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Questions and Answers
MRI uses the property of nuclear magnetic resistance to image nuclei of atoms inside the body.
MRI uses the property of nuclear magnetic resistance to image nuclei of atoms inside the body.
False
One disadvantage of MRI is that it can cause severe burns if RF transmitters are mishandled.
One disadvantage of MRI is that it can cause severe burns if RF transmitters are mishandled.
True
The main magnet in an MRI system requires a magnetic field strength of up to 5T for clinical use.
The main magnet in an MRI system requires a magnetic field strength of up to 5T for clinical use.
False
MRI scanners are not affected by the presence of metallic devices within a patient's body.
MRI scanners are not affected by the presence of metallic devices within a patient's body.
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Better contrast resolution and tissue discrimination are considered advantages of MRI.
Better contrast resolution and tissue discrimination are considered advantages of MRI.
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Gradient coils in an MRI system are used to produce uniform magnetic fields.
Gradient coils in an MRI system are used to produce uniform magnetic fields.
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Claustrophobia can make it difficult for patients to undergo MRI scans.
Claustrophobia can make it difficult for patients to undergo MRI scans.
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The components of an MRI system include a computer system and a documentation system.
The components of an MRI system include a computer system and a documentation system.
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Gradient coils for the z axis are known as Helmholtz pairs.
Gradient coils for the z axis are known as Helmholtz pairs.
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RF coils are responsible for both starting and stopping RF pulses in the MRI system.
RF coils are responsible for both starting and stopping RF pulses in the MRI system.
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Gradient coils are located outside the bore of the primary magnet.
Gradient coils are located outside the bore of the primary magnet.
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The x coil creates a varying magnetic field from top to bottom.
The x coil creates a varying magnetic field from top to bottom.
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The net magnetization vector turns towards the longitudinal plane during RF excitation.
The net magnetization vector turns towards the longitudinal plane during RF excitation.
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Protons rotate around their axis at 63,000,000 rotations per second.
Protons rotate around their axis at 63,000,000 rotations per second.
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Saddle coils are used for the z axis in MRI systems.
Saddle coils are used for the z axis in MRI systems.
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RF coils operate at high energy and short wavelength compared to typical radio waves.
RF coils operate at high energy and short wavelength compared to typical radio waves.
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Study Notes
Magnetic Resonance Imaging (MRI)
- MRI is a medical imaging technique used in radiology to visualize detailed internal structures
- MRI utilizes the property of nuclear magnetic resonance (NMR) to image nuclei of atoms within the body
- The MRI image displays radio frequency signal intensities emitted by magnetized tissue during the imaging process
- Tissue becomes magnetized due to the presence of protons, which are the magnetic nuclei of hydrogen atoms
- When placed in a strong magnetic field, some protons align with the field, generating tissue magnetization
- The presentation outlines the indications, advantages, disadvantages, and components of the MRI system
Indications
- MRI is a medical imaging technique used to visualize detailed internal structures
- It leverages the property of nuclear magnetic resonance (NMR) to create images
- The concept of an MRI image is built upon the display of radiofrequency signal intensities emitted by the magnetized tissue
Advantages of MRI
- No ionizing radiation, avoiding short and long-term effects
- Variable thickness imaging, possible in any plane
- High contrast resolution and tissue discrimination
- Multiple imaging sequences for characterizing abnormal tissue
- Detailed images without intravenous contrast enhancement
Disadvantages of MRI
- High cost
- Dangerous for patients with metallic devices inside their bodies
- Difficult for claustrophobic patients due to confined space
- Movement during scanning may create blurry images
- RF transmitters can cause burns if mishandled
- Limited availability
Components of the MRI System
- Magnet: Crucial component and the most expensive part of the MRI scanner, a superconducting magnet is typically used
- The magnetic field strength is limited by FDA recommendations to 3 Tesla only. This magnet, cooled by liquid helium, is housed in a specialized cryostat with a horizontal bore
- Gradient coils: Generate deliberate variations in the main magnetic field. Three sets, one for each direction (x, y, and z)
- These coils allow for localization of slices and phase/frequency encoding in images. The z-axis coils use Helmholtz pairs, and x and y use paired saddle coils. These coils work in conjunction with RF pulses to form slices and voxels. They generate additional magnetic fields within the main field to create varied magnetic fields
- RF coils: These coils act as antennas, transmitting and receiving RF signals
- They are loops of wire (circular or rectangular), placed inside the gradient coils
- These coils are responsible for creating the magnetic field used to rotate the protons in the tissue, and detect the signals emitted by these protons during relaxation
- RF pulses Excitation : Protons jump to higher energy states to absorb radiation
- RF pulses Relaxation : Protons return to their initial state, emitting radiation
- The RF signal is received and converted from analog to digital, temporary storage in image space (case space). A computer process the digital signal using Fourier transformation to display an image
- The system also includes power supplies, a computer system, a documentation system and cooling methods
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Description
This quiz covers the fundamental concepts of Magnetic Resonance Imaging (MRI), including its principles, indications, advantages, and components. Explore how MRI utilizes nuclear magnetic resonance to visualize internal structures of the body through the alignment of protons in a magnetic field.
