Units of Radiation Measurement (International System) SI
Indirect Hit Theory
the theory of the radiation hitting the cytoplasm of the cell and dispersing its energy to the DNA molecule.
2) Any Amount of Radiation could cause and effect
3) No threshold for damage
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
Is the susceptibility of cells, tissues, organ systems, organisms, or any living substance to the injurious action of radiation
These Factors determine the quantity of scatter radiation.
*) OID (object to image distance)
*) Body part thickness
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)
Linear Energy Transfer (LET)
Unit of measurement for energy transferred to the tissue based on the type of radiation (quantity of absorbed dose)
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.
Shielding patients gonadal area
gonadal area should always be shielded except for when they are in the area of clinical interest.