Imaging Technologies II Flashcards

1
Q

Definition of a particles

A

2 protons, 2 neutrons (He nucleus)

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2
Q

Definition of B- particles

A

An electron

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3
Q

Definition of B+/positrons

A

antiparticle of electron

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4
Q

Definition of isomeric transition

A

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

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5
Q

Definition of half life

A

The time then for half the nuclei to decay

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6
Q

Definition of nuclear magnetic resonance

A

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

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7
Q

Definition of resonance frequency

A

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

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8
Q

Types of radioactive emissions

A
a particles
b particles (b-)
positrons
y radiation
xrays
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9
Q

Alpha decay

A

Natural radioactive elements heavier than Pb

Unstable radionuclide ejects a (helium nucleus)

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10
Q

Beta minus decay

A

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

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

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11
Q

Beta plus decay

A

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

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

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12
Q

Positron annihilation and detection

A

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

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13
Q

Isomeric transition

A

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

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

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14
Q

Decay kinetics

A

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

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15
Q

Half life

A

Time taken for half the nuclei to decay

T1/2 = In2/lambda

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16
Q

Penetrating ability of a, b, y, xray

A

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

17
Q

Imaging in nuclear medicine

A

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

18
Q

How do positron emission tomography machines work (PET)

A

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

19
Q

How do single photon emission tomography machines work (SPECT)

A

Similar to CT, rotate y camera around patient

20
Q

Positron emitting tracers

A

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

21
Q

Nuclear magnetic resonance

A

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

22
Q

Resonance

A

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

23
Q

How does NMR work?

A

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

24
Q

Why is NMR good?

A

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

25
Q

Why is the hydrogen nucleus important

A

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

26
Q

Components of an MRI machine

A

Magnet
Gradient coils
RF coils

27
Q

Foundations for ultrasound imagine

A

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

28
Q

Ultrasound imaging modes

A

2B/B mode imaging
Obstetric ultrasound
3D imaging

29
Q

How does ultrasound imaging work?

A

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

30
Q

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

A

154000 x T / 2

31
Q

What is A mode scanning

A

1D imaging

32
Q

What is M mode imaging

A

Repeated A scans of a moving target

Good for measuring tissue motion

33
Q

What is B mode scanning

A

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

34
Q

Developments in image display

A

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

35
Q

3D ultrasound technology, matrix array transducers

A

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

36
Q

Modern ultrasound systems

A

More compact, faster

Onboard image analysis