Exposure MRT 122 Final
A digital image that displays a "gray" appearance would indicate what technical problem to the radiographer? 1. excessive penetration 2. equipment failure 3. underexposure 4. overexposure
1 and 4
The lead aprons worn by radiographers/radiologists must have what minimum level of lead equivalency if the kVp level is above 100 kVp?
0.5mm Pb/Eq
When necessary, to control patient movement, you can decrease your exposure time by one‑half if you increase your mA by: (to maintain equal IR exposure)
100%
The standard image matrix size for digital fluoroscopy is:
1024 x 1024
Adjust the technique from 20 mAs @ 80 kVp (3-phase, 6 pulse) to the appropriate technique when using single-phase equipment.
40 mAs 86kVp
A patient comes in for a right knee x‑ray in a fiberglass cast. The patient's left knee measures 13cm. Because of the size, you also decide to use a grid cassette (8:1 ratio). Using the chart below, what technical factors you would use? Procedure: KNEE Projection/Position: AP, obl, lat. IR Placement: tabletop Distance: 45" kVp: 60 cm\\mAs\\mA\\sec. 6‑7\\3.3\\100\\.033 8‑9\\5\\10\\.05 10‑11\\6.6\\100\\.067 12‑13\\10\\150\\.067
40 mAs @ 65kVp
Identify the standard SIDs that should be used for mobile radiography.
40" 56" 72"
T or F: Almost all of the heat generated in an x-ray tube occurs at the filament.
False
T or F: Federal Guidelines mandate that the fluoroscopic exposure cannot exceed 10 mGy/minute.
False
T or F: It is safe to use the same charts for single-phase and three-phase x-ray equipment.
False
T or F: Overexposed digital image display quantum mottle
False
T or F: Positioning problems can be fixed post processing
False
T or F: The Anode Cooling Chart calculates cooling for radiographic imaging exams and the Housing Cooling Chart calculates cooling for fluoroscopic exams.
False
T or F: The Radiographic Rating chart reports the amount of time that should elapse between exposures.
False
T or F: The electrostatic lenses within the Image Intensifier reduce static during fluoroscopy.
False
T or F: The image distributor (beam splitting mirror) is utilized with non-digital fluoroscopy equipment.
False
T or F: The job of the TFT is to collect the electronic charge and send it to the ABC.
False
T or F: The percentage of scattered x‑ray photons will be greater when selecting 50 kVp than when selecting 100 kVp.
False
T or F: The voltage (kV) selected on the control panel determines the number of waves per unit of time.
False
T or F: Vignetting results in more electrons striking the center of the input phosphor.
False
T or F: When using an Image Intensifier with a large input phosphor, the resulting fluoroscopic image will have increased detail.
False
T or F: When using the Radiographic Rating Chart, the curved lines indicate mAs values.
False
T or F: With digital fluoroscopy, a CCD device absorbs x-ray photons and converts the energy to light photons.
False
T or F: With digital fluoroscopy, the ADC converts the light intensity from the output phosphor to a digital value.
False
T or F: X‑rays produced by Compton Interaction are desirable since those x‑rays increase the number of photons reaching the IR.
False
T or F: During non-digital fluoroscopy, the film camera utilizes 90% of the light given off from the output phosphor for film exposure.
True
T or F: Flux gain is the effect of the output phosphor conversion efficiency when changing the electron energy to an increased number of light photons.
True
T or F: If a phosphor material absorbs more x-ray photons, then the Quantum Detection Efficiency (QDE) increases.
True
T or F: In an Image Intensifier, the reduction in the image size at the output phosphor results in increased brightness.
True
T or F: Referring to the Radiographic Rating Chart, if the intersection of the exposure time and kVp falls below the mA curve, the technique is considered safe to use.
True
T or F: Regulations specify that the minimal source-to-object distance for mobile fluoroscopy equipment is 12 inches.
True
T or F: The curves on the anode cooling chart labeled heat units per second are used to calculate heat accumulation during fluoroscopic exams.
True
T or F: The half value layer is the thickness of an absorbing material required to reduce the number of photons in the beam to half.
True
T or F: The output phosphor absorbs electron energy and emits light photons.
True
T or F: The percentage of x‑ray photons attenuated is greater when imaging a 30cm patient's abdomen as compared to a 20cm patient's abdomen.
