Magnetism - Hardware Control Flashcards
High field scanners typically have field strengths greater than or equal to:
1.5 Tesla
Consistent room temperature of 65-75°F, humidity of 50-70%, and sufficient air flow in the MR scan room is recommended to:
Make patients less vulnerable to the RF heating effects
In a cross sectional view of the MR magnet design, which coils are closest to the patient?
Radiofrequency coils
The RF coils are closest to the patient, leading to the primary component causing RF absorption in the patient
The liquid cryogens are cooled in a superconducting magnet at a temperature of _________?
4° Kelvin
Which of the following is NOT a magnetic field associated with MR imaging?
Gravitational earth magnetic fields
The purpose of shimming the magnet is to:
make the B0 field as homogenous as possible
The array processor is responsible for:
Reconstructing the images using the Fourier transform
The array processor is responsible for reconstructing the collected MR images/data using the Fourier transform, and is located in the MR equipment room.
In order for energy to be efficiently transferred between a transmitter and receiver, the two must be at the same:
Frequency
In order for energy to be efficiently transferred between a transmitter and receiver, the two must be at the same frequency
The _____ is located within an equipment room.
RF power amplifier
The RF power amplifier is located within an equipment room
During a quench of the MR system, patients and employees should be evacuated from the scan room to avoid ______________.
All of the above
Field strength at magnet isocenter is measured in units of:
Tesla
Field strength at magnet isocenter is measured in units of Tesla, the SI derived unit of magnetic field measurement.
The unit of measurement of the magnetic field surrounding the periphery of the MR scanner is expressed as:
Gauss
The unit of measurement of the magnetic field surrounding the periphery of the MR scanner is expressed as Gauss.
The intensity limit for a static magnetic field in clinical use is limited by the Food and Drug Administration (FDA) to _____________?
4 Tesla
The intensity limit for a static magnetic field in clinical use is limited by the Food and Drug Administration (FDA) to 4.0 tesla (T) strength.
The patient image display with sequence parameter visualization is located in the _________.
Scan control room
The patient image display with sequence parameter visualization is located in the scan control room on the operator console.
The local RF coil used to image a human brain is typically located/kept in the __________.
Magnet room
The local RF coil used to image a human brain is typically located/kept in the magnet room.
The CPU used to plot and adjust slices in an MR sequence is located:
Scan control room
The CPU used to plot and adjust slices in an MR sequence is located in the scan control room at the technologist operator console.
Radiofrequency (RF) shielding can be achieved by lining the scanner room walls with:
Copper
Radiofrequency (RF) shielding can be achieved by lining the scanner room walls with copper.
The location of the coils installed in the MRI scanner, from the inner point closest to the patient to the outer most edge, are:
Radiofrequency coils, gradient coils, shim coils, main magnet
The location of the coils installed in the MRI scanner, from the inner point closest to the patient to the outer most edge, are: RF radiofrequency coils, gradient coils, shim coils, main magnet
The liquid cryogens most often used to maintain field strength in a super conducting MR system are:
Helium
The coil construction in an MR system, from the innermost aspect to the outer
Radiofrequency coils, gradient coils, shim coils, main magnet
Doubling the magnetic field strength will:
Yield an increase of double the SNR
Doubling the magnetic field strength will double the SNR.
What type of magnet is used with most systems currently manufactured?
Superconducting
The superconducting magnet is the most commonly used system in MR imaging today
Passive shielding can be accomplished by lining the MR room with ___________.
Steel
Magnetic field shielding can be accomplished via active or passive shielding methods. Passive shielding can be accomplished by lining the MR room with steel
Active shielding can be defined as:
Superconducting windings within the MR scanner, reducing the fringe magnetic field
Active shielding requires the implementation of superconducting windings within the construction of the MR scanner to oppose a portion of the magnetic field.
_________ would be used to contain the RF in an MR magnet room
Copper
Copper would be installed to contain the RF in an MR magnet room.
___________ could be used to line the walls and/or floors of the MR magnet room to reduce the fringe field, and is defined as __________ shielding.
Steel; passive
Referring to SAR impact on the patient, all of the following parameter changes negatively impact pulse duty cycle EXCEPT:
Reduction in # slices
Doubling field strength will result in what impact on SAR potential, if any?
Quadruple SAR
In acquiring ACR QA data, Image 212 is used to evaluate for what quality measure?
Geometric accuracy – Z gradient
Transmit gain is a quality measure evaluating for?
Accuracy of flip angles
What is the daily/weekly QA/QC indicator testing for the accuracy of the magnetic field in determining coil tuning and consistent magnetic field strength?
Center frequency
The duty cycle can be viewed as the:
active gradient time
The duty cycle is defined as the time the gradients are active during a TR period, the “gradient working time.”
