Rad Bio Flashcards
Based on reports of the UNSCEAR and BEIR V committees, the ICRP suggests a risk estimate of excess cancer mortality per Sv:
- Working population
- High dose and high dose rates
- Low dose and low dose rates
- General population
- High dose and high dose rates
- Low dose and low dose rates
Working population
- 8 x 10-2 per sievert for high doses and high dose rates
- 4 x 10-2 per sievert for low doses and low dose rates
General population
- 10 x 10-2 per sievert for high doses and high dose rates
- 5 x 10-2 per sievert for low doses and low dose rates
- **Slightly higher for general because increased susceptibility of young people
Occupational exposure of fetus should not exceed _________ for total gestational period (10 months)
- 0.5mSv/month
- What are deterministic effects?
- How are they proportional to dose?
- Give examples
- Radiation effects that will definitely occur once a certain threshold dose has been reached
- The severity of the deterministic effect is proportional to the dose of radiation
- Ex:
- Cataracts (2Gy)
- Erythema
- Fibrosis
- Hematopoietic damage (5-8Gy)
- What are stochastic effects?
- How are they proportional to dose?
- Give examples
- Effects that occur without a threshold dose –> basis of ALARA
- Probability of effects are proportional to dose
- Ex: cancer, genetic mutations
- What is lethal dose?
- What does LD50/60 mean?
- What is the LD50/60 for humans?
- Lethal dose - dose of ionizing radiation sufficient to cause death
- LD50/60 is the dose of radiation that will kill 50% of people within 60 days
- LD50/60 for humans = 4 Gy
Radiation exposure to the fetus results in different effects depending on the period of development the exposure occurs in. What is the primary effect of radiation exposure during the following:
- Pre-implantation (0-9 days)
- Organogenesis (10-6 weeks)
- Fetal period (6 weeks to term)
- Pre-implantation (0-9 days)
- Most sensitive to lethal effects
- All or nothing effect
- Organogenesis (10-6 weeks)
- Greatest amount of intrauterine growth retardation
- Congenital malformations
- Fetal period (6 weeks to term)
- Greatest amount of permanent growth retardation
- Permanent fertility changes
Radiation exposure during what period of gestation results in peak mental retardation?
- Peak sensitivity to mental retardation from 8-15 weeks
Ionization chamber
- What radiation does it detect?
- What is the primary use of this detector?
- Advantages
- Disadvantages
Ionization chamber
- Detects x-rays and gamma rays
- Used most commonly to measure exposure rates from a patient who has received radioactive material
- Advantages
- Wide exposure range (1 mR/hr to several thousand mR/hr)
- Can measure low-energy radiation (20 keV)
- Disadvantages
- Accurate +/- 10%
- Saturated depending on energy, pressure, and temp
- Slow response time (3-4 sec)
- Large size
What are examples of ionization chambers?
- Quality-assurance testing
- Pocket dosimeter, dose calibrators
- Detectors of most x-ray machine phototimers
- Some CT scanners (xenon)
Proportional counters
- What radiation does it detect?
- What is the primary use of this detector?
- Advantages
- Disadvantages
Proportional counters
- Alpha and beta particles
- Used in laboratories; not used in medicine
- Advantages
- Can differenatiate between types of radiation
- Disadvantages
- Special probes needed
- Slow response time
Geiger-Muller counters
- What radiation does it detect?
- What is it primarily used for?
- Advantages
- Disadvantages
Geiger-Muller counters
- Detects all radiation (alpha particles require special probe)
- Survey instrument to detect g and b contamination, exposure rates and release levels
- Advantages
- Rapid response
- Detects small amounts of radiation
- Disadvantages
- Cannot distinguish between types of radiation
- Dependent on energy of incident photon
- Lose calibration over time
- Paralyzable
What is the annual occupational effective dose limit per year?
- 50 mSv per year
- Exposure monitoring is required when workers are likely to receive 10%
Radiation workers lifetime cumulative effective dose (CED) should not exceed _____________.
- Age in years x 10mSv
- Does not include exposure from natural background or due to required medical imaging procedures individual underwent
What is radiation dose at which bone marrow syndrome, GI syndrome, or CNS syndrome occur?
- 3-8 Gy = bone marrow syndrome; death in 30 days
- >10 Gy = GI syndrome; death in 10 days
- >100 Gy of x-ray or gamma = CNS syndrome; death in hrs
T/F: There is a dose rate effect for induction of malignancies following radiation exposure
- True
- Fewer malignancies induced if a dose is spread out over a period of time over a low dose rate than if it were delivered at once during an acute exposure
