Protracted
dose delivered continuously per long time period at low doe (brachytherapy, radioactive seeds)
Fractionated
dose delivered in equal fractions separated by 24 hours (rad therapy)
Stages of ARS response
- Prodromal - w in hours of at least 1 Gyt, hrs to days, dose dependent
- Latent Period - no symptoms up to 1 week
- Manifest Illness - syndrome symptoms
- Recovery or Death
Recovery or Death Doses
whole body sublethal (near lethal) dose (2-3 Gyt) recovery in 3 months
whole body lethal dose (6-10Gyt) death occurs
Hematopoietic Syndrome
1-10 Gyt - bone marrow syndrome
.25 Gyt - lower # of lymphocytes
.5 Gyt - lower platelets
Death will occur within 6-8 weeks of 2 Gyt + dose
Recovery w in 3 wks - 6 mths of 2 Gyt or less dose
Gastrointestinal Syndrome
6-10 Gyt - has threshold dose, peaks at 10 Gyt, death within 3-10 days
Prodromal - 24 hrs
Latent - up to 5 days
Death due to electrolyte imbalance, fluid loss, infection
Cerebrovascular Syndrome
50 Gyt +
Death within few hrs to 3 days
Latent - 24 hrs
Repair + Recovery with ARS
- repair enzymes activated when exposed to sublethal doses
- can usually fix with occasional mutations that lead to late effects
- oxygenated cells repair better
- rad injuries are cumulative
Local tissue damage
How tissues/organs respond to rad differently depends on
1. radiosensitivity
2. reproductive characteristics
3. growth rate
Skin
- very radiosensitive, epidermis contains stem cells
- 2 Gyt to skin area will cause erythema w in 24-48 hrs, effects will increase over next week or 2
- wet then dry desquamation (outer layer skin shedding)
Radiodermatitis
skin reddening and inflammation due to exposure, leads to cancer and lesions
Reproductive cell dose limits
.1 Gyt low sperm ct
.25 Gyt chromosomal damage
2 Gyt temp sterility
5 Gyt perm sterility
