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BUSHONG FINAL
chapter 10 thru 18
| Question | Answer |
|---|---|
| Spatial resolution improves with decreased _____ blur | screen, motion, geometric |
| Higher speed image receptors generally produce images with _____. | increased noise |
| The slope of the _____ portion of the characteristic curve shows the film contrast. | straight line |
| In general radiography, the useful optical densities lie between _____ and _____. | 0.25, 2.25 |
| The inherent base density plus fog density in film is _____. | 0.1-0.3 |
| A film with a characteristic curve showing a high slope would be useful when _____ is needed. | high contrast |
| An image receptor with _____ can be used over a greater range of exposures. | wide latitude |
| The three primary geometric factors affecting image quality are _____. | magnification, distortion, and focal spot blur |
| What is the formula for the magnification factor? | MF = SID/SOD |
| The best way to minimize magnification is to use a _____. | long SID small OID |
| Subject contrast is affected by _____. | patient thickness |
| Distortion can be reduced by _____. | placing the object plane perpendicular to the image plane |
| Radiographic image quality is improved when the _____ is increased. | source image distance |
| Patient thickness affects image quality by affecting _____. | magnification radiographic contrast focal spot blur |
| The technologist primarily controls radiographic contrast by varying the _____. | kilovoltage |
| Image-forming x-rays include those which have been _____. | transmitted without interaction scattered through Compton interaction |
| Which kVp selection would result in the most scattered x-rays in the image-forming beam? | 90 kVp |
| Approximately _____% of the x-ray beam incident on the patient is transmitted through the patient without interaction to become part of the image-forming beam. | 0%-9% |
| The x-ray interaction that contributes to the clear parts of the image is _____. | photoelectric interaction |
| Compton scatter contributes to _____. | image noise |
| The three primary factors influencing the intensity of scatter in the image-forming beam are _____. | kVp, field size, and patient thickness |
| Photoelectric interactions increase when _____ is decreased. | kVp |
| Scatter radiation increases as _____ increases. | field size |
| The x-rays that are transmitted through the patient without interaction contribute to _____. | useful information |
| Contrast resolution is improved by _____. | tight collimation lowering kVp patient compression |
| The most commonly used beam restricting device is the _____. | variable collimator |
| The use of a compression device will increase _____. | contrast |
| Lowering kVp _____ patient dose and _____ image contrast. | increases, increases |
| The use of _____ improves contrast and reduces patient dose. | collimation |
| Beam restriction with a(n) _____ is only accurate at a fixed SID. | aperture diaphragm |
| The main purpose of the gelatin emulsion in radiographic film is to _____. | protect the base |
| Crystals in film emulsion consist of _____ and _____. | silver bromide, silver iodide |
| The overcoat on radiographic film is a protective covering of _____. | gelatin |
| Latent image formation occurs during film _____ | processing |
| A contaminant in the silver halide crystal creates the _____. | image fog |
| Photon interactions free the electrons from _____ atoms in the silver halide crystal | bromide iodide |
| The latent image is made up of _____ atoms. | silver |
| Photon interactions in the emulsion occur with exposure to _____. | x-rays light |
| High contrast film contains _____ silver halide crystals of _____ size. | smaller, uniform |
| Film is made with double emulsion to enhance film _____. | speed |
| The layer of screen that lies closest to the film is the _____. | protective coating |
| The light-emitting efficiency of the intensifying screen is improved by the _____. | added dyes |
| Screen characteristics are determined by the _____. | size of the phosphor crystals thickness of the phosphor layer phosphor composition |
| A phosphorescent material emits light _____. | for a period of time after stimulation |
| An intensifying screen is an example of _____. | luminescence fluorescence |
| The intensification factor is a measurement of screen _____. | speed |
| The intensification factor is the exposure required _____ divided by the exposure required _____. | without screens, with screens |
| The intensification factor increases with increased _____. | kVp |
| The ability of an intensifying screen to absorb x-rays is called _____. | detective quantum efficiency |
| Image noise in increased with increased _____. | conversion efficiency (CE) |
| Both the isotropic emission of light from screen phosphor crystals and the added reflective layer contribute to _____ | conversion efficiency |
| What are the four primary exposure factors? | kVp, mAs, time, and SID |
| Changes in kVp affect _____. | optical density image contrast image noise |
| An increase in mAs causes _____ in beam quality and _____ in beam quantity. | no change, an increase |
| There is a direct relationship between the quantity of x-rays and the _____. | milliamperage |
| Beam penetrability is increased if _____ is/are increased. | kVp |
| A _____% increase in kVp has the same effect on optical density as doubling the mAs. | 15 |
| A radiograph with a long scale of contrast will have _____ latitude and _____ contrast. | wide, low |
