• nonionizing (long wavelength, low energy)
• ionizing (short wavelength, high energy)

• microwaves
• electromagnetic fields (ex: high tension electric wires)
• US lithotriposy- focused US and shock waves (thermal injury from US and shear force from pressure waves)
• UV radiation
  • UV-A (320-400), UV-B (280-320), and UV-C (200-270) (UV B and C prevented from entering earth via ozone layer, but thninning due to polutants)
    • pollutants like CFC's will decrease stratospheric ozone

• particulate radiation
• nonparticulate radiation

• alpha particles
  • low penetration with high ionizing power (high LET)- block by paper
  • medically important when deposited internally
    • ex: radon in lung
• beta particles
  • somewhat greater penetration than alpha (1-2 layers), but weaker ionizing power (low LET)- block by wood
• neutrons- noncharged, high mass particles
  • high energy neutrons
  • penetrating, high ionizing energy (high LET)
    • ex: from radiotherapy units or atomic bombs

• good tissue penetration- block with lead
• examples
  • X rays
  • gamma rays
  • cosmic rays

• curie (Ci)- measures decay events
  • measure of activity
• roentgen- measures ionization intensity
  • measure of exposure
• rad- measure energy absorbed per gram of tissue
  • measure of absorbed dose
• rem- measures tissue damage
  • measure of dose equivalent
• sievert- measures tissue damage

• LET- energy lost per distance (amount of energy transfered to tissue/path length)
  • high LET=more tissue ionizations, thus more tissue damage
• RBE- relative LET of irradiation forms compared to cobalt gamma rays (RBE=1)
  • RBE of 4 means neutron beam is 4 times as damaging to tissue as X ray photons
  • high RBE = more tissue damage

• indirect- water forms free radicals
• direct effects break bonds within DNA, faulty repairs predispose to genetic damage and malignancy

• LET, RBE of source, dose, dose rate (rads/min)
• kind and amount of tissue exposed (increased mitotic rate and regenerative activity increase radiosensitivity)
• age of individual (young more sensitive)
• tissue factors
  • oxygen content (increase free oxygen radicals causing more injury)
  • heat (increase sensitivity)

• terrestirial uranium using for radon gas
  • alpha particles emits uranium and radon
  • exposure via inhaled (aerosol) and water leading to lung cancer
  • HIGH RISK
• cosmo (gamma) rays- mainly in space and affects frequent fliers
• medical
  • modern dx X ray and radiopharmaceuticals cause little radiation injury
  • cancer radiotherapy damages surrounding tissue (may induce second cancers years after)
• atomic reactor accidents
• nuclear weapons

• chromosomal damage
  • inhibit mitosis or causes mitosis linked cell death (cells fail to divide or die in metaphase when they wouold divide)- usually months or yrs after radiation event
  • carcinogenesis (mutation, activate oncogenes)
  • congenital defects of irradiated embryo or fetus (microcephaly, mental retardation)- leads to abortion, leukemia increase in offspring
  • teratogenesis- damage to germinal cells of ovary or testes
• vascular injury
  • edema or hemorrhage lead to
  • cellular anoxia causing
  • repair leading to
  • fibrosis
  • all this causes disfigurement and reduced mobility

• erythema
• edema
• pigmentation
• depigmentation
• dermatitis
• alopeicia
• mucositis
• hemorrhage
• ulceration
• necorsis
• infection
• atrophy
• scaring
• cataracts
• cancer

• acute: necrosis, edema, hemorrhage
• chronic
  • atrophy of cells
  • arterioschelorosis
  • fibrosis
  • cancer

• hematologic syndrome (1-8 Gy's)
  • onset wks-months
  • infection
  • anemia/pancytopenia
  • hemorrage
  • prognosis- most recover if tx
• GI syndrome (8-20 Gy's)
  • onset in days
  • emesis
  • diarrhea
  • hemorrhage
  • prognosis- usually fatal in 10-14 days
• cerebral/CV syndrome (20+ Gy's)
  • onset- hrs
  • convulsions
  • coma
  • death

Remember, prodrome if dose over 1 Gy and onset in minutes to hours is closely related to dosage

• usually at >4500 rads
• onset 1-8 wks
• damage to endothelium, alveolar and bronchial cells
• acute inflammation with exudate in alveolar spaces
  • fibrin rich deposits = hyaline membranes
• desquamation of alveolar and bronchial cells
• depletion of surfactant

• this is 8-12 months
• permenant damage of endothelium and type I alveolar cells
• reactive epithelial proliferation and squamous metaplasia
• organization, and you will see alveolar and interstitial fibrosis

• leukemia- associated with whole body irradiation (esp. fetuses and children) 
• thyroid cancer- uptake of I¹³¹ when young
• lung carcinoma- inhale radioactive nuclides (uranium miners, smokers, radon)
• breast, lung, salivary gland tumors- induced by therapeutic radiation mostly in adults
• skin cancers- UVB light becoming more common
• osteosarcoma (bone cancer from radionuclides uncommon)
  • Ra²²⁶
  • Sr⁹⁰
  • Ca⁴⁵
  • Am²⁴¹
  • Pu^238,239

• 1 Gray = 100 rad = 1 centriGray (cGy)
• 1 rad = 10 milliSieverts

• cancer cells dont repair radiation damage as well as normal cells
  • fractionation (dividing dose) allows normal cells surrounding tumor to repair between doses
• cancer cells generally as radiosensitive as parent cells and stage of differentiation
  • leukemias are generally radiosensitive
  • carcinomas that are not radiosensitive
    • lung cancer
    • pancreatic cancer
    • bladder cancer
    • gliomas
    • melanoma
    • osteosarcomas

• radiosensitizing
  • oxygen (hypoxic cancer cells survive)
  • heat hyperthermia
  • alkylating agents
• radioprotective agents
  • anti inflammatory drugs (cortisone)
  • anti oxidants
  • free radical scavengers

• dose of 100 rem- mildly depressed blood count and nausea, vomitting of 10% of patients within 48 hrs
• dose of 350 rem- severe bone marrow depression, and great majority have nausea, vomitting within 12 hrs, half die without suportive care
• dose of 500 rem- half die with supportive care
• dose of 1000 rem- great majory die despite supportive care

• skin- erythema, epilation, desquamation, necrosis/ulceration
• cataracts
• permenant sterility

• thermal injuries
• cataracts
• retinal burns

• possible leukemia, brain cancer (if so, risk very low)

• burns, carcinogenic (damage chromosomal NA by producing free radicals), and may also be immunosuppressive (decreased cellular immunity by damaging Langerhans cells) leads to skin cancer

• cause actinic keratosis and cataracts