MRI Basics

MRI

detects the change in the direction of the rotational axis of protons found in the water that makes up living tissues. Sensitive to detecting soft tissue abnormalities.

T1

___ weighted images involve pulse sequences that feature a short TR

TR parameter

amount of time between RF pulses

brighter

_____ T1 tissues appear brighter on T1 weighted images

T2

____ weighted images involve pulse sequences that feature a long TE

TE parameter

amount of time between TF pulses and the echo

long

____ T2 tissues appear brighter on T2 weighted images

T1 Weighted Image

Protein fluid cysts, melanin, Gadolinium, fat and hemorrhage appear bright on ______

T2 weighted image

Water, simple water consisting cyst, edema, inflammation, fat, and hemorrhage appear bright on ______

Suppression Technique

suppress signal intensity making it appear darker.

Fat Supression

most commonly used suppression technique to help identify lipomas. Useful after administration of gadolinium.

Gadolinium

MRI contrast administered IV or intraarticular. Enters the blood stream, enhances parenchyma and then excreted by the kidneys. Can see phases of kidney fulfillment and can highlight renal masses.

Intravenous or intraarticular

Gadolinium can be administered...

T1

Gadolinium yields a brighter signal by shortening the ____ relaxation time. Utilize ___ weight images with fat suppression post gadolinium.

Pregnancy and Nephrogenic systemic fibrosis

Gadolinium is contraindicated in...

- non-invasive

- no radiation

- detailed look into tissue

- pregnancy okay if risk to benefit radio is appropriate (2-3rd trimester safe)

Pros of MRI

- longer

- more expensive

- ferromagnetic objects (surgical clips, staples, FB)

- Mechanical devices not compatible (pacemaker, pain skim, insulin pump, cochlear implants)

- claustrophobia

Cons of MRI

T1 weighted image of spinal cord

T2 weighted image of spinal cord