True
T or F: The photocathode releases electrons in a process known as photoemission.
True
T or F: The speed of the rotor/anode influences the heat capacity of the x-ray tube.
True
T or F: Use of a CCD results in minimal screen lag.
True
T or F: kVp controls subject contrast
True
What is the purpose of the ADC?
convert electronic charge to numerical (digital) value
The job of the ADC in digital fluoroscopy is:
convert electronic signal to digital value
What is the function of the photomultiplier tube?
convert light photons to an electronic charge
A rapid increase in the temperature of the anode will result in:
cracking of the anode
The photosensitive material that is utilized in a charge-coupled device is:
crystalized silicon
A non-scintillator based flat panel detector:
does not use a material to convert x-ray photons into light
The purpose of the voltage across the image intensifier is to:
draw the electrons from the photocathode & propel them toward the output phosphor
In digital radiography, the bit system is used to describe the:
dynamic range
For DR imaging, the charged electrodes under the active layer collects ______________ which are used to determine the charge sent to the ADC.
electrons
The "anatomical image pattern" emitted by the photocathode is formed by:
electrons
The electrons flowing toward the output phosphor are concentrated and accelerated by which part of the Image Intensifier?
electrostatic lenses
In CR imaging, the phosphor is combined with an activator "europium" to provide:
energy retention for future processing
A digital image that appears "white" in the thickest region would indicate what technical problem to the radiographer?
excessively low kVp
The thickness of the "in focus" layer in tomography is determined by the:
exposure arc
What are "phantom" images that might be seen on tomographic images?
false images that don't correspond with existing structures
Holding the rotor switch unnecessarily will eventually result in:
filament break
The most common cause of x-ray tube failure is:
filament break
The total brightness gain of an Image Intensifier is determined by:
flux gain x minification gain
The plane that coincides with the fulcrum is called the:
focal plane
Current flow always moves in a direction :
from + to -
A large image matrix size for digital radiography produces:
greater resolution
As a general rule, grids should be used when radiographing body parts:
greater than 10cm
The most accurate method of converting the x‑ray technique when using grids, is to change the technical factors based on:
grid ratio
Identify the factors that increase image contrast. Select all that apply.
grid ratio increase, closer collimation
Scatter radiation decreases the overall radiographic contrast. Of all the answers listed below, indicate which group of factors will give the greatest reduction in scatter radiation AND retain the best radiographic detail.
grids, beam‑limiting devices, decreased OID, optimal kVp
How does the number of pixels correspond to the image resolution?
h # of pixels = h resolution
List 4 factors that will contribute to low contrast on the resulting digital image.
h kVp Incorrect histogram No grid (if using above 80 kVp) Insufficient coning Thicker part size Increased tissue density Extreme over-exposure (h mAs)
How would a decrease in the dynamic range be displayed?
high contrast
When using CR, what would be the result if a "KUB" radiographic exposure were processed with the "hand" LUT selected?
high contrast
Subject density refers to:
how patient tissues determine the resulting image darkness
The fluoroscopic tube lead shutters should be adjusted to extend only to the size of the:
input phosphor
Identify the factors that increase IR exposure. Select all that apply.
kVp increase, mA increase, exposure time increase
The amount of scatter radiation increases when the:
kilovoltage increases
Overexposed digital images will demonstrate:
low contrast
When using CR, what would be the result if a "knee" radiographic exposure were processed with the "chest" algorithm selected?
low contrast
How does the input phosphor size affect image detail?
low input phosphor size high image detail
Compare the following 2 images: Radiographic image A is performed using 60 kVp and 10 mAs. Radiographic image B (of the same anatomy) is performed using 70 kVp and 5 mAs. When comparing the 2 images, Radiographic image B will demonstrate:
lower image contrast
The ability of the anode to store heat is measured in terms of heat units. Which one of the following formulas would be used to calculate the number of heat units produced in three-phase/12-pulse fully rectified x-ray equipment?
mA x seconds x kVp x 1.40
Sharpness of detail on a radiograph is dependent on all of the following except: size of the focal spot SID immobilization OID mAs
mAs
The film camera records the image given off by which of the following parts of the Image Intensifier?
