7M-Chapter4: Digital Image Acquisition
Choose all of the following statements that are accurate pertaining to the role of kVp in radiographic image production (choose 3)? a. As kVP in increased, penetrating ability of the x-ray increases b. as kVp increased, more x-rays exit the patient to strike the image receptor c. as kVp is decreased, wavelength decreases d. as kVp increases, receptor exposure increases e. as kVp decreases, receptor exposure remains constant because mAs controls receptor exposure
a, b, d.
A software function that evens the brightness displayed in the image is called: a. smoothing b. equalization c. postprocessing d. subtraction
a. But smoothing may negatively impact resolution
Distortion that occurs when the x-ray beam is angled along the long axis of a part is: a. elongation b. magnification c. minification d. foreshortening
a. this results in the part appearing longer than it is
A material that absorbs x-ray energy and emits part of that energy as visible light is called: a. diode b. scintillator c. TFT d. cathode
b.
An indicator of the dose level needed to acquire an optimal image is: a. detective quantum efficiency b. detector size c. TFT size d. dynamic range
b.
Elongation and foreshortening are examples of: a. size distortion b. shape distortion c. motion d. distortion caused by short SID and long OID
b.
Improper use of grids may result in an image artifact known as: a. SNR b. moire pattern c. elongation d. foreshortening
b.
Mathematical codes used to generate the digital image are called: a. binary codes b. algorithm c. binary digits d. bytes
b.
The CR reader unit scans the IP with a(n): a. infrared light b. laser c. sonar d. visible white light
b.
The function of contrast is to: a. make the image appear sharper b. compensate for uneven anatomic structures c. brighten the image d. make detail visible
b.
The number of pixels making up the digital image is the: a. pixel depth b. matrix size c. pixel pitch d. field of view
b.
The range of receptor exposures that provides a quality image is called: a. detector latitude b. exposure latitude c. histogram d. dynamic range
b.
The smallest resolvable area in a digital imaging device is: a. detector size b. detector element c. matrix size d. focal spot size
b.
The smaller area represented in a digital image is the: a. image matrix b. pixel c. voxel d. bit
b. picture element
Receptor exposure may be defined as: a. amount of remnant radiation striking the image receptor b. dose area product c. DQE d. Differences in dark areas on a radiographic image
b. dose area product
Which of the following describes the relationship between receptor exposure and the use of grids? a. grids always reduce receptor exposure b. grids reduce receptor exposure unless mAs are increased to compensate c. grids reduce receptor exposure by only absorbing scatter radiation d. receptor exposure increases as grid ratio increases
c.
Which of the following governs the relationship between SID and receptor exposure? a. reciprocity law b. 15% rule c. inverse square law d. Ohm's law
c.
The best scatter cleanup is achieved with the use of: a. air gap technique b. focused grids c. crosshatch grids d. parallel grids
c. But crosshatch grids prevent angling of the tube and are extremely susceptible to grid cutoff
Lower spatial resolution may be caused by which of the following factors? a. short OID b. long SID c. small focal spot d. wide pixel pitch
d.
Which of the following terms describes the highest spatial frequency that can be recorded by a digital detector? a. spatial resolution b. contrast resolution c. MTF d. Nyquist frequency
d.
When AEC is used , increasing the kVp: a. increase the exposure time b. increases the image contrast c. decreases the exposure time d. has no effect on image quality
d. AEC is set to terminate the exposure after a certain amount of radiation has passed through the ionization chamber. Changes in kVp will have no effect on receptor exposure, but have some effect if kVp is substantial.
