Imaging II

using twice as much mAs as needed will result in?

adequate image brightness and unnecessary patient radiation exposure

the number of bits that determines the number of shades of gray that can be displayed in an image?

bit depth

which is of the following is a measurement of the efficiency of an IR in converting the x-ray exposure receives to a quality image?

DQE- detective quantum efficiency

which of the following factors does not affect spatial resolution?

Grid

the ability to distinguish many shades of gray from black to white

contrast resolution

DQE is highly dependent upon?

energy of x-rays

without exposure technique compensation, increasing the OID by 4 for a knee image would?

increase magnification, decrease exposure to the IR, and increase contrast

if the FOV is increased for a fixed matrix size, then the pixel size is ?

increased

decreasing collimation results in? (larger field of view)

increased patient exposure, increased scatter, and lower image contrast.

which of the following results in improved spatial resolution?

increased pixel density and decreased pixel pitch

What is the result of a larger field size?

increased production of scatter, more tissue irradiated, and decreased collimation.

a _____ recorded as a single numerical value representing a ______ level on a display monitor?

pixel, brightness

allows visualization fo all shades of gray

post-processing

what allows visualization of all shades of gray

postprocessing

inflatable air and fiberglass splints do not require any increase in exposure?

true

no DR imagine system can resolve an object smaller than the pixel size?

true

with too little mAs and kVp, computer processing will adjust image brightness and contrast, but noise will be visible?

true

wood aluminum and solid plastic splints may require that exposure factors be increased but only if they are in the path of the primary beam?

true

increase kVp by ___ and decreases mAs by ___

15%, half

what is the purpose of the grid?

increase contrast and reduce/absorb scatter

patient radiation dose consideration ?

20-50% reducing rate

the human eye can only visualize ___ shades of gray

30

what is the GCF for a 8:1 ratio grid?

4 [ 5:1 = 0, 4:1 = 1. 5:1 = 2, 6:1 = 3, 8:1 = 4, 12:1 = 5, 16:1 = 6]

anatomically programmed technique

A radiographic system that allows the radiographer to select a particular button on the control panel that represents an anatomic area, which is preprogrammed set of exposure factors are displayed and can be selected

image brightness is dependent on ?

nothing, it is a post-processing technique

is a measure of the imaging systems ability to display the contrast of anatomic objects varying in size?

Modulation Transfer function

pixel bit depth is determined by the?

ADC analog-to-digtial converter

quality control test tools have been designed to measure the amount of blurring as a function of spatial frequency, what is the tool ?

Bar pattern, this test tool with spatial frequencies up to 20 lp/mm. Such tools can measure the limiting modulation of each spatial frequency pattern and can use those data to construct an MTF curve

which if the following provide an indication of patient radiation risk during a radiographic?

DAP and KAP

Any alteration of the tube, part, and/or IR is considered to be?

CR misalignment and size distortion

the measure of x-rays absorption efficiency

DQE

contrast media is used to increase contrast when imaging areas of ____ subject contrast

Low

the description of the ability of an imaging system to render anatomic objects of different sizes onto an image

Modulation Transfer Function

is a standard formula for converting analog data into to discrete digital units to accurately represent the analog signal or imaging data in digital radiography?

Nyquist Frequency

Increasing or decreasing the mA results in a ____ change in mAs?

Porportional

Hyposthenic

similar to sthenic but more slender and taller build

Which of the following are not secondary factors that affect the beam?

Tube output; (generator output is a secondary factor)

a technique chart should be established for ?

a specific radiographic tube

increasing the tube filtration results in an X-ray beam with?

both higher energy and fewer quantity of photons

if the matrix size is increased for a fixed FOV, then the pixel size is?

decreased

what effect does an increased kVp have on subject contrast?

decreased

what is the relationship between FOV and pixel size for a fixed matrix size

direct

the product of mA and exposure time is _____ to the quantity of x-rays produced?

directly proportional

the property of the x-ray beam that imputes the unsharpness on the image is beam ______?

divergence

the ability of the detector to accurately capture the range of photon intensities that exit the patient ?