output phosphor
The function of aperture diaphragms, cones and collimators is to: (indicate all that apply)
reduce scattered radiation to IR, reduce patient dose
When using a wave pattern to depict electrical current, which of the following is considered a true statement?
the distance from one peak to the next is the wavelength
As the wavelength of an x-ray photon increases, how do the other photon characteristics change? (Indicate all that apply)
the energy decreases, and the frequency decreases
The basic concept of linear tomography is that:
the tube & IR move in opposite directions in relation to the pivot point
Three-phase equipment is more efficient than single-phase equipment because:
the voltage never drops to zero
If the computer assigns a low numerical value to a pixel, that would be consistent with which of the following? Indicate all that apply.
thicker anatomical part, low keV, low IR exposure
The "window width" feature controls which characteristic of the digital image?
window width adjusts the gray scale of an image.
The PBL device controls:
x-ray field size
Three-phase/12-pulse current produces what amount of voltage ripple?
4%
How many heat units are produced by the technique stated below? 105 kVp, 700 mA, 0.1 sec., 3-phase/12 pulse
10,290 HU
T or F: Alternating current operates of a frequency of 60 Hertz.
True
T or F: Collimation of the x‑ray beam will enhance the image sharpness.
True
DR DIRECT DIGITAL IMAGING Explain step-by-step how the direct digital image is produced (include steps from exposure g to array g to image).
-Exit radiation strikes array (amorphous selenium) -X-rays ionize the amorphous selenium atoms ejecting free electrons -The free electrons are collected on the + electrodes on the TFT -The TFT sends the electronic charge to the ADC -The ADC converts the charge to a digital signal -The digital signal is displayed on the computer screen
CR DIGITAL IMAGING When the imaging plate is placed in the reader/processor and extracted from the cassette, explain step-by-step how the retained energy (latent information) is released and how the CR plate returns to "neutral" status.
-the plate is placed into the reader -the reader then scans each pixel which releases the stored energy -after each pixel is assigned a numerical value -the image then is reconfigured by the computer -finally it goes through by being erased by being exposed to excessive light so the electrons are dispersed
During non-digital image intensified fluoroscopy, the milliamperage range is:
.5 - 5 mA
How much lead equivalency must radiographer's lead gloves have if his/her hands are placed in the primary beam?
0.25mm Pb/Eq
The lead drape that may be attached to the image intensifier must have what minimum level of lead equivalency?
0.25mm Pb/Eq
When selecting the small filament, the effective focal spot size would be:
0.3 - 1.0 mm
The mirror within the collimator provides how much aluminum equivalency filtration to the x-ray beam?
1.0mm Al/Eq
A hand is x-rayed on the DR bucky at a 45" SID. The hand is 4" from the DR plate. What is the magnification factor?
1.1
The SID is 100cm and the object being radiographed is placed 20cm from the IR. What is the magnification factor?
1.25
When performing dry plaster cast radiography, the kVp should be increased _____ over the kilovoltage used for non‑casted anatomy.
10 kVp
A portable AP projection of the chest is ordered on a patient in ICU. The patient has been bedridden for a period of time, and there is suspected fluid in the lungs. To visualize the fluid levels, you place the patient in the semi-erect position. The previous AP supine projection used 3 mAs @ 80 kVp, 40" SID. Using the "Rule of Thumb" method, what distance and technique should be used with the patient in the semi-erect position?
12 mAs @ 72" SID
A series of 6 x-ray exposures are made, each at 70 kVp, 300 mA, and 0.1 sec. using single-phase full-wave rectified equipment. What is the total heat unit input to the x-ray tube anode?
12,600 HU
To maintain an overall equal image density, a technique of 250 mAs @ 78 kVp should be converted to ________ mAs @ 90 kVp.
125 mAs
Three-phase/6-pulse current produces a waveform that exhibits what percentage of voltage ripple?
13% ripple
An average adult technique for an AP abdomen is 20 mAs, 80 kVp. What technique could be used for an eight‑year old child?
15 mAs, 75 kVp
A patient presents himself in the Radiology Dept. for skull radiographs. The patient has indicated to you that he cannot move, so you decide to perform a shoot-through lateral of the skull (rather than turn the patient). 20mAs would be used for a routine lateral on‑bucky (12:1), but you will be using a grid cassette (8:1) for the shoot‑through lateral. What mAs should be used?
