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Increasing kVp has what effect on the wavelength of the x-ray photon?
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RAD 121
Unit 2 - Image Production
| Question | Answer |
|---|---|
| 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. (how do you get 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; LOW 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 |
| SUBJECT CONTRAST is also called | DIFFERENTIAL ABSORPTION; TISSUE CONTRAST |
| 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 generator 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 |
| ______ 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. (unmodified) |
| 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 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. Causes 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 _____. Orth p118 | 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
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