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RAD 121

Unit 2 - Image Production

What is kVp? force applied to move, drive, push electrons from cathode to anode. It determines the kinetic energy of the electrons crossing in the x-ray tube by controlling the speed of electrons.
Increasing kVp has what effect on the wavelength of the x-ray photon? DECREASES wavelength (increased energy)
Increasing kVp has what effect on the frequency of the photons in the beam? INCREASES the frequency
Increasing kVp has what effect on the exposure rate of the beam when all other factors remain constant? INCREASES the exposure rate (more energy, more photons)
What is exposure rate? x-ray intensity; output P116-117 S
What three things does kVp control? 1. Beam QUALITY 2. photon ENERGY 3. PENETRABILITY
kV is the controlling factor for _____ _____? SUBJECT CONTRAST (differential absorption) this is the patient
What is exposure latitude? Range of techniques that will produce a quality image without violating ALARA
kV influences _____ _____. EXPOSURE LATITUDE
Increasing kVp has what effect on amount of scatter? INCREASES the amount of scatter and secondary radiation produced
Quality is also known as _____, _____. It is represented numerically by _____. PENETRABILITY, INCREASED ENERGY OF PHOTONS; HVL - Half Value Layer
What is HVL? HALF VALUE LAYER - the amount of material needed to reduce an xray beam by 50% - measured in AIR KERMA
What effect does increased kVp have on photoelectric absorption? DECREASED photoelectric absorption
Increased kVp with a decrease in mAs results in _____ patient dose. LOWER patient dose
Increased kVp increases transmission which _____ patient dose. LOWER patient dose
What is contrast? one of the properties that comprise visibility of details or the difference between adjacent receptor exposures
Describe HIGH CONTRAST with five details. SHORT SCALE; fewer shades of gray; NARROW dynamic range; MORE contrast (whites/blacks); WIDE difference in adjacent receptor exposures
Describe the five most influential factors for SHORT SCALE. low kVp; low filtration; high grid ratio; high OID; More beam restriction (right collimation)
How are kVp and image contrast related? INVERSELY - more kVp, less contrast
What is DYNAMIC range? Range of grays available to construct image (range of exposures the IR can detect)
What is SUBJECT CONTRAST? The range of difference in intensity of the x-ray beam after it has been attenuated by the subject. Absorption characteristics of anatomic tissue imaged dependent upon quality of x-ray beam.
What is IMAGE CONTRAST? the radiograph must exhibit difference in brightness level in order to differentiate among anatomic tissues. causing a range of brightness from differential absorption of x-ray photons.
Describe LOW CONTRAST with five details. LONG SCALE; MORE shades of gray; WIDE dynamic range; LESS contrast; NARROW difference in adjacent receptor exposures
Describe the five most influential factors for LONG SCALE. HIGH kVp; HIGH filtration; LOW grid ratio; LOW OID; less beam restriction (little to no collimation)
What are the 10 influencing factors of CONTRAST? Digital IR (pixel bit depth); ANATOMICAL part (thicker, more scatter); FSS, Anode Heel & mAs - no effect; OID (more, more contrast); FILTRATION - more, less contrast; Grid - more; less scatter; up contrast; Collimation; Generator - up power, down contrast
What is the function of image contrast? Ability to visualize differences in receptor exposures displayed (enhance diagnostic quality of specific anatomy)
SUBJECT CONTRAST is dependent on _____ and _____. kVp and anatomic part
What are the 6 characteristics of Anatomic Tissue? 1. Atomic #, 2. Density, 3. Age, 4. Gender, 5. Body Habitus, 6. Pathology/Cast
What are 3 of the most radiolucent materials in the body? Air/Gas; Fat/Cartilage; Hollow organs (empty); Muscles; Hollow organs (esophagus)
What are 3 of the most radiopaque materials in the body? solid/fluid filled organs; bone; tooth enamel; prosthesis
What is tissue thickness influenced by? 1. Age 2. Gender, 3. part position, 4. Body Habitus, 5. Pathology or condition
What is contrast media? Allows the radiologist to visualize soft tissue structures by increasing tissue contrast
Name and list a positive contrast medium and its effect. Barium/Iodine - radiopaque; increases tissue density
Name and list a negative contrast medium and its effect. Air/Gas - radiolucent; decreases tissue density
What is a double contrast medium and why do we use them? Combination of positive(barium) and negative(air) contrast; used to better visualize soft tissue structures without obscuring
High mAs and low kVp equal _____ contrast. HIGH contrast
Low mAs and high kVp equal _____ contrast. LOW contrast
What is filtration? elimination of low energy x-ray photons by inserting an absorbing material in the path of the primary beam. (increasing filtration, increases avg energy of x-ray photon, decreases contrast also decreases receptor exposure).
