radiation 1. energy traveling through space or matter, ultimately to be absorbed by another body....

RADIATION

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RADIATION

Energy traveling through space or matter, ultimately to be absorbed by another body.

Marchiori, Dennis (2005). Clinical Imaging. St. Louis, MO: Elsevier Mosby. 2

http://home.howstuffworks.com/light-bulb.htm

RADIATION

•Heat•Light•Sound

Its energy is usually classified by its ability or inability to ionize

matter.Marchiori, Dennis (2005). Clinical Imaging. St. Louis, MO: Elsevier Mosby.

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CLASSIFICATION OF RADIATION

•Non-Ionizing Radiation

•Ionizing Radiation

http://zeus.mirtna.org/new-radiation-symbol-original.png5

NON-IONIZING RADIATION

• Includes the spectrum of ultraviolet (UV), visible light, infrared (IR), microwave (MW), radio frequency (RF), and extremely low frequency (ELF).

• Non-ionizing radiation can pose a considerable health risk to potentially exposed workers if not properly controlled.

http://www.osha.gov/SLTC/radiation_nonionizing/index.html6

IONIZING RADIATION

• Subatomic particles or waves that are energetic enough to detach electrons from atoms or molecules.

• Particle Radiation• Electromagnetic Radiation

*The ability of (photons) to ionize an atom or molecule depends on their wavelength.


Types of Ionizing Radiation

Alpha ParticlesStopped by a sheet of paper

Beta ParticlesStopped by a layer of clothingor less than an inch of a substance (e.g. plastic)

Gamma RaysStopped by inches to feet of concreteor less than an inch of lead

RadiationSource

©Health Physics Society http://hps.org/8

Particle Radiation

• Sub-atomic particles with mass (e.g., alpha and Beta particles, electrons,

protons and neutrons).

http://www.osha.gov/SLTC/radiation/index.html9

ELECTROMAGNETIC RADIATION

• Radio waves, microwaves, visible light, gamma and x rays are all examples of electromagnetic waves.

• Electromagnetic waves are produced by the motion of electrically charged particles. They act like waves and like a stream of particles (called "photons") that have no mass.

• The photons with the highest energy correspond to the shortest wavelengths.


UC Regents http://ds9.ssl.berkeley.edu/LWS_GEMS/2/em.htm

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History of Radiology

• November 11, 1895, Wilhelm Conrad Roentgen

• Roentgen the first Nobel prize in physics in 1901

www.fortbend.k12.tx.us/campuses/documents/Teacher/2008%5Cteacher_20081121_1142_2.ppt

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1st X-ray? Roentgen’s Wife’s Hand

X-ray of a colleagues hand after presenting the“new ray” to the Physics – Medical Association


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• PHOTONS– No weight - No charge

• Penetration in materials– At low energies, a photon can be stopped by

a very thin (almost flexible) layer of lead or several centimeters of tissue

– At higher energies, inches of lead might be necessary to stop a photon and they can pass right through a human

– Photon energy is measured in eV or Kev– Diagnostic X-Rays range from 20-150 Kev

X-RAYS


Units of Measurement

• SI Unit for radiation exposure – Coulombs/kilogram (C/Kg)– 1 Roentgen = 2.58 X 10^-4 C/Kg

• SI unit for absorbed dose– Gray (Gy)– 1 Gy =100 Rad

• SI Unit for activity– Becquerel (Bq) = 1 disintegration/ second– Curie (Ci) = 3.7 X 10^10 disintegrations/

second


MECHANISM OF ACTION

http://www.osha.gov/SLTC/radiationionizing/introtoionizing/slidepresentation/slide05.jpg17

Bremsstrahlung Radiation

Describes the production of x-ray photons by accelerating a stream of electrons to energies of several hundred kilovolts with velocities of several hundred kilometers per hour and colliding them into a heavy metal target material.

The abrupt acceleration of the charged electrons produces Bremsstrahlung photons.

http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/xrayc.html#c218

Bremsstrahlung Photons

• Accelerated charges give off electromagnetic radiation, and when the energy of the bombarding electrons is high enough, that radiation is in the x-ray region of the electromagnetic spectrum.

http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/xrayc.html#c219

Mechanism of Action

• Electrons are released by a hot cathode filament into a vacuum tube.

• The electron beam collides into a high voltage anode made of heavy metal, this rapidly accelerates the electrons, creating X-Rays.

Whaites, Eric; Roderick Cawson (2002). Essentials of Dental Radiography and Radiology. Elsevier Health Sciences. pp. p.15–20.

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http://www.antonine-education.co.uk/Physics_A2/Options/Module_6/Topic_7/topic_7_x.htm

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Mechanism of Action

• When X-rays pass through materials the energy of the beam is reduced or attenuated:– scattering; the X-ray photons are reradiated

as lower energy photons– Photoelectric effect where an electron gets

ejected. Photons of visible light are given off as the atom comes out of the excited state

– Compton scattering where both an electron and a lower energy X-ray photon are emitted

– Pair production where a very high energy photon interacts with the nucleus of an atom.

