FLAIR
Fluid Attenuated Inversion Recovery
Anatomical Position
Body erect. Face, toes, and palms facing forward. Arms at the side.
Which imaging plane directly correlates to CT?
Axial
What are 3 main considerations for MRI image quality?
SNR, CNR, and Spatial Resolution.
SNR
Ratio of the amplitude of the signal received to the average amplitude of the noise.
What is signal?
Voltage induced in the receiver coils.
What is noise?
Random frequencies in space and time.
Higher or lower SNR is better?
Higher
To get better resolution, must signal be increased or lowered?
Lowered
What is contrast?
Difference in relative brightness between pixels.
Contrast is affected by which two factors?
Intrinsic (within body)
Extrinsic (operator controlled variables)
High contrast vs low contrast
High = drastic difference between signals
What determines the resolution of an image?
Number of pixels (picture elements). More pixels = better resolution.
Slice thickness is?
Depth in an MRI image.
The height and width of an MRI image is controlled by?
Field of View (pixel is the face)
What is a Voxel? What is it determined by?
Voxel represents a volume of tissue within the patient. Determined by pixel area and slice thickness.
When is FLAIR usually used?
When MS is suspected.
Weighting of fat?
Bright for all.
Weighting of fluid?
T1- dark
T2- bright
FLAIR- suppressed
Weighting of white matter?
T1- bright
T2- dark
FLAIR- dark
Weighting of gray matter?
T1- dark
T2- bright
FLAIR- bright
Weighting of air?
T1- very dark
T2- very dark
FLAIR- very dark
Weighting used for?
T1- anatomy
T2- pathology
FLAIR- mainly brain (MS)