dynamic range

the number of gray shades that an imaging system can reproduce

dynamic range

the range of exposures that should be used to produce a diagnostic image and is likely established by the preferences or needs of the imaging department

exposure latitude

Fiberglass cast require an increase in exposure factors from the values used for the same part without a case?

false

an ideal imaging system is one that produces an image that appears exactly as the object. Such system would have an MTF equal to 0.

false

an image with decreased contrast resolution increase the visibility of anatomic details and the ability to distinguish among small anatomic areas of interest.

false

an imaging system that has a low MTF can display anatomic detail with improved visibility?

false

an imaging system with higher spatial frequency response has worst spatial resolution

false

because digital IR response is linearly related to radiation intensity, image contrast changes with changing radiation exposure

false

image contrast is dependent on kVp?

false

geriatric patients may require increased exposure techniques, with an increased exposure time.

false, decrease exposure techniques with an decreased exposure time.

in order to reduce patient exposure what exposure factors should be considered?

higher kVp, lower mAs

if lower than needed kVp is selected, the digital image will have?

higher subject contrast, and increased quantum noise

the ______ the DQE of a system, the _____ the radiation exposure to produce a quality image

higher, Lower

____the SNR will improve the quality of the digital image

increasing

____ kVp, ____ penetration and _____ absorption?

increasing, increases; decreases.

Milliamperage and Exposure Time

is directly proportional to radiation quantity exiting the X-ray tube.

Hypersthenic

large, stocky buld

digital image quality is improved with?

larger size matrix and smaller size pixels; ;larger matrix size and larger pixel bit depth, and larger pixel bit depth and smaller sized pixels

digital image quality improves with a _____ matrix size that includes a _____ number of ______ pixels

larger; greater; smaller

High kVp results in?

less variation in the x-ray intensities exiting the patient

what is the problem with very low techniques for digital imaging

low SNR and Noise

a ____ kVp requires_____ exposure time to reach the predetermined amount of exposure?

low; more

a combination of rows and columns

matrix

Shape distortion can be created by?

misalignment of anatomic part, angling of central ray, misalignment of the IR

the ability of an imaging system to render anatomic objects of different sizes onto an image?

modulation transfer function

what effect does an increase kVp have on image contrast?

no effect

limits contrast resolution

noise

sthenic

normal or average build

is the determined by an ADC?

pixel bit depth

what determines the number of shade of gray that can be displayed?

pixel bit depth

a greater number of pixels per unit area?

pixel density

distance measured from the center of a pixel to an adjacent pixel

pixel pitch

In digital imaging, spatial resolution is limited to the ____ of the pixel?

size

Kilovoltage affects beam?

quantity and quality

what is the process of assigning a numerical value to represent a brightness value?

quantization

Higher spatial frequency indicates better spatial resolution. which image modality has the best spatial resolution ?

screen-film mammography

the portion of the image-forming x-rays that represents anatomy?

signal

an image composed of ___pixels has ___ spatial resolution?

smaller, increased

relates to the number of line pairs in a given length, usually millimeters?

spatial frequency

DR is limited by one deficiency

spatial resolution

is the ability to render small objects on the image

spatial resolution

is the ability to resolve and render small objects on the image?

spatial resolution

what a re the most important characteristics of an imaging modality ?

spatial resolution and contrast resolution

SOD can be determined by?

subtracting the OID from the SID

if a digital IR Is underexposed or overexpose, the computer will adjust for the exposure error, but the image quality and/or patient exposure may be comprised.

true

increasing the CNR increases the visibility of anatomic details

true

Instead of dose creep, ________ creep should be used with digital imaging systems. The result will again be a reduction in patient dose.

technique creep

Digital image receptors have a wide dynamic range?

true

Plaster casts require an increase in exposure factors compared with that needed to image the same part without a cast

true

digital imaging has the ability to lower a patients dose because of the linear manner in which the IR responds to x-rays

true

increasing the number of lp/mm resolved in the imaging system results in improved spatial resolution?

true

asthenic

very slender