PRACTICE QUESTIONS FROM CLASS Flashcards
- What are the two theories used to describe the basic prinicples of MRI?
Classical Theory and Quantum Theory
- What is the Lamor equation and describe each parameter of this equation?
It is used to measure the precessional frequency using the strength of the magnetic field and the gyro-magnetic constant of hydrogen.
- What is free induction decay?
As T2 decay occurs, there is a decrease in the signal produced and this is the FID (induction of reduced signal)
- What are the MRI weightings used?
T1, T2 and Proton Density
- Why is imaging contrast needed?
To show pathologies and differentiate between different anatomy structures
- Name two categories that diagnostic imaging contrast usually depends on.
Intrinsic and Extrinsic (Can change ext)
- A spin echo T1 weighted sequence uses a ____ TR and ____ TE.
- A spin echo T1 weighted sequence uses a short TR and short TE.
A T2 weighted image has a____ TR and a ____ TE
A T2 weighted image has a long TR and a long TE
A proton density has a ___ TR and a ____ TE
A proton density has a long TR and a short TE
- Name a disadvantage of a GRE (Gradient Echo) MRI sequence?
It is very susceptible to any metal as there is no compensation for the field inhomogeneities.
- What are three types of magnets?
Permanent magnets, super conducting (what we use) and electromagnets
- Name the three types of magnetisim
iamagnetism, ferromagnetism, paramagnetism
- Three motions of an atom?
Nucleus spins on axis, electrons spin on own axis, electrons orbit nucleus
- What does the the yellow triangle with MR on it mean?
MRI conditional – can take into room and around magnet then can under certain conditions stated.
- Give any four tips for dealing with claustrophobic patients?
Feet first, support person, can perform some prone, do not strap down, worst case scenario = GA, give breaks, give a mirror / fan
- What is phase mismapping artefact also known as?
Ghosting or blurring artefact
- What is the artefact called seen on the outer edges of the this abdominal Fiesta MRI coronal image?
Moire artefact
- Which two cranial nerves are seen when imaging the IAMs?
Vestibulocochlear and facial nerve (VII and VIII)