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Diagnostic Imaging

Quiz Review #1

QuestionAnswer
Define cathode: A negatively charged electrode within the x-ray tube. It comprises a filament and a focusing cup
Define anode: A positively charged electrode within the x-ray tube. It consists of a target ad, in a rotating anode tubes, a stator and rotor
Define Actual Focal Spot The size of the area on the anode target that is exposed to electrons from the tube current
Define Effective Focal Spot The focal spot size as measured directly under the anode target. (Where it hits the patient.)
Define Heel Effect Produced by the uneven intensity of the primary beam, the intensity decreases rapidly toward the anode. Basically how the beam hits the focal spot means that there is a higher concentration of radiation closer to the cathode.
What is the Heel Effect and what causes it? It is the effect where-in the intensity of the x-rays are higher on the cathode side of the beam and is due to the angle of the target used to focus the beam down toward the film.
Define Radiographic density: The amount of overall blackness produced on the image after processing.
Define Radiographic contrast: The degree of difference between adjacent densities.
Define Kilovoltage peak: How fast the electrons are sent across and thus their penetrability. This controls the contrast, Long scale has many shades of grey (abdomen = more kvp) and short scale is black and white with few shades of gray (bone = low kVp)
Define Milliamperage: The amount of electrons sent across and thus the volume of x-rays created. Overall blackness of the film.
Define Focal film distance: The distance between the grid and the anode focal spot. Also known as the grid radius
Define Object film distance: The distance from the image detector to the part of the body being radiographed.
Define Dosimetry: The measurement of ionizing radiation. Lifetime amount is linked to your Social Security Number.
Define Maximum Permissible Dose: This is the maximum amount of radiation a person should be exposed to and it is set by the National Council on Radiation Protection and Measurements (NCRP)
What is the Maximum Permissible Dose? 5 rem/yr
Define Scatter radiation: Radiation that has deviated from it’s original trajectory by hitting an object such as the table.
Define rem: amount of ionizing radiation exposure taking into account different sources & biological effect (they take factors such as age, location, etc give them a “quality factor” of x then take your rads & times them by the quality factor to get the rem)
What does rem stand for? Roentgen equivalent man
Quality factors are often measured in what? mRem (milirems)
1 Sievert equals how many rems? 100
Rems are often given what unit of measure? Sievert (Sv)
Define Roentgen – R: A measure of radiation exposure or x-ray machine output
Define Rad: amount of ionizing radiation
What does ALARA stand for and what does it mean? As Low As Reasonably Achievable which is the workplace principle that basically means we try to keep our exposure as low as possible
X-rays are a form of what type of radiation? electromagnetic
List 3 forms of electromagnetic of radiation not including x-rays. Radio, Microwave, Infrared, Ultraviolet
Define wavelength: The distance between two successive crest or troughs of a wave.
What is the symbol used to denote wavelength? Lambda
Wavelength is measured in what? nanometers nm
X-rays are typically how many nanometers? between 0.1 nm to 1.0 nm
Define quanta: The minimum amount of energy that can be gained or lost by an atom
Describe how x-rays are generated in the x-ray tube. Electricity enters the cathode, transformer boils off e- which move to the filament. The anode’s transformer positively charges it causing the free e- to fly across to the positively charged target where they bounce off & down at the film
Where is the filament located? Inside the focusing cup
Which side of the x-ray tube is negatively charged? cathode
Which side of the x-ray tube is positively charged? anode
Concerning the electron interaction with the target, what present results in heat? 99%
Concerning the electron interaction with the target, what present results in x-ray generation? 1%
Small effective focal spots produce better what? Detail
Small effective focal spots lack the ability to do what? cover larger areas
When would you choose the small focal spot over the large focal spot? You choose the smaller focal point unless you have to see a larger area
State the significance between a rotating anode and a stationary anode: With the stationary anode the e- are hitting the actual focal point in the same place where as with the rotating it has a larger surface area for the focal point which allows for better heat dissipation
What is tube overload? Caused by the mAs and kVp setting being too high. Basically there’s too much e- being sent across to the target or they’re being sent too fast and it causes the tungsten to overheat.
What kind of damage does tube overload cause? Too much heat causes the anode to crack
What is tube saturation? The kVp is set too low and instead of being focused across and transformed into x-rays or heat the free electrons are attracted to the glass.
What kind of damage does tube saturation cause? The glass cracks.
How can you take advantage of the anode heel effect? You can take advantage of this by positioning the denser tissues closer to the cathode end.
