Roentgen (x-ray tube)
Wilhelm Roentgen in 1895
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discovered while experimenting with a cathode xray tube
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Ionization is the production of ions
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basic unit of measuring ionizing radiation exposure.
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unit of energy patient exposed to
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RADIATION DOSE AND SAFETY
In the modalities of conventional radiography, CT, and fluoroscopy images are produced using ionizing
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radiation.
Three Fates of Radiation During an Imaging Procedure
1). Transmitted radiation; is the radiation that passes through the patient and interacts with the
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detector to create the image.
2). Absorbed radiation; is the radiation that interacts with the tissues of the patient, depositing its
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energy in those tissue; it is the source of the patient radiation exposure.
3) Scatter radiation; is not transmitted or absorbed by the patient.
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MEASUREMENTS OF RADIATION
The absorbed radiation is measured by the absorbed dose.
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1 mSv is the dose produced by exposure to 1 milligray (mG) of radiation. (1 Sv = 1000 mSv) (1 Gy = 1000
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mGy)
BIOLOGICAL EFFECTS OF RADIATION
Direct - ionizing radiation interacts with DNA, creating immediate damage.
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The cell could either: die, repair itself, or be altered creating a mutation.
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TYPES OF BIOLOGICAL EFFECTS
1) Deterministic effects (nonrandom): This is damage that occurs when a threshold level is met.
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Examples of these effects are: erythema (skin reddening), cataracts to lens of the eye, sterility (temporary/
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permanent), & epilation (loss of hair)
2) Stochastic effects (random): Damage that may occur at any level of exposure, without a
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threshold dose.
Stochastic effects are “invisible damage”
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examples; Hereditary effects and cancer
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PRACTICES FOR RADIATION SAFETY
1) Managing time of exposure:
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2) Increasing the distance from the source:
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3) Using appropriate shielding materials:
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DOSIMETER
Dosimeters are devices used to measure the amount of energy deposited by ionising radiation.
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ACUTE RADIATION SYNDROME
The sequence of events that lead to death within days or week following high levels of radiation exposure.
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Four periods
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1) Prodromal period; The immediate response to radiation that includes signs and symptoms of radiation
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sickness.(minutes up to several days)
2) Latent period; The time after exposure during which there is no sign of radiation sickness and is a time
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of apparent well being that may be mistakenly seen as early recovery.(few hours/few weeks. )
3) Manifest illness; The actual manifestation of illness caused by the radiation exposure.(last from hours up
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to several months. )
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4) recovery Or death (several weeks up to two years.)
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The three classic ARS Syndromes are:
1) Bone marrow syndrome; syndrome will usually occur with a dose between 0.7 and 10 Gy (70 – 1000
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rads
2) Gastrointestinal (GI) syndrome; Lethal syndrome that is caused by doses from 10 to 50 Gyt or 1000
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to 5000 Rad and occurs within a few days
3) Cardiovascular (CV)/ Central Nervous System (CNS) syndrome: Lethal syndrome that is
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caused by doses above 50 Gyt or 5000 Rad and occurs within hours
RADIATION CARCINOGENESIS
is a major concern associated with radiation exposure.
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radiation- induced cancers at doses of 500 mSv (millisievert). (1 mSv = 0.001 Sv).
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