If SID is doubled, what may be said about receptor exposure? a. receptor exposure doubles b. receptor exposure is reduced by one half c. receptor exposure is reduced by new mAs squared d. receptor exposure is reduced to one fourth
d. This is another way of asking about the inverse square law
The adjustment in technical factors required when using beam restriction is: a. increase kVP b. decrease kVp to reduce the number of Compton interactions taking place c. decrease mAs to reduce the number of Compton interactions taking place d. increase mAs to compensate for the number of rays removed from the primary beam
d. rays that have been removed from the beam must be restored by increasing mAs. Area being irradiated still remain smaller
To reduce patient dose, exposure technique in digital imaging should be adjusted by: a. lowering kVp b. increasing mAs c. shortening SID d. increasing kVp
d. In congruence with ALARA
Choose all that describes the outcome of using low kVp (choose 3): a. high contrast b. few gray tones c. long scale contrast d. short scale contrast e. low contrast f. many gray tones
a, b, d
Quantum noise limits ability to see: a. detail b. contrast c. fatty tissue d. additive pathologies
a.
The number of pixels/mm in an image is called: a. pixel density b. bit depth c. pixel pitch d. matrix depth
a.
The process of assigning a value to each pixel to represent a gray tone is called: a. quantization b. scintillating c. nyquist frequency d. sampling
a.
The radiographic image is formed by: a. exit rays striking the image receptor b. laser light c. cosmic rays d. electrons and heat
a.
The use of filtration: a. greatly reduces receptor exposure because of the absorption of short wavelength x-rays b. Greatly reduces radiographic receptor exposure because of the absorption of high-energy x-rays c. increases radiographic receptor exposure by removing long wavelength x-rays d. has little effect on receptor exposure because x-rays removed from beam are not image producing rays
a.
Distortion may be described as: a. misrepresentation of an anatomic structure on the image b. foreshortening c. elongation d. magnification
a. b,c,d are all examples of distortion
More uniform penetration of anatomic structures occurs when what level of kVp is used? a. low b. high c. kVp does not affect penetration d. level at which photoelectric interaction predominates
b.
The available gray scale of an imaging system is determined by: a. pixel pitch b. bit depth c. exposure latitude d. image latitude
b.
The thicker part of anatomy should be placed under which aspect of the x-ray tube? a. central ray b. cathode c. anode d. collimator
b.
The useful image acquisition area of an image receptor is: a. detector element b. detector size c. TFT size d. dynamic range
b.
Undesirable fluctuations in brightness are called: a. MTF b. image noise c. quantization d. scintillation
b.
Choose all that will result in higher spatial resolution (choose 3): a. long SID b. long OID c. short SID d. short OID e. large focal spot f. small focal spot
a, d, f
Bit depth is equal to: a. 2 (nth power) b. 4096 shades of gray c. pixel pitch d. bit times bytes
a.
Choose all the factors below that result in poor spatial resolution (choose 4): a. Long SID b. Long OID c. Large Focal spot d. small focal spot e. patient motion f. magnification
b, c, e, f All impact the geometry of the image.
Which of the following is a graphical representation of pixel values? a. dynamic range b. luminance c. look-up table d. histogram
d.
The relationship between kVp and receptor exposure may be described as: a. directly proportional b. direct, although not proportional c. governed by the 15-50 rule d. controlled by x-ray tube current
b. Governed by the 15% rule
A primary advantage to digital fluoroscopy is: a. postprocessing manipulation of the image b. radiation dose to the patient is substantially lower c. no radiologist is needed d. lower cost
a.
The active portion of a CR is: a. ABC b. PSP c. DQE d. SNR
b. Photostimuable phosphor
As beam restriction increases (becomes tighter): a. receptor exposure increases b. receptor exposure increases as a result of focusing of x-rays c. receptor exposure decreases d. receptor exposure is not affected
c.
Receptor exposure was formerly called: a. contrast b. detail c. density d. distortion
c.
The appearance of digital images on technologist's monitor is: a. the same as on radiologists' monitor b. substantially better than on radiologists' monitors c. not as good as on radiologists' monitors
c.
The space from the center of a pixel to the center of the adjacent pixel is called: a. pixel density b. bit depth c. pixel pitch d. matrix depth
c.