| A radiograph is taken using 75 kVp @ 20 mAs. Which change in technique would increase contrast but maintain the same density? | 65 kVp @ 40 mAs |
| At least a _____% change in mAs is necessary to produce a visible change in optical density | 30 |
| A radiograph taken using 65 kVp @ 10 mAs is too light. Which technique would double the optical density while producing a wider scale of contrast? | 75 kVp @ 10 mAs |
| Which technique would give the highest patient dose? | 65 kVp/300 mA @ 0.1 sec |
| The small focal spot will provide a _____. | finer detail of image |
| Beam quality is improved when the _____ is increased, but _____ has no effect on beam quality. | kilovoltage, milliamperage |
| Both beam quality and beam quality are increased by _____ | increasing kVp using 3-phase voltage |
| Added filtration has the effect of _____ the beam quality and _____ patient dose. | increasing, reducing |
| Which medical condition may require a lower technique? | emphysema |
| When only the optical density needs to be changed, only the _____ should be adjusted | mAs |
| Sharpness of detail can be improved by increasing _____. | SID |
| In a variable kVp technique chart, the optimal mAs is set for each body part and there is a _____ kVp increase for each cm of thickness. | 2 |
| A variable mAs technique chart has a set kVp and specific mAs settings for _____. | small, medium, and large parts every 2 cm of thickness |
| With automatic exposure control the exposure is terminated when the optimum _____ is reached. | OD |
| Modern day computers use _____ to store information. | silicon chips |
| The following computer component temporarily stores data for processing. | hard disk drive |
| Digital radiography was first introduced by _____. | Kodak in 1975 |
| T/F Computed radiography cassettes and film/screen cassettes can be used interchangeably with any x-ray imaging system. | true |
| Computed radiography screens respond to radiation with _____. | photostimulable luminescence |
| A photostimulable phosphor in a metastable state will emit light _____. | immediately when stimulated by light over time |
| Europium is the _____ of the photostimulable phosphor. | activator |
| The photostimulable phosphor screen is handled in a _____. | reader |
| The four steps of creating an image with computed radiography are _____. | metastable state, stimulate, read, and erase |
| Optical filters are used to filter out the _____ light and allow the _____ light to reach the photodetector. | stimulating, emitted |
| The output signal from the photostimulable phosphor plate is converted from analog to digital by the _____. | photodetector |
| Computed radiography and screen-film imaging both have a(n) _____. | latent image |
| T/F Spatial resolution, contrast resolution, noise, and artifacts are identical in screen-film imaging and computed radiography. | FALSE |
| With computed radiography the contrast is _____. | constant regardless of radiation exposure |
| The computed radiography image has _____. | wide exposure latitude improved contrast resolution |
| The laser beam must be less than 100 nm in diameter in order to maintain _____. | high spatial resolution |
| Switching from screen-film imaging to computed radiography can _____ patient dose. | reduce |
| Digital imaging techniques are always applied to _____ | computed tomography (CT) ultrasound magnetic resonance imaging |
| In digital radiography, the latent image is formed on the _____. | radiation detector |
| In digital fluoroscopy, each matrix pixel represents _____. | atomic number and mass density |
| In digital radiography, the brightness of the image is determined by _____. | pixel values |
| Digital imaging could only be developed after advances were made in _____. | microprocessors semiconductor memory |
| Computed radiography developed in the 1970s with the use of _____ as the image receptor. | phosphor |
| Scanned projection radiography was developed as a complement to _____. | computerized tomography |
| What is the most recent development in digital radiography image receptors? | direct capture solid-state devices |
| In digital radiography, spatial resolution is improved with increased _____. | matrix size |
| The dynamic range determines the degree of _____ in the image | contrast resolution spatial resolution motion blur |
| Spatial resolution is determined by the ratio of _____ to _____. | field of view, matrix size |
| Scanned projection radiography differs from conventional radiography in the lack of _____. | scattered x-rays |
| In scanned beam radiography, the spatial resolution is determined by the _____. | number of detectors |
| Computed radiography uses (a) _____ for latent image formation. | photostimulable phosphor |
| Conventional x-ray tubes and cassettes are used with _____ radiography systems. | computed |
| What are the 4 most important characteristics of radiographic image quality | spatial resolution, contrast resolution, noise, optical density |
| T/F kVp is responsible for radiographic quality | TRUE |
| Optical density | Degree of black on an image. |
| Focal-spot blur | loss of spatial resolution that is caused by a large effective focal spot, a short SID, and a long OID |
| Quantum mottle | The random nature in which x-rays interact with the image receptor; too few photons to cover the image receptor uniformly. |
| Latitude | The range of radiation exposure, the image receptor responds with ODs |
| What principally determines radiographic spatial resolution? | Focal spot size |
