Imaging Technologies II

Question 1

Definition of a particles

Answer 1

2 protons, 2 neutrons (He nucleus)

Question 2

Definition of B- particles

Answer 2

An electron

Question 3

Definition of B+/positrons

Answer 3

antiparticle of electron

Question 4

Definition of isomeric transition

Answer 4

Nuclear process where a nucleus with excess energy following the emission of an a/b particle emits energy without changing the mass/atomic no

Question 5

Definition of half life

Answer 5

The time then for half the nuclei to decay

Question 6

Definition of nuclear magnetic resonance

Answer 6

When nuclei absorb energy from a radiofrequency waves applied at a specific frequency in a magnetic field

Question 7

Definition of resonance frequency

Answer 7

Natural frequency of a system, frequency needed for most efficient energy transfer

Question 8

Types of radioactive emissions

Answer 8

a particles
b particles (b-)
positrons
y radiation
xrays

Question 9

Alpha decay

Answer 9

Natural radioactive elements heavier than Pb

Unstable radionuclide ejects a (helium nucleus)

Question 10

Beta minus decay

Answer 10

Electron created in transformation = b-
v= antineutrino created in transformation

Atomic no increases by 1
Neutron no decreases by 1
Mass no, unchanged

Question 11

Beta plus decay

Answer 11

Positron created in transformation = b+
v= neutrino created in transformation

Atomic no decreases by 1
Neutron no increases by 1
Mass no, unchanged

Question 12

Positron annihilation and detection

Answer 12

Tracer decays and emits positron
Annihilation occurs with e-, releases 2 y photons at 180
Detected with 511keV

Question 13

Isomeric transition

Answer 13

Nucleus with excess energy emits y after loss of a/b-/b+

99m 43 Tc emits y without changing atomic mass/no

Question 14

Decay kinetics

Answer 14

Rate of decay = dN/dt = -lambda N
Lambda= decay constant
N= no of nuclei
1st order process

Question 15

Half life

Answer 15

Time taken for half the nuclei to decay

T1/2 = In2/lambda

Question 16

Penetrating ability of a, b, y, xray

Answer 16

a stopped by tissue
b stopped by perspex
y, xray stopped by lead

Question 17

Imaging in nuclear medicine

Answer 17

Radioactive iodine image of thyroid
Widespread availability of 99m Tc, y
Gamma camera, image y emitting radioisotopes

Question 18

How do positron emission tomography machines work (PET)

Answer 18

Ring of detectors to count coincidental y photons released from positron releasing F18

Question 19

How do single photon emission tomography machines work (SPECT)

Answer 19

Similar to CT, rotate y camera around patient

Question 20

Positron emitting tracers

Answer 20

Short half lives
Cyclotron needed for production
Wide range of clinical, research applications
Oncology currently use 18FDG

Question 21

Nuclear magnetic resonance

Answer 21

When nuclei absorb energy from a radio frequency wave applied at a specific frequency in a magnetic field

Question 22

Resonance

Answer 22

Natural frequency of a system, most efficient energy transfer occurs here
NMR requires radio waves of the right frequency

Question 23

How does NMR work?

Answer 23

Sample placed in strong magnetic field
Irradiated with radio waves at resonance frequency
Radiowaves reemitted by sample, signal analysed

Question 24

Why is NMR good?

Answer 24

Standard method for chemical analysis and non destructive testing
MRI involves localising the signal with magnetic field gradients to form image

Question 25

Why is the hydrogen nucleus important

Answer 25

H1, simplest isotope, highest NMR sensitivity, high abundance in body MRI uses H in H2O, as a result won't show bone

Question 26

Components of an MRI machine

Answer 26

Magnet Gradient coils RF coils

Question 27

Foundations for ultrasound imagine

Answer 27

Hydrophone invented to locate icebergs Patent for metal defect detections Used for human imaging

Question 28

Ultrasound imaging modes

Answer 28

2B/B mode imaging Obstetric ultrasound 3D imaging

Question 29

How does ultrasound imaging work?

Answer 29

Emit short ultrasound pulse, listen to what is reflected back Detects waves reflected from tissue structures Tissue properties determine amount of reflected energy, absorbed by it

Question 30

How to work out the distance from the transducer to the tissue?

Answer 30

154000 x T / 2

Question 31

What is A mode scanning

Answer 31

1D imaging

Question 32

What is M mode imaging

Answer 32

Repeated A scans of a moving target | Good for measuring tissue motion

Question 33

What is B mode scanning

Answer 33

2D imaging Move A mode transducer to different positions Create 2D image from 1D lines Needs beam with good lateral resolution

Question 34

Developments in image display

Answer 34

Analogies can converter Maximum brightness stored, doesn’t depend on exposure time Displayed on TV at it forms

Question 35

3D ultrasound technology, matrix array transducers

Answer 35

Phased array with elements in matrix Steer and focus in all directions Volume made from multiple lines Easier to understand

Question 36

Modern ultrasound systems

Answer 36

More compact, faster | Onboard image analysis