Radiation Biology 1 Acute Radiation Syndrome Early and

Radiation Biology 1 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 2 Prodromal stage Latent stage Manifest illness Erthema

Radiation Biology History 1895 -Roentgen announces discovery of X-rays 1896 -(4 months later) Reports of skin effects in x-ray researchers 1902 -First cases of radiation induced skin cancer reported 1906 -Pattern for differential radiosensitivity of tissues was discovered. 3

Largest sources of man-made radiation are medical and dental x-rays. 4

THE EARLY YEARS 5

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Radiation Accidents 7

Slotin Accident Look for the footprints toward the end of the video 8

How Does Radiation Damage Occur?

Radiation cause biological changes Technologists should have an understanding of: • Cellular biology • How radiation interacts with cells in order to protect oneself and the patient. 10 Radiation Biology

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

Cellular Level 12

Possible Effects to Cells 1. Radiation may pass through cell without doing any damage. 2. Damage may occur but be repaired. 3. The damaged cell may reproduce in its damaged form. 4. The cell may die.

Cellular Levels No damage Injury/damage Cells incorrectly repair Cells die 14 • Radiation passes thru individual without any damage to cells • Radiation causes injury to cell but cell is able to repair damage • Cells repair but incorrectly causing deformity • Radiation causes cell to die

Undamaged Cell

Damaged Cell

Cell Sensitivity Law of Bergonie and Tribonde au 17 • 1. Stem cells are radiosensitive. • 2. The younger the tissues and organs, the more radiosensitive • 3. When level of metabolic activity is high, radiosensitivity is high • 4. As proliferation rate for cells and growth rate for tissues increases, the radiosensitivity increases.

Cell Sensitivity Early Effect: (ACUTE) q radiation response occurs within minutes/days after exposure acute radiation syndrome-3 types, depending on exposure local tissue damage q Late Effect: (CHRONIC) q 18 radiation response not observable for months or years leukemia cataracts other cancers local tissue damage Life span shortening genetic damage

Linear Response to radiation: A. Non-threshold: Assumes no dose is safe B. Threshold: Assumes minimum dose needed to produce a response A dose response relationship is produced by extrapolating high dose experimental data to low doses. 19

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. 20 Cell Sensitivity

Basic Cell Structure 1. Two parts: Nucleus- contains DNA 2. Cytoplasm is 80% water 1. 21 DNA is at risk when a cell is exposed to ionizing radiation

Two Basic Cell types Genetic: Reproductive Cells Cell Structure 22 Somatic: All other cells, nonreproductive cells

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.

HOH+ recombine to H 2 O 24

25 Direct Effect Indirect Effect • Photon ionizes “master molecule” • Master molecule is destroyed, cell dies, damaged • Photon ionized non-critical molecule • Transfer energy to master molecule • Most frequently water molecules

26 Let’s Play Jenga !!

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. 27

28 B 3…. . miss……. . A 4…. . hit……. You sunk my Battleship!!!

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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)

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ACUTE RADIATION SYNDROME Acute Radiation Syndrome – full body exposure given in a few minutes. 33

Look around, be a Rad Geek Military Nuclear Accidents Proliferation of Fluoroscopy Exams and Radiation Safety 34

Early Effects-ARS Each syndrome has 3 main sub-stages prodromal stage latent stage manifest illness cell death/repair 35

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 36

ACUTE RADIATION SYNDROME § Hematologic syndrome § Prodromal § Latent § manifest § GI syndrome § Prodromal § Latent § manifest § CNS syndrome § Prodromal § Latent § manifest 37

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

1. Hematologic : results in infection, hemorrhage & anemia 2. Gastrointestinal : results in diarrhea, nausea & vomiting, fever 3. Central Nervous System : results in convulsions, coma, & eventual death from increased intracranial pressure. CNS least sensitive in ADULTS – MOST sensitive in the FETUS 3 Acute Radiation Syndromes 41

42 Cherynobyl Fall out

For Chernobyl: o o 43 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 v Local Tissue Effect v Erythema v Cataracts v Life Span Shortening v Cancers/Malignancies v Genetic Effects 44

Late Effects of Radiation 1. 2. 45 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 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. Fukushima, Japan 46

Radiation Protection Cardinal Principles of Radiation Protection Time Distance Shielding ALARA 47

Cardinal Principles of Radiation Protection Time, Distance and Shielding 48

Cardinal Principles of Protection Triad of Radiation Safety 1. Time 2. Distance 3. Shielding *Apply to the patient & Technologist 49

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Skin burns from 30 min of beam on time 51 Over Radiation to Skin Too much time under beam

. 7 of an hour is approximately 42 miutes 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 52