| Describe the equipment used in sensitometry | sensitometer optical step-wedge densitometer which measure OD |
| What is the importance of processor quality control in an imaging department? | improper optical density, loss of contrast image artifacts. |
| List factors related to film processing that may affect the finished radiograph. | Concentration of processing chemicals; chemistry agitation; development time and temperature. |
| What three principal geometric factors may affect radiographic quality? | Focal spot size, SID, and OID. |
| List and explain the five factors that affect subject contrast. | kVp; effective atomic number, tissue mass density, patient thickness, and patient shape. |
| in screen film Describe the H & H contrast curve. | graph of the slope of the H&D curve as a function of OD. |
| in screen film Discuss the factors that influence radiographic optical density and contrast. | changes in either image-receptor contrast or subject contrast. OD is affected by total exposure and mAs. Proper exposure is the best control the radiologic technologist can exercise. |
| in screen film what is the reciprocity law and explain its influence on radiography. | is proportional to the total energy imparted to the radiographic film. the OD will be the same and therefore, the mAs is constant. |
| Three factors that affect scatter radiation in screen film | kVp, field size, and patient thickness. |
| in screen film what is Image contrast | The degree of black, gray, and white appearance of a radiograph. The more black and white, the higher the contrast. |
| Grid cutoff | exposure of image receptor is not uniform because of misalignment of the grid. |
| Collimation | confines the useful x-ray beam to the anatomic structure under examination. |
| in screen film what is the PBL device | Positive beam-limiting device; an automatic, variable-aperture, light-localizing collimator |
| Air-gap technique in screen film | Remove the grid and allow 15 cm or more between the patient and the image receptor(OID) |
| in screen film Image-forming x-rays | The x-rays transmitted through the patient and scattered in the patient that interact with the image receptor and contribute to the image formation. |
| in screen film What happens to image contrast and patient dose as more filtration is added to the x-ray beam? | Increasing beam filtration reduces both image contrast and patient dose |
| in screen film Name the devices used to reduce the production of scatter radiation | Diaphragm, cone, cylinder, variable-aperture light localizing collimator |
| List two reasons for restricting the x-ray beam | Improve image contrast. Reduce volume of tissue irradiated, and therefore, reduce effective dose. |
| Why does lowering kVp increase the patient dose in Screen film!! | mAs must be increased (thus increasing the patient dose) in order for the exposure of the image receptor to remain the same |
| in screen film When should the x-ray field exceed the size of the image receptor? | Never. |
| what is the Intensification factor in screen film. | ratio of exposure without a screen to that with a screen to produce the same optical density |
| Diagram the cross-sectional view of a radiographic film designed for use with a pair of radiographic intensifying screens. | overcoat, emulsion, adhesive layer, base, adhesive layer, emulsion, overcoat. |
| Discuss the two types of luminescence and how they are associated with radiographic intensifying screens and fluoroscopic screens. | exhibit no phosphorescence. Fluoroscopic screens may exhibit some phosphorescence. Both screens fluoresce. |
| Describe a technique designed to test for good screen-film contact | By radiographing a wire-mesh test tool |
| Define or describe DQE and CE | DQE is the detective quantum efficiency. It represents the probability that an x-ray will be absorbed by a radiographic intensifying screen. CE is the conversion efficiency. It represents the amount of light emitted by each absorbing event |
| What is the importance of spectral matching in selection of screen-film combinations? | If the emission spectrum of the screen is not matched to the film absorption spectrum, a loss of contrast will result, and patient dose must be increased considerably to produce adequate optical density |
| Imaging plate | A photostimulable phosphor bound in a cassette as an image receptor is an imaging plate |
| Signal sampling | The time varying analog signal from the photodetector is processed and digitized with attention paid to proper sampling time (time between samples) and quantization (the value of each sample). |
| Metastable electron | An electron in an excited energy state beyond its normal orbital energy state. |
| Polychromatic | A broad spectrum of wavelengths (colors) of visible light. |
| Prompt emission | Electrons raised to an excited state by x-ray exposure return to the ground state with an immediate emission of light. There is no latent image with these electrons. |
| Storage phosphor | A phosphor such as barium fluorohalide, The latent image is stored in the phosphor. |
| Photodiode | silicon solid state device sensitive to light. It converts light into an electrical signal. |
| How is the latent image formed in computed radiography? | Electrons are energized by x-ray interaction into excited metastable energy states. They remain in these excited states until released by exposure to laser light. |
