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Effects of Radiatio

Early and Late Effects of Radiation

QuestionAnswer
In the 1920's and 30's, how were RT's checked for radiation exposure? Through blood testing once a week.
What is considered Early Effects of Radiation? Response to radiation occurring within hours or days.
What is the worst possible effect of radiation and today's diagnostic worries? Death is the most severe, but in diagnostic radiation today the most worrisome is skin effects.
Can diagnostic x-rays cause acute effects or death? No, diagnostic beams are not intense enough or large enough to cause death.There is no "whole body" exposure in today's diagnostic x-rays.
How have studies been done on the effects of radiation? From accidents such as Chernobyl 1986, 3-mile Island 1979 and Atomic bombs during WWII. Also convicts have been used in studies.
What is acute radiation syndrome? The sequence of events that follow high-level radiation exposure leading to death within days or weeks.
What are the three syndromes of acute radiation syndrome? Hematologic death, gastrointestinal (GI) death and Central nervous system death (CNS).
In addition to the 3 lethal syndromes, Four periods are associated with acute radiation lethality? The Prodromal Period > 100 rad(Sickness immediately,can last hours or days),Latent Period 100-10000 rad(seem to be better,think you are recovering),then manifest illness(depending on dose), then recovery or death.
What period has acute clinical symptoms that occur within hours of exposure and contiunue for up to a day or two? N/V/D The Prodromal Period. The severity of the symptoms are dose related. Prodromal dose approx. >100 Rad.
Which period does the patient seem free of visible effects and mistakenly thought to be early recovery from a moderate radiation dose. The Latent Period. It is misleading giving no indication of the extensive radiation response yet to come. Latent dose 100-10,000 rad
Hematologic-dose,days prodromal,latent, manifest illness, mean survival time? 200-1000 rad dose, Prodromal period lasts several days,mild symptoms. Latent-as long as 4 weeks, seem fine, Manifest illness-V/D, malaise,lethargy & fever 2-4 weeks.iF If dose not lethal revovery in 2-4 wks up to 6 months. Mean survival time 10-60 days.
GI- dose,days prodromal,latent, manifest illness, mean survival time? 1000-5000rad. Prodromal period-V/D within hours for up to a day, next latent period 3-5 days(no symptoms),manifest illness-N/V/D,anorexia,bloody stools, electrolyte imbalance, death within 4-10 days.intestines
What is the principal cause in the GI syndrome death Severe damage to the cells lining the intestines.
What is the principal cause of hematologic syndrome? A reduction in white cells, red cells and platelets.
CNS-dose,days prodromal,latent, manifest illness, mean survival time? >5000rad.Min.of exp.severeN/V,nervous &confused,skin burning sensation,may lose vision,conciousness in hrs.Latent-symptoms subside,disappear up to 12 hrs. Manifest illness-sypmtoms of prodromal period appear worse and outcome is always death.MST-0-3 days
What is LD 50/60? The Lethal Dose of radiation to the whole body that causes 50% of irradiated subjects to die within 60 days.
Radiation induced death in humans follows a ______, ______ dose-response relationship. non-linear, threshold.
The ultimate cause of death in CNS syndrome is? Elevated fluid content of the brain.
As the whole body radiation dose increases, the average time between exposure and death decreases. What is this called? MST- Mean survival time.
How much of GI lining is replaced daily compared to skin cell replacement daily? 50% of GI lining is replaced daily(high proliferation rate) whereas 2% of skin cells are replaced daily.
True or False - When only part of the body is being irradiated, rather than the whole body a higher dose is required to produce a response. True
Every organ or tissue of the body can be affected by partial-body irradiation. What is the effect and the results? The effect is cell death which results in shrinkage or atrophy of the organ or tissue.
What is the outermost layers of the skin? Epidermis has 5 layers.
Name the 5 layers in order from outermost to inner. 1.Stratum corneum (horny layer)2. stratum lucidum (clear layer)3.stratum granulosum(granular layer)4.stratum spinosum(prickle layer)5.stratum germinativum(germinal layer)
What are the two layers of the innermost skin? Dermis or "true skin" has 2 layers:1.papillary layer(finger prints)2.reticular layer (blood & nerves pass through)
What is layer under the skin? Hypodermis (loose connective tissue)
What is the largest organ in the body? Skin
What are the functions of skin? Used for protection, excretion of water & waste products. Regulates body temp.
