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Clinical Imaging > L1. Conventional Projection Radiography > Flashcards

L1. Conventional Projection Radiography Flashcards

1
Q

Radiation and public risk perception of x-ray technology

A

Risk of using radiation for x-ray technology varies depending on various factors including whether radiation is manmade vs. natural

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2
Q

Examples of factors that make communication of radiation risk challenging

A

Radon
Medical uses
Nuclear accidents
Lifestyle factors e.g microwaves, radio, sun

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3
Q

The key to radiation protection

A

Understanding risk vs. benefit

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4
Q

What is an X-Ray?

A

Form of electro magnetic (EM) radiation

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5
Q

Electromagnetic radiation

A

Spectrum depicting different energy levels of individual photons, in relation to wavelength/frequency of photons

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6
Q

Examples of low frequency, non-ionising radiation

A

Phones
Communication wires
Radio
Microwave
Visible light

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7
Q

Examples of high frequency, ionising radiation

A

Ultraviolet
X-Ray
Gamma ray

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8
Q

Order of electromagnetic spectrum (low to high)

A

Radio
Microwave
Infrared
Visible
Ultraviolet
X-Ray
Gamma Ray

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9
Q

Ionising radiation

A

Radiation with sufficient energy to remove electrons from their shells can cause ionisation

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10
Q

Ionisation in human cells due to radiation exposure

A

DNA may be damaged directly or indirectly

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11
Q

Indirect ionisation

A

Through free radical formation e.g. ionised water -
Thought to cause most biological damage because water is much more abundant than DNA

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12
Q

History of X-Ray

A

Discovered in 1895 by German physicist & mathematician Dr. Wilhelm Conrad Roentgen who received first nobel prize for developing the first X-Ray tube

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13
Q

What year was X-Ray first introduced in Ireland?

A

1896

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14
Q

Characteristics of X-Ray

A

Invisible
Electrically neutral
No mass
Travel at speed of light in vacuum
Cannot be optically focused
Travel in straight lines
Cause some substances to fluoresce
Cause chemical changes in radiographic and photographic film
Can penetrate the human body
Can produce secondary radiation
Can cause damage to living tissue

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15
Q

Protons

A

Positive charge

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16
Q

Neutrons

A

Neutral

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17
Q

Electrons

A

Negative charge

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18
Q

Where do X-Rays come from?

A

X-rays produced when rapidly moving electrons that have been accelerated through a potential difference of order 1kV to 1mV strikes a metal target

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19
Q

Production of X-Rays (more detail)

A

Electrons from a hot filament are accelerated onto a target anode. When electrons are suddenly decelerated on impact, some of the kinetic energy is converted into EM energy as X-rays.

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20
Q

How much energy supplied is converted into X-radiation during this process?

A

Less than 1%, with the rest being converted into the internal energy of the target

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21
Q

Polychromatic radiation

A

Photons produced will have a range of energies

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22
Q

Voltage produced by X-ray tube

A

100,000V

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23
Q

How many volts used for finger scan?

A

48-50 thousand volts

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24
Q

X-ray interaction processes

A

When radiation passes through matter, it is attenuated by processes of absorption and scattering

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25
Q

Attenuation

A

Results in a reduction in the intensity of the incident radiation beam

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26
Q

Absorption

A

Results in transfer of energy from x-ray photon to atoms of the material - the photon’s energy is totally absorbed

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27
Q

Scattering

A

Involves photon deflection from original course, it only loses energy to material it is passing through

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28
Q

Contribution of x-rays to radiographic image formation

A

A beam of x-ray photons is produced using an x-ray tube
The beam is passed through a patient’s body
Some tissues will attenuate more than others
Beam of photons exiting the patient is more intense in some places than others
An image receptor (digital) reacts to x-ray photons and captures image
Areas of receptor subject to more radiation gain more signal, displayed as darker on film

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29
Q

Photoelectric absorption

A

Incident photon interacts with electron of inner shell, with incident photon completely absorbed

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30
Q

Compton scattering

A

Interaction between incident photon and an outer shell electron results in electron ejection and scattering

Main source of staff exposure

Protective shielding used to prevent exposure

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31
Q

Beam attenuation

A

The beam emitted from the patient contains the radiologically significant information needed to make a diagnosis

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32
Q

Factors affecting the amount and type of attenuation that happens

A

Atomic number of tissue
Density of tissue
Thickness of tissue
Energy of x-ray beam

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33
Q

Atomic number and density of air

A

7.78, 1.29kg/m^3

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34
Q

Atomic number and density of fat

A

6.46, 916kg/m^3

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35
Q

Atomic number and density of water

A

7.51, 1000kg/m^3

36
Q

Atomic number and density of muscle

A

7.64, 1040kg/m^3

37
Q

Atomic number and density of bone

A

12.31, 1650kg/m^3

38
Q

The human body acts as an ______________ during x-ray

A

Attenuator

39
Q

Air as an attenuator

A

Air will absorb fewer photons allowing more photons reach the image receptor creating a greater image receptor exposure

40
Q

Fat as an attenuator

A

Soft tissue similar to muscle but lower density and atomic number

41
Q

Muscle as an attenuator

A

Soft tissue withh higher atomic number and density to fat leading to greater attenuation of the beam

42
Q

Bone as an attenuator

A

Calcium content and high atomic number with the greatest tissue density. Greatest absorber of photons with less reaching image receptor.

