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Radiation BiologyRadiation BiologyCellular LevelCellular Level
Cell SensitivityCell Sensitivity
Radiolysis of WaterRadiolysis of Water
Direct Effect/Indirect EffectDirect Effect/Indirect Effect
Target TheoryTarget Theory
Radiation EffectRadiation Effect
Early EffectsEarly Effects
Prodromal/Latent period/Manifest IllnessProdromal/Latent period/Manifest Illness
Hematopoietic SyndromeHematopoietic Syndrome
GI SyndromeGI Syndrome
CNS SyndromeCNS Syndrome
Local tissue damageLocal tissue damage
Late EffectsLate Effects
Local Tissue EffectLocal Tissue Effect
Life Span shorteningLife Span shortening
Radiation ProtectionRadiation Protection
Time Distance ShieldingTime Distance Shielding
Shield TypesShield Types
ALARAALARA
Radiation BiologyRadiation Biology
Largest Largest sources of sources of man-made man-made radiation radiation are are medical medical and dental and dental x-raysx-rays.
THE EARLY YEARS
Radiation BiologyRadiation Biology
Cellular LevelCellular Level
{{Cellular LevelsCellular Levels
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
Cell SensitivityCell Sensitivity
Cell Sensitivity
Linear Response to radiation:
1. Non-threshold
• Assumes no dose is safe
2. Threshold assumes
• Minimum dose needed to produce a response
A dose response relationship is produced by extrapolating high dose experimental data to low doses.
Table 2-3: Groups Studied for Radiation Effects
Scott Sorenson, 2000.
Groups Studied for Health Effects American Radiologists Nuclear weapon survivors Radiation-accident victims Radiation-accident victims Marshall Islanders (Atomic bomb fallout) Residents with high levels of environmental radiation Uranium miners Radium watch-dial painters Radioiodine patients Ankylosing spondylitis patients (radiation therapy) Thorotrast patients (radioactive contrast material) Diagnostic irradiation in-utero Cyclotron workers
Cell SensitivityCell Sensitivity
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.
Basic Cell StructureBasic Cell Structure1.1. Two parts:Two parts:
1.1. Nucleus- contains Nucleus- contains DNADNA
2.2. Cytoplasm is 80% Cytoplasm is 80% waterwater
2.2. DNA is at risk DNA is at risk when a cell is when a cell is exposed to exposed to ionizing radiationionizing radiation
Cell StructureCell Structure
Ionization radiation interacts with a water (H2O). Water dissociates into2 ions. This process creates free radicals. These are uncharged moleculescontaining as single unpaired electron in outer shell.
Radiolysis of Water
1.1. H 2 O molecules -H 2 O molecules -2.2. Ejection of electron Ejection of electron
= free radical = free radical 3.3. H2 0 2 = hydrogen H2 0 2 = hydrogen
peroxideperoxide
HOHHOH++ recombine to recombine to HH22OO
Let’s Play Jenga !!Let’s Play Jenga !!
Target theory suggests that a key molecule must beinactivated. The key molecule is assumed to be DNA.
• When interaction occurs between radiation and target molecule, it isWhen interaction occurs between radiation and target molecule, it is considered a “hit”considered a “hit”
• An indirect hit has a larger target area because of the mobility An indirect hit has a larger target area because of the mobility of the free radicalsof the free radicals
• Radiation acts randomly. Radiation acts randomly.
B3…..miss……..A4…..hit…….You sunk my Battleship!!!B3…..miss……..A4…..hit…….You sunk my Battleship!!!
ACUTE RADIATION ACUTE RADIATION SYNDROMESYNDROME
◊ Three different levels of exposure effects:
◊ Hematologic syndrome◊ GI syndrome◊ CNS syndrome
Acute Radiation Syndrome – full body exposure given in a few minutes.
Early EffectsEarly Effects
Each syndrome has 3 main sub-stagesEach syndrome has 3 main sub-stages
prodromal stageprodromal stage
latent stagelatent stage
manifest illnessmanifest illness
cell death/repaircell death/repair
Total Body Response Total Body Response to Radiationto Radiation
Acute Radiation SyndromesAcute Radiation Syndromes – – full full body exposure given in a few body exposure given in a few minutes.minutes.
