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Radiation in Medicine

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Rasmi Shrestha

on 17 April 2013

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Transcript of Radiation in Medicine

In Medicine Radiation Dosimetry
definitions Reducing Your Risk
In General...
Use medical procedures involving radiation only when they are essential to diagnose an injury or illness.
For clinically or medically required exposures, the benefit to the patient should outweigh the risk associated with the exposure. (BALANCED RISK!!)
Employers should use innovative techniques, engineering controls, and administrative controls to keep occupational exposures “As Low as Reasonably Achievable” (ALARA). •Exposure: •Absorbed dose: Gamma rays are more harmful
than alpha rays. -a measure of the energy deposited in a medium by ionizing radiation
-unit = gray (1 Gy = 1 Jkg -1) = 100 rad (aka ionizing dose) •Quality Factor: •Dose Equivalent: the amount of electric charge per mass unit, produced in a body due to ionizing radiation Differing effects
on different cells -relates the absorbed dose to the biological effect of that dose
-the product of absorbed dose times the quality factor for the radiation involved Reproductive cells very radiation sensitive
Nerve cells not so sensitive
With increasing exposure:
Topical burns
Nausea, diarrhea, fever (radiation sickness)
Loss of hair
Cancer, leukemia
Death Radiation Effects on Humans measuring the dose of radiation [received by a person] emitted by a radioactive source name and info Radiation Badges a dimensionless factor that takes into account the fact that different radiations have different effects even when they deposit the same energy in a body the formation of or separation into ions by heat, electrical discharge, radiation, or chemical reaction the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or ions Balanced Risks For Example: Balance the Risks with the Benefits We want to eat fat foods, we accept the risks of heart disease. Radiation is another risk which we must balance with the benefit. The benefit is that we can have a source of power, or we can do scientific research, or receive medical treatments. The risks are a small increase in cancer. Risk comparisons show that radiation is a small risk, when compared to risks we take every day. Steps to Reduce Your Risk: ALARA Concepts: The three (3) major principles to assist with maintaining doses ALARA are :
– minimizing the time of exposure directly reduces radiation dose.

–doubling the distance between your body and the radiation source will divide the radiation exposure by a factor of 4.

-using absorber materials such as Plexiglas for beta particles and lead for X-rays and gamma rays is an effective way to reduce radiation exposures. Monitor exposure time carefully
Use only procedures that convey net benefit
Keep exposures as low as reasonably achievable
Do not exceed recommended limits for dose
Lead aprons (reduce stray radiation) Patients Procedures to limit or minimize risk of contamination or exposure
Monitor radiation exposure (film badge), Beta,Gamma -ray, X-ray, and neutron monitoring Practitioner Use lab coat in locations where radioactive material used, handled, or stored
Use disposable gloves
Monitor hands before and after leaving work area
No eating, drinking, or smoking in work area
Clearly label radioactive material Practitioner procedures to minimize risk:
Lead, concrete, water: X-rays and -rays
Neutrons: mass (lead, steel)
Lead aprons (patient) Shielding
(patient and practitioner) http://www.brainpop.com/science/energy/radioactivity/ Brief Review of Half Life Radiological half-life (physical half-life):
Time for half of radioactive isotope to decay
Biological half-life: TB
Time for the body to get rid of half of the radioactive isotope
Effective half-life: TE
Effective half-life of isotope, including both radiological and biological effects Radiation Therapy External Beam Radiation Internal Radiation Therapy Radiation delivered from outside the body

X-rays or Gamma rays (whose energies vary from 200keV to 5 MeV) directed in VERY narrow beams to cancerous cells

The radiation destroys the DNA of cancerous cells, and the uncontrolled cell division stops. Use isotopes which emit -rays, -particles (electrons)
Radioisotope injected in body, and becomes localized in affected organ.

Example- Thyroid cancer: I-131, once in the bloodstream, accumulates in the thyroid gland, and kills cancerous cells there. Where radioactive source implanted in body near locale to receive radiation
Use beta and gamma emitters to localize energy deposition
Radioactive source is local
Reduce illumination of healthy tissue
Place catheters for placement of wire
Example: Ir-192 and breast cancer, mouth cancer Brachytherapy Laws of Bergonie and Tribondeau regarding sensitivity of cells to ionizing radiation

More sensitive when cells are:
High metabolism
Dividing rapidly
These characteristics make cancer cells more susceptible to radiation damage than normal cells Radioactive Half Life Formula There are three types of Half-Life
Radiological Half-life
Biological half-life
Effective half-life Radiological half-life Also Known as Physical Half-life.
It is the period of time for half of radioactive isotope to decay. Biological Half-life Time for the body to get rid of half of the radioactive isotope It is excreted (eliminated) from the living body, by urine, feces, sweat etc. It is not as precise as physical half life.
It is useful to compute effective half life Effective half-life of isotope, includes both radiological and biological effects EFFECTIVE HALF LIFE The physical half-life is unaffected by anything that we humans can do to the isotope High or low pressure or high or low temperature has no effect on the decay rate Time required to reduce the radioactivity level of an internal organ or of the whole body to exactly one half its original value. THE END http://www.cancercompass.com/learn/cancer-information/breast-cancer/treatment/internal-radiation-brachytherapy
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