Units of Radiation Measurement (Traditional Units)
Units of Radiation Measurement (International System) SI
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
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
2) Any Amount of Radiation could cause and effect
3) No threshold for damage
Example of Stochastic effect
2) Genetic defects
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
Is the susceptibility of cells, tissues, organ systems, organisms, or any living substance to the injurious action of radiation
affect the individual only
effects future generations
These Factors determine the quantity of scatter radiation.
*) OID (object to image distance)
*) Body part thickness
Major Types of Scatter
1) Coherent Scatter
2) Photoelectric Scatter
3) Compton 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
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
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.
Lymphocyte is the MOST sensitive cell in the human body.
(note: Immature, non specialized cells are most radio sensitive)
Nerve Tissue is the MOST radioresistent matter in the body
(note: Mature, specialized cells are most radioresistent)
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)
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.
NCRP / SCRP LAW TITLE 17
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
Shielding patients gonadal area
gonadal area should always be shielded except for when they are in the area of clinical interest.
laid directly on patient
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
Thickness of Glove shields
Thickness of Apron Shielding
#1 reason for repeated radiography
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