MRI Flashcards
(40 cards)
Basic principles include all of the following except:
1) uses high magnetic field & radio frequency pulses
2) Uses ionizing radiation
3) multi planar images take longer
4) has good contrast resolution
5) may use IV contrast (i.e: gadolinium)
6) will take 30-60 min
2) does NOT use ionizing radiation
(T/F) the magnet is always on in an MRI
TRUE
What objects are considered projectile hazards “missile effect”?
- oxygen cylinders
- fire extinguishers
- monitoring equipment
(SQ) hx of foreign body?
- orbital trauma
- plain radios
- anatomic position relative to sensitive structures
(SQ) hx of implant/device, issues?
- displacement
- heating
- alteration of device operation
- imaging artifacts
(T/F) for stents and filters that are nonmagnetic, its ok to scan now
true!
(T/F) Pacemakers and implantable defib. are CI to MRI
TRUE
What is an absolute CI to MRI?
intracranial aneurysm clips; do plain films or CT’s
- titanium clips are ok tho
When in doubt if something is a CI, what should you do?
consult “list” or MRI department
Which of the following is not generally safe for MRI?
1) surgical hemostasis clips/sutures
2) IUD
3) radioactive seed implants
4) ortho fixation hardware & joint replacements
NONE; all are generally safe
(T/F) you should remove all metallic objects except for hearing aids or drug patches before entering MRI
FALSE; remove everything & wear gown
What can you do for pt if the have issue w/ noisy MRI?
give them ear plugs or headphones
What can you do for pt that has claustrophobia?
communicate w/ tech, sedatives, open MRI
What can occur due to use of gadolinium in pts w/ renal disease and should be screened prior?
nephrogenic systemic fibrosis- widened tissue fibrosis that involves skin thickening, contractures, and immobility
What occurs in the resting stage of MRI?
Resting state: Hydrogen nuclei (protons) behave like small magnets
Magnetization: Hydrogen nuclei align w/ the strong magnetic field
Excitation: RF pulses→ protons absorb energy and are deflected
Relaxation: Protons return to pre-excitation & emit energy (signal)
What occurs in the magnetization stage of MRI?
Resting state: Hydrogen nuclei (protons) behave like small magnets
Magnetization: Hydrogen nuclei align w/ the strong magnetic field
Excitation: RF pulses→ protons absorb energy and are deflected
Relaxation: Protons return to pre-excitation & emit energy (signal)
What occurs in the excitation stage of MRI?
Resting state: Hydrogen nuclei (protons) behave like small magnets
Magnetization: Hydrogen nuclei align w/ the strong magnetic field
Excitation: RF pulses→ protons absorb energy and are deflected
Relaxation: Protons return to pre-excitation & emit energy (signal)
What occurs in the relaxation stage of MRI?
Resting state: Hydrogen nuclei (protons) behave like small magnets
Magnetization: Hydrogen nuclei align w/ the strong magnetic field
Excitation: RF pulses→ protons absorb energy and are deflected
Relaxation: Protons return to pre-excitation & emit energy (signal)
MRI will detect the signal emitted and display what?
display the intensity of the signal coming from each point
Difference b/w T1 recovery and T2 decay?
T1 recovery: rate at which protons re-align w/ the field
T2 decay: rate at which protons “de-phase” w/ each other
Diff. b/w T1 weighted image and T2 weighted image?
T1 weighted image: Fluid is dark, hypo-intense, low signal
T2 weighted image: Fluid is bright, hyperintense, high signal
What’s bright on T1 vs T2?
Bright on T1: Fat, blood, protein, contrast enhancement
Bright on T2: Fluid (CSF, Bile, Urine)
What’s dark on a T1 and T2 image?
cortical bone, air, fibrous tissue
Indications for MRI of liver?
- lesion detection to screen for hepatocellular carcinoma in cirrhosis, chronic hepatitis
- lesion characterization for focal liver lesion “problem solving”
