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Why was AEC originally developed?
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Which AED works by using a gas-filled chamber?
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PRI-II
AEC/APR
| Question | Answer |
|---|---|
| Why was AEC originally developed? | To provide consistency in exposure and images |
| Which AED works by using a gas-filled chamber? | Ionization chamber system |
| Where is the sensor located in an AED with a gas filled chamber? | Between the patient and the IR |
| Where is the sensor located in an AED that converts light to electrical signals? | Behind the IR |
| AED that convert light to electrical signals are considered? | Exit type |
| AED that use gas filled chambers are considered what type of AED? | Entrance type |
| AEC controls what factor? | Time only |
| Which AED works by converting photons to light and then electrical signals? | Phototimers |
| Which AED is considered the first generation device? | Phototimers |
| What would happen if film screen radiography exam required an exposure time faster than the minimum response time of the AEC sensors? | Image would be overexposed, because it would continue to to accept photons until the MRT was reached |
| With film screen radiography which factor would be adjusted to manipulate the contrast? | KVP |
| In digital radiography which factor would be adjusted to manipulate the contrast? | None, KVP does provide change, but it is not consistent. It is mainly controlled by computer-processing |
| What is the appropriate setting for backup time/mAs? | 150%-200% of the expected exposure |
| What is the purpose of backup time/mAs? | Safety feature in the event the equipment malfunctions of the tech does not use the appropriate technical factors |
| When using film screen, what happens when an outside detector is selected for an AP thoracic spine? | The system shuts off prematurely and the image appears underexposed |
| When doing a film screen study using AEC, what will happen to the density in the area of interest when changing from -1 to +1 density? | Density is increased by 50% |
| The typical minimum response time on modern x-ray equipment: | 1 ms |
| What is the most common cause for repeating images done with film screen and AEC: | Patient centering |
| What is the optimal KVP starting point for small extremities? | 60 kVp |
| How does increased kVp affect density (film screen) or exposure (digital imaging)? | There is no change to density |
| What are the basic functions of AEC: | -Radiation is transmitted thru pt. -Exit radiation is converted to electrical signal -Once predetermined amt of radiation is reached exposure is terminated |
| The predetermined amount of radiation reaching the detector is known as being _________ and who sets it? | Calibrated Service personnel |
| Who determines the standards for calibration of machine? | Department |
| The two basic types of AEC systems: | -Phototimers -Ionization chamber |
| Most common type of AEC system used today? | Ionization chamber |
| Most reliable type of AEC system is ________: | Ionization chamber |
| Type of AEC system least prone to failure: | Ionization chamber |
| Phototimer AEC systems use ________? | PMT or PD |
| Which AEC system uses a fluorescent screen and a device that converts the light to electricity? | Phototimers |
| Phototimers are also known as __________ type devices: | Exit |
| _______ detectors are light paddles coated in fluorescent material: | Phototimers or Exit-type devices |
| The fluorescent material used in phototimer systems is comprised of what two materials? | Lucite with phosphors |
| What component of the phototimer (Exit type) system converts light to electrical signals: | Photomultiplier or photodiode |
| Basic function of phototimer systems: | -Radiation interacts with paddles & produces light -Light is transmitted to remote PMT or PD -Light is converted to electric current & then amplified to electrical charge -Timer is tripped and exposure stops - |
| The electrical charges are __________ to the radiation received by light paddles: | Proportional |
| All AEC systems use ________, they are also called what other names: | Detectors Sensors Cells |
| The AEC devices that measure the amount of radiation transmitted: | Sensors or cells |
| Basic function of ionization chamber system: | -Ionization chamber is exposed to exit radiation -Air in chamber is ionized creating an electrical charge -Charge travels along wire to timer circuit -Timer is tripped and exposure stops when calibrated limit is reached |
| Electrical charge is proportional to the radiation received in the ______ _______: | Ion chamber |
| AEC affects what factor reaching the IR: | Quantity |
| kVp controls what three factors: | -Contrast -Penetration -Patient Exposure |
| A decrease mA can be used for what two reasons? | -Increase time -Change FSS |
| When kVp is decreased what will happen to time, mAs & patient exposure? | All increase |
| When kVp increases all other factors ________? | Decrease |
| Adequate kVp must be selected to ______ & _______? | -Penetrate the anatomical part -Produce adequate contrast |
| Increased mA does what to time? | Decreases |
| Increased time ________ mA? | decreases |
| The shortest exposure time a system can produce is known as: | Minimum response time |
| Minimum response time is used for: | -Pediatrics -Motion control |
