Module 4 Flashcards
Describe the possible cell injury from x-rays
Radiation Carcinogenesis
Ionization
Free radical formation
Define ionization
Process by which an electrically stable/neutral atom or molecule gains or loses electrons and acquires a positive/negative charge; unstable
What effect does ionization have on possible cell injury?
When x-rays pass through living tissues, ionization of certain chemicals, especially water in the cells, can result in biological effects
Define free radical formation
An uncharged (neutral) atom or molecule that exists with a single electron in its outer shell that is highly unstable and reactive
What effect does free radical formation have on possible cell injury?
Free radicals can recombine without causing changes
Free radicals can combine with other free radicals
Free radicals can combine with other molecules to form toxins
What are the two theories of radiation injury?
Direct theory and indirect theory
Define direct theory
Cell damage occurs when ionizing radiation directly hits critical areas within the cell like the DNA
Define indirect theory
X-ray photons are absorbed within the cell and the formation free radicals produce toxins which damage the cell
Define dose-response curve
It’s the correlation of the amount/dose of radiation received with the response of the tissue
What are the 3 types of dose-response curve?
Linear curve, non-threshold linear curve, and threshold curve
Explain the linear curve
Response of the tissue is proportional to the dose
Explain the non-threshold linear curve
No matter how small the dose, some damage occurs
Explain the threshold curve
Below a certain dose/level, no response is seen
What factors influence or determine radiation injury?
Total dose Dose rate Amount of tissue irradiated Cell sensitivity Age
Define total dose
Quantity of radiation received or absorbed; more damage occurs with larger tissue absorption
Define dose rate
Rate at which exposure to radiation occurs and absorption takes place. More radiation damage takes place with high dose rate because there is rapid delivery without time for cell repair
Describe amount of tissue irradiated
Total body exposure is of greater concern than localized areas of the body
Define cell sensitivity
More damage occurs in rapidly dividing cells and younger cells
Describe how age influences radiation injury
Children are more susceptible to radiation damage than adults
Describe the short-term effects of radiation exposure
Effects associated with large amounts of radiation seen within minutes, days, weeks
Describe the long-term effects of radiation exposure
Associated with small amounts of radiation absorbed repeatedly over time seen within years or exposure
Describe the genetic effects of radiation exposure
Effects not seen in the person irradiated, but in future generations
Describe the somatic effects of radiation exposure
Seen in the person irradiated; examples = burns, cancer, or leukemia
Describe the effects of radiation on cells, tissues, and organs
The Law of Bergoine and Tribondeau
What is the Law of Bergoine and Tribondeau?
States that the radiosensitivity of cells is directly proportional to their reproductive activity (mature cells are least affected), inversely proportional to their degree of differentiation (younger tissue/cells are more radiosensitive), and directly proportional to their metabolic activity (radiosensitivity increases with metabolic activity)
What are the critical tissues and organs that are exposed to radiation in the head/neck area?
Skin
Thyroid
Lens of the eye
Bone marrow
List the cells in descending order of sensitivity that are effected by radiation
WBC RBC Immature reproductive cells Epithelial cells Endothelial cells Connective tissue cells Bone cells Nerve cells Brain cells Muscle cells
What are the units used in the traditional system?
Roentgen (R)
Radiation absorbed dose (RAD)
Roentgen equivalent in man (REM)
What are the units used in the SI system?
Coulombs/kilogram (C/kg)
Gray (Gy)
Sievert (Sv)
Name some common sources of radiation exposure?
Background
Medical/Dental
Give an example of background radiation
Always present in the environment, cosmic (from stars), and terrestrial (from earth/air)
Give an example of human made radiation
luminous wristwatches, TV’s, and fallout from atomic weapons
Give an example of medical/dental radiation
x-rays; accounts for most radiation exposure
How can we discuss the risks of radiation with our patients?
Compare the radiation to other risks
Find something the patient can relate to
Let them know the risk is less than many other everyday activities
We need to educate the patient so they understand the importance vs the risk
What do we do to reduce radiation?
Film speed (F speed) Digital x-rays (reduce by 50%) Collimation (rectangular) Technique (long PID) Exposure (use higher kVp)
