ARRT STUDY GUIDE Flashcards
When was the first case of human injury from X-Ray
1895
When was Roentgen’s Paper Announcing Discovery of X - Ray?
1895
When was the first case of Cancer caused by X rays?
1902
Since when is most of our understanding of the biological effects of radiation?
World War 2
What percentage of the population’s exposure to manmade radiation is from Medical Industry?
90%
What percent of the Medical radiation exposure can be eliminated?
30%
What is the body distribution of X Ray Percentages?
Thoracic 50%
Abdomen 25%
Extremities 17%
Head and Neck, Other 8%
At what rate are X Ray exams increasing?
7%
What are primary factors and techniques that affect radiation dose?
KVP
MAS
Target to film Distance
Technique Chart
What ancillary factors affect Radiation dose?
Generator design
how are X rays produced?
Energy conversion when a fast-moving stream of electrons is suddenly decelerated in the target (anode) of an x ray tube.
What are x ray filters made of?
Aluminum
What do filters do?
absorb the less penetrating x rays before reaching the patient.
What is one of the most important things a Doctor can do while taking x rays to reduce radiation?
Collimation
What materials can cassette holders be made of?
Aluminum
Bakelite
Carbon Filber
What do Grids do?
Reduce scatter radiation
What is inside of a Cassette?
Intensifying screens
What is the purpose of an intensifying screen?
Convert the X ray beam into light to expose the films.
What is the Kilovoltage (kVp)?
Determines maximum Photon energy of the X ray beam.
What is Milliampere - Seconds (mAs)
X ray tube current time Milliamps and time
What is target to film distance?
Distance to target of x rays made of tungsten
What is the optimal target to film distance (SID/TFD)?
40 Inches
What are the Primary Factors?
KVP MA Time Distance Calipers
What is a technique chart used for?
Correlate body part measurement with Primary factors.
What is radiographic contrast largely dependent on?
the body part
what two things happen when an x ray photon interacts with matter?
it’s either absorbed or scattered
What factors affect scattered radiation?
KVP Used
Field Size
Part Thickness
Tissue Density
What are the different Generator designs?
Single Phase
Three Phase
Medium/High Frequency
Constant potential
Why are 3 phase and Med/High Frequency generators better?
High MA available for short Exposure times
High effective Kilovoltage
Near Constant Potential
What is Brems/Breaking Radiation?
Fast electrons decelerating at the target
When the Kinetic energy of electrons are transformed into electromagnetic energy the spectrum energies are?
Heterogenous
Polyenergetic
Polychromatic
When an incoming electron knocks out or displaces an orbital electron from a target atom it produces?
Charactoristic x rays
What is the x ray tube made of?
Pyrex glass
The Pyrex encloses a vacuum and contains which two major parts?
The cathode which is Negative
The anode which is positive
Where are electrons released from?
Heated tungsten filament
How many volts are used in diagnostic x ray?
50,000 to 120000
What percentage of the energy deposited in the target is converted to X rays?
1 percent, the rest is heat that gets dissipated
What lines the inside of the housing that holds the x ray tube?
Lead
Where is the useful beam emitted from the x ray tube?
The Window
What does the number of x rays depend on?
the number of electrons that flow from the filament (cathode) to the target (anode)
3 different quantities of electrons flowing per second are?
100
200
300
What is the anode angle in most x ray machines?
12 to 20 degrees
What does the size of the focal spot influence?
Resolution of the image
What causes the “Heel Effect”?
result of the Line-Focus principle that distributes radiation intensity more on the cathode side than on the anode side.
at 40 TFD, the anode end on a 14 x 17 film with receive a relative exposure of what percentage?
73%
at 40 TFD, the Cathode end on a 14 x 17 film with receive a relative exposure of what percentage?
105%
at 72 TFD, the anode end on a 14 x 17 film with receive a relative exposure of what percentage?
87%
at 72 TFD, the Cathode end on a 14 x 17 film with receive a relative exposure of what percentage?
104%
What happens to “Heel Effect” in smaller films?
Has a smaller role
Long wavelength X rays are?
Low energy
Filtration helps the beam become less Polychromatic? True or False?
True (More monochromatic)
By using added filtration the radiation dose can be reduced by what percent?
42% using 2.5 aluminum filter
What is the HVL?
Half Value Layer, thickness required to reduce x ray intensity to half
What does the inherent filtration include?
X ray tube
Tube Housing
Glass Window
Inherent filtration is equivelent to?
0.5 lead
What should be used in scoliosis x rays?
light weight leaded plastic compensating filters
To protect the breast area during scoliosis exams, what can be done.
Breast shield
exam P to A
Besides reducing radiation to the patient what else does collimation do?
improve contrast and detail
What is a shadow shield?
radio opaque substance that casts shadow over testis or ovaries.
Gonad sheilds must not be lass than ? lead equivalent?
0.5
If the gonads are within 5cm to the primary x ray beam you must?
use shields
What does a grid consist of?
Lead strips separated by radiolucent spacers
What happens to x rays that are traveling obliquely through the grid?
they are absorbed
What is the grid ratio?
Ratio between the height of the lead strips, and the interspace distance between them.
What does the grid pattern refer to?
orientation of the lead strips on their longitudinal axis.
What is a linear grid?
lead strips are parallel to each other on the longitudinal axis.
What is a focused grid?
Lead strips are angled slightly so that they focus at some distance.
What is a parallel grid?
Lead strips are parallel when veiwed in cross section.
What is the Bucky Grid?
