FREE MRI Knowledge Questions and Answers
Magnets formed of ferrous material found naturally or from blocks or slabs.
Naturally ferromagnetic materials have a high magnetic permeability and a long half-life of magnetization, which makes them suitable for use as permanent magnets. By matching the magnetic domains within ferromagnetic materials, a high magnetic field is applied to the material to produce these magnets. Permanent magnets don't require an external power source to create their own magnetic field once they are magnetized. They are frequently utilized in many different applications, including speakers, generators, and motors.
Most superconducting magnets have a (horizontal or vertical) magnetiic field and are of the design type __.
One kind of superconducting magnet that is frequently utilized in many different applications is the solenoid. Its central axis is encircled by wire coils in a cylindrical form. A solenoid usually generates a homogeneous magnetic field that is parallel to the cylinder's axis. The term "solenoid horizontal" in the provided response denotes that the cylinder's axis is aligned horizontally and that the solenoid is oriented in a horizontal direction. As a result, a horizontal magnetic field will be produced by the solenoid.
This kind of magnetic shielding confines the fringe field by using metal—typically steel—in the scan room walls.
The use of metal, usually steel, in a scan room's walls to contain the fringe field produced by a magnetic source is known as passive magnetic shielding. The magnetic field can be contained by this kind of shielding without the need for active control devices or external power. The magnetic field lines are instead redirected and absorbed by the metal's natural qualities, keeping them from leaving the scan room and interfering with surrounding objects or people.
To form a magnet field, wires are arranged side by side.
The process of aligning wires side by side results in a solenoid magnet. A solenoid is an electric current-carrying coil of wire that produces a magnetic field as the current passes through it. The magnetic field created by the wires arranged side by side is more powerful and consistent. For this reason, in this instance, a solenoid magnet is the appropriate solution.
Positive susceptibility is present in these materials, however when exposed to an external magnetic field, they will stay magnetized even after the field is removed.
Positive susceptibility, or the attraction to a magnetic field, is a characteristic of ferromagnetic materials. Furthermore, even after the external magnetic field is eliminated, they can still be magnetized. The material's magnetic moments aligning to produce a strong magnetic field is what causes this behavior. As a result, the statement provided appropriately characterizes ferromagnetic materials.
By adding more loops and circuitry, these coils increase the efficiency with which the MR signal is induced in the coil and raise SNR by about 40% when compared to coils of the same size.
In order to increase the magnetic resonance (MR) signal induction efficiency within the coil, quadrature coils are constructed with extra loops and circuits. When compared to coils of the same size, this design innovation helps to boost the signal-to-noise ratio (SNR) by about 40%.
This magnet has a strength of up to 0.3 T, can be switched off, and can be used in both horizontal and vertical field systems.
According to the provided information, the magnet has strengths of up to 0.3 T, may be switched off, and can be used in both horizontal and vertical field systems. The word "resistive" implies that this kind of magnet works with materials that have the ability to regulate the strength of the magnetic field and switch it off when necessary. Based on the information given, "Resistive" is the appropriate response.
Substances in the presence of an applied magnetic field that show a modest rise in magnetic field. They exhibit both positive and low susceptibility.
When subjected to an external magnetic field, materials classified as paramagnetic exhibit a modest rise in their magnetic field. Their atomic or molecular magnetic moments line up with the applied field, which is the cause of this. Their magnetic response is modest and parallel to the applied field due to their low and positive susceptibility.
These materials are employed as T2 contrast agents because they show positive susceptibility, are stronger than paramagnetic materials but weaker than ferromagnetic materials.
Positive susceptibility to a magnetic field is exhibited by superparamagnetic materials. They are not as strong as ferromagnetic materials, but they are still stronger than paramagnetic materials. Superparamagnetic materials can improve the visibility of specific tissues or structures in magnetic resonance imaging (MRI) because they are frequently utilized as T2 contrast agents.
Magnets that use liquid helium or cryogen to cool the wires after applying direct current to a coil of wire.
Because superconducting magnets use direct current supplied to a coil of wire cooled by immersion in liquid helium or cryogen, the provided correct answer is "Superconducting." The wires' temperature is lowered by this cooling process, which enables superconductivity—the property of conducting electricity with zero resistance—in the wires.
This kind of magnetic shielding confines the main magnet's field by using other magnets and their corresponding magnetic fields.
Using additional magnets and their magnetic fields to contain or lessen the magnetic field of the primary magnet is known as "active magnetic shielding." By creating opposing magnetic fields to cancel out or constrain the field of the primary magnet, this approach actively manipulates the magnetic field. This is not the case with passive magnetic shielding, which absorbs and reroutes the magnetic field through the use of high-permeability materials. As a result, the selected right response of "active" is consistent with the justification supplied.