16 mAs
Using the Agfa CR System, properly exposed imaging plates should produce an overall "Lgm" value of:
2.0 - 2.2
A polyp is seen in the frontal sinuses of a patient. Radiographically, the polyp measures 2.5 cm from side-to-side. Using a magnification factor of 1.2, what is the actual size of the polyp?
2.08cm
What is the amount of lead (equivalency) that surrounds the Image Intensifier and acts as a protection for the radiographer and radiologist?
2.0mm Pb/Eq
Which of the following materials is used in the DR active layer? Thin film transistor Barium fluorohalide Calcium Tungstate Amorphous Selenium
4 only
An AP projection of the knee is ordered on a patient in traction. The patient measures 10cm in the front-to-back direction. A patient of this size would typically require 10 mAs @ 60 kVp, 40" SID. Because the traction bar interferes with the placement of the tube, the SID is set at 20". How would you adjust the mAs?
2.5 mAs
What is the minimum filtration level required by law for all fluoroscopy tubes?
2.5mm Al/Eq
An AP projection of the thoracic spine is done using 10 mAs @ 80 kVp, 40" SID. The resulting image shows an appropriate overall density, but the anatomy appears overpenetrated. What technique that would produce a more diagnostic image using optimum kVp.
20 mAs @ 70kVp
An AP abdomen is performed using 20 mAs, 80 kVp, 40" SID. The resultant image demonstrates a light region at the thickest part of the abdomen along with insufficient penetration. Indicate what factors you would use for the repeated radiograph.
20 mAs @ 86 kVp
When attempting to maintain equal image density, an increase in kilovoltage from 80 kVp to 86 kVp would require a reduction in mAs of:
25%
Which kVp level should be selected for pediatric fluoroscopic procedures?
25% kVp reduction from adult technique
When performing a fluoroscopic procedure, what is the potential difference that is maintained across an Image Intensifier between the photocathode and the anode?
25,000 volts
An erect A.P. chest x‑ray is performed using 72"SID. The patient measures 20 inches from front‑to‑back; the heart is 4 inches from the anterior chest wall. The IR is directly behind the patient's back (no measurable distance). What percentage is the patient's heart magnified over the patient's true heart size?
29%
An average adult technique for an AP elbow is 4 mAs, 60 kVp. What technique could be used for a 1‑year old child?
2mAs, 55kVp
The speed of light is:
3 x 10^10 cm/sec
A patient is admitted to ICU and a AP projection of the chest is ordered. Due to the patient's condition, you must perform the exam with the patient recumbent using a 40" SID. If 10mAs @ 80kVp is an appropriate technique to be used at 72", what would be needed @ 40" SID?
3.1 @ 80
A lateral cervical spine technique of 16 mAs, 70 kVp produces optimum image density with 3-phase/12-pulse equipment. Based on this information, which factors should be used with single-phase equipment?
32 mAs, 76 kVp
A satisfactory image of the abdomen is made using 14"x17" collimation @ 25 mAs. If 11"x14" collimation is required to better demonstrate the kidney area, what mAs should be used?
32.5 mAs
Three-phase current with full-wave rectification results in:
360 pulses per second
The P.A. Axial projection of the sigmoid colon (done as part of a Barium Enema Series) requires the x-ray tube to be angled 35o caudad with the IR in the bucky. To maintain an overall 45" SID, the new vertical distance on the overhead indicator should read:
38"
A radiographic image is taken using 30 mAs @ 60 kVp. The image is correctly penetrated but shows a slight decrease in image density. How much mAs should be used for the repeat exposure to see a noticeable density increase?
39 mAs
A specific x-ray tube has a heat storage capacity of 200,000 HU. With three-phase/12-pulse equipment, how many consecutive exposures can be made in rapid sequence using 200 mA, 2 sec, 80 kVp before exceeding the capacity of the tube?
4
Using the "Rule of Thumb" Method, explain how the exposure factors should be adjusted when changing the SID for mobile radiography.