The number of electrons boiled off the cathode and consequently the number of x-rays produced are controlled by: a. kVp b. SID c. mAs d. OID
c. mAs controls the electrons flowing in tube and striking anode. Directly controls the number of x-rays produced.
In digital radiography inappropriate collimation causes: a. a fogged image b. pixel unresponsiveness c. DICOM incompatibility d. histogram analysis error
d.
Magnification is caused by: 1. short SID 2. long SID 3. short OID 4. long OID a. 2,3 b. 1,4 c. 1,3 d. 1 only
b. the optimum conditions are longer SID and shorter OID
As speed class decreases: a. the likelihood of noise increases b. noise is unaffected c. patient exposure increases d. sharpness decreases
c. More total exposure is required to produce a useable image.
What converts light into a charge? a. diode b. cathode c. AC to DC converter d. photodiode
d.
Digital imaging is driven by: a. kVp b. mAs c. IR speed class d. exposure
d. Total exposure reaching the IR.
Spatial resolution is: a. photographic representation of the part being radiographed b. controlled by kVp c. controlled by mAs d. geometric representation of the part being radiographed
d. controlled by SID, OID, focal spot size, pixel pitch
The primary controlling factor(s) of contrast is (are): a. mAs, which control the energy of the x-rays preduced b. kVp which primarily controls the quantity of x-rays produced at the target c. focal spot size which controls the quantity and quality of x-rays produced d. kVp and bit depth
d. kVp controls the wavelength and penetrating ability of beam. Digital imaging: window width can be used to manipulate contrast
Quality assurance of digital imaging requires the uniformity of processing codes to ensure: a. image appearance consistency b. faster throughput c. less heat loading on the anode d. smoother integration into PACS
a
Choose all that are true concerning grids (choose 3): a. contrast improvement factor is the measure of the ability of a grid to enhance contrast b. grid selectivity is the ratio of primary radiation transmitted through the grid to secondary radiation transmitted through he grid c. grids are used when part thickness is less than 10 cm d. GCF is the amount of increase in kVp necessary when converting from nongrid to grid techniques e. the primary purpose of grids is radiation protection f. the main function of grids is to prevent Compton scatter from reaching the IR g. grids prevent the production of scatter
a,b, f Grids are used over part of thickness of 10 cm. Grids conversion factors are used to change mAs. Grids don't prevent the production of scatter, just absorb it.
A radiographic image with few gray tones, primarily exhibiting black and white, would be described as having what type of contrast? 1. long scale 2. short scale 3. low 4. high a. 2 and 4 b. 1 and 3 c. 1 and 4 d. 2
a.
Digital image receptors are more sensitive to: a. scatter and background radiation b. fluorescent lights c. free electrons d. free radicals
a.
If SID is reduced by one half, what must be done to mAs to maintain a constant receptor exposure? a. reduce mAs to one fourth its original value b. reduce mAs to half its original value c. increase mAs by four times its original value d. increase mAs by two times its original value
a.
The 15% rule states that: a. receptor exposure may be halved by decreasing kVp by 15% b. kVp should be 15% of the mAs selected c. receptor exposure may be halved by increasing kVp by 15% d. at least a 15% change in mAs is required to make a change visible
a.
When a nongrid technique using 10 mAs and 75 kVp is changed to a 12:1 grid using 75 kVp. what new mAs must be used to create the same image? a. 50 mAs b. 2 mAs c. 40 mAs 120 mAs
a. Grid conversion factor or bucky factor for a 12:1 grid is 5 times the original mAs.
Excessive processing of the detail image may: a. degrade visibility of anatomy b. provide additional anatomic information c. enhance visibility of desired anatomy d. increase patient dose
a. The more the image is processed the greater the opportunity for image degradation.
As speed class increases: a. the likelihood of noise increases b. the likelihood of noise decreases c. patient exposure increases d. sharpness increases
a. This may allow for higher kVp and lower mAs, which causes an increase in quantum mottle or noise.
