M2 Topic 3: Outcomes of Medical Radiation Patient care Flashcards
(42 cards)
1
Q
What happens to radiation once generated or emitted by a source?
A
Absorbed
- Heating, excitation, ionisation effects
Attenuated
- Partial absorption and scattering of original radiation
Transmitted
- Energy passes through medium w/o interacting at all
- Maintains amount of energy and direction of propagation of original source
Reflected
- Ultrasound
2
Q
Types of ionisation interactions
A
No interaction
- Transmission (goes straight through medium, maintains energy and direction of propagation)
Absorption interactions
- Photoelectric interactions
- Pair production
- Photonuclear disintegration
Attenuation interactions
- Raleigh scattering
- Compton scattering
3
Q
What are photoelectric interactions?
A
Where lower x-ray energies are fully absorbed by inner shell electron, which is ejected from atom, creating an ion
- Outer shell electron moves into vacancy, releasing its excess energy as a characteristic photon as it moves into lower energy shell
4
Q
What is a pair production?
A
Photon’s energy absorbed by nucleus and converted into electron positron pair
- Only occurs when energy of incident photon is higher than 1.022 MeV
5
Q
What is photonuclear disintegration?
A
Nuclear absorption of gamma photons (even with higher energies)
- Photon energy absorbed and converted into variety of neutrons, protons, or alpha particles (depends on energy of gamma ray and specific nucleus involved)
6
Q
What is Raleigh scattering?
A
Photons are scattered in a new direction without change in energy
7
Q
What is Compton scattering?
A
At higher energies, may occur where photons collide with free or loosely bound outer shell electrons, transferring some of their energy to eject electron from atom.
- Incident atom is scattered in process and continues with reduced energy
8
Q
Challenges of scatter radiation in medical radiations
A
- Inaccuracies in image (detector cannot determine direction or angle of origin for each individual photon)
- Reduction of image contrast and clarity
- Can lead to radiation dose being delivered to unwanted parts of the body
9
Q
How are digital images formed?
A
Radiographic film
- Contains a layer of material that initially interacts with radiation energy upon exposure, then developed into an image using a chemical reaction
Done via direct or indirect conversion
10
Q
Direct conversion
A
Radiation energy directly converted into electrical signal
- Semiconductor, high voltage layer, causes movement of electrons whereby electron charge is collected via electrodes
- Thin Flat-panel Transistor (TFT) Array, reads electrical charges and transfers them to image processor
11
Q
Indirect conversion
A
Energy is first converted into light (scintillation detectors), which is then converted into electrical signal
- Scintillator, converts x-ray to visible light
- Photodiode, coverts visible light to charge
- Thin Flat-panel Transistor (TFT) array, reads electrical charges and transfers them to image processor
12
Q
Where do the digital images go after direct/indirect conversion?
A
Image is digitally reconstructed via computer algorithm and displayed on monitor.
- Saved using DICOM file format which can be easily shared and viewed
13
Q
What is post-processing?
A
Manipulate raw data to highlight range of anatomical features
- Improve quality of resulting image
- Show anatomy from different view or perspective
- Better interrogate image
- Can more confidently answer clinical question or objectives of care
Note: cannot overcome laws of physics, must be mindful of ensuring initial radiation parameters and exposures have been optimised as much as possible
14
Q
Types of ionising medical imaging technology
A
- General x-ray
- Computed tomography (CT)
- Dual energy x-ray absorptiometry (DEXA)
- Orthopantomograms
- Angiography
- Mammography
- Fluoroscopy
15
Q
What is a general x-ray?
A
- Uses x-rays to create images inside body (2D image of 3D anatomical structure)
- Used to diagnose fractures, infections, and abnormalities in bones and certain tissues
16
Q
What is a CT scan?
A
- Combines multiple x-ray images taken from different angles to create detailed cross-sectional images of the body
- Useful for diagnosing complex conditions, includes cancers, cardiovascular diseases, internal injuries
17
Q
What is dual energy x-ray absorptiometry (DEXA)?
A
- Measures bone mineral density using two x-ray beams at different energy levels
- Mainly used to diagnose osteoporosis and assess fracture risk
18
Q
What is an orthopantomogram? (OPG)
A
- Panoramic dental x-ray, captures entire mouth in single image
- Evaluates teeth, jaw, and surrounding structures
19
Q
What is an angiography?
A
- Uses x-rays and contrast dye to visualise blood vessels
- Used to diagnose/treat vascular conditions
20
Q
What is mammography?
A
- Use of low dose x-rays to create detailed images of breast tissue
- Aids early detection and diagnosis of breast cancer
21
Q
What is fluoroscopy?