40" SID --> 56" SID: double mAs 56" SID --> 72" SID: double mAs 40" SID --> 72" SID: quadruple mAs
An AP axial projection of the clavicle requires a 25o cephalad angle with the IR in the bucky. To maintain an overall 45" SID, the new vertical distance on the overhead indicator should read:
41"
The lateral projection of the thoracic spine utilizes a 15o cephalad angulation with the IR placed in the bucky tray. To maintain an overall 45" SID, the new vertical distance on the overhead indicator should read:
44"
An A.P. abdomen survey film is taken of a patient who has ingested 6 iodine tablets. The technique used is 32mAs, 70kVp, coned to a 14"x17" film size. If a smaller film (10"x12") is requested of the right upper quadrant to better see the gallbladder, what logical technique should be used?
45 mAs, 70kVp
A chest radiographic image is taken using 12 mAs, 80 kVp, 36" SID. To produce an accurate image of the heart & lung without magnification, a repeat radiographic image is ordered using 72" SID. How would you adjust the technique?
48 mAs
If a technique of 100 mAs is appropriate for single-phase equipment, what mAs should be used with three-phase/12-pulse equipment?
50 mAs
What is the total heat generated during the following procedure: Five skull exposures are performed in a sequence using three-phase/6-pulse equipment with a technique of 60 kVp, 120 mAs.
50,400 HU
Of the following sets of exposure factors, which one will produce the highest image contrast? 80kVp 100mAs 40"SID 8:1 grid 50kVp 100mAs 40"SID 12:1 grid 70kVp 100mAs 40"SID 8:1 grid 90kVp 100mAs 40"SID 5:1 grid
50kVp 100mAs 40"SID 12:1 grid
TV monitors used as part of a fluoroscopic set-up typically utilize:
525-line display
What is the optimum kVp-level for the PA projection of the hand?
55kVp
What ratio grids are preferred for mobile radiography?
5:1 or 6:1
In accordance with Federal Guidelines, what are the length regulations for the exposure cord on a mobile unit?
6 feet
Single-phase current with half-wave rectification results in:
60 pulses per second
What is the optimum kVp-level for the AP projection of the knee?
60kVp
A radiographic image is taken using 30 mAs @ 60 kVp. The image shows a slight decrease in image density AND is slightly underpenetrated. How much kVp should be used for the repeat exposure to see a noticeable penetration and density increase?
65 kVp
To maintain an overall equal image density, a technique of 100 mA, 0.5 seconds @ 80 kVp should be converted to 50 mA, 2 second @ _________ kVp.
68 kVp
A technique for an ankle radiograph for a patient measuring 7cm would be 6 mAs, 60 kVp. What would you use if the patient had their ankle casted in wet plaster?
6mAs, 75kVp
When performing tomography on anatomy that exhibits low subject contrast, which of the following arcs (angles) would be appropriate?
7 degrees
How many heat units are produced by the technique stated below? 100 kVp, 150 mA, 0.5 sec., single-phase/2 pulse
7,500 HU
If a patient's kidney measures 13cm (from side‑to‑side) on the x‑ray image with a magnification factor of 1.67, what is the patient's actual kidney size (from side‑to‑side)?
7.78
What is the optimum kVp-level for the lateral projection of the thoracic spine?
70kVp
Of the following sets of exposure factors, which one has the greatest IR exposure? 70kVp 100mAs 36" SID 70kVp 200mAs 32" SID 75kVp 50mAs 40" SID 80kVp 25mAs 40" SID
70kVp 200mAs 32" SID
What is the optimum kVp-level for the Swimmer's Method of the thoracic‑spine?
75-80kVp
You will be x‑raying a patient with a shoulder that measures 12cm. The technique chart indicates that 8 mAs @ 70 kVp should be used for a shoulder image on a patient measuring 14cm. If 14cm is the lowest measurement on the chart, what technique would you use?
8 @ 66
An exposure arc that could be used for zonographic imaging would be:
8 degrees
Total brightness gain in image intensification fluoroscopy ranges from:
8,000 - 25,000
What is the optimum kVp-level for the AP projection of the lumbar spine?
80kVp
What is the optimum kVp-level for the AP projection of the abdomen (KUB)?
85kVp
The exposure arc is the angle between the:
CR position at the start of the exposure and the end of the exposure
The flat panel detector that uses light, a mirror and a focusing lens is the:
Charge coupled device (CCD)
What does DQE stand for, and what does it describe?
Detective quantum efficiency (DQE) - a measure of the sensitivity and accuracy by which the image receptor converts the incoming data to the output viewing device
What does LUT stand for?