Which of the following describes the relationship between mAs and receptor exposure? a. Receptor exposure is directly proportional to mAs b. receptor exposure is inversely proportional to mAs c. recptor exposure is directly proportional to mAs squared d. mAs controls the number of electrons boiled off the anode and the number of x-rays produced
a. Whatever is changed in mAs directly impacts receptor exposure
Beam part receptor alignment latitude describes: a. the latitude of collimation that still allows the software to detect collimated edges b. the alignment that maintains ALARA requirements c. exposure latitude d. acceptable distortion of the image
a. detection of collimated edges is crucial to obtaining an accurate histogram
Grid cutoff may be describe as: a. decreased density in the middle of the radiograph caused by the use of a parallel grid inserted upside down b. decreaed density on a radioigraph as a result of absorption of image forming rays c. increased density in the center of a raidograph caused by the use of focused grid inserted upside down d. decreased density on the edges of a radiograph
b. A is incorrect: decreased density in middle would not be caused by used of inverted parallel grid. C is incorrect: density would decrease int he middle of this radiograph. D is incorrect: density could decrease across the entire radiograph.
An artificial increase in display contrast at an edge of the image is: a. smoothing b. edge enhancement c. contrast resolution d. spatial resoltion
b. Enhances visibility of detail.
A high SNR, provides an image with: a. poor spatial resolution b. higher spatial resolution c. poor contrast d. higher distortion
b. There is a greater difference between the signal and any noise that may be present.
A grid with lead strips and aluminum interspacers that are angled to coincide with the divergence of the x-ray beam is called a: a. parallel grid b focused grid c crosshatch grid d. rhombic grid
b. These grids can be used only within a certain range of SIDs, as stated on the label on the grid.
Given an original technique of 30 mAs and 80 kVp, which of the following would produce an image with double the receptor exposure? a. 60 mAs, 90 kVp b. 30 mAs, 92 kVp c. 15 mAs, 80 kVp d. 30 mAs, 70 kVp
b. Use of the 15% rule to increase kVp results in doubling the density. Equal receptor exposure as doubling mAs.
The primary controlling factors of receptor exposure: a. kVp and mAs b. mAs and SID c. SID and OID d. SID, OID, Fss
b. mAs controls the electrons flowing through the x-ray tube and striking the anode. Directly controls the number of x-rays produced. In digital, manipulated by window level.
Optimal spatial resolution may be created using which of the following factors? a. large focal spot b. narrow pixel pitch c. long OID d. short SID
b. pixel pitch is very important to detail in digital imaging
Quality assurance and maintenance of CR cassettes include erasing plates at least: a. daily b. every 48 hours c. every 3 months d. weekly
b. But erasing daily is better and preferred
In digital fluoroscopy, what equipment should be used to view the images? a. conventional view box b. high-resolution monitor capable of displaying millions of pixels c. high-definition television d. plasma television required
b. The monitor must be high resolution
The actual patient dose as measured by a meter embedded in the collimator is: a. RAD b. DAP c. REM d. doubling dose
b. digital imaging takes into account the total dose to the patient
Choose all that describe the outcome of using high kVp (choose 3): a. high contrast b. few gray tones c. long scale contrast d. short scale contrast e. low contrast f. many gray tones
c, e, f
If the exposure field is not accurately recognized, the histogram will contain data: a. outside the exposure field, narrowing the histogram b. inside the exposure field, widening the histogram c. outside the exposure field, widening the histogram d. inside the exposure field, narrowing the histogram
c.
Quality assurance and maintenance of CR cassettes include cleaning and inspecting the plates at least: a. daily b. every 48 hours c. every 3 months d. weekly
c.
Smoothing software may result in: a. enhanced fine detail b. less distortion c. loss of fine detail d. increased distortion
c.
What allows more anatomic structures to be captured during an exposure? a. contrast resolution b. spatial resolution c. dynamic range d. MTF
c.