How does the power supply affect contrast? Waveform produced by generator influences quality of beam. (Increasing generator power, increases energy and decreases contrast)
How does the target material affect contrast? Anode must have high enough atomic mass to generate needed "k" shell interactions (increased atomic #, increased energy and increased quality)
What is the primary beam? Beam exiting the x-ray tube - prior to reaching patient
What is secondary radiation? radiation emitted during interactions in tissues - exiting patient to directly expose the IR
How does tissue type influence the production of secondary radiation and scatter? increased atomic # means increased attenuation/absorption and decreased transmission. (increased fluid increases scatter production and decreases contrast)
How does volume of tissue influence the production of secondary radiation and scatter? increased volume means increased scatter and secondary radiation and decreased contrast
How does energy of the x-ray beam influence the production of secondary radiation and scatter? more energy means higher penetration(kVp) and lower subject contrast; more power means more interactions, more scatter and more secondary radiation
What is backscatter? Scatter that occurs from beam back towards TUBE - patient is the main source
How do you reduce backscatter? Patient is the main source of this. It travels in many directions before reaching the IR causing fogging (decreased contrast). To reduce use COLLIMATION
What are the Power factors for Grid Factor ratios? 1 phase 1 pulse = 1 1 phase 2 pulse = 2 3 phase 6 pulse = 3 3 phase 12 pulse = 4
What effect does mAs have on image contrast? NO EFFECT
What effect does kVp have on image contrast? INVERSE - increased kVp, decreased contrast
What effect does OID have on image contrast? DIRECT - increased OID, increased contrast
What effect does SID have on image contrast? NO EFFECT
What effect does Focal Spot Size have on image contrast? NO EFFECT
What effect does Grid have on image contrast? DIRECT - increased grid, increased contrast
What effect does Beam Restriction have on image contrast? DIRECT - increased beam restriction, increased contrast
What effect does Field Size have on image contrast? INVERSE - increased field size, decreased contrast
What effect does Patient Thickness have on image contrast? INVERSE - increased part thickness, decreased contrast
What effect does Patient Motion have on image contrast? NO EFFECT
What effect does Filtration have on image contrast? INVERSE - increased filtration, decreased contrast, increased avg. energy of x-ray beam
What effect does CR Angle have on image contrast? NO EFFECT
Increased kVp will _____ transmission increase
Increased kVp will _____ Compton scatter increase
Increased kVp will result in _____ scale of contrast longer
Increased kVp will _____ quantity of photons (because electrons are sped up and gain kinetic energy (produce more x-ray photons/second at the target) increase
If you double the kVp, receptor exposure will increase by a factor of? 4,5, or 6
AC comes in at _____Hz which means ____ cycle per second. 60; 60
What is air gap and how does it influence receptor exposure and contrast? The space between the patient anatomy and IR. Increasing OID decreases receptor exposure and increases contrast. This causes magnification (size distortion).
The mAs required to maintain receptor exposure is ______ proportional to the relative output factor. How is it mathematically stated? Inversely; (Old Output Factor / New Output Factor) = (New mAs / Old mAs) solved by cross multiplication.
What effect does generator have on contrast? increased power and decreased contrast
The construction of the generator results in _____ pulses and it affects _____ _____ various; radiation output
3 phase generators produce a _____ quality beam than a single phase. Higher
3 phase generators produce ________ contrast long/low (goes through part and more shades of gray)
_______ phase and pulse will cause an increase in receptor exposure unless mAs is adjusted. (that's why we have the formula) increasing
Changes in ______ must be adjusted when changing power supply(generator type). mAs
Power supply (phase and pulse) are ______ related to mAs. inversely
the incident XR photon is a low energy (generally less than 20 KeV). When such low-energy incident photon interact with tissue atoms they are not ionized. instead atoms absorbs the energy causing excitation then releasing it in a new direction(scatter) Coherent Scattering. It also increases patient dose.
This interaction occurs throughout the diagnostic range(high or low kev) An incident XR photon enters a tissue atom, interacts w/ an outer orbital electron and ejects it as recoil or compton scatter electron, losing 1/3 of energy and in a new direction. Compton Scattering (modified scattering)
The energy of the Compton scattered photon is equal to the difference in energy between _______ photon and ________ electron. incident photon and recoil electron.
The energy of the recoil electron is equal to its ______ energy plus the _____ energy it acquires when leaving the atom. binding energy plus the kinetic energy
Compton interaction is represented by the following formula: energy of the incident photon equals the sum of (the energy of compton scatter photon, electron binding energy, and kinetic energy of the ejected electron).
Compton scattering ______ follow its original path through the body to strike the IR. It strikes the wrong place creating _____ doesn't; Fog/Noise
How can we decrease Compton scatter? w/ the use of shields, shield ourselves and use grid whenever possible
Compton scatter does not depend on the atomic # of the atom but is dependent on the energy of the ______ photon incident
Compton scattering is the major source of __________ occupational exposure/Rad Tech dose
where the incident xr photon is completely absorbed by an inner-shell electron causing the electron to speed up to where it is flung out. ejected electron is called ___. cascade effect happens where 2ndary photon are produced and contribute to pt. dose. Photoelectric events; photoelectron
_______ from photoelectric events has enough kinetic energy to undergo interactions of its own before filling a vacancy in another atom elsewhere. photoelectron
the photoelectron has kinetic energy that is equal to difference btwn the incident x-ray photon and the binding energy of the inner-shell electron. The formula is: the energy of the incident photon equals (the binding energy of the electron plus the kinetic energy of the photoelectron).