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Mechanism of Action Cont…

When X-rays are reduced or attenuated, any of the previous methods can do immense damage to biological material:

• Water is ionized to form free radicals• At the molecular level, enzymes, RNA and DNA are

damaged, and metabolic pathways are interfered with. • At the sub-cellular level cell membranes are damaged,

along with the nucleus, chromosomes, and mitochrondria

• Cellular level, cell division is damaged. Cells can die, or be transformed to malignant growth.

• Tissue and organ damage. There can be disruption to the central nervous system, death of bone marrow and the lining to the gastro-intestinal system, leading to sickness and death. Cancers may arise.

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Mechanism of Toxicity

•Radiation impairs biological function by hydrolyzing water in cells producing highly reactive free that damage the cell, this free radicals break chemical bonds ,damage cell walls, organelles, and DNA. Affected cells are either killed or inhibited in division.

Cells with a high turnover rate (e.g.. Bone marrow, epithelial coverings such as skin, gastrointestinal tract, and pulmonary system) are more sensitive to radiation. Lymphocytes are particularly sensitive.

http://books.google.com/books?id=vuec3nTovyUC&pg=PA327&lpg=PA327&dq=Mechanism+of+toxicity+in+ionizing+radiation&source=web&ots=iU9Hvn4XOS&sig=zftmDZCBKuefw4jYobR_KsfX8es&hl=en&sa=X&oi=book_result&resnum=7&ct=result#PPA327,M1

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Mechanism of Toxicity (cont)

• Radiation also causes a poorly understood inflammatory response and micro vascular effects after moderately high doses (e.g. 60rad).

• Radiation effects may be deterministic or stochastic. • Deterministic effects are associated with a threshold

dose and usually occur within an acute time frame (within a year).

• Stochastic effects have no known threshold and may occur after a latency period of years (eg cancer)


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• Toxic Dose– Various terms are used to describe radiation

exposure – rad (radiation absorbed dose) – rem (radiation equivalent, man) are

measureable dose. •Rad is the unit of radiation dose commonly

referred to in exposures, whereas rem is useful in describing dose-equivalent biological damage. For most exposures, these units can be considered interchangeable.


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– Acute Effects. Exposure to more than 75 rad causes nausea and vomiting. Exposure to more than 400 rad is potentially lethal without medical intervention. Vomiting within 1-5 hours of exposure suggests an exposure of at least 600 rad. Brief exposure to 5000 rad or more usually causes death within minutes to hours.

– Carcinogensesis. Radiation protection organizations have not agreed on a threshold dose for stochastic effects such as cancer.

27http://books.google.com/books?

id=vuec3nTovyUC&pg=PA327&lpg=PA327&dq=Mechanism+of+toxicity+in+ionizing+radiation&source=web&ots=iU9Hvn4XOS&sig=zftmDZCBKuefw4jYobR_KsfX8es&hl=en&sa=X&oi=book_result&resnum=7&ct=result#PPA327,M1

Toxicity thresholds

Mechanism of Toxicity (cont)Recommended exposure limits.

Exposure to the general population. The national Council on Radiation Protection (NCRP) recommends a maximum of 0.5 rem per person per year.

Radiation during pregnancy. Established guidelines vary but generally recommend a maximum exposure of no more than 50 mrem per month (NCRP)

http://books.google.com/books?id=vuec3nTovyUC&pg=PA327&lpg=PA327&dq=Mechanism+of+toxicity+in+ionizing+radiation&source=web&ots=iU9Hvn4XOS&sig=zftmDZCBKuefw4jYobR_KsfX8es&hl=en&sa=X&oi=book_result&resnum=7&ct=result#PPA327,M1 28


– A single chest x-ray results in a radiation exposure of about 15 millirem to the patient and about 0.006 mrem to nearby health care personnel (at a distance of 160 cm).

– A head CT scan gives about 1 rad to the head; an abdominal CT scan may give as much as 2-5 rad to the area of concern.

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Exposure guidelines for emergency health care personnel. To save a life, the NCRP-recommended maximum

exposure for a rescuer is 50 rem whole-body exposure.

Recommended exposure limits.


Body Clearance Mechanisms

• There is no body clearance mechanism for radiation.

• The human body deals with the radiation by healing the chromosomal breaks with adhesions . It has been speculated that the healing of chromosome breaks, following exposure of mammalian cells to ionizing radiation, may be mediated by the enzyme telomerase.

