MRI Safety & QA Exam 1

https://quizlet.com/675119830/mri-safety-qa-exam-1-flash-cards/?x=1jqY

When is it acceptable to perform an MRI exam on a patient with a cardiac pacemaker?

if the pacemaker is conditional

True or False: For most studies, if the contrast agent is to be effective one must complete the pulse sequence within 8 minutes of the injection

false

Family members accompanying patients into the MR suite:

must be screened as though they were having the exam themselves

All sedated MRI patients should be monitored:

visually/verbally

with a pulse oximeter

It typically takes about ______ weeks for an implant, stent, coil, or filter to become securely attached to a vessel wall

4-6

What is the most frequent complication with the use of sedatives and anesthetics?

respiratory depression and upper airway obstruction

Biological effects have been reported in humans as the result of exposure to:

static magnetic field above 2T

As a conductive medium (blood) moves across a magnetic field, an effect known as magnetic hemodynamic effect occurs, resulting in:

elevated T-wave

Gradient magnetic fields are a safety concern because they:

induce currents in conductors

Time varying magnetic fields have been reported to have caused:

Mild cutaneous sensations and images of flashing lights &

Involuntary muscle contractions and cardiac arrhythmias

FDA limit on time varying magnetic fields:

Once the patient experiences peripheral nerve stimulation

The imaging sequence that is of most concern for time varying magnetic field effects is:

EPI (echo planar imaging)

FDA whole body RF absorption limit

4 W/kg

The term used to describe RF absorption

SAR (specific absorption rate)

RF absorption is measured in:

Watts per kilogram

RF antennae effects can cause:

thermal injury and flames

RF heating is more of a concern in imaging sequences using:

FSE (fast spin echo)

____ are usually allowed to enter the scan room in high magnetic field systems:

copper tools

The possibility of reaction should always be considered in patients after the injection of gadolinium, but anaphylactic reactions may be higher risk in patients with:

asthma & allergic respiratory disorders

What is an absolute contraindication to conventional MR procedures?

ferromagnetic stainless steel aneurysm clips

People with pacemakers should remain outside of which fringe field line?

5 gauss

Current induction within a device or lead wire due to gradient magnetic fields is more likely to occur in which area?

periphery of the magnet bore

The slew rate refers to the ____?

rapidity of the time varying field

Where should the main ECG cable be placed?

straight out of the bore

The cable for the pulse oximeter is made of which material?

fiber optic

T2* gradient echo flip angle

20

STIR TI

150

FLAIR TI

2000

Scan time formula

TR x Matrix x NEX / ETL

Scan time formula for fast spin echo

TR x Phase Matrix x NEX / ETL

voxel volume formula

Pixel area x slice thickness = Voxel volume

(answer cubic 3)

180 degree RF pulses use ___ times the power of 90 degree RF pulses

4

The safety committee of the ____ determined that pregnant employees can safely enter the scan room, but should leave while the RF and gradient fields are employed

ISMRM

Eddy currents

in frequencies below 100 MHz, 90% of the absorbed energy results from tissue currents induced by the magnetic component of the RF field

FDA SAR limit for temperature increase (core of the body)

1 celsius

FDA SAR limit for temperature increase (head)

38 Celsius

FDA SAR limit for temperature increase (trunk)

39 Celsius

FDA SAR limit for temperature increase (extremities)

40 Celsius