Critical Temperature: the temperature of a gas or vapour in its critical state. Above this temperature, a gas cannot be liquefied by pressure alone.
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Environmental ImpactMRIs have made both a positive and negative impact in regards to energy consumption and maintenance.
MRIs currently use superconductive magnets for clinical use. When these magnets are in use, they do not require any external power to maintain a current flow and field strength. In addition no heat is dissipated from the wires. They are able to form strong fields without too much energy consumption or cooling requirements. Due to their ability to achieve stable, high magnetic fields with little or no electrical power consumption, superconducting magnets now greatly outnumber other magnet types among both research and clinical MRI facilities (Padmani 2014). However there is one concern with the increasing use of this diagnostic technique. Superconducting magnets are manufactured of wire made of NbTi or NbSn alloys which need to be cooled to below 10 K (-263°C) to be superconducting in the field. Therefore the wires need to be cooled constantly in a bath of liquid helium to maintain a constant current in the field. Large amounts of helium are needed to cool the superconducting wire to temperatures as low as 4 degrees Kelvin. However, this cooling requires large amounts of helium. MRI machines consume about 7000 tons of helium annually. In 1996, it was estimated that the US used about 2.6 billion scf. Roughly about 5 billion scf of helium is used annually. That would mean 27% of the U.S.'s helium is being allocated towards the use of MRI's every year. Sources conflict on the exact amount of extractable helium left on the planet, but the amount is finite. MRI's are costly, and with a growing population, are not sustainable. However, the MRI have become such a staple of modern medicine that we cannot simply abandon using it. Therefore more energy efficient MRI's are needed. Shoujun Xu has developed a method to eliminate the need for cryogenics using a optical atomic magnetometers. Such developments are promising for the future of medical imagining (Nam 2012). |
Secondary Impacts |
The parts of an MRI are expensive to build because the stronger the magnetic field, the greater the size, weight and cost. For superconducting magnets, the large size and weight are due to the large number of loops of superconducting wire needed to produce a stronger field. The more wire required means the more that needs to be manufactured in industrial plants. This means the manufacture of the wire can lead to an increase to greenhouse emissions which adds to global warming.
Another secondary impact, relates to the amount of noise MRIs make during the scan. When scan is currently underway, the machine creates a lot of noise that can bother the hearing of the patient being examined especially in children. It creates noise pollution that has potential to harm the patient due to the noisy surroundings of the MRI. |
Summary |
Positive Impacts:
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