Radiation Biology. Radiation Biology. Acute Radiation Syndrome Early and Late Effects of Radiation Exposure Radiolysis of Water Target Theory Poison Water Theory Direct/Indirect Hit Theory Law of Tribondeau and Bergonie
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Radiation Biology Radiation Biology Acute Radiation Syndrome Early and Late Effects of Radiation Exposure Radiolysis of Water Target Theory Poison Water Theory Direct/Indirect Hit Theory Law of Tribondeau and Bergonie Cardinal Principles of Radiation Protection-Time, Distance, Shielding -patient -Technologist
Terminology • Acute radiation syndrome • Chronic radiation syndrome • Radiosensitivity • Radiolysis of water • Target theory • Direct/indirect hit • Threshold • Linear/non-linear • Somatic effects • Genetic effects • Early effects • Late effects • Prodromal stage • Latent stage • Manifest illness • Erthema
Slotin Accident Slotin Accident Look for the footprints toward the end of the video
Ionization • Ionizing Radiation can remove tightly bound electrons from their atomic orbits • This causes the atom to become charged or ionized • The atom can then react with neighboring atoms, forming new chemical bonds
Possible Effects to Cells • Radiation may pass through cell without doing any damage. • Damage may occur but be repaired. • The damaged cell may reproduce in its damaged form. • The cell may die.
Cell Sensitivity • Early Effect: (ACUTE) • radiation response occurs within minutes/days after exposure • acute radiation syndrome-3 types, depending on exposure • local tissue damage • Late Effect: (CHRONIC) • radiation response not observable for months or years • leukemia • cataracts • other cancers • local tissue damage • Life span shortening • genetic damage
Linear Response to radiation: Non-threshold: Assumes no dose is safe Threshold: Assumes minimum dose needed to produce a response A B A dose response relationship is produced by extrapolating high dose experimental data to low doses.
Cell Sensitivity Diagnostic radiology is almost exclusively concerned with the late of effects for radiation exposure. This assumes a linear non-threshold dose-response relationship. No dose is considered safe.
Basic Cell Structure • Two parts: • Nucleus- contains DNA • Cytoplasm is 80% water • DNA is at risk when a cell is exposed to ionizing radiation
Cell Structure Two Basic Cell types
Radiation Damage Mechanisms 1. Direct Action: Direct ionization of the DNA molecule, which may result in genetic damage. 2. Indirect Action: Radiation ionizes water, which causes free radicals to form. Free radicals attack targets such as DNA. Much more common.
Target Theory Target theory suggests that a key molecule must be inactivated. The key molecule is assumed to be DNA. • When interaction occurs between radiation and target molecule, it is • considered a “hit” • An indirect hit has a larger target area because of the mobility • of the free radicals • Radiation acts randomly.
B3…..miss……..A4…..hit…….You sunk my Battleship!!!
Damage from Radiation Exposure • Acute • High dose in short time • Local: burns, hair loss, desquamation, blistering, damage to blood vessels, sterility, cataracts • Whole-body: reduction in blood cell counts, nausea, radiation sickness • Chronic • Low dose over long period of time • Cancer, anemia, cataracts
Appearance of Biological Effects • Prompt/Acute effect – effects seen immediately after large doses of radiation are delivered over a short period of time • Examples: radiation sickness and burns • threshold of 50 rad • Delayed effects- may appear months or years after a radiation exposure • Examples: cataract formation and cancer induction • threshold depends on effect (may be no threshold)
ACUTE RADIATION SYNDROME Acute Radiation Syndrome – full body exposure given in a few minutes.
Look around, be a Rad Geek Military Nuclear Accidents Proliferation of Fluoroscopy Exams and Radiation Safety
Early Effects-ARS Each syndrome has 3 main sub-stages prodromal stage latent stage manifest illness cell death/repair
Total Body Response to Radiation • Acute Radiation Syndromes – full body exposure given in a few minutes. • 3 stages of response: 1. Prodromal -NVD stage (nausea, vomiting, diarrhea) 2. Latent Period-Feels well while undergoing biological changes 3. Manifest Illness-Full effects felt, leads to recovery or death
ACUTE RADIATION SYNDROME • Hematologic syndrome • Prodromal • Latent • manifest • GI syndrome • Prodromal • Latent • manifest • CNS syndrome • Prodromal • Latent • manifest
Hematopoietic Syndrome (Hematologic) • Prodromal Stage: Mild symptoms appear within a few hours and last for several days • Latent Period: May last up to 4 weeks • Manifest Illness: Vomiting, diarrhea, fatigue and fever – Decline in blood cells – Recovery in 2 to 4 weeks…May last up to 6 months • Possible death due to infection, dehydration or hemorrhage
Gastrointestinal Syndrome • Prodromal Stage: Vomiting and diarrhea occur within hours and last up to one day • Latent Period: Lasts 3-5 days • Manifest Illness: Nausea, vomiting and diarrhea – Worsens to bloody stools • Death within 4 to 10 days after exposure primarily due to intestinal cell damage – Also damage to blood-forming tissue results in hemorrhaging and dehydration.
Central Nervous System Syndrome • Prodromal Stage: Severe nausea and vomiting within a few minutes – Nervousness, confusion, burning skin, vision loss, possible loss of consciousness • Latent Period: May last up to 12 hours, or not at all • Manifest Illness: Disorientation, loss of muscle control, breathing problems, seizures, coma • Death within a few days of exposure – due to increased fluid in brain (pressure) – Death occurs before hematologic and gastrointestinal symptoms appear
3 Acute Radiation Syndromes • Hematologic : results in infection, hemorrhage & anemia • Gastrointestinal : results in diarrhea, nausea & vomiting, fever • Central Nervous System : results in convulsions, coma, & eventual death from increased intracranial pressure. CNS least sensitive in ADULTS – MOST sensitive in the FETUS
For Chernobyl: • 11,000 mrem- current background in red zones • 12 mrem is your average background radiation. • This is a thousand times greater than the normal background level of radiation • Approximately 15-20% of babies are born healthy.
Late Effects • Late Effects • Local Tissue Effect • Erythema • Cataracts • Life Span Shortening • Cancers/Malignancies • Genetic Effects
Late Effects of Radiation • Somatic Effects: develop in the individual who is exposed • Most common: • Skin Damage, Cataract formation & Carcinogenesis • Genetic Effects: develop in future generations as a result of damage to germ cells.
Fukushima, Japan Fukushima 50 occupational exposure due to rescue work After reading this article, write your thoughts on the rescue workers in Japan. Include allowable exposures to workers, possible acute affects, their prognosis for long term health.
Radiation Protection • Cardinal Principles of Radiation Protection Time Distance Shielding • ALARA
Cardinal Principles of Radiation Protection Time, Distance and Shielding
Cardinal Principles of Protection • Triad of Radiation Safety 1. Time 2. Distance 3. Shielding *Apply to the patient & Technologist