MRI

Question 1

What is the Larmor Equation

Answer 1

precession frequency = gyromagnetic ratio x field strength

Question 2

precession frequency is directly proportional to:

Answer 2

magnetic field strength

Question 3

What two things does the RF pulse do?

Answer 3

1. decreases the longitudinal magnetization and 2. it causes the protons to sync up and precess in-phase (which establishes a transverse magnetization)

Question 4

Who is allowed entry into level III space

Answer 4

level 1 and level 2 personnel (level 2 are people in the radiology department)

Question 5

what is the most commonly reported adverse event associated with MRI?

Answer 5

thermal injuries

Question 6

long TR, long TE

Answer 6

T1

Question 7

short TR, short TE

Answer 7

T2

Question 8

long TR, short TE

Answer 8

PD

Question 9

what type of image when combined with DWI, would generate contrast in a diffusion weighted image?

Answer 9

T2

Question 10

type of curve for recovery of longitudinal magnetization

Answer 10

exponential curve approaching 100% over time

Question 11

T1 definition

Answer 11

time at which the longitudinal magnetization is 63% of its final value

Question 12

time at which the longitudinal magnetization is 63% of its final value

Answer 12

T1

Question 13

Duration of an MRI scan

Answer 13

Tr x Npy x Nex

Question 14

MRI slice thickness equation

Answer 14

thickness = transmit RF/ (SS gradient x k)

Question 15

less gradient does what to slice thickness?

Answer 15

thicker slice

Question 16

More gradient does what to slice gradient?

Answer 16

thinner slice

Question 17

parameters that improve MRI spatial resolution

Answer 17

big matrix, small FOV, thinner slices

Question 18

parameters that improve MRI SNR

Answer 18

small matrix, large FOV, thicker slicer, stronger field strength, smaller surface coils, more excitations (longer TR, shorter TE), narrow receiver bandwidth

Question 19

Answer 19

Question 20

What is special about HASTE?

Answer 20

a turbo spin echo techinique that is used for sequential acquisition of high resolution T2 weighted images.

HASTE uses a shingle-shot technique to acquire sufficient data for an entire image from a single TR.

It collects fewer data points per repetition time (TR) interval. Only about half of k-space is acquired per TR and symmetry is used to fill the remaining half.