Gradient Coils

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

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

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

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

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

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

A. Parallel imaging

B. ½ NEX

C. Rectangular field of view

D. Phase encoding reduction technique

A. Parallel imaging

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

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

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 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 (Gauss per centimeter and Millitesla per meter)

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

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

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)

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

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 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

The primary biological effect of radiofrequency is:

A. Tissue heating

B. Asphyxiation

C. Hyperthermia

D. None of the above

A. Tissue heating

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

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

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

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

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

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

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

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

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 decent of a gradient from zero to its maximum amplitude

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

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%

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

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