Look Up Table
A satisfactory radiograph of the shoulder is made using the following factors: 70 kVp 40 mAs 40"SID 14"x17" collimation Without changing the SID or collimation, decrease the mAs to 20 mAs, and increase the kVp to 100 kVp How will this technique change affect the overall IR EXPOSURE?
IR exposure will increase
A satisfactory radiograph of the shoulder is made using the following factors: 70 kVp 40 mAs 40"SID 14"x17" collimation Without changing the kVp, mAs or collimation, decrease the SID 36". How will this technique change affect the overall IR EXPOSURE?
IR exposure will increase
A satisfactory radiograph of the shoulder is made using the following factors: 70 kVp 40 mAs 40"SID 14"x17" collimation Without changing the SID or collimation, decrease the kVp to 59 kVp, and increase the mAs to 80 mAs. How will this technique change affect the overall IR EXPOSURE?
IR exposure will not change
A satisfactory radiograph of the shoulder is made using the following factors: 70 kVp 40 mAs 40"SID 14"x17" collimation Without changing the kVp, reduce the collimated field size to 8"x10", and increased the mAs to 60 mAs. How will this technique change affect the overall IR EXPOSURE?
IR exposure will not change
Using the Fugi CR System, an image with a "S" value below 75 would be:
Overexposed
What 2 steps must be taken to adequately visualize air-fluid levels on a portable chest image?
Place patient erect or semi-erect for at least 5 minutes Keep beam in horizontal alignment
Compare the following 2 images: Radiograph A is taken of shoulder anatomy using 20 mAs @ 65 kVp. Radiograph B is taken of the same shoulder anatomy using 10 mAs @ 70 kVp. Indicate three of the following statements that are true.
Radiograph A demonstrates greater IR exposure Radiograph B demonstrates longer scale of contrast Radiograph A demonstrates higher contrast
Which of the following x-ray tube charts is dependent on the speed of the anode rotation?
Radiographic rating chart
Using the Fugi CR System, an image with a "S" value above 600 would be:
Underexposed
Explain step-by-step how the "latent image" is formed after the exit radiation strikes the imaging plate.
X-ray photon energy strikes the phosphor crystals, causing electrons within the crystals to move from their normal orbital location to a higher energy level. Some, but not all, of the electrons raised to a higher energy level spontaneously return to their resting energy state by emitting energy as light. The electrons that remain in their higher energy state form the latent image in the receptor.
If the rotor bearings fail and an exposure is then taken, the result will be:
a bullet hole melt on the anode
Size distortion increases with:
a decrease in source‑image receptor distance
A routine IVU technique is 50 mAs @ 70 kVp for the static image of the kidney area. Using this information, answer the following 2 questions. a) How much mAs should be used for a wide-angle tomographic image of the kidney area? b) Based on your answer to 2a, indicate the specific mA that would be necessary if the wide-angle tomographic exposure requires a 5-second exposure time?
a. 65mAs b. 65/5 = 13 ... 13mA
A tomographic procedure of the pelvis is requested to r/o fracture of the body of the ilium. the patient' overall pelvic measurement is 24cm front-to-back the suspect area is approximately 6cm from the anterior skin surface the iliac body is approximately 5cm from front-to-back the procedure will be done with the patient in the supine position a 2cm pad will be placed on the table surface for patient comfort a. At what level should the fulcrum be set to visualize the body of the ilium with the patient supine? b. Suggest an appropriate arc for the subject contrast of this part? c. List at least 2 other "section levels" that would also image the ilium?
a. fulcrum should be set to 20cm b. an appropriate arc would be have to be above 10 degrees for bony structures. lets say 15 degrees c. 2 other section levels including 20cm would be 18cm and 22cm
The ABC device:
adjusts the exposure factors automatically
X-ray interaction with which of the following tissues would result in the least amount of scatter?
air-filled structures
Identify 4 radiation safety measures (for yourself & others) that should be used during mobile radiography.
