Essay: The MRI system – Magnetic Resonance scanners

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The MRI system has prompted a revolution in the field of cognitive neuroscience, since it has allowed researchers to map the brain function noninvasively in response to task demands. However, acquiring images from this system generates some substantial acoustic noise, which creates a problem to the imaging studies of speech, hearing and the language (Chambers, Bullock, Kahana, Kots & Palmer, 2007). On the other hand, there is only on criteria for reducing the generated acoustic noise within this system, and that is using micro-perforated panels that are placed in the bore of the MRI scanner. These panels are able to be used onto the existing scanners at a minimum cost and they are also suitable for sterile surroundings. Although this method may result into quantifiable lower levels of noise, measured with the microphones in an empty MRI system, this method has not been tried with a patient in the scanner bore, which normally affects the acoustic noise field. A Magnetic Resonance Imaging scanner usually produce strong stationary magnetic field through the aid of a superconducting coil that is bathed in liquid helium (Katsunuma, 2002). When an object is introduced in this field, hydrogen atoms in this object orient antiparallel or parallel to the magnetic field pattern. The favorable energy state make the hydrogen atoms in the object to align parallel thus creating a net of magnetization Mo parallel as compared to the static field Bo. The hydrogen atoms in the object are mainly found in fat and water, which are in abundance within the human brain.

The main source of noise during Magnetic Resonance imaging process is the gradient coil and the surrounding tools (Katsunuma, 2002). During the process of imaging, a series of gradient fields are applied transiently so as to provide spatial data to the measured signal. For a researcher to produce these gradient fields, electric current is passed through the coil that is located in the strong stationary magnetic field. In this case, Lorentz forces are produced due to the current in the magnetic field hence, resulting in the vibrations of the equipment and the acoustic noise (Katsunuma, 2002). As the amount of current is increased in the coils, the amount of Lorentz forces acting on the coil also increases and hence results in creation of louder noise. The Lorentz forces are always turned on and off as the current transmitted in the coils is switched on and off, hence causing the coils and surrounding equipment to vibrate. This current habit on higher field strengths indicate just how the acoustic noise concerns will always be on the rise.

Although Magnetic Resonance scanners allow researchers and medical practitioners to non-invasively acquire information concerning the human body, the noise generated by these scanners during the scanning process poses a great cause of concern for the patients undergoing the imaging process and to the researchers carrying out the experiments. These amounts of noise levels generated during imaging process are estimated to be over 100 dB and they are as loud …

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