MRI gradient coils

The gradient slew rate is the:

A. Time it takes for the gradient to reach its full amplitude

B. Time it takes longitudinal magnetization to regrow

C. Time between TI and initial RF pulse

D. Rate of speed of ascent or descent of a gradient from zero to its maximum amplitude

D. Rate of speed of ascent or descent of a gradient from zero to its maximum amplitude

RF (radiofrequency) energy is:

A. Low energy non-ionizing radiation

 B. Low energy ionizing radiation

 C. High energy non-ionizing radiation

 D. High energy ionizing radiation

A. Low energy non-ionizing radiation

The strength of the gradient over a specific distance is known as the: 

A. Slew rate

 B. Rise time

 C. Duty cycle

 D. Flux lines

A. Slew rate

Cables from RF coils and gating/trigger leads should be:

A. Coiled, preferably into a figure "8"

 B. Nicely formed into loops in the magnet bore

 C. Resting on the patient's arm or leg to immobilize the cables

 D. Braided and positioned straight in the bore

 D. Braided and positioned straight in the bore

The effects of time varying magnetic fields can include all of the following EXCEPT:

A. Peripheral nerve stimulation

 B. Magnetophosphenes

 C. Acoustic damage and/or hearing loss

 D. Warmth and/or increase in body temperature

D. Warmth and/or increase in body temperature

The effects of time varying magnetic fields can include peripheral nerve stimulation, acoustic damage/hearing loss, magnetophosphenes ("seeing stars").

A technique utilized to reduce the MRI scan time which requires the use of an array coil is:

 A. Parallel imaging

 B. 1/2 NEX

 C. Rectangular field of view

 D. Phase encoding reduction technique

A. Parallel imaging

The orientation of the main magnetic field in a high field, superconducting, short bore magnet is:

 A. Vertical

 B. Cylindrical

 C. Horizontal

 D. Asymmetrical

 C. Horizontal

The coil construction in an MR system, from the innermost aspect to the outer:

 A. Gradient coils, radiofrequency coils, shim coils, main magnet

 B. Main magnet, radiofrequency coils, gradient coils, shim coils

 C. Shim coils, radiofrequency coils, gradient coils, main magnet

 D. Radiofrequency coils, gradient coils, shim coils, main magnet

D. Radiofrequency coils, gradient coils, shim coils, main magnet

If a transverse/axial slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient's body.

 A. X gradient

 B. Y gradient

 C. Z gradient

 D. Shim coils

C. Z gradient

Z gradient is utilized to acquire axial/transverse images on a patient lying supine/prone in the magnet.

The ______________ is the speed rate of ascent or descent of a gradient from zero to its maximum amplitude, either positive or negative

 A. Slew rate

 B. Rise time

 C. Duty cycle

 D. Fringe field

A. Slew rate

A coil that is not properly tuned to the correct magnetic field strength will result in:

 A. Patient injury

 B. FID artifacts

 C. Signal loss

 D. Improvements in resolution capabilities

 C. Signal loss

Which of the following's primary biological effect is tissue heating/deposition?

 A. Static magnetic fields

 B. Gravitational earth magnetic fields

 C. Time varying magnetic fields (gradient)

 D. Oscillating magnetic fields (radiofrequency)

D. Oscillating magnetic fields (radiofrequency)

The primary biological effect of radiofrequency fields is:

 A. Tissue heating

 B. Asphyxiation

 C. Hyperthermia

 D. None of the above

A. Tissue heating

Multiple coil elements combined with multiple receiver channels make a:

 A. Surface coil

 B. Circularly polarized coil

 C. Quadrature coil

 D. Phased array coil

 D. Phased array coil

A phased array coil is comprised of multiple coil elements combined with multiple receiver channels.