Which of the following affects receptor exposure? a. atomic mass of the x-ray tube anode b. X-ray tube angle c. atomic number of the cathode filament
c.
Which of the following maintains image brightness over a wide range of exposures? a. AEC b. bit depth c. automatic rescaling d. detector size
c.
Grid ratio is defined as: a. the ratio of the lead strips to the space between them b. the thickness of the lead strips divided by the thickness of the aluminum interspacers c. the ratio of the height of the lead strips over the distance between the lead strips d. the ratio of the distance between the lead strips over the height of the lead strips
c. Expressed as H/D
As the amount of beam filtration is increased: a. contrast increases b. there is no effect on contrast c. contrast decreases d. contrast increases because the beam is harder
c. the overall wavelength of the beam is shorter, resulting in lower contrast
Digital system operate at what speed class? a. 200 b. 400 c. 100 d. the speed class chosen by the radiographer
d.
Grid frequency is defined as: a. the same as grid ratio b. the amount of lead in the grid (expressed in terms of focusing distance) c. how often a grid is used d. the amount of lead in the grid (expressed as the number of lead strips per inch)
d.
The portion of contrast that is caused by variations in the anatomy or that is secondary to pathologic changes is called: a. radiographic contrast b. anatomic contrast c. pathologic contrast d. subject contrast
d.
The smallest exposure change able to be captured by a detector is called: a. spatial resolution b. exposure latitude c. pixel d. contrast resolution
d.
The variation of c-ray intensity along the longitudinal axis of the x-ray beam describes: a. beam collimation b. positive beam limitation c. anode heel effect d. x-ray emission spectrum
d.
Visible differences in adjacent structures on a radiographic image describe: a. receptor exposure b. spatial resolution c. signal loss d. contrast resolution
d.
mAs directly control: a. the energy of the x-ray emission spectrum b. the quality and quantity of x-rays produced at the cathode c. the quality and quantity of x-rays produced at the anode d. the quantity of x-rays produced at the anode
d. mAs is a quantitive factor
Differential absorption of the x-ray beam is a function of: a. Compton scatter b. atomic mass of anatomic structures c. mas d. photoelectric interaction
d. photoelectric interaction results in absorption of incoming photons. Very influenced by atomic number, not atomic mass.
What effect does beam restriction have on contrast? a. decreases contrast by focusing the x-ray beam b. decreases contrast because of higher kVp level used c. increases contrast by focusing the x-ray beam d. increases contrast because of reduction in the number of Compton interactions that occur
d. Compton interactions produce scatter, which causes contrast to decrease
What effect does the use of radiographic grids have on contrast? a. decreases contrast b. increases contrast c. no effect on contrast d. increases contrast by absorbing scatter radiation
d. Many of the scatter photons are being absorbed by the grid, resulting in higher contrast
Used of the air gap technique: a. works because x-rays are absorbed in the air between the patient and the film b. should occur when possible c. may cause some magnification because of decreased OID d. Works because scatter radiation travels in divergent paths and misses the IR as a result of increased OID
d. Not used much, it is particularly effective on lateral cervical spine radiographs.
Use of technique charts: a. is unnecessary for any exam because of AECs b. does not require that the part thickness by measured with calipers c. is usually based on fixed mAs and variable kVp d. is helpful when manual techniques are used
d. Techniques charts are generally not needed for exams when AECs are used.
The range of SIDs that may be used with a focused grid is called: a. grid ratio b. Objective plane c. anticuff distances d. grid radius
d. Using focused grid of it's grid radius will result in grid cutoff.
Distortion that occurs when the x-ray beam is angled against the long axis of a part is: a. elongation b. magnification c. minification d. foreshortening
d. this results in the part appearing shorter than it is
The expression of image quality provided by a detector is called: a. MTF b. matrix size c. SNR d. nyquist frequency
a.
