Unit 1: Exam 1

Question 1

There are three types of motion present within an atom, they are:

Answer 1

Electrons spinning, electrons orbiting and the nucleus itself spinning.

Question 2

The _________________ of hydrogen produces a significant vector that is used in clinical MRI.

Answer 2

Net magnetic vector

Question 3

At 1.5T the precessional frequency of Hydrogen is:

Answer 3

63.86 MHz

Question 4

The laws of electromagnetic induction refer to three individual forces:

Answer 4

Motion, magnetism and charge

Question 5

The Hydrogen atom is utilized in MRI because:

Answer 5

It is very abundant in the human body

Question 6

The _______________ is the time from the application of one RF pulse to the application the next pulse for each slice and is measured in milliseconds

Answer 6

TR

Question 7

The decay of transverse magnetization is called ____________.

Answer 7

T2 decay

Question 8

The recovery of 63% of longitudinal magnetization in the tissue is called _______________.

Answer 8

T1 relaxation time

Question 9

The __________is produced when coherent (in phase) magnetization cuts across the coil.

Answer 9

MRI signal / Echo

Question 10

The ____________ is the time from the application of the pulse to peak of the signal induced in the coil and is also measured in milliseconds (ms).

Answer 10

TE

Question 11

The influence of B0 produces an additional spin, or wobble of the magnetic moments of hydrogen around B0. This secondary spin is called:

Answer 11

Precession

Question 12

The Larmor frequency states, the Larmor frequency of a __________ is proportional to the magnetic field strength it experiences.

Answer 12

Hydrogen Nucleus

Question 13

In a T2 weighted image

Answer 13

TE controls the amount of T2 weighting so the TE must be long

Question 14

The factors that affect image contrast in diagnostic imaging are usually divided into two categories:

Answer 14

Intrinsic & Extrinsic contrast parameters

Question 15

Sequences that use a 180 degree pulse to regenerate a signal are called:

Answer 15

Spin echo pulse sequence

Question 16

_________________ are generated by coils of wire situated within the bore of the magnet.

Answer 16

Magnetic field gradients

Question 17

The time taken to rephase after the application of 180 degree
RF pulse equals the time the NMV took to diphase when the 90 degree RF pulse was withdrawn is called:

Answer 17

TAU

Question 18

Whether a gradient field adds or subtracts from the main magnetic field depends on the direction of the current passing through the gradient coils, this is called:

Answer 18

Polarity

Question 19

Gradients that dephase are called ______ & gradients that rephrase are called ___________.

Answer 19

Spoilers / rewinders

Question 20

The middle of the axis of the gradients remains at field strength of the main magnetic field and is termed:

Answer 20

Magnetic isocenter

Question 21

Fat remains bright on T2 weighted images due to the multiple RF pulses which reduce the effects of spin-spin interactions in fat & this is known as:

Answer 21

J coupling

Question 22

TE at which the operator wishes to weight the resultant image is called _______________.

Answer 22

Effective TE

Question 23

Another modification to Single shot fast spin echo is a reverse flip angle excitation pulse which is applied at the end of the echo train. This is called?

Answer 23

DRIVE (driven equilibrium)

Question 24

This gradient echo was initially developed for imaging of the heart & great vessels but is now used for spinal imaging.

Answer 24

Balanced

Question 25

_______________ is used in brain & spine imaging to see Periventricular & cord lesions more clearly.

Answer 25

FLAIR

Question 26

Gradients can be used to dephase & rephase the residual magnetization. _______________ is the opposite of rewinding.

Answer 26

Gradient spoiling