangarlu for giving such an interesting talk about the importance of ultra-high field MRI in the healthcare system.
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