43
Q

Contrast agents

A

Introduction of high density agents into low density regions to enhance differences between organs of body during x-ray e.g. barium, iodine, air

44
Q

Darkness on an x-ray indicates

A

Low density regions which do not attenuate x-ray - radiolucent e.g. lungs containing gas

45
Q

How can contrast agents be applied?

A

Orally
Rectally
Intra-venously
Intra-arterially

46
Q

Fluoroscopy

A

Taking multiple low-dose x-ray images in succession to create a real time, stop motion video

47
Q

Applications of fluoroscopy

A

In the surgical theatre - check fixation of devices
GIT system and blood vessel imagery (angiography)

48
Q

Limitation of conventional projection radiography

A

2D image does not fully represent 3D structure, therefore images are taken from multiple angles

49
Q

Harmful effects of ionising radiation

A

Pose risk to patients, staff, public and unborn children
Can often lead to radiation burn, hair loss

50
Q

Tissue reactions

A

When radiation exceeds threshold level, tissue function compromised due to cell death beyond tissue capability

51
Q

Tissue reaction side effects

A

Skin reddening
Cataract
Permanent sterility
Acute radiation syndrome (ARS)

52
Q

Higher dose of radiation

A

Increases risk of cell damage and death

53
Q

Severity of radiation effects

A

Proportional to dose received over threshold

54
Q

Threshold of tissue reactions

A

Much higher than doses delivered during standard general radiographic examinations

55
Q

Stochastic effects

A

Cell DNA damage can lead to mutation, replication and cancer

Effects random in nature

Somatic - occurs in individual
Genetic - occurs in offspring

56
Q

Any amount of radiation carries a risk however

A

Smaller amount of radiation, lower risk with the probability of occurence assumed proportional to dose received

57
Q

There is NO threshold….

A

below which zero effects can occur

58
Q

Stochastic effects additional info

A

Cardiovascular disease risk
Increased risk of developing childhood cancer

59
Q

Pillars of Risk Reduction

A

Justification
Optimisation
Dose limitation

60
Q

Ways to optimise staff dosage

A

Time
Distance
Shielding/protection

61
Q

Xray and pregnancy

A

Low dose administered to pregnant woman to reduce risk of childhood cancer

Young, undifferentiated tissue more sensitive to mutation

Greater risk of stochastic effects in youths

Justification and optimisation key for pregnant cases

62
Q

PROS

A

Accessible
Fast
Cost effective
Short waiting lists
Minimal preparation
Minimally invasive

63
Q

CONS

A

Limited detail on soft tissue organs
Limited detection of early diagnosis in bone disease
Non specific findings in some disease processes
2D image of 3D image structure
Anatomy only, limited functional and physiological info

64
Q

Clinical applications of CP radiography

A

Chest
Skeletal trauma
Imaging for exclusion
Follow up
Suspected physical abuse (SPA)

65
Q

Summary of CP radiography

A

Xrays pass through patient
Some attenuated, some pass through patient to detector
Density, atomic number and thickness can influence penetration

66
Q

How do we overcome the limitation of the 2D image?

A

Take images from multiple angles

67
Q

Assessment of skeletal trauma

A

Fracture/dislocation
Presence and severity
Healing or infection

68
Q

Signs of fracture

A

Disrupted cortical outlines
Radiolucent lines
Misalignment of bony fragments etc.

69
Q

Aswell as visible disruption to bony anatomy…

A

skeletal trauma may be associated with other signs on projection radiographs such as fluid levels, visible fat pads etc.

70
Q

Fat fluid level..

A

where blood and fat have leaked from the fractured bone, and the less dense fat lies on top of the more dense blood

71
Q

Fracture healing

A

Checkup assessment to monitor healing where avascular necrosis indicates insufficient healing

72
Q

Degenerative changes assessed with projection radiography

A

Osteoarthritis (joint space lost, sclerotic bones, subchondral cyst) and rheumatoid arthritis (loss of joint spaces, ulnar deviation, soft tissue swelling and hitchhiker’s thumb)

73
Q

Assessment of bone or joint pain

A

Tumours (osteocarcoma - bone cancer) show heterogenous, areas on new bone formation (white)

74
Q

Paget’s disease

A

Excessive bone remodelling

75
Q

Advantages of projection radiography

A

Readily available
Fast
No waiting lists
Cost effective
Minimal prep required by patients
Non-invasive in almost all cases
Contrast is minimally invasive
Radiation dose lower than alternative modalities

76
Q

Limitations of projection radiography

A

Use of ionising radiation
Generates a 2D image of 3D anatomy
Limited visualisation of soft tissue structures
Can be limited in early diagnosis in bony disease e.g bony metastasis
Non-specific findings in some disease processes
Possible allergic reactions to contrast agents

77
Q

Radiation dosage

A

More projection xrays carried out however lower dosage than CT scan

78
Q

Larger denser body parts usually…

A

require higher doses of radiation

79
Q

Chest mSv

A

0.02

80
Q

Lumbar spine mSv

A

0.57

81
Q

Knee mSv

A

0.00058

82
Q

Abdomen mSv

A

0.4

83
Q

Example of projection radiography in research

A

Etanercept - tumour necrosis factor used in treatment of rheumatoid arthritis

84
Q

Research to improve radiography

A

Optimisation of patient imaging e.g. studies investigating radiation dose and image quality

85
Q

Forensic studies

A

Widely used tool in forensic examination

86
Q

Oldest form of radiographic imaging

A

Conventional projection radiography based on attenuation of xray photons by different tissues

Clinical Imaging (2 decks)

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