Radiation Injury

Description

• Radiation in this chapter refers to ionizing radiation
• Alpha (α) – helium nucleus; does not penetrate skin
• Beta (β) – electron; penetrates tissue a few cm
• Gamma (γ) – photon; penetrates body
• Neutron – very penetrating; not detected by Geiger counter, but neutron emitters also emit γ radiation
• Radioisotope/radionuclide – chemical element that emits radiation from its nucleus:
  • Radioactivity cannot be destroyed, only relocated or shielded
  • Being radioactive does not change element's other chemical and physical properties, such as heavy metal toxicity
• Exposure/irradiation – patient has been in presence of ionizing radiation:
  • Whole body or only certain areas may be exposed
• Contamination – radioactive material where it is not desired:
  • Internal – within body (e.g., lung)
  • External – outside body (skin, hair, clothing)
• Dose – amount of radiation energy absorbed by tissue:
  • Units and conversions:
    • 1 gray (Gy) = 100 rad
    • 1 sievert (Sv) = 100 rem
  • For β and γ radiation:
    • 1 Gy = 1 Sv = 100 rad = 100 rem

• Children are more sensitive to radiation injury
• Potassium iodide is most protective for children and should be given promptly if contamination with radioactive iodine (I-131) is suspected

• Developing fetus is very sensitive to radiation
• Pregnant staff should not care for radioactively contaminated patients

Etiology

• Ionizing radiation leads to cellular injury
• Damage to blood vessels leads to endarteritis and loss of tissue blood supply
• Higher rates of cell division within an organ make it more sensitive to radiation:
  • Bone marrow and GI tract are very sensitive
  • Muscle and nerve are less sensitive
• Acute radiation syndrome (ARS) occurs in stages following whole-body exposure:
  • Prodromal: Acute radiation injury leads to acute inflammation (0–48 hr)
  • Latent: If the acute phase of injury is survived, inflammation and symptoms subside (0–2 wk)
  • Manifest illness: At higher radiation doses, organ failure then develops
  • Recovery or death (usually from infection) follows
• Sources of radiation include medical devices, therapeutics, nuclear weapons, and industry