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Questions and Answers
What is the primary function of gradient coils in MRI technology?
What is the primary function of gradient coils in MRI technology?
Which set of gradient coils is typically used for the z-axis?
Which set of gradient coils is typically used for the z-axis?
How is gradient strength typically measured?
How is gradient strength typically measured?
What occurs when current is fed into a gradient coil?
What occurs when current is fed into a gradient coil?
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What are the expected capabilities of stronger gradient coils, such as those providing 15 or 20 mT/m?
What are the expected capabilities of stronger gradient coils, such as those providing 15 or 20 mT/m?
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What is created by the forces exhibited by a gradient coil?
What is created by the forces exhibited by a gradient coil?
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What aspect of the gradient coil allows for imaging at different depths?
What aspect of the gradient coil allows for imaging at different depths?
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Which parameter does NOT affect the magnetic field strength produced by a gradient coil?
Which parameter does NOT affect the magnetic field strength produced by a gradient coil?
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Study Notes
Gradient Coils: Types and Function
- Gradient coils create deliberate variations in the main magnetic field (Bo)
- There are typically three sets of gradient coils, one for each direction (x, y, and z)
- Variations in the magnetic field allow for localization of image slices and phase/frequency encoding
- Z-axis coils are Helmholtz pairs
- X and Y-axis coils are paired saddle coils
How Gradient Coils are Produced
- Magnetic field strength is proportional to current, number of loops, loop size, and spacing
- Changing these parameters increases or decreases magnetic field strength in a specific direction
- Gradient strength is measured in units of G/cm or mT/m
- Stronger gradients (15 or 20 mT/m) enable high-speed, high-resolution imaging
- Gradient coils are sets of wires in the magnet, creating additional magnetic fields superimposed on the main field.
- There are three sets of wires for creating magnetic fields in X, Y, and Z directions.
- Current is fed into the Z-gradient to generate a field in the Z direction.
- Gradient coils produce a linear gradation or slope in magnetic field strength from one end of a solenoid to the other.
- The resulting field can increase or decrease magnetic field on either side of isocenter.
- Coils are tightly fixed in resin to minimize vibration and noise
Components of MRI Systems
- MRI systems use three sets of gradient coils (x, y, and z)
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