Barium studies usually start at ___ kVp and you must choose the appropriate technique bc of absorption. 90
Photoelectric interactions depend on the energy of the incident x-ray photon and the _____ of the tissue atoms w/ which they interact. Atomic #
MeV stands for? megaelectron volts
occurs only with very high-energy photon of 1.02 MeV or greater. When the incident xr photon has enough energy to escape interaction with the orbital electron and interacts w/ the nucleus of the tissue. A ______ and ___ are produced. Pair production; positron and electron
For positron and electrons produced by pair productions to exist they must each have energy of ____ MeV (the energy equivalent of an electron and energy greater than 1.02 MeV is shared btwn the two as kinetic energy.) 0.51 MeV
Occurs when photon w/ extremely high energies of more than 10 MeV strike the nucleus of the atom and make it unstable. For the nucleus to regain stability, it ejects a nuclear proton, neutron, or alpha particle. Photodisintegration
Both of theses interactions do not occur in radiography bc the energy levels required far exceed the kVp range used in diagnostic x-ray production. Photodisintegration and Pair prodution
Used in Rad therapy.... less penetrating, will destroy tissues if allowed to sit on the tissue. photodisintegration Beta particles
What are the 5 factors affecting the emission spectrum? mA, kVp, tube filtration, generator type, target material
In the emission spectrum, what represents most of the x-ray beam? continuous portion
In the emission spectrum, this is reduced to the highest energy K-characteristic bar discrete line
in the discrete emission spectrum, the x-axis is the ____ and the y-axis is the _____ x-ray energy; # of each type of x-ray photon
the continuous emission spectrum illustrates ________ production. the x-axis represents ____ and the y-axis _____ Bremsstrahlung x-rays; x-ray energy (keV) and # of x-ray photons emitted (quantity).
Brems photon energy depends on the strength of the _____ electron attraction to the nucleus and can range from just above 0 to the maximum kVp selected on the control panel with most being 1/3 of the kVp selected. filament
On a graph of the brems photon, the right side of the curve touches down at the _____ selected and the peak is approximately _____ of the kVp indicated. kVp; 1/5 fig 10.5 p119 Orth
AOFC, an increase in ____ will increase the amplitude of both the continuous and discrete portions of the spectrum. mA p120 Orth
beam quantity refers to the total # of x-ray photons in a beam and is affected by? mAs, kVp, distance, and filtration
An increase in quantity increases the _______ patient dose
if kVp is doubled, the intensity(quantity) increases by a factor of ____ 4
x-ray photon that makes it from the beam to the IR is called ____ and is composed of transmitted and scattered radiation. remnant
is the difference btwn the x-ray photons that are absorbed photoelectrically versus those that penetrate the body. differential absorption
A higher kVp _____ the number of interactions overall but the number of Compton interactions _____ in comparison to the number of photoelectric interactions. reduces, increase
x-rays are attenuated exponentially and generally reduced by ___% for each 4-5 cm of tissue thickness. 50%
increasing the compactness of the atomic particles will ___ beam attenuation. (tissue density) increase
Higher kVp increases the energy of the x-ray beam and will ____ beam attenuation. decrease
Together, visibility of detail is determined by brightness, contrast, and receptor exposure
A ______ image is evaluated by the amount of brightness (light emission) of the display monitor. digital
a ____ image is evaluated by the amount of density or overall blackness after processing film
The radiograph must exhibit differences in _____ and ____ in order to differentiate among the anatomic tissues. receptor exposures(brightness) and image contrast
Tissue contrast/ differential absorption is dependent on ___ and the amount and type of ______ kilovoltage; irradiated material
This describes the imaging systems ability to distinguish between objects that are similar in subject contrast (attenuation characteristics) contrast resolution
One of the two types of contrast resolution, it is the number of receptor exposure intensities/brightness lvls that can be stored and/or displayed on digital image. Gray scale
one of the two types of contrast resolution, it pertains to film/screen the range of blackening/densities visible on film. Scale of contrast
It is the processing code that lets us change radiographic contrast after the image has been taken. Window Width
Increasing part thickness or increasing field size(collimation) will increase _____(making it to the IR) and create a ____ scale of contrast scatter; longer
A high atomic number or high tissue density will create a _____ attenuation of x-ray photons greater
This contrast media makes tissue less dense. Air
Ratio of secondary/scatter to exit radiation for abdomen? 90/10
Ratio of secondary/scatter to exit radiation for chest? 50/50
To maintain receptor exposure with an increase in grid ratio, you must increase _____. The formula is?! mAs, GF2/GF1 x mAs1 = mAs 2; OR mAs1/mAs2 = GF1/GF2
____ kVp is usually used when a grid is used. Also ____ kVp is used when no grid is used. 70 kVp grid in use; 60 kVp no grid
describe Quantum Noise Model Visible as brightness or density fluctuations. Increased, this is the result from photon-deficiency(happens when too few x-ray photons reach IR), thus providing no useful information. It is visible in digital imaging.
Created by: Larobbins