Moving grid, more radiation, but less grid on x rays
What four conditions may result in grid cutoff?
Upside down grid
Crooked grid
Grid off center
Off focus grid
What is beneficial about grids with higher ratios?
remove scatter before it reaches the film
As a general rule Grid ratios up to 8:1 are satisfactory at tube potentials below what KVp?
90
If the Tube Potentials exceeds 90 what Grid ratio is used
10:1 , 12:1
Most grids used in practice today are?
focused grids
What grids are most x ray tables equiped with?
Linear grids
What is film sandwiched between in a cassette?
two intensifying screens
All x rays except those extremities lebow 8cm thickness are taken using ?
intensifying screens
What percentage of the x rays that hit the intensifying screens react?
30%
What percentage of the darkening of the film is produced by the intensifying screens?
95%
When using film without intensifying screens how much more x rays are needed?
20-50 times more.
What does the intesification factor mean?
speed of the screens
How much less radiation are rare earth screens?
2 - 5 times less
What are the old style screens made of?
Calcium Tungstate
What speed are medium calcium tungstate screens?
100
What exposure settings changes will result in 75% less radiation?
calcium tungstate 100 versus Rare earth 400
What is the light sensitive material in the emulsion of an x ray?
Silver Bromide Crystal
How must films be stored?
In an upright position
Which type of film should be used with Calcium Tungstate screens?
Blue - Violet
Which type of film should be used with Rare Earth screens?
Blue - Green
What type of emulsion are the screen films?
double emulsion
What do x rays produce when interacting with Phosphor substrate?
Light
Intensifying screens reduces patient radiation by how much?
95%
What are the different film speeds available?
1 - Slow Speed
2.5 - Intermediate Speed
10 - High Speed
What is (S) Speed defined as?
Reciprocal of the radiation dose in Rads required to produce density of 1.0 above base and fog
(S) = 1/R
If an intermediate film is replaced by a high speed film, the x ray exposure is?
25% as much as with Intermediate film
See diagram page (20) in syllabus
What can happen if x ray film is handled rapidly?
Static Marks
How often should a sensomatic strip be run through the x ray machines?
Once a day
If you use high Kvp then you can use lower?
MAS
What does lowering the KVP do to patient dose?
increases patient dose
If you increase KVP beyond an optimum range what happens?
long grayscale contrast
Increasing KVP can do what effect to the patient’s body?
Decrease skin radiation, but increase organ radiation.
What are some advantages to High KVP techniques?
Reduced skin radiation Shorter exposures Increased radiographic lattitude Improved control of contrast Less heat in x ray tube
What is the Tube Current?
Ma
What is the main cause of having to retake films?
wrong MAS or KVP
What do photo timers do?
measure the amount of radiation passing through the patient and sutomatically terminate the exposure.
What are some body parts that use 72” TFD?
Chest X ray, Lateral cervical
What is the inverse square law formula?
Calculating exposure difference
Where should calipers be placed?
Part where central ray enters the body
What percent of cases will require minor adjustments aside from the technique chart?
10 to 25%
There may be a difference between response of rare earth screens versus regular , what is the difference?
2:1 as it goes from 90kvp to 60kvp
In the human body what is the most important factor affecting attenuation?
Tissue density
HIgh contrast between air and soft tissues is created entirely because of what?
density differences.
Will disease processes change tissue densities?
yes
Which would need less exposure and emphysema patient or pneumonia?
Emphysema
What percent of radiation flows through the patient and is unaffected to form the image?
5 percent, remnant radiation
Tissues with less densities transmit what to the radiograph?
more rays
What are the densities of each tissues?
Water and Muscle the same
Fat 10 percent less
The primary radiation that exits the human body consists of what?
non interacting and small angle scattered photons and carries the x ray image.
What direction are secondary photons in?
scattered
What are secondary or scattered photons called
compton effect
Whats the only process that takes effect above 80 kVp?
Compton effect
What is the absorption event probability?
Photoelectric Absorption
The photoelectric absorption is dependant on what?
The atomic number
Which is the photo effect greater for high energy or low energy x rays?
low energy
What is the predominant mode of x ray interaction at higher energies?
Compton effect
What direction is the scatter radiation of Compton effect?
isotropic
What can happen is there is too much isotropic scattering? (compton effect?)
Film darkening
what percent of radiation reaching the film is scattered?
more than 50%
What 4 factors determine quantity of scatter radiation?
kVp
Part Thickness
Field Size
Tissue Denisty
Which is a more effective way to produce x rays single or 3 phase?
3 phase
What percentages are retakes for each type of personal?
2% for experienced
10% for non experienced
What percentage of retakes are due to error in exposures?
50%
What is CT
3 angles of images that are put together by computer
What generation of CT is used today?
3rd and 4th
How does the 3rd CT generation work?
Rotate-Rotate Geometry
How does 4th gen CT work?
Stationary Rotate
What type of CT has a fixed ring and only the scanners move around the patient?
Stationary rotate / 4th gen
What type of CT has less radiation and better image quality?
Neither, Both 3rd and 4th gen are the same
What is the radiation does for CT?
1 to several RADS
What type of switch is used for mobile CT?
Dead-Man
How far away from Mobile CT does the operator stand?
6 feet
What is the source to skin distance for Mobile CT
12 inches
What are the two classes of radiation biological impact?
Genetic and Somatic
What are 4 somatic changes from radiation?
Superifical Tissue
Cancer
Cateract, life shortening, infertility
Injury to fetus