Radiation Biology. Cellular Level Cell Sensitivity Radiolysis of Water Direct Effect/Indirect Effect Target Theory Radiation Effect Early Effects Prodromal/Latent period/Manifest Illness Hematologic Syndrome GI Syndrome CNS Syndrome Local tissue damage Late Effects
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Radiation Biology Cellular Level Cell Sensitivity Radiolysis of Water Direct Effect/Indirect Effect Target Theory Radiation Effect Early Effects Prodromal/Latent period/Manifest Illness Hematologic Syndrome GI Syndrome CNS Syndrome Local tissue damage Late Effects Local Tissue Effect Life Span shortening Radiation Protection Time Distance Shielding Shield Types ALARA
Cell Sensitivity • Early Effect: • radiation response occurs within minutes/days after exposure • acute radiation syndrome • local tissue damage • Late Effect: • 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.
Diagnostic radiology is almost exclusively concerned with the late of effects for radiation exposure. This assumes a linear non-threshold dose-response relationship. However, no dose is considered safe. Cell Sensitivity
Basic Cell Structure • Two parts: • Nucleus- contains DNA • Cytoplasm is 80% water • DNA is at risk when a cell is exposed to ionizing radiation
Two Basic Cell types Cell Structure
Radiolysis of Water Ionization radiation interacts with a water (H2O). Water dissociates into 2 ions. This process creates free radicals. These are uncharged molecules containing as single unpaired electron in outer shell.
H 2 O molecules - • Ejection of electron = free radical • H2 0 2 = hydrogen peroxide Radiolysis of Water
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!!!
Early Effect • Prodromal/Latent/Manifest Illness • Hematologic syndrome • GI syndrome • CNS syndrome • Late Effects • Local Tissue Effect • Erythema • Cataracts • Life Span Shortening • Cancers/Malignancies • Genetic Effects Radiation Effects
Early Effect • Prodromal/Latent/Manifest Illness • Hematologic syndrome • GI syndrome • CNS syndrome • Local Tissue Damage
Each stage has 3 main sub-stages prodromal stage latent stage manifest illness cell death/repair Early Effects
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 Total Body Response to Radiation
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 3 Radiation Syndromes
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. Exposure in soil & water
Late Effects • Local Tissue Effect • Erythema • Cataracts • Life Span Shortening • Cancers/Malignancies • Genetic Effects Late Effects
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. Late Effects of Radiation
Cardinal Principles of Radiation Protection Time Distance Shielding • ALARA Radiation Protection
Cardinal Principles of Radiation Protection Time Distance and Shielding
Triad of Radiation Safety 1. Time 2. Distance 3. Shielding *Apply to the patient & Technologist Cardinal Principles of Protection
Time Skin burns from 30 min of beam on time Over Radiation to SkinToo much time under beam
Acute Localized Radiation Effects The Table 2-2 provides examples of possible radiation effects to skin caused by typical fluoroscopy exposures. Note that patient and technique factors can substantially increase exposure rates, significantly reducing the time necessary for the subsequent effect. Table 2-2: Dose and Time to Initiate Localized Radiation Effects .7 of an hour is approximately 42 miutes
This is an actual arm tatoo. Now that’s dedication ! Inverse square law Inverse square law Inverse square law
Shielding A lead protective shield is placed • Between the x-ray tube and the individuals exposed • Absorbs unnecessary radiation
Contact • Shaped • Shadow TYPES OF SHIELDING
Shadow Shields Breast ShieldShadow shields
1. TECHNOLOGIST . 25 mm LEAD • Lead apron • Gloves • Thyroid shield • Glasses 2. PATIENT – . 5 mm LEAD • Gondal Shielding SHIELDING
ALARA As Low As Reasonably Acheivable