• Antioxidants help aid the rest of the body against free radicals.

http://cat.inist.fr/?aModele=afficheN&cpsidt=2158918

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Side Effects

•X-ray Exam–Side effects are limited–Painless, without sensation–Very little reaction for most

•Long term or high dose exposure (General)–Nausea–Vomiting –Trouble Swallowing–Fatigue–Decrease in PLT’s and Lymphocytes

•Decreased Immune Function–DEATH!!! (extremely high dose)

–Health Castle

Side Effects

• Organ Specific– Skin

• Erythema – desquamation (reversible)• Hair loss at

– Mucous Membranes• Fibrin Plaquing• Urinary and Bladder Changes• Visceral Changes (secretory)

– Reproductive Organs• Irreversible damage to gametes• Sterility

– Bone• Suppress osteoblast activity• Decrease number of osteocytes

– NIH.gov

Side Effects

• Creation of ROS (mechanism not fully understood)

• Breast Cancer– Increased dose increases risk– Age at time of dose is the most significant factor– Risk does increase equally among different exposure

groups– Followed same temporal pattern as non-exposed

• Age appears to be a factor in breast cancer– Journal of National Cancer Institute

“Case” Study

• 130 Doctors from South Wales and Oxford• Questionnaire Exam• Low Score = 0% (5) High Score = 59%• Extremely Underestimated the amount of

radiation– 97%!!!!!! By as much as 16 times

(arteriogram/chest xray)• 6 – Radiation in Ultrasound?• 11 – Radiation in MRI?

–BMJ

Conclusion

NATE DOGG’S SOAP BOX TIME, YAY!

Radiation Sickness

http://videos.howstuffworks.com/discovery-health/14590-human-atlas-radiation-sickness-video.htm

REFERENCES1. Marchiori, Dennis (2005). Clinical Imaging. St. Louis, MO: Elsevier Mosby. 2. http://zeus.mirtna.org/new-radiation-symbol-original.png 3. ©Health Physics Society http://hps.org/4. UC Regents http://ds9.ssl.berkeley.edu/LWS_GEMS/2/em.htm5. www.fortbend.k12.tx.us/campuses/documents/Teacher/2008%5Cteacher_20081121_1142_2.ppt6. http://www.osha.gov/SLTC/radiationionizing/introtoionizing/slidepresentation/slide05.jpg 7. http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/xrayc.html#c2 8. Whaites, Eric; Roderick Cawson (2002). Essentials of Dental Radiography and Radiology. Elsevier

Health Sciences. pp. p.15–20. 9. http://www.antonine-education.co.uk/Physics_A2/Options/ Module_6/Topic_7/ topic_7_x.htm 10. http://books.google.com/books?

id=vuec3nTovyUC&pg=PA327&lpg=PA327&dq=Mechanism+of+toxicity+in+ionizing+radiation&source=web&ots=iU9Hvn4OS&sig=zftmDZCBKuefw4jYobR_KsfX8es&hl=en&sa=X&oi=book_result&resnum=7&ct=result#PPA327,M1

11. http://cat.inist.fr/?aModele=afficheN&cpsidt=215891812. Yochum and Rowe, Essentials of Skeletal Radiology, 2nd edition, Williams and Wilkins, 1995.13. "Radiation Side Effects." Health Castle. 2009. 10 Jan 2009

<http://www.healthcastle.com/se_radiation.shtml>.14. "Radiation Therapy and You: Support for People With Cancer." National Cancer Institute. 2009. 08

Jan 2009 <http://www.cancer.gov/cancertopics/radiation-therapy-and-you/page7>.15. "Fact Sheet: What We Know About Radiation." National Institute of Health. 2007. 28 Dec 2008

<http://www.nih.gov/health/chip/od/radiation/#xfive>.16. Dudziak, Matthew E. D.D.S., et.al.. "The Effects of Ionizing Radiation on Osteoblast-Like Cells in

Vitro." Plastic and Reconstructive Surgery 106(2000): 1049-1061.17. Riley, P.A.. "Free Radicals in Biology: Oxidative Stress and the Effects of Ionizing Radiation ."

International Journal of Radiation Biology 65(1994): 27-33.18. Land, C.E.. "Breast cancer risk from low-dose exposures to ionizing radiation: results of parallel

analysis of three exposed populations of women." Journal of the National Cancer Institute 65(2001): 353-376.

19. Radiation Therapy. (2009, January 10). In Wikipedia the Free Encyclopedia. Retrieved 18:38, January 10, 2009, from http://en.wikipedia.org/w/index/php?title=Radiationtherapy&oldid=267745411

20. S Shiralkar, A Rennie, M Snow, R B Galland, M H Lewis, and K Gower-Thomas Doctors' knowledge of radiation exposure: questionnaire study BMJ, Aug 2003; 327: 371 - 372.

21. http://home.howstuffworks.com/light-bulb.htm22. http://videos.howstuffworks.com/discovery-health/14590-human-atlas-radiation-sickness-video.htm

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radiation 1. energy traveling through space or matter, ultimately to be absorbed by another body....

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