| How do we reduce backscatter radiation in computed radiography, and why? | The imaging plate is backed with lead to absorb backscatter radiation, which would increase the background noise on the image |
| What is the difference between fast scan and slow scan? | Fast scan is the rapid back and forth of the laser beam. Slow scan is the mechanical drive of the imaging plate through the reader. |
| What is the difference between an analog signal and a digital signal? | An analog signal is a continuous modulation of an electrical signal. A digital signal has discrete values, making it more compatible with computer techniques |
| What are the three subsystems of a CR reader? | Mechanical drive system, optical beam shaping and collecting systems and computer control system |
| How is the latent image made visible in computed radiography? | By stimulating the metastable electrons with an intense beam of laser light |
| Fan x-ray beam | An x-ray beam collimated to appear as a cooling fan. Used in CT and SPR |
| Charge-coupled device | A charge-coupled device is solid state system that converts light into an electrical signal with very high spatial resolution. |
| Scintillation phosphor | Scintillation phosphors, such as NaI, CsI, and other similarly behaving crystals that emit light in response to an x-ray interaction. |
| Spatial frequency | Measured in line pair per millimeter. |
| Tomosynthesis | The acquisition of several projection radiographs from different angles in digital form that are then reconstructed into layered images |
| What are the two principal phosphors used in DR? | Cesium iodide (CSI) and gadolinium oxysulfide (GdOS). |
| By what four methods can a digital radiograph be produced? | Charge-coupled device, cesium iodide married to amorphous silicon, gadolinium oxysulfide married to amorphous silicon, and amorphous selenium. |
| How does pixel size in CCD DR compare with that in other forms of DR? | The CCD has smaller pixels |
| Why is fill factor important? | In DR, the smaller the pixel size, the less the fill factor. Lower fill factor requires increased patient dose, so it’s a tradeoff. |
| What properties make GdOS a good DR image receptor? | GdOS has higher detective quantum efficiency (DQE). |
| What is the meaning of “sensitivity” in DR? | Sensitivity in DR is how low an x-ray intensity can be detected for imaging. |
| Describe the role of an AMA-TFT assembly. | An active matrix array thin-film transistor (AMA-TFT) assembly is an image receptor for digital radiography. |
| What is meant by “limited spatial resolution?” | spatial frequency associated with the 0.1 MTF as the limiting spatial resolution expressed in lp/mm. |
| What are the capture, couple, and collection stages for a-Se–based DR? | Capture = selenium, coupling = selenium, collection = thin film transistor. |
| In screen film Rad where is the latent image stored? | In Screen film the Latent Image is stored in the Emulsion |
| Describe destructive pathology | causing the tissue to be more radiolucent |
| Describe constructive pathology | increase mass density or composition, causing the tissue to be more radiopaque |
| High kVp = | Low contrast images |
| What relationship does the Characteristic curve describe? | describe the relationship between OD and radiation exposure |
| What is the TFT | The TFT is a charge-sensitive device that collects electrons |
| With CSI digital radiography, what is the collection element? | The collection element is silicon sandwiched as a TFT |
| Describe Amorphous Selenium Digital radiography | a-Se is a direct DR process by which x-rays are converted to electric signal. |
| Describe cSI/a-SI | is an indirect DR process by which x-rays are converted first to light and then to electric signal. |
| Describe CSI/CCD | CsI/CCD is an indirect DR process by which x-rays are converted first to light and then to electric signal. |
| Cesium iodide (CsI) scintillation phosphor can be used as | as the capture element for image-forming x-rays. This signal is channeled to a CCD through fiberoptic channels |
| Gadolinium oxysulfide or CsI is used to | Gadolinium oxysulfide or CsI is used to capture x-rays. The light from these scintillators is conducted to an AMA of TFTs, whose sensitive element is a-Si. |
| A screen that emits light after an exposure terminates is exhibiting? | Conversion efficiency |
| what is MTF | the ability of an imaging system to render objects of different sizes onto an image. Objects with high spatial frequency are more difficult to image |
| WHAT IS SNR | is that portion of the image-forming x-rays that represents anatomy |
| what is the coupling element in DR? | The coupling element is that which transfers the x-ray–generated signal to the collection element. The coupling element may be a lens or fiberoptic assembly, a contact layer, or a-Se. |
| what is the collection element in DR | The collection element may be a photodiode, a charge-coupled device (CCD), or a thin-film transistor (TFT). The photodiode and the CCD are light-sensitive devices that collect light photons |
| what is pixel shift? | Reregister an image to correct for patient motion |
| what is the function of the grid? | The grid is designed to transmit only x-rays whose direction is on a straight line from the x-ray tube target to the image receptor. Scatter radiation is absorbed in the grid material |
| Flat fielding corrects? | the heel effect, creates uniform exposure. Automatic calibration from gain and offset images. |
| what is signal interpolation | pre-processing that averages the defective pixels. |
Created by:
MARCOZING