The strength of the gradient magnetic fields are measured in:

 A. Gauss per centimeter

 B. Tesla per echo

 C. Watts per kilogram

 D. Millitesla per meter

 E. A and D

 E. A and D ( Gauss per centimeter/ Millitesla per meter)

The gradient rise time is defined as the:

 A. Time it takes for the gradient to reach its full amplitude

 B. Time it takes longitudinal magnetization to regrow

 C. Time between TI and initial RF pulse

 D. Speed rate of ascent or descent of a gradient from zero to its maximum amplitude

 A. Time it takes for the gradient to reach its full amplitude

The ____________ is responsible for the knocking noise the system makes while the sequence is in progress.

 A. Patient table moving from one slice location to another

 B. RF energy being transmitted

 C. Rapid change/switching of the magnetic field by the gradient coils

 D. Patient knocking on the bore to get out

 C. Rapid change/switching of the magnetic field by the gradient coils

When going from a linear coil to a quadrature coil:

 A. Available FOV is reduced

 B. Parallel imaging is eliminated

 C. SNR is decreased by 40%

 D. SNR is increased by 40%

 D. SNR is increased by 40%

Applying two gradients simultaneously during slice selection would:

 A. Produce an artifact

 B. Produce an oblique slice

 C. Produce partial volume averaging

 D. Result in an equipment fault

 B. Produce an oblique slice

A 6 inch surface coil is able to receive signal:

 A. 6 inches deep into the patient

 B. 3 inches deep into the patient

 C. 2 inches deep into the patient

 D. 1 inch deep into the patient

 B. 3 inches deep into the patient

RF heating is more of a concern in ________ sequences.

 A. Gradient echo

 B. Inversion recovery

 C. Fast spin echo

 D. Time of flight

 C. Fast spin echo

RF heating is more of a concern in fast spin echo sequences due to the multiple echo train lengths, leading to potential increases in tissue heating.

Utilization of surface coils yields all of the following EXCEPT:

 A. Increased FOV capability

 B. Localized, smaller FOV capability

 C. Increased SNR

 D. Smaller slice thickness

 A. Increased FOV capability

Utilization of surface coils yields a more localized, smaller FOV (field of view) capability, with increased SNR, thus providing opportunity for thinner slices on most systems.

Which of the following has been documented to cause muscle contractions, cardiac arrhythmias, mild cutaneous sensations and visual light flashes?

 A. Time varying magnetic fields (gradient)

 B. Static magnetic fields

 C. Oscillating magnetic fields (radiofrequency)

 A. Time varying magnetic fields (gradient)

The duty cycle is defined as the:

 A. Time it takes for the gradient to reach its full amplitude

 B. Time it takes longitudinal magnetization to regrow

 C. Time between TI and initial RF pulse

 D. Time the gradients are on during a TR period

 D. Time the gradients are on during a TR period

If a coronal slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient's body.

 A. X gradient

 B. Y gradient

 C. Z gradient

 D. Shim coils

 B. Y gradient

The measurement of radiofrequency absorption is delineated as:

 A. Watts per pound

 B. dB/dT

 C. Volts per kilogram

 D. Watts per kilogram

 D. Watts per kilogram

Current FDA limits on time varying magnetic fields are:

 A. 23T/sec

 B. 5G/cm

 C. 20G/cm

 D. Once the patient experiences peripheral nerve stimulation

 D. Once the patient experiences peripheral nerve stimulation

If a sagittal slice plane has been selected, the __________ is enabled to alter the magnetic field around the patient's body.

 A. X gradient

 B. Y gradient

 C. Z gradient

 D. Shim coils

 A. X gradient

Magnetic field inhomogeneity is expressed in:

 A. Watts per kilogram

 B. Gauss per centimeter

 C. Tesla per meter

 D. Parts per million

 D. Parts per million (ppm)

Which of the following sequences would be more at risk for the effects that time varying magnetic fields can cause?

 A. SE

 B. FSE

 C. GE

 D. EPI

 D. EPI

EPI (Echo Planar Imaging) sequences can have more of a detrimental effect on patients with regards to time varying magnetic fields.