Introduction to Cross Sectional Imaging Flashcards
Axial Plane
- Separates body into superior and inferior parts
- Allows for correlation to CT images
Sagittal
- Separates body into left and right parts
- Directly midline is known as midsagittal
- Often done first to help plan other planes/images
Coronal
- Separates the body into anterior and posterior
- Not done routinely
Oblique
Passes diagonally between the axes of 2 other planes
SNR
Signal to noise ratio
- Ratio of the amplitude of the signal received to the average amplitude of the noise
- Noise represents random frequencies in space and time
- Greater the signal, greater the image quality
- Higher SNR is good
Does MRI signal have to be sacrificed for another variable?
Ex: To get more resolution, do we need to lower the signal?
Yes
CNR
Contrast to noise ratio
Contrast:
- Difference in relative brightness between pixels
- Measured by the eye’s ability to distinguish areas of high and low signal
High Contrast
CNR
Drastic difference between the signals
Low Contrast
CNR
Little difference between the signals
Spatial Resolution
Number of pixels contained in an image
Are MRI images scanned in 3D?
Yes
Voxel
Volume of tissue within the patient, and is determined by the pixel area and the slice thickness
What are the 3 image weightings? What’s the purpose of different weightings?
T1
T2
FLAIR
Different weightings give us different contrast/appearance
Hyperintense (image weighting)
High signal
Hypointense (image weighting)
Low signal
Isointense (image weighting)
Same signal qualities
T1 Image Weighting
Fat = Bright (hyper intense) Fluid = Dark (hypo intense) White matter = Bright Grey matter = Dark Air = Dark
T2 Image Weighting
Fat = Bright Fluid = Bright White matter = Dark Grey matter = Bright Air = Dark
What does FLAIR stand for?
Fluid attenuated inversion recovery
Flair Image Weighting
Fat = Bright Fluid = Suppressed White matter = Dark Grey matter = Bright Air = Dark
Purpose of the different image weightings?
T1 = Anatomy T2 = Pathology Flair = Brain scans
