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RAD 1333 - Exam 4 Questions and
Correct Answers Updated 2025 Graded A
_____ ______ _______ •is a function of the fluoroscopic unit that maintains the overall appearance of the fluoroscopic image (contrast and brightness) by automatically adjusting the kilovoltage peak (kVp), milliamperage (mA), or both. - ANS• Automatic Brightness Control (ABC) •ABC is slightly slow in its response to changes in patient tissue thickness and tissue density. This is visible as a lag in the image brightness on the monitor as the tower is moved over the patient. ______ ______ - refers to the length of each pulse (how long exposure lasts per pulse) - ANSPulse width
- Generally, less than 6 ms for pediatrics and less than 10 ms for adults. ______ _______ is the product of flux gain and minification gain which results in a brighter image on the output phosphor. - ANSbrightness gain _______ ______ - Accelerating electrons increases light intensities at output phosphor. - ANSflux gain _______ _______ refers to how many pulses occur per second of operation - ANSpulse rate
- Generally, 1 pulse/second to 30 pulses/second
________ _______ - Reduction in size of output phosphor image compared with that of input phosphor image increases light intensity. - ANSminification gain ________ ________ a feature that uses pulsed beam technology to reduce radiation output necessary for the image & patient radiation dose - ANSpulsed fluoroscopy __________ is the kVp value that is high enough to ensure penetration of the part but not too high to diminish radiographic contrast. - ANSOptimal kVp ___________ disease of condition that increases the absorption characteristics of the part making it more difficult to penetrate. - ANSAdditive disease
- Pages disease where the spine breaks down then adds on calcification (ankylosing spondylitis?) _____________ diseases or condition that decreases the absorption characteristics of the part making it less difficult to penetrate. - ANSdestructive diseases
- emphysema
- A typical fluoroscopy systems have spatial resolution capabilities of ____ - ____ lp/mm - ANS4 - 6 lp/mm
- Visible light emitted from the output phosphor is converted to an electronic (video) signal by the ___ ________. What two devises are commonly used today to accomplish this? - ANSTV camera Camera tubes (vidicon/plumbicon) Charge-coupled device (CCD) •________ _______ _______ is a light sensitive semiconducting device that generates an electrical charge when stimulate by light and stores this charge in a capacitor. - ANSThe Charge-coupled device (CCD) •Although the term brightness gain is still used, it is now more common to express increase in brightness with the term __________ _________ - ANSconversion factor. •The _______ monitor is made up of several layers; the heart of which is the liquid crystal layer sandwiched between polarizing layers. - ANSLCD or liquid crystal display •The photodetector is ___________ _________, which is liquid and can be painted onto a substrate, is the material that makes flat-panel detectors possible. - ANSamorphous silicon
- Gives the ability to convert light to an electrical signal
A critical component in technique chart development is to determine the minimal _______ value that adequately penetrates the anatomic part being radiographed. - ANSkVp Abdominal x-ray when the patient has excessive gas, the exposure may be terminated prematurely Abdominal x-ray when the patient has had some type of positive contrast or the presence of a metallic prosthesis may cause excessive exposure. - ANSSometimes the best solution is a manual technique!!! So we should not be using AEC on a sunrise that has had a total knee replacement? aNOTHER critical feature when using AEC is the correct positioning with the correct detector - ANSyou must position a lat. spine over the center of the bucky because you are using the center cell for AEC If the center detector is selected for a PA chest radiograph, the bone will receive sufficient exposure but the lungs (area of interest) will be overexposed (thats why you select the two side detectors)
- this is not as important in IR as it was in Film-screen because IR can adjust the exposure error are pre-establishes guidelines used by the radiographer to select standardized manual or AEC exposure factors for each type of radiographic examination. - ANSAnatomically programmed anatomy
