L 13: Radiation Cataractogenesis Flashcards
1
Q
Nuclear Cataract
A
Causation linked to Smoking
2
Q
Cortical Cataract
A
Causation linked to diabetes & excess UV-B
3
Q
Post subcapsular cataract
Board question
A
Causation linked to steroids, diabetes, and IR
4
Q
Supranuclear Cataract
A
Causation linked to AD, Down’s Syndrome
5
Q
Radiation induced Cataracts
A
- Ionizing radiation of sufficient exposure also causes cataracts
- Increase in dose decreases latent period before cataract development
- no, high LET radiations are effective at inducing cataracts:
- At high doses, RBE = 10 for neutrons
- At low doses, RBE = 50 for no
- RT patients
2.2 – 6.5 Gy to eye: 12% development opacity, progressive (cataracts)
6.5 – 11.5 Gy to eye: 12% development opacity, stationary (little improvement) - Latent period:
6m. – 35y.
2.5 – 6.5 Gy- ~8y.
6.5 – 11.5Gy - ~4y.
6
Q
Cataracts are dependent on
A
- Radiation type
- Radiation dose
- Radiation fractionation
- Radiation dose-rate
- Animal species and genetic background
- Age and gender of animal at exposure
- Life-span of the animal
- Diet and presence of certain drugs
7
Q
Dose
A
- > 2Gy
- Dose dependency was seen
8
Q
Underlying mechanism
A
9
Q
Summary
A
- Cataracts are a deterministic effect of radiation—have a dose threshold
- Radiation-induced cataracts develop from the subcapsular posterior region of the lens
- As the dose is increased, the latency period for development of the cataracts is decreased.
10
Q
NCRP annual dose limit for occupational exposure for the lens
A
50 mGy absorbed dose