3 stages of response:3 stages of response:1. 1. ProdromalProdromal -NVD stage -NVD stage
(nausea, vomiting, (nausea, vomiting, diarrhea)diarrhea)
2. 2. Latent PeriodLatent Period-Feels well -Feels well while undergoing biological changeswhile undergoing biological changes
3. 3. Manifest IllnessManifest Illness-Full effects -Full effects felt, felt, leads to leads to recovery or deathrecovery or death
3 Radiation Syndromes
1.1. HematologicHematologic : results in infection, : results in infection, hemorrhage & anemiahemorrhage & anemia
2.2. GastrointestinalGastrointestinal : results in diarrhea, : results in diarrhea, nausea & vomiting, fevernausea & vomiting, fever
3.3. Central Nervous System Central Nervous System : results in : results in convulsions, coma, & eventual death from convulsions, coma, & eventual death from increased intracranial pressure.increased intracranial pressure. CNS least sensitive in ADULTS –CNS least sensitive in ADULTS – MOST sensitive in the FETUSMOST sensitive in the FETUS
Cherynobyl Fall outCherynobyl Fall out
Exposure in soil & Exposure in soil & waterwater
For Chernobyl:For Chernobyl:
o 11,000 mrem- current background in red zones 11,000 mrem- current background in red zones o 12 mrem is your average background radiation.12 mrem is your average background radiation.o This is a thousand times greater than the This is a thousand times greater than the
normal background level of radiation normal background level of radiation o Approximately 15-20% of babies are born Approximately 15-20% of babies are born
healthy. healthy.
Late Effects
◊Late Effects◊Local Tissue Effect
◊Erythema◊Cataracts
◊Life Span Shortening◊Cancers/Malignancies◊Genetic Effects
Late Effects of Late Effects of RadiationRadiation
1. Somatic Effects: develop in the individual who is exposed
Most common: Skin Damage, Cataract
formation & Carcinogenesis
2. Genetic Effects: develop in future generations as a result of damage to germ cells.
Fukushima, JapanFukushima, 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 prognosisfor long term health.
Cardinal Principles of Radiation Cardinal Principles of Radiation ProtectionProtection
TimeTime
DistanceDistance
ShieldingShielding
ALARAALARA
Radiation ProtectionRadiation Protection
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Cardinal Principles Cardinal Principles of Radiation of Radiation ProtectionProtection
Time Distance and ShieldingTime Distance and Shielding
Cardinal Principles of Protection
Triad of Radiation SafetyTriad of Radiation Safety
1. 1. TimeTime
2. 2. DistanceDistance
3. 3. ShieldingShielding
*Apply to the patient & Technologist*Apply to the patient & Technologist
Over Over Radiation to Radiation to
SkinSkinToo much Too much
time under time under beambeam
Skin burns from 30 min of beam on time
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
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ShieldingShielding
A lead protective shield is placed A lead protective shield is placed
Between the x-ray tube and the Between the x-ray tube and the individuals exposedindividuals exposed
Absorbs unnecessary radiationAbsorbs unnecessary radiation
TYPES OF SHIELDINGTYPES OF SHIELDING
1.1. ContactContact
2.2. ShapedShaped
3.3. ShadowShadow
Breast ShieldBreast ShieldShadow shieldsShadow shields
SHIELDINGSHIELDING1. TECHNOLOGIST . 25 mm LEAD1. TECHNOLOGIST . 25 mm LEAD Lead apronLead apron GlovesGloves Thyroid shieldThyroid shield GlassesGlasses
2. PATIENT 2. PATIENT – – . 5 mm LEAD. 5 mm LEAD Gondal ShieldingGondal Shielding
As Low As Reasonably AchievableAs Low As Reasonably Achievable
Primary Barriers Primary Barriers
Stay out of primary beamStay out of primary beam
Image Wisely Image Wisely
Image Wisely website
PROTECTING THE PROTECTING THE PATIENTPATIENT
RISKRISK
VS. VS.
REWARDREWARD