Sekvence Flashcards
(22 cards)
What three tissue properties primarily determine MRI signal contrast?
Proton density (PD), T1 relaxation time, and T2 relaxation time.
What does T1 relaxation time represent in MRI?
Time for protons to realign with the magnetic field after excitation (spin-lattice relaxation).
What does T2 relaxation time represent in MRI?
Time for protons to lose phase coherence in the transverse plane (spin-spin relaxation).
How does fat appear on T1-weighted MRI images?
Bright (high signal) due to short T1 relaxation time.
How does cerebrospinal fluid (CSF) appear on T1-weighted images?
Dark (low signal) due to long T1 relaxation time.
Compare white matter and grey matter signal on T1-weighted images.
White matter is brighter than grey matter.
How does fluid (CSF, edema) appear on T2-weighted images?
Bright (high signal) due to long T2 relaxation time.
How does fat appear on T2-weighted images without fat suppression?
Bright (high signal), but can be suppressed with fat saturation techniques.
Compare grey matter and white matter signal on T2-weighted images.
Grey matter is brighter than white matter.
Which tissues appear bright on proton density (PD) weighted images?
Tissues with high proton density such as fat and fluid.
How does fibrocartilage appear on PD-weighted images?
Dark (low signal).
What does FLAIR suppress and what lesions does it highlight?
Suppresses free fluid (CSF) signal; highlights lesions near CSF such as multiple sclerosis plaques.
What does STIR suppress and what is it used to detect?
Suppresses fat signal; used to detect edema and inflammation.
What does diffusion weighted imaging (DWI) detect?
Areas of restricted water diffusion, e.g., acute ischemic stroke.
What does an ADC map show in diffusion imaging?
Quantitative measure of diffusion; low ADC values indicate true restricted diffusion.
What do T2* and SWI sequences detect?
Magnetic susceptibility effects, highlighting hemorrhage, calcifications, and venous structures.
Mnemonic for T1-weighted image signal characteristics?
“Fat is bright, fluid is dark.”
Mnemonic for T2-weighted image signal characteristics?
“Fluid is bright, fat is bright (unless suppressed), grey matter brighter than white matter.”
On T1-weighted images, which is brighter: white matter or grey matter?
White matter.
On T2-weighted images, which is brighter: grey matter or white matter?
Grey matter.
Signal intensity of fat on T1, T2, and PD images?
T1: High (bright)
T2: High (bright)
PD: High (bright)
Signal intensity of CSF on T1, T2, and PD images?
T1: Low (dark)
T2: High (bright)
PD: High (bright)