Increasing OID - Exposure time increased Excessive collimation - Exposure time increased Increased density control - Exposure time increased - ANS Dose Monitoring - The cumulative or total air kerma can be monitored during fluoroscopic procedures - ANSDose-area product (DAP) or kerma area product (KAP) - measures the exposure in air & the area of the x-ray beam at the entrance level of the patient (DAP meter is embedded in collimator - it knows the size of FOV you used when you made the exposure). Fixed kVp-Variable mAs Because x-rays are attenuated exponentially, a general guideline is that for every 4-5 cm change in part thickness, the mAs should be adjusted by a factor of 2. Either double or half your mAs - ANS how can a different kind of IR effect AEC? - ANSEach AEC system is calibrated to a specific type of IR. Different types of IRs cannot be interchanged. how can Improper collimation effect AEC? - ANSInsufficient collimation - may result in excessive scatter causing exposure to terminate too quickly Excessive collimation - may result in too long an exposure
How do AEC devices determine when to shut off exposure? - ANSRadiation is transmitted through the patient > it is converted into an electrical signal > triggering the termination of exposure. How does fluor differ from diagnostic? - ANS• Fluoroscopy differs from radiographic imaging by its use of continuous or pulsed beam of x-rays to create images of moving internal structures that can be viewed on a monitor. If the radiographer wants to decrease the exposure time for a particular exam, he/she may do so by increasing the mA - ANSincreasing the mA - decreases the exposure time Decreasing the mA - increases the exposure time Image intensification is a process in which: - ANSThe exit radiation from the anatomic area of interest is converted to visible light by the input phosphor (converts X-ray to light) The light intensities are equal to the intensities of the exit radiation and are converted to electrons by the photocathode. The electrons are focused and accelerated toward the anode (due to the potential difference within the tube) by the electrostatic focusing lenses. The electrons strike the output phosphor releasing visible light that is converted to an electronic (video) signal by the TV camera for transmission to the viewing monitor.
Refers to the shortest exposure time that the system can produce. This could pose a problem with pediatric or uncooperative patients.
- With most modern AEC systems, the minimum response time is ... - ANS1 ms Most modern systems have a magnification capacity of ______ - _____ x the input diameter - ANS1.5 to 4 note card for flux gain calculation - ANS pediatric patients Small size may require a reduction in exposure (kVp & mAs). Quicker exposure times may be necessary (manual techniques). Note - Exposure factors used for the adult skull can be used for pediatric patients age ____ _________ because the skull is completely developed at this point. - ANS6 years and older recommended millimeters of lead for ... lead apron: protective curtain: bucky slot covers: - ANS5 mm 2.5mm 2.5mm Refers to the maximum length of time the x-ray exposure will continue when using an AEC system. - ANSBackup time
The backup time acts as a safety mechanism when an AEC system fails or the equipment is not used properly we want a backup time because it could be set to the wall Bucky but youre using the table so it makes a super long exposure. We do not want this Setting the backup time at ______-______ of the expected exposure time is appropriate. - ANS150% - 200% Backup time set too short - exposure prematurely terminated Backup time set too long - patient receives unnecessary radiation should density controls be used on a regular basis? - ANSNo. Why>>? Technique charts can vary greatly in terms of their design, but regardless of the type, some common characteristics are included: - ANSPrimary exposure factors - kVp, mA, s Common accessory devices used - IR, TT, grid/no grid or grid ratio, AEC (if Bucky in use), focal spot size, SID, etc. The actual amount of mAs used for an image is displayed immediately after the exposure (sometimes only for a few seconds). - ANSmAs readout The radiographer should take note of this information:
- It can give the radiographer manual technique ideas
- This light is transmitted to remote photomultiplier tubes or photodiodes that convert this light into electricity.
- The timer is tripped, and the radiographic exposure is terminated when a sufficiently large charge has been received.
- Phototimer AEC devices are considered as exit-type devices. Why? - ANSBecause their detectors are positioned behind the IR Therefore, radiation must exit the IR before it is measured by the detectors. The CCD has some advantages over the camera tubes: - ANS- They are more sensitive to a wider range of light intensities
- They show no geometric distortion of the fluoroscopic display image.