The three basic x-ray machine controls that a user might adjust to a radiograph with the proper exposure are what? mAs(milliamperage), kVp(kilovoltage peak), and time
What are the two types of electrical circuits present in every x-ray tube? high and low voltage with the kVp being the high voltage and the mAs being the low voltage
Define the variables used in choosing x-ray equipment. Where you are physically having to give the radiograph. Where on the patient you are radiographing. Type of radiograph: Barium swallows are repeated exposures done in quick succession. Size of animal: A large animal don’t fit on the stationary units
The main source of radiation exposure for veterinary personnel comes from what? scatter radiation
What are the “big three” of radiation safety? Increase Shielding, Increase Distance, Decrease Time
What are the different modalities of diagnostic imaging? Nuclear Scintigraphy, Computed Tomography, Magnetic Resonance Imaging, Endoscopy, Ultrasonography, Radiology
What does CT stand for in CT scan? Computed Tomography
What does MRI stand for? Magnetic Resonance Imaging
Does Nuclear Scintigraphy emit ionizing radiation? Yes
Does Computed Tomography emit ionizing radiation? Yes
Does Magnetic Resonance Imaging emit ionizing radiation? No
Does Endoscopy emit ionizing radiation? No
Does Ultrasonography emit ionizing radiation? No
Does Ultrasonography emit ionizing radiation? No
Does Radiology emit ionizing radiation? Yes
What are the two ends of the x-ray tube? cathode, anode
What are the primary components of the cathode? Focusing cup, Filament(s), Filament wiring
What are the primary components of the anode? anode disk, focal spot (actual), Induction motor, rotor, rotor bearings, stators/coils
What type of metal is used for the filament(s)? tungsten
What part of the anode is made of tungsten? The target
Why might a rotating anode be used? Because heat is more dispersed and dissipates faster with a rotating anode because it's not hitting the same point the whole time
What is the function of kVps in radiology? penetration of ionizing radiation, it controls the contrast
What is the function of mAs in radiology? amount of ionizing radiation, it controls the density
What type of radiograph would you use long scale kVp for? something you need to see many shades of gray in such as the abdomen
Do long scale radiographs have a high or low kVp? High
Which type of radiograph (short or long) has many shades of gray? long scale
What type of radiograph would you use short scale kVp for? radiographs where you will have black and white with few shades of gray
Do short scale radiographs have high or low kVp? Low
Which type of radiograph (short or long) has a few shades of gray and is mostly black/white? short scale
What is exposure time? It refers to the amount of time the beam is penetrating
What are the benefits of a shorter time exposure? Less blur due to patient movement, less exposure to ionizing radiation
What are the downsides of a shorter time exposure? Detail quality is reduced
what is the average time exposure? 1/120th of a second to 1/10th of a second
mAs is short for what? milliamperage x seconds
What does mA stand for? milliamperage
What type of rectification is used to produce x-rays? Full wave 3 phase
What are some types of machines used in radiology? Portable, Mobile unit, Stationary, Digital, Fluoroscopy
When would you use a Fluoroscopy machine? Barium swallow, hysterosalpingogram (basically when you need multiple radiographs in quick succession to understand the functioning level of an organ)
What are the advantages to a digital machine? image displays directly on the monitor, no film, no screens, no processing required
What is the biggest disadvantage to digital machines? People often forget that it is still using ionizing radiation and may not take the necessary precautions OR may do several radiographs because it wasn't perfect exposing the patient and themselves more than necessary
What are the 3 types of Rectification? Half-wave, Full-wave(single phase), Full-wave (3 phase)
What is Rectification? The process of converting alternating currents into direct current/into a straight line and continuous pulsing
Which tissues are most affected by ionizing radiation? Any that have rapid growth of cells such bone marrow or reproductive organs
What are the effects of ionizing radiation? They largely have no effect, but a small percent can cause Repairable cell damage, non-repairable cell damage, or even death of the cell
What is FFD? Focal Film Distance, distance from the tube head to the image receptor (film)
What is the standard FFD in vet medicine? 24-26"
What is the NCRP? National Council on Radiation Protection and Measurements
What is the NCRP responsible for? Reccomends Maximum Permissible Dose and Workplace principles of safety
How is radiation monitored? Dosimeter or film badge
Where should the Dosimeter or film badge be worn? outside the protective attire so that it can measure scatter radiation
How are the dosimeters tracked for each person? They are sent to a federally approved laboratory and are connected to social security numbers
What are the sources of exposure with radiography? Primary beam, x-ray tube head, scatter radiation
What 8 tissues are most affected by radiation? Lymphatic(immune system), Blood forming tissues(marrow, thymus, spleen), Thyroid gland, Eyes, Reproductive organs, Developing fetus, Intestinal epithelium, Skin
Why are eyes so affected when they don't have rapidly dividing cells? because they are open and the lenses magnify
What is PPE? Personal Protective Equipment
What PPE is required for radiographs? Apron, gloves, thyroid shield
What piece of PPE is not required, but is recommended? lead lined glasses
What are the two types of radiation effects? Somatic and Genetic
What does Somatic mean? occurring within the lifetime of the individual
What does Genetic mean? occurring in future generations
Doses of radiation are what over a lifetime? cumulative
How do you minimize radiation exposure? Increase Shielding, Increase Distance, Decrease Time
How much do gloves reduce exposure by with the primary beam? 25%
What is the Inverse square law? Double the distance from the beam will decrease the beam intensity by one fourth
What are the OSHA standards for restricted areas? Sign must be posted, access controlled, Proper construction and design of room, NO ONE under 18 or pregnant may be in this area when the equipment is in use
Is the darkroom a restricted or unrestricted area? Unrestricted
Define Gray (Gy) used to define rad 1 Gy = 100 rad
Created by: Adeprey4311