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.
Timer (msec)
number of x-rays in beam (quantity)
kVp selector
Voltage across the x-ray tube, determines the penetrating power of the generated x-ray aka:
energy of beam (quality)
influences the number of x-rays (quantity)
Also determines contrast of an image (ability to see differences between subtle changes in opacity)
Controls x-ray quality and quantity
Lower contrast -> higher kVp
Higher contrast -> lower kVp
What does scatter radiation do to an image?
Decrease the contrast
Factors that increase scatter radiation?
The greater the body area exposed to radiation the greater the amount of scatter
How can you decrease scatter radiation?
Limit the beam to just the area of interest aka collimating the beam
What do Collimators do?
They restrict the x-ray beam to a confined region & improve image quality (better contrast) by reducing scatter radiation
True or False: Collimators do not remove all radiation outside the field or scatter radiation
True
What is a grid?
Devices that are used to prevent scatter radiation from reaching the film. Scatter radiation decreases film quality by reducing image contrast.
They are composed of hundreds of alternating lead strips.
What do cassettes and screens do?
Cassettes hold the film and screens are on the inside of the cassette. The screen produces light after x-ray absorption. The light exposes the film.
What is radiographic film composed of?
Blue tinted base material (polyester) with an silver emulsion on one or both sides
How do detector elements impact resolution?
Smaller detector elements have better resolution than large detector elements
Do conventional film radiographs or digital systems provide superior spatial resolution?
Conventional
Digital Image
Matrix of numbers
LUT
Look up table
How many views are needed for image interpretation?
Two views at 90* angles because it is a 2-dimensional image of a 3-dimensional object
What are the 5 basic radiographic opacities?
Metal - lightest |
Bone |
Soft tissue |
Fat |
Air - darkest V
Order is based off of differential absorption of x-rays
What is the summation effect?
When two objects are superimposed over each other the overlapping portions of the object will appear more opaque
What is the silhouetting effect?
When two objects of the same subject density are in contact, they will appear to blend together radiographically
Magnification
Refers to the enlargement of the image relative to the actual size of the object being imaged
The further the object is from the film the ____ the magnification
Greater
The ____ the TFD the greater the degree of magnification
Shorter
How does distortion affect an image?
It will cause unequal magnification. If the object is not in the center of the beam there will be distortion. If the cassette
What are 2 ways you can cause distortion?
If the object is not in the center of the beam there will be distortion. If the cassette is not perpendicular to the x-ray beam there will be distortion of the image.
What does a R lateral view look like?
The patient is laying on their side with their right side closest to the film. Their legs should be facing away from you.
What does a L lateral view look like?
The patient is laying on their side with their left side closest to the film. Their legs should be facing towards you.
DPA
Dorsal palmar. The beam is going from the front to the back of a forelimb. No difference in radiographic appearance if we did a palmar-dorsal view.
DPL
Dorsal plantar
DMPLO
Dorsal Medial Palmar Lateral Oblique
Entered dorsal medial and exited on palmar lateral.
DLPMO
Dorsal Lateral Palmar Medial Oblique
Entered on the dorsal lateral side and exit palmar medial side. Flip it for the correct orientation.
Lateral-Medial View (lateral view)
Coming from the lateral (far side) and going through the medial (near side). Have to flip for the correct orientation
How do you name a radiographic projection?
Step 1: Right or left
Step 2: Medial, lateral, dorsal, palmar, plantar, cranial, caudal, proximal, distal or combination
Step 3: If oblique view, use oblique with angle
What does the name of the view tell you?
Indicates the direction of travel of the x-ray beam
What terms do you use when you are above the humerus or femur?
Cranial and caudal
What terms do you use when you are below the humerus/femur and are at the carpals/tarsals?
Dorsal & Palmar in front limbs, dorsal and plantar in the hind limbs
What does inners and outers mean?
Inners in DMPLO: MP
So medial structures are projected palmar
Outers in DMPLO: DL
So lateral structures are projected dorsally
Inners in DLPMO: LP
Lateral structures are projected palmar
Outers: Medial structures are projected dorsal
What are the 3 different types of skyline views for carpus?
Distal row, proximal row, distal radius
What percentage of horses have the 1st carpal bone?
33%
What percentage of horses have the 5th carpal bone?
10%
How can you tell between a radial and intermediate carpal bone in a lateral view?
The intermediate carpal bone has a concave dorsal surface and the radial carpal bone has a convex dorsal surface
What is a flexed lateral view?
Foot is elevated, carpus held in flexion, beam centered at middle carpal joint.
What is the skyline view for tarsus?
Calcaneus
When is the best time to take a radiograph?
During inspiration
