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STUDY GUIDE (limited scope of practice)

Units of Radiation Measurement (Traditional Units)

1) Roentgen
2) RAD
3) REM
4) Curie

Units of Radiation Measurement (International System) SI

1) Coulomb/Kilogram
2) Gray
3) Sievert
4) Becquerel


The Measurement of the ionization of air by X-ray or gamma rays


Radiation Absorbed Dose


Radiation Equivalent Man. Measurement of absorbed radiation that deals with biologic damage


Maximum Permissible Dose. which was replaced and is now called "Effective Dose Equivalent" EDE


SI Unit of in-air exposure
* Traditional Unit name would be Roentgen


SI Unit of Absorbed Dose
* Traditional Unit name would be RAD


SI Unit of equivalent dose and affective dose
* Traditional Unit name would be REM

Primary Beam

Radiation that passes through the collimator. also known as the useful beam.


the imparting of the charge to an atom by removal or addition of an electron.

Two types of interactions

Direct Hit and Indirect Hit

Direct Hit Theory

the theory of radiation hitting the DNA molecule itself.

Indirect Hit Theory

the theory of the radiation hitting the cytoplasm of the cell and dispersing its energy to the DNA molecule.


photons from the primary beam that have changed direction after striking an object


As Low As Reasonably Achievable

Stochastic Effect

1) Random
2) Any Amount of Radiation could cause and effect
3) No threshold for damage

Example of Stochastic effect

1) Cancer
2) Genetic defects

Non-Stochastic Effect

1) Not Random
2) Needs a specific amount of radiation to cause a problem
3) Does have a threshold

Example of Non-Stochastic effect and there threshold

*) Temporary Sterility - 200rems
*) Permanent Sterility - 500rems
*) Erythemia (red skin) - 200rems
*) Epilation (hair falls out) - 1000rems


Level or point of exposure at which a reaction occurs


Any amount of radiation has an effect

Radio sensitivity

Is the susceptibility of cells, tissues, organ systems, organisms, or any living substance to the injurious action of radiation

Somatic Effect

affect the individual only

Genetic Effect

effects future generations

These Factors determine the quantity of scatter radiation.

*) KVP
*) Time
*) OID (object to image distance)
*) Body part thickness

Major Types of Scatter

1) Coherent Scatter
2) Photoelectric Scatter
3) Compton Scatter

Coherent Scatter

this is the classic type of scatter - this is very low energy type of radiation not generally reproducible with machines we deal with low kvp 30 and below

Photoelectric Scatter

an x-ray photon gives up all its energy (total absorption) to an inner shell electron. this causes what is known as characteristic radiation and is responsible for the contrast between bone and soft tissue

Compton Scatter

This is the most common interaction and most dangerous. this accounts for most of the scattered radiation produced during diagnostic procedures

Law of Bergonie and Tribondeau

Deals with the radio sensitivity of cells to radiation.

The Law states that a cells radio sensitivity is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation.

Most Radiosensitive

Lymphocyte is the MOST sensitive cell in the human body.

(note: Immature, non specialized cells are most radio sensitive)

Most Radioresistent

Nerve Tissue is the MOST radioresistent matter in the body

(note: Mature, specialized cells are most radioresistent)

Atomic Number

atomic number of tissue increase - absorbed dose increases (bone will absorb more than soft tissue)

L. E. T.

Linear Energy Transfer

Linear Energy Transfer (LET)

Unit of measurement for energy transferred to the tissue based on the type of radiation (quantity of absorbed dose)

Particulate Radiation

Is classified as High energy LET radiation

Diagnostic "X-ray" Radiation

Is classified as Low energy LET radiation

R. B. E.

Relative Biological Effectiveness

Relative Biological Effectiveness (RBE)

Biologic damage resulting from radiation interaction with tissue increase as the LET of radiation increases (SID, Time, KVP, Collimation affect patient dose)

Acute Radiation Syndrome / Short Term Effect

Great amount of radiation is delivered over a short time. (i.e.. seconds, minutes, hours)

Somatic Effect (Early vs Late)

Early effects - will happen within a set amount of time based on the absorbed dose.

Late effects - can happen later 1 year or more after radiation dosage - based on amount of absorbed dose.


2% field light accuracy (SID)


help remove / absorb the harmful "long wavelengths" in an x-ray beam

Two Types of Filtration

Added and Inherent Filtration

Minimum Total Filtration

2.5mm of aluminum or eq. for a machine over 70kvp

#1 way to reduce patient exposure to radiation.

Collimate to the area of clinical interest

Most common type of collimation used

Variable Rectangular

Shielding patients gonadal area

gonadal area should always be shielded except for when they are in the area of clinical interest.

Contact Shielding

laid directly on patient

Shadow shielding

hangs from tube housing and cast a shadow, good for sterile technique.

When do you use shielding

you must shield everyone of reproductive age (males and females)

Thickness of gonadal shielding

0.5mm lead

Thickness of Glove shields

0.25mm lead

Thickness of Apron Shielding

0.25mm lead

#1 reason for repeated radiography

Bad technique

State of California Title 17

Deals with all laws pertaining to x-ray

Violation of radiation control laws

This is a Misdemeanor Violation

X-rays are to be done when

From Written authority from the doctor and for medical reasons

Occupational Personnel Exposure limit

5rem or 50mSv

Cumulative Exposure limit

1rem x age or 10mSv x age

General Public Exposure limit

0.1rem annually or 1mSv

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