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Clinical Imaging > L1. Conventional Projection Radiography > Flashcards

L1. Conventional Projection Radiography Flashcards

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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
Attenuation
Results in a reduction in the intensity of the incident radiation beam
26
Absorption
Results in transfer of energy from x-ray photon to atoms of the material - the photon's energy is totally absorbed
27
Scattering
Involves photon deflection from original course, it only loses energy to material it is passing through
28
Contribution of x-rays to radiographic image formation
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
29
Photoelectric absorption
Incident photon interacts with electron of inner shell, with incident photon completely absorbed
30
Compton scattering
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
31
Beam attenuation
The beam emitted from the patient contains the radiologically significant information needed to make a diagnosis
32
Factors affecting the amount and type of attenuation that happens
Atomic number of tissue Density of tissue Thickness of tissue Energy of x-ray beam
33
Atomic number and density of air
7.78, 1.29kg/m^3
34
Atomic number and density of fat
6.46, 916kg/m^3
35
Atomic number and density of water
7.51, 1000kg/m^3
36
Atomic number and density of muscle
7.64, 1040kg/m^3
37
Atomic number and density of bone
12.31, 1650kg/m^3
38
The human body acts as an ______________ during x-ray
Attenuator
39
Air as an attenuator
Air will absorb fewer photons allowing more photons reach the image receptor creating a greater image receptor exposure
40
Fat as an attenuator
Soft tissue similar to muscle but lower density and atomic number
41
Muscle as an attenuator
Soft tissue withh higher atomic number and density to fat leading to greater attenuation of the beam
42
Bone as an attenuator
Calcium content and high atomic number with the greatest tissue density. Greatest absorber of photons with less reaching image receptor.
43
Contrast agents
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
Darkness on an x-ray indicates
Low density regions which do not attenuate x-ray - radiolucent e.g. lungs containing gas
45
How can contrast agents be applied?
Orally Rectally Intra-venously Intra-arterially
46
Fluoroscopy
Taking multiple low-dose x-ray images in succession to create a real time, stop motion video
47
Applications of fluoroscopy
In the surgical theatre - check fixation of devices GIT system and blood vessel imagery (angiography)
48
Limitation of conventional projection radiography
2D image does not fully represent 3D structure, therefore images are taken from multiple angles
49
Harmful effects of ionising radiation
Pose risk to patients, staff, public and unborn children Can often lead to radiation burn, hair loss
50
Tissue reactions
When radiation exceeds threshold level, tissue function compromised due to cell death beyond tissue capability
51
Tissue reaction side effects
Skin reddening Cataract Permanent sterility Acute radiation syndrome (ARS)
52
Higher dose of radiation
Increases risk of cell damage and death
53
Severity of radiation effects
Proportional to dose received over threshold
54
Threshold of tissue reactions
Much higher than doses delivered during standard general radiographic examinations
55
Stochastic effects
Cell DNA damage can lead to mutation, replication and cancer Effects random in nature Somatic - occurs in individual Genetic - occurs in offspring
56
Any amount of radiation carries a risk however
Smaller amount of radiation, lower risk with the probability of occurence assumed proportional to dose received
57
There is NO threshold....
below which zero effects can occur
58
Stochastic effects additional info
Cardiovascular disease risk Increased risk of developing childhood cancer
59
Pillars of Risk Reduction
Justification Optimisation Dose limitation
60
Ways to optimise staff dosage
Time Distance Shielding/protection
61
Xray and pregnancy
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
PROS
Accessible Fast Cost effective Short waiting lists Minimal preparation Minimally invasive
63
CONS
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
Clinical applications of CP radiography
Chest Skeletal trauma Imaging for exclusion Follow up Suspected physical abuse (SPA)
65
Summary of CP radiography
Xrays pass through patient Some attenuated, some pass through patient to detector Density, atomic number and thickness can influence penetration
66
How do we overcome the limitation of the 2D image?
Take images from multiple angles
67
Assessment of skeletal trauma
Fracture/dislocation Presence and severity Healing or infection
68
Signs of fracture
Disrupted cortical outlines Radiolucent lines Misalignment of bony fragments etc.
69
Aswell as visible disruption to bony anatomy...
skeletal trauma may be associated with other signs on projection radiographs such as fluid levels, visible fat pads etc.
70
Fat fluid level..
where blood and fat have leaked from the fractured bone, and the less dense fat lies on top of the more dense blood
71
Fracture healing
Checkup assessment to monitor healing where avascular necrosis indicates insufficient healing
72
Degenerative changes assessed with projection radiography
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
Assessment of bone or joint pain
Tumours (osteocarcoma - bone cancer) show heterogenous, areas on new bone formation (white)
74
Paget's disease
Excessive bone remodelling
75
Advantages of projection radiography
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
Limitations of projection radiography
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
Radiation dosage
More projection xrays carried out however lower dosage than CT scan
78
Larger denser body parts usually...
require higher doses of radiation
79
Chest mSv
0.02
80
Lumbar spine mSv
0.57
81
Knee mSv
0.00058
82
Abdomen mSv
0.4
83
Example of projection radiography in research
Etanercept - tumour necrosis factor used in treatment of rheumatoid arthritis
84
Research to improve radiography
Optimisation of patient imaging e.g. studies investigating radiation dose and image quality
85
Forensic studies
Widely used tool in forensic examination
86
Oldest form of radiographic imaging
Conventional projection radiography based on attenuation of xray photons by different tissues

Clinical Imaging (2 decks)

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