- They are smaller in size and works well in digital imaging. The difference in AEC systems lies in the type of device that is used to convert radiation into electricity. - ANStwo types: Phototimers - 1st generation of AEC, uncommon today Ionization chambers - Most AEC systems used today are this type - You may hear photo cells There are several advantages to using a Flat-panel detector (FPD) as opposed to an image intensifier: - ANSThey produce less electronic noise (due to less electrical components in the system)
- Signal to noise ratio increase means an increase in spatial resolution They replace spot-film and other recording devices. They provide a rectangular FOV, better contrast resolution, higher spatial resolution, higher DQE, wider dynamic range, and post-processing options. They do not produce the pincushion effect, vignetting, or any other artifacts that are associated with the II. They do all of this with as much as 50% lower radiation dose to the patient!!! this concept states that different parts of the same size can be radiographed by use of the same exposure factors, provided that the minimal kVp value needed to penetrate the part is used in each case. Knee is 10 cm, if a shoulder is also 10cm, you should be able to use the same technique - ANScomparative anatomy this piece of equipment can provide both static and dynamic images along with two- and three-dimensional images - ANSO-arm Two Forms of flat-panel detectors may be used for fluoroscopic applications: - ANSCesium iodide amorphous silicon indirect-capture detector Amorphous selenium direct-capture detector
Greater assurance of part penetration what are advanctages to Variable kVp-Fixed mAs technique chart - ANSAdvantages Easy to construct and simple to use At low kVp levels, small changes in kVp may be more effective than changing mAs what are disadvantages to Variable kVp-Fixed mAs technique chart - ANSDisadvantages Changing kVp can also affect the contrast Less accurate for part thickness extremes, adequate penetration is not assured what are examples negative contrast agents - ANSair and carbon dioxide
- decrease the attenuation of the x-ray beam
- transmit more radiation through the anatomic part.
- produce less brightness than adjacent tissues.
- Does not require an increase exposure factors
- Maybe an intussusception occurred on a ped, they may just use air contrast enema what are examples Positive contrast agents - ANSbarium and iodine
- high atomic number
- absorb more x-rays (increase attenuation)
- produce more brightness than adjacent tissues.
- Requires a change in exposure factors what are the parts of a phototimer?
Phototimers use a fluorescent (light-producing) screen and a device that converts light into electricity. - ANSPhotomultiplier tube - electronic device that converts visible light energy into electrical energy Photodiode - a solid-state device that converts visible light energy into electrical energy What does automatic exposure control determine? - ANSAEC device determines the exposure time (NOT THE MA) what does raising the kVp do to the AEC? What about lowering the kVp? - ANShigher kVp - shorter exposure time needed to reach predetermined exposure for AEC device Lower kVp - longer exposure time needed to reach the predetermined exposure for AEC device What is AEC? - ANSa system used to consistently control the amount of radiation reaching the image receptor by terminating the length of exposure. What is an image intensifier tube made of? - ANSGlass envelope: houses the parts & allows a vacuum Input phosphor: (made of Cesium iodide) converts exit radiation to visible light.
filtration, and exposure pulse width. - ANSAutomatic exposure rate control (AERC what occurs when insufficient information is present to create the image - ANSNoise This is ultimately due to insufficient quantity of x-rays Although other factors may contribute to noise, the solution generally comes back to increasing the mA (quantity of radiation). what two things result in a Pincushion appearance (distortion) of the image in fluoroscopy? - ANSInaccurate focusing of the e- from the periphery of the photocathode The curved shape of the photocathode. When it becomes necessary to compensate for an additive or destructive disease or condition, it is fundamentally correct to make changes in the kVp since kVp affects the penetrating ability of the primary beam. How much should we change the kVp - ANSA minimum change of 15% in kVp is recommended. When using mobile c-arm fluoro units SSD should be no less than _________ - ANS12in (30cm) When using stationary fluoro units the source-to-skin distance (SSD) should be no less than _______ - ANS15in (38cm)
- Its a set 15 inches from the bottom of the table to the patient why is detector selection critical when performing an exam with AEC? - ANSExample: If you have the table bucky selected when performing a chest the table detectors are waiting to receive the exposure and will not cut the exposure to the chest unit off because the exposure is not directed to the correct detector. Therefore, the backup timer will be reached and the patient will receive excessive exposure..
