JHU Abstract 2014-The Physics of Medical Detection Devices, Specifically MRI

The Physics of Medical Detection Devices, Specifically MRI


Emily Larkin (Hereford High School),  Jeremy Smith (Hereford High School),  Tyler Bradley (Towson High School), Dr. Morris Swartz (Johns Hopkins University)


                 The study of medicine is applied physics. As doctors use medical devices to make diagnoses or to understand natural or manufactured biological compounds, they are fundamentally using laws and equations of physics through computer modules. One such detection device is MRI (Magnetic Resonance Imaging). I used an pNMR (pulsed Nuclear Magnetic Resonance) machine to understand how a natural and induced magnetic field can create a response in compounds that ultimately leads to an MRI scan, a three-dimensional soft-tissue image, differentiating between blood, bone, and viscera. With the pNMR and knowledge of physics, I concurred that chemical compounds with various structures react with different amplitudes of pulses to the applied field (created with an electromagnet) due to the accessibility of the nucleus given shielding created by electrons surrounding the molecules. Although the pNMR machine used lacked the computing technology of an MRI to quickly differentiate and calculate these pulses, I saw the importance of optimizing the signal. I also observed that as the delay time between the A and B pulses increases, the amplitude of the subsequent B pulse decreases in the pattern of an exponential decay. I believe this is because as the time increases, on the scale of tenths of milliseconds, the number of atoms that "spin out" of the electric field in the z axis increases, meaning that they are "relaxed" and therefore will not contribute to the amplitude of the B signal. In medicine, such technology is important as the basis of MRI scans to detect irregularities inside the body, but it also is used in the direct study of biological compounds. NMR is one of the leading devices being used to comprehend the structure of macromolecules such as proteins, oligonucleotides, and oligosaccharides. It can also be used in drug manufacture as a way to understand the structure of new drugs, and how this structure plays into their functionality in the body. Obviously, as medicine is approaching an age where diagnosis and description is based on the genome and proteome, further applications of NMR are needed to meet the demand.