What was the first biological response to the skin after radiation exposure? Erythema. a single dose of 300-1000 rad, may result within the 1st or 2nd day after exp.
What is the latent period of skin exposure? After the first wave of erythema, it subsides only to be followed by a 2nd wave that reaches intensity in about 2 weeks.
What is SED/50, and the dose? Skin Erythema dose required to affect 50% of those irradiated is 500 rad.
What is another response of skin radiation besides erythema? Epilation or hair loss.
What are "grenz rays"? Soft rays 10-20kVp were used as treatment for ringworm.
What is the rad level that effects the gonads? As low as 10 rad.
What are thought to be a cause of late effects? Multi-hit aberrations (multi chromosomes hit (worse than a DNA hit)
What is radiodermatitis? IN early radiologists doing fluoro w/o gloves got discolored, callused, weathered hands and forearms.
What are epidemiologic studies? Studies of large # of people exposed to a toxic subtance, when the 3 of persons affected is small. These studies are difficult because of unknown dose & frequency.
What are late effects? The results of low doses given over a long period of time. Like how RT's get it.
What are some late effects on skin? Skin cancer or other non-malignant changes.
What is the dose-response relationship for radiation induced cataracts? Non-linear, threshold. Cataracts occur on the posterior pole of the lens.Latent periods ang. 15 years.Non-linear, threshold response.
At worst, humans exposed to radiation can expect a reduced life span of what? 10 days for every rad.
What are response on chromosomes? Irradiation of blood-forming organs can cause early and late effects by hematologic depression: Early decreased white count;Late effects-leukemia(can take up to 20 years)
What is the threshold dose for cataracts? EStimated 200rad or 1000 rad fractionated dose.
Radiation induced malignancies (leukemia)follow what kind of dose response? Linear, non-threshold dose response. Chances of Leukemia increase as dose increases.
A-bomb survivors had up to 100 times more incidence of leukemia, What was the latent period and the at risk period? Latent period was 4-7 years and at risk period was up to 20 years.
What were the studies on thyroid cancer? Ann Arbor- children that had thymus gland irradiated 20-3 rad (from scatter)got thyroid cancer 20 yrs. later, Rochester -kids thyroid radiated w/ no collimation (300 rad)& kids exposed to fallout during an A-bomb test.
What are the late effects of skin cancer? Starts with radiodermatitis, follows threshold dose response with a 5-10 year latent period. Number of cases is dose-dependent.
During fluoroscopy what are the risks of breast cancer? What about mammography? In fluoro there is a 10 times incident of breast CA of pts. facing toward fluoro, but most pts are on their back so no increase there. Mammo= benefits vs risks.
Minors (up to 50%) died of lung cancer once thought to be from the dust, later found to be what? Radon gas (poor ventilation)Linear-non-threshold.
What was given to patients for testing that was later found to be causing liver cancer? Old contrast called "thorostast" made from 1925-1945.
What is BEIR and NCRP? Committee on Biologic Effects of Ionizing Radiation and National Council on Radiation Protection and Measurements. They studied mortality rate in detail and found that radiology is a safe field.
How does Radiation effect Pregnancy, before, during and after? Before preg.- interrupted fertility, during preg.-possible congenital effects, After preg.-suspected genetic effects.
How much dose affects fertility? Low dose chronic irradiation does not effect fertility.
When is the most radiosensitive time in-utero? 1st 3 months are the most radiosensitive.
Why should patient and tech always wear protective gear during exposure? During the 1st two weeks after fertilization (when pt. may not know they are pregnant)
What are the effects of dose related exposure during the first two weeks? Prenatal deatrh, neonatal death, congenital abnormalities, malignancy induction, general impaired growth, genetic effects, mental ret
Affects during weeks 2-10 in-utero? Bone or neurologic abnormalities may occur resulting in neonatal death. This is rare (1% increase in neonatal death)Leukemia is most common effect.
What do a-bomber survivors' offspring have a higher incidence of? Mental retardation.
Nothing has been proven with doses in medical radiology so we always assume what? Linear, non-threshold doses and ALARA principles.
Maximum Population sample required to show that the given radiation dose significantly elevated the incidence of leukemia. 6,000,000=5rad, 1,600,00=10rad, 750,000=15rad, 500,000=20rad, 100,000=50rad.
Created by: sewwhat4