always wear full lead on yourself including nursing staff that needs to be in the room visitors and other staff that are not needed need to leave the room take the exposure cord to the maximum distance shield patient, and other patients that can not leave the room
Which of the following is necessary for a DR exam? Analog/digital converter Radiation detector Photostimulable phosphor imaging plate Laser scanner
analog/digital converter and radiation detector
Which of the following factors listed below play a part in disproportional magnification? (indicate all that apply)
angulation of the part, and angulation of the tube
Size distortion occurs because different body parts are situated:
at various OIDs within the body part
The x-ray/patient interaction that results in x‑ray photons that give the image a gray, foggy appearance is called:
compton interaction
Which type of phosphor is utilized in the photostimulable imaging plates for CR?
barium fluorohalide bromide
How could you best control the voluntary motion of a patient?
better communication
X-ray interaction with which of the following tissues would result in the least amount of x-ray transmission?
bone
X-ray interaction with which of the following tissues would result in a moderate amount of scatter? (indicate all that apply)
bone, muscle, and fat
The image intensifier has the ability to increase the amount of light given off at the output phosphor. This effect is called:
brightness gain
Which of the following will, in general, result in more patient radiation exposure to a given anatomical part during a fluoroscopy exam?
cassette spot film
The Image Intensifier's input phosphor is generally composed of:
cesium iodide
Rectification is a process which:
changes alternating current to pulsating direct current
If the small focal spot of the x‑ray tube is used instead of the large focal spot, the penumbra will:
decrease
For an exposure of the pediatric preschool group (2 yrs. to 6 yrs.), how much should the mAs be changed as compared to an average adult technique?
decreased 25%
Quantum mottle dramatically affects image detail. This phenomenon is caused by:
decreased mAs
Magnification of a radiographic image can be reduced by the use of a/an:
decreased object-image receptor distance
Geometric unsharpness can be controlled by:
decreasing the OID
In order to maintain equal density on a repeat radiographic image, an increase of 15% of the original kVp can be compensated for by:
decreasing the mAs by one‑half
"Window leveling" controls which characteristic of the digital image?
density/brightness
A satisfactory radiograph of the shoulder is made using the following factors: 70 kVp 40 mAs 40"SID 14"x17" collimation Without changing the mAs, SID or collimation, decrease the kVp to 60 kVp. How will this technique change affect the overall image CONTRAST?
image contrast will increase
Resolution on a radiograph may be improved by which of the following:
immobilizing the part to be examined
As the patient thickness increases, the amount of attenuation would:
increase
During tomography, as the exposure arc (angle) increases, the radiographic detail:
increases
A satisfactory AP radiograph of the shoulder has been taken using the following factors: 70 kVp 40 mAs 40" SID collimated to 14"x17" 8:1 ratio grid only one specific factor or condition is changed from the original set of factors; all other factors and conditions remain the same. Indicate how this single factor would change the resulting radiograph. If the SID was decreased to 20" and the mAs was decreased to 10mAs, this would primarily increase:
magnification
Size distortion refers to:
magnification
The source-to-object distance for stationary, fixed fluoroscopic equipment must be:
maximum of 15 inches
The frequency of electrical current is:
measured in hertz
Describe spatial frequency.
measures distance between pairs of lines to determine frequency
The increase in brightness that occurs because the output phosphor is smaller in size than the input phosphor is called:
minification gain
What does MTF stand for, and what does it describe?
modulation transfer function. measures the accuracy of an image compared to the original object
All tomographic radiography uses the principles of:
motion to blur out superimposing structures
Using standard fluoroscopy equipment with a constant SID, how can the anatomical part be magnified?
move the Image Intensifier further from patient
The frequency of electrical current is the measurement of:
number of waves that occur per second
Anatomical detail that is displayed on the radiographic image outside the collimated area is due to:
off-focus radiation
To produce a diagnostically-acceptable image while maintaining a low patient dose, the radiographer should utilize:
optimum kVp; low mAs
The film camera records the anatomical information given off by which part of the Image Intensifier?
output phosphor
Indicate 4 measures the radiographer should take prior to bringing mobile equipment into a patient's room?
park mobile unit outside room build up a rapport with the patient prior to entering ask all visitors and non essential associates to leave rearrange room to compensate for the mobile unit (put room back together prior to leaving)
Which of the following factors would affect scatter radiation (indicate all that apply):
patient thickness, kVp, and beam collimation
Focal spot size influences:
penumbra
The unsharpness around the edges of an anatomical part is referred to as:
penumbra
In the Image Intensifier, the anatomical image pattern is formed by electrons released by the:
photocathode
Attenuated radiation is the result of which of the following: (indicate all that apply)
photons absorbed by the patient, photons scattered away from IR
The term "fulcrum" as associated with tomography, is defined as the:
pivot point
Which video camera produces the least amount of screen lag?
