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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

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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

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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