#2 Flashcards
(400 cards)
What is TR (time repition) in MRI pulse sequence?
Time between each RF pulse, varies from 500msec to 4000msec
What is TE (time echo)?
Time each RF to listening for signal generated by patient varies from < 40msec to 100msec>
What determine the type of image created?
TR and TE times
Time Repetition
Time Echo
T1 in MRI (Time 1) main characteristics
- Weighted image with short TR (500msec) and short TE (40msec)
- Water is dark (CSF, edema, synovial fluid - NOT water in fat)
What does the pathology look like on a T1 film?
Usually dark on T1 due to edema (most pathologies have edema with water)
T2 MRI main characteristics:`
Weighted image - long TR (1500-4000msec)
- Long TE (80-100msec)
- Water is BRIGHT
T2 allows what?
System to go back to neutral state
- Listened long enough for echo signal, so now we see water that looks brighter, and can now see edema
what color is bone marrow on T2 MRI?
Gray
What does fat look like on MRI?
It re-aligns quickly and appears as bright white on MRI
- Fatty tumors, subcutaneous fat, yellow marrow
Contrast in MRI (signal intensity) is related to ____ ?
How tightly bound water is to time
Describe the Hydrogen properties in MRI contrast formation?
Hydrogen is more loosely bound in fat than water substance like CSF; re-aligns faster in fat than CSF
Spin-echo flip angle?
90 degrees
Gradient echo flip angle:
< 90 degrees
SE T1: (Fat color)
-
Fat image
- Structures containing fat appear brighter/whiter (bone marrow, subcutaneous fat);
SE T1: (Water containing) -
- Edema, neoplasm, inflammation, CSF, large amounts of Fe) appears DARK
* long TR, short TE
SE T1 is standard or not?
Standard
SE T2 first echo:
Proton density, good anatomical detail, has properties of both T1 and T2
- Not done anymore
SE T2 second echo water image (loosely bound)?
Loosely bound water (neoplasms, edema, inflammation, healthy nucleus puposus, CSF) appear bright/white
What is the appearance/what does it detect of tightly bound or low water content on SE T2 second echo?
Ligaments, menisci, tendons, calcium, sclerosis, cortical bone or large amounts of Fe appear dark/black
Main charac. of SE T2 second echo?
- Classic Image
- Standard
- MRI is the ONLY one that can see water in an IVD
FSE, fast spin echo:
Multiple echoes/TR, faster exam time, good in neuroimaging especially spine myelographic images
- Very sensitive to EDEMA
Gradient Echo:
Fast MRI using short TR and TE with (flip angle)
- >90 degrees
- Provides a T2 image in less time, but does sacrifice some signal
- Terms: GRE, GRASS, FLASH, FISP, MPGR, SPGR
Fat Suppression:
Technique that suppresses signal from fat, making small areas of pathology (often appearing bright because of edema) more evident and increasing the overall sensitivity of the exam, usually accomplished
(STIR)
- VERY SENSITIVE TO WATER
Techniques providing function information:
Kinematic (kMRI) functional joint movement



















































































