A
- Real-time moving images of internal structures using continuous x-ray beams
- Guides diagnostic and therapeutic procedures
22
Q
Types of non-ionising medical imaging technology
A
- Ultrasound
- Magnetic resonance imaging (MRI)
23
Q
What is an ultrasound?
A
- Uses high-frequency sound waves to create real time images of internal structures
- Useful for examining soft tissues, pregnancies and guidance of certain medical procedures
24
Q
What is an MRI?
A
- Uses strong magnetic fields and radio waves to produce detailed images of organs and tissues
- Effective for visualising brain, spinal cord, joints, and soft tissues using low energy EMR
25
Nuclear medicine imaging technology focus
Focuses on physiological imaging
- Provides info on how well a particular organ or cell of interest is metabolising the radiopharmaceutical administered
26
What is a 3D PET/CT fusion? (Nuclear medicine)
- Combines PET and CT to provide metabolic and anatomical info in single image
- Useful for accurately diagnosing and staging cancers, planning, monitoring treatment
27
What is 2D whole body scanning? (Nuclear medicine)
- Produces 2D images of entire body (similar to general x-ray)
- Provides functional info about any bone abnormalities or cancer spread
28
What is dynamic imaging? (Nuclear medicine)
- Captures sequential images over time to visualise physiological processes (blood flow, organ function)
- Useful for diagnosing and monitoring conditions affecting heart, kidneys, liver and other organs
29
What are the biological effects of radiation?
- Treatment option by acting on DNA of cells to induce cell death
- Cause genetic changes in cellular DNA, can manifest many years after exposure
Influenced by dose received, type of radiation and characteristics of ells exposed
30
What is a nucleus?
- Control center of the cell
- DNA provides instruction manual for how each cell coordinates growth and division, metabolism and energy use
- Production of proteins that drive functions of body
31
What are the main molecules found in the human body?
Water
- Makes up nearly 2 thirds of body
Lipids (fats)
- Composed of long chains of carbon and hydrogen atoms + oxygen-containing carboxyl group at one end
Carbohydrates
- Commonly rings of carbon, hydrogen + oxygen atoms
- Both lipids + carbs = energy source for cell
Proteins
- 20 amino acid combos
- Carbon, hydrogen, oxygen, nitrogen, sometimes sulfur
- Linked together by peptide bonds to form long chains, drives nearly all cellular functions
Nucleic acids
- DNA and RNA, made of 5 main nucleotides
- Carbohydrate, phosphate group, nitrogenous base
Minerals
- Essential for various bodily functions, such as bone formation, nerve transmission, oxygen support
32
Examples of changes to bodily molecules due to radiation
When water exposed to ionising radiation, produces highly reactive species such as hydroxyl radicals, hydrated electrons and hydrogen atoms
- Further react to form molecular hydrogen and hydrogen peroxide, which can cause significant chemical changes in molecules they interact with
- Reactive species generated can go on to disrupt other biomolecules or structural parts of a cell, where these biomolecules can also be chemically disrupted themselves, already impacting other biomolecules and cellular structures
33
Can radiochemical changes following exposure to ionisation occur in all materials? Irrespective of if they are living or not?
Yes
- The exact changes that arise vary, depending on type of radiation, and chemical compounds present in irradiated material
34
How long does it take for living cells/tissues/organisms to respond to chemical changes from radiation exposure?
Can take between hours or years
35
What determines a cell's ability to repair itself from radiation damage?
Nucleus (as it contains instructions for reparation)
- If damaged, ability to repair is significantly reduced
Several sites of damage within one cell also affect this ability
36
What is radiobiology?
Study of various molecular processes that are triggered in response to radiochemical changes following exposure to ionising radiation
37
How many different types of cells are there?
400
- Ranges in size
- Variation in exact dose of radiation required to induce biological effects on these cells
38
What are the two types of effects on biological cells from ionising radiation?
- Deterministic effects
- Stochastic effects
39
Deterministic effects
- Effects predetermined
- Occur when specific threshold of radiation dose has been exceeded
Examples are...
- Radiation burns
- Acute radiation syndrome
- Sterility
- Effects of radiotherapy
40
Stochastic effects
- Random, occur by chance
- No set threshold for effect
- Can occur years after exposure = linked to longer term health conditions
Examples
- Cancer development
- Hereditary effects
41
What is the therapeutic window?
There is a difference in radiation responses between tumour and normal cells
Thus..
- Tumour cells die at lower doses of radiation compared to normal cells
42
Why don't some cancers benefit from treatment even though there is a therapeutic window?
- Size of the window can vary depending on type of cancerous and normal cells being irradiated
- When window is too narrow, dose required to kill tumour cells is too close to the dose that would also damage normal cells (risks don't outweigh benefits)
