Intro to Radiology Flashcards
What are X-rays?
Form of electromagnetic radiation
What does wavelength equal to?
Speed of light/Frequency
The shadow (silhouette or outline of an object) is?
2-dimensional image created from the shadow of the object
What can X-rays do to tissues? Can it be felt?
X-rays can penetrate matter and causes biological damage to tissue (can ionize atoms). It cannot be felt or seen.
What happens to film the more exposure it gets?
Gets darker
What is the main molecular effect of ionizing radiation?
To produce ions that further result in changes in molecular composition
What is the main target of ionizing radiation?
DNA (critical target)
DNA damage may be repaired or may produce cellular mutation and death
What is the indirect effect of biological changes induced by radiation?
Production of free radicals that can diffuse far enough to reach and damage the critical target (DNA, RNA, proteins)
What is radiosensitivity?
The relative susceptibility of cells, tissues, organs, or organisms to the harmful effect of ionizing radiation
Which cells are more radiosensitive?
Stem cells are more radiosensitive than mature cells
Which tissue is more radiosensitive?
Young tissue is more radiosensitive than old tissue
Which tissue metabolism is more radiosensitive?
Tissue with high metabolic activity is more radiosensitive than tissue with low metabolic activity. Ex. Gonads > sensitivity than skin
Does proliferating tissue with high growth rates more or less radiosensitive?
More radiosensitive
What are the general types of chronic low-level radiation injury?
Genetic effects (radiation-induced mutation), carcinogenesis, effects on growth & development (fetus or child), reduced life span, cataract
What does ALARA stand for and what are the 3 basic principles of ALARA?
As Low As Reasonably Achievable
3 basic principles: Distance, time, shielding
What does the Time principle of radiation safety mean?
Minimize the time of exposure to radiation
Minimize holding patients by using sedation, positioning devices, and develop good technique chart to minimize retakes
What does the distance principle of radiation safety mean?
Maximize your distance from the radiation source. Double the distance from the source will reduce exposure by 1/4 (I = 1/d^2)
How to reduce the distance from radiation sources?
Do not manually hold portable X-ray machines, cassettes, or cassette holders. Stand away from the x-ray tube. Law required to document when person holds animal or cassette during exposure.
What does the shielding principle of radiation safety mean?
PPE: lead aprons, gloves, and thyroid shields should be worn whenever you will be in the radiation field.
What does lead PPE protect you from?
Only protects from scatter radiation
When should/should not wear your radiation badge?
Badge must be worn outside permanent apron or thyroid shield. It should not be worn if undergoing diagnostic procedures.
What is MPD?
Maximum permissible dose
What is MAD?
Lifetime max accumulative dose
MAD = age in yrs X 1 rem (1000 mrem)
What is the MPD per year?
5,000 mrem/yr
What are the steps to produce an X-ray?
1st step (Prep)
Electrons are generated by electrical current through the filament in the cathode
2nd step (Expose)
X-rays produced when electrons interact with metal in the anode (Tungsten)
mA selector
Number of x-rays in beam (quantity)
controls the current to the filament, the more current applied to this circuit, the hotter the filament becomes, the hotter the filament, the more x-rays will be produced
Focal Spot Selector
Trade-off between resolution and quantity of radiation. Most x-ray tubes have two filaments in the cathode: one is a small filament used for low-output exposures where high detail is needed and one is a large filament used for high output exposures.