Gradient coils

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

X gradient

RF (radiofrequency) energy is:

High energy non-ionizing radiation

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

Radiofrequency coils, gradient coils, shim coils, main magnet

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

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

The primary biological effect of radiofrequency fields is:

Tissue heating

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

horizontal

The gradient slew rate is the:

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

Magnetic field inhomogeneity is expressed in:

Parts per million (ppm)

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

Braided and positioned straight in the bore

The duty cycle is defined as the:

Time the gradients are on during a TR period

Utilization of surface coils yields all of the following EXCEPT:

• Increased FOV capability

• localized, smaller FOV capability

• Increased SNR

• Smaller slice thickness

smaller slice thickness

The gradient rise time is defined as the:

Time it takes for the gradient to reach its full amplitude

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

• SE

• FSE

• GE

• EPI

EPI

The strength of the gradient magnetic fields are measured in:

Gauss per centimeter & millitesla per meter

Multiple coil elements combined with multiple receiver channels make a:

Phased array coil

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

Slew rate

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

Oscillating magnetic fields (radiofrequency)

A 6 inch surface coil is able to receive signal:

3 inches deep into the patient

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

parallel imaging

Applying two gradients simultaneously during slice selection would:

Produce an oblique slice

RF heating is more of a concern in ________ sequences.

Gradient echo

The measurement of radiofrequency absorption is delineated as:

Watts per pound

When going from a linear coil to a quadrature coil:

SNR is increased by 40%

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

Slew rate

Current FDA limits on time varying magnetic fields are:

Once the patient experiences peripheral nerve stimulation

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

Y gradient

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

signal loss

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

Time varying magnetic fields (gradient)

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

z gradient

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

• peripheral nerve stimulation

• Magnetophosphenes (visual light flashes)

• Acoustic damage and/or hearing loss

• Warmth and/or increase in body temperature

Warmth and/or increase in body temperature