Topic 7: ionizing radiation health effects Flashcards
2 effects of radiation risk
1) Stochastic
2) Deterministic
Describe stochastic effects
- Likelihood = by laws of probability = related to dose received
PRINCIPLES:
1) No threshold limit below which stochastic effect cannot occur - Greater dose = greater risk
2) Chance of cancer effect is probability related BUT severity of effect is not - Severity is not related to dose
How to calculate the statistical risk
- Calculate dose equivalent limits
What is the risk for effect from dental panoramic X-ray?
- 0.1 mSv = 0.015% * 0.1
What is the risk of effect from CT angio?
- 12 mSv = 0.015% * 12
Types of stochastic cancer effects
1) Somatic
2) Hereditary
Parts of body with high radiosensitivity
- Bone marrow
- Spleen
- Thymus
- Lymph nodes
- Gonads
- Eye lens
- Lymphocytes
Parts of body with medium radiosensitivity
- Skin
- Mesoderm organs = liver/heart/lungs
Parts of body with low muscle radiosensitivity
- Muscle
- Bones
- NS
Define ALARA principle
- Minimize risk of cancer by applying
Describe hereditary effects
- Caused by radiation-induced damage to genetic material in germ cell
- Biological damage to chromosomes = shows up in future generations
- Therefore efforts to reduce radiation to gonads min
Describe deterministic effects
PROPERTIES:
1) Severity will increase with dose
2) Threshold exists which below effect will not occur = effect will always occur if threshold reached
- Associated with large doses
- Doses due to = nuclear or radiation-related incidents + radiotherapy
1 Sv is equivalent to?
50,000 X-rays + 100 whole body CT-scans
Describe risk-benefit analysis
- Tool for managing risk on daily
- Applied on patient exams NOT workers = not benefit to them
Describe risk-benefit for X-rays
- Distinct benefit
- Necessary to control factors
- Legislation = no irradiation intentionally unless valid clinical indication
- Clinician determines benefit outweighs risk
Give benefits of X-ray
- Save life due to correct diagnosis
- Correct treatment due to diagnosis
- Eliminate disease = affect management of patient
- Radiotherapy
- Make diagnosis with exam which is less morbid/mortality than alternative = scan > explorative surgery
Explain the process of justification
- If result of exam will change clinical management of patient = justified
- To exclude injury/disease = justified
- Justified = no other possible to check outcome over means
FACTORS: - Age
- Pregnancy status
- Availability of other diagnostic procedure
Describe risk of gamma rays
- No safe dose limit
- Therfore must justify + discuss need for exam + quantify risk
How to find estimates of chance of risk
- Equivalent background dose
- Statistical risk
- Comparison to general cancel risk
- Comparison to everyday activities
- Lost life expectancy given in days
Compare X-ray dose to flight + background radiation at sea level
- 4-hour flight
- 28 days at sea level
What is the increase in tumor development due to CT?
- Risk increases by 0.05%
What is the purpose of managing radiation dose during diagnostic procedures?
- Avoid deterministic effects
- Reduce probability of stochastic effects