plumbicon
For DR fluoro, the charged electrodes adjacent to the active layer collects ______________ which are used to determine the charge sent to the ADC.
positive ions
Which of the following will result in the filament wire breaking prematurely?
pressing the rotor switch unnecessarily
The thin opaque filter that is adjacent to the output phosphor screen
prevents the light photons from interacting with the photocathode
During digital fluoroscopy, the milliamperage range is:
pulsed and uses a high mA
HVL is used to measure x‑ray beam:
quality
Underexposed digital images will demonstrate:
quantum mottle
What is the histogram?
representation of pixel intensity
A satisfactory AP radiograph of the shoulder has been taken using the following factors: 70 kVp 40 mAs 40" SID collimated to 14"x17" 8:1 ratio grid only one specific factor or condition is changed from the original set of factors; all other factors and conditions remain the same. Indicate how this single factor would change the resulting radiograph. If a 16:1 ratio grid is substituted, this would primarily increase:
resolution
A satisfactory AP radiograph of the shoulder has been taken using the following factors: 70 kVp 40 mAs 40" SID collimated to 14"x17" 8:1 ratio grid only one specific factor or condition is changed from the original set of factors; all other factors and conditions remain the same. Indicate how this single factor would change the resulting radiograph. If the SID is increased to 72", this would primarily increase:
resolution
A satisfactory AP radiograph of the shoulder has been taken using the following factors: 70 kVp 40 mAs 40" SID collimated to 14"x17" 8:1 ratio grid only one specific factor or condition is changed from the original set of factors; all other factors and conditions remain the same. Indicate how this single factor would change the resulting radiograph. If the field size is collimated to 10"x12", this would primarily increase:
resolution
A foreshortened image:
results from an inclined/angled object
Which of the following shapes would result in the greatest distortion? Indicate all that apply. round thin flat thick
round, and thick
A satisfactory AP radiograph of the shoulder has been taken using the following factors: 70 kVp 40 mAs 40" SID collimated to 14"x17" 8:1 ratio grid only one specific factor or condition is changed from the original set of factors; all other factors and conditions remain the same. Indicate how this single factor would change the resulting radiograph. If the kVp is increased to 80kVp, and the mAs is decreased to 20mAs, this would primarily increase:
scale of contrast
Dynamic range in digital radiography refers to the:
scale of contrast
The exposure time for tomography should be consistent with which of the following statements.
should be lengthened to allow for tube movement
What does SNR stand for, and what does it describe?
signal to noise ratio. incoming information compared to random background information
Unequal magnification of various parts of the anatomy being radiographed is referred to as:
size distortion
Of the following answers, which one will produce a radiograph with the greatest detail?
slow speed, small focal spot, increased SID
Repeated exposures at or slightly exceeding the tube rating chart guidelines will result in:
small pits on the anode
Which of the following factors listed below have a primary effect of magnification?
source-image receptor distance
The size of the image matrix controls the:
spatial resolution
If the computer assigned a high numerical value to a pixel, that would be consistent with which of the following? Indicate all that apply.
thinner anatomical part, high keV photon energy, high IR exposure, high mAs
The "Nyquist Sampling Criterion" is used for which of the following:
to assure the frequency cycle of the electronic signal is sampled twice
What is the purpose of the TFT device employed for DR imaging?
to store and send the electronic signal to the ADC
A digital image that displays a "grainy" appearance would indicate what technical problem to the radiographer?
underexposure
In the make-up of the (variable-aperature) collimator, which level of lead shutters reduces off‑focus radiation?
upper-level
The Charge-Coupled Device:
uses a photosensitive material to capture the "light" image
A digital x-ray image being seen on the monitor demonstrates the correct appearance and image density. The anatomical part was exposed using 80 kVp @ 10 mAs; the lgm number is 1.4. In order to adjust the lgm number to be within the appropriate range, explain what technique should be used.
we want the lgm to be 2.0-2.2 to be known as a "ideal" exposure. Every time we double the mAs the lgm will increase .3 . With that being said we need to double it twice which will give us 40mAs and 80kVp