| If mA is set too high to reach the minimum exposure time how will this affect film & digital? | -Film, will be too dark -Digital, EI #s out of range and pt. dose increased |
| The maximum exposure time allowed during an AEC examination is known as _______: | Backup time |
| Phillips uses density controls of (-) or (+) 1-4, each increment is roughly? | 10%-15% |
| If density controls are being used routinely to achieve adequate exposure, what needs to happen? | Equipment needs to be recalibrated |
| If a machine is calibrated for a 400 speed and a 200 screen speed is used, how will it affect the image and why? | It will take longer for the sensors to fill so the image will be overexposed |
| If more than one sensor/cell is used the measure of radiation and electrical signal is ________: | Averaged |
| Improper patient centering can result in: | Underexposure or overexposure |
| The detector size is set by ______: | Manufacture |
| Over collimation can result in _______ _______: | Prolonged exposure |
| If AEC is calibrated for a slow IR and a fast IR is used the result will be __________: | Overexposure |
| If AEC is calibrated for a fast IR and a slow IR is used the result will be _________: | Underexposure |
| Are APR and AEC the same? | No |
| APR stands for: | Anatomically programmed radiography |
| APR can include both _____ and _________ techniques: | AEC & Manual |
| APR can or can not be alter once selected: | Can be adjusted by tech once a selection has been made |
| _____ is a preprogramed set of factors: | APR |
| APR operates the _____ on all equipment: | Same |
| _____ is controlled by integrated circuit or computer chip that has been programmed with exposure factors for different exposures and projections: | APR |
| ________ are established guidelines used by the radiographer to select standardized manual or AEC exposure factors for each type of radiographic examination: | Exposure technique chart |
| Exposure technique charts are used to provide what two purposes? | Consistent quality images & reduce repeats |
| Factors on the expsoure technique chart must include: | -kVp -mAs (possibly seperated) -Type of IR -Grid -SID -Possibly FSS |
| Standardization of technique charts must be done within _________: | The dept. |
| For technique charts to work efficiently, what two things must occur? | -Equipment must be functioning properly -Proper measurements must be taken |
| Measurements should be taken from which portion of the anatomical structure being examined? | -The midpoint or -The thickest portion |
| What are the two types of technique charts? | -Variable kVp/Fixed mAs -Fixed kVp/Variable mAs |
| Baseline kVp should be increased by ____ for every _____: | -2 -1 cm |
| What are the disadvantages of a variable kVp/fixed mAs technique chart? | -Changing kVp also affect contrast -Less accuracy at extreme ends -Part penetration |
| Variable kVp/Fixed mAs charts are effective with which two types of examinations? | -Pedis -Small extremities |
| At what kVp range is more effective to change kVp rather than mAs? | Lower level |
| Advantages of a fixed kVp/variable mAs technique chart: | -Charts can be completed in patient groups vs individual 1 cm adjustments -every 4-5 cm increase in thickness mAs in adjusted by a factor of two |
| Optimal kVp ranges for the following anatomical parts; Chest, Neck, Abdomen, Sm. extremities, Lg. extremities, shoulder girdle, Hip/pelvis: | Chest=100-130, Neck=75-80, Abdomen=70-80, Small ext.=50-60,Large ext.=65-75,Shoulder girdle=70-80, Hip/pelvis=75-85 |
| _____ ____ are not standardized, they are meant to provide a common range of values for different anatomical areas: | Optimal kVp ranges |
| Advantages to using fixed kVp/variable mAs charts: | -Easier to use -More consistency -Part penetration is mor accurate -More uniform contrast -Increased accuracy at the extreme measurement ends |
| Optimal kVp ranges for cervical, thoracic, lumbar/sacrum, coccyx, sternum/SC joints, Skull/headwork, ribs: | C-spine=70-80, T-spine=75-85, L-spine/Sacrum:AP/Obl=75-80, Lat=85-95, Spot=95-100, Coccyx=75-85, Sternum/SC joints: Obl=60-70, Lat=70-75, Skull/headwork=70-80, Ribs: Above=65-70, below=70-80 |
| Conventional radiography demonstrates ______? | Superimposition of structures |
| Conventional tomography demonstrates _________? | Unsuperimposed structure, by blurring structures above and below a specific plane |
| Main uses of tomography? | Nephrotomography study to visualize kidney stones |
| How does linear tomography work? | The IR and tube move in opposite directions to blur structure above and below the specific plane of interest |
| The principal advantage of tomography is ______? | Improved contrast resolution |
| A larger tomographic angle will result in _______? | More blurring of the objects above and below the fulcrum point |
| A smaller tomographic angle will result in ________? | Less blurring of the objects above and below the fulcrum point |
| The larger the tomo angle the ________ the tomographic slice: | Thinner |
| The tomo angle and the tomo slice have a ________ relationship: | Inverse |
| The smaller the tomo angle the ________ the tomo slice: | Thicker |
| What is zonography? | When tomo angle of less than 10 degrees is used, it is utilized when subject contrst of the object is so low that a thin slice would result in poor image |
| Zonography is used what what type of examinations? | Chest and renal examinations |
Created by:
akhernandez19