magnetism Flashcards
What types of magnets are used in Magnetic Resonance Imaging (MRI)?
In MRI, permanent magnets and electromagnets are used. Electromagnets are further divided into resistive and superconducting magnets.
What are permanent magnets composed of, and what is their typical magnetic field strength?
Permanent magnets are composed of permanently magnetized ceramic bricks assembled to generate a strong magnetic field. They are typically very heavy and limited to magnetic fields no higher than 0.3T.
What is the main characteristic of superconducting magnets that allows them to conduct electricity with no resistance?
The main characteristic is superconductivity, which is the property of a wire to conduct electricity with no resistance when kept extremely cold.
How is the wire in superconducting magnets kept cold, and what is the typical temperature?
The wire is kept cold by immersing it in a cryogen, such as liquid helium, at a temperature of -269°C.
What is the range of magnetic field strengths produced by superconducting magnets for routine clinical imaging?
Superconducting magnets produce magnetic fields of 1.5T to 3T for routine clinical imaging.
Why do permanent magnets cost very little to operate once they are in place?
Permanent magnets cost very little to operate once in place because they do not require power to maintain their magnetic field
What needs to be periodically replaced in superconducting magnets, and why?
The liquid helium used to keep the wire cold needs to be periodically replaced to maintain the superconducting state.
