Physics Chapters 16, 17, 18, 21, & 22

What would the MTF of an imaged object equal if the image was an exact representation of the object? 1 0.1 0.5 0

1

A higher MTF at lower spatial frequencies in digital radiography is attributed to which characteristic(s)? (1) Dynamic range (2) Postprocessing (3) Detective quantum efficiency (DQE)

1 and 3 only Digital radiography has higher MTF at low spatial frequencies. This higher MTF is primarily due to the expanded dynamic range and higher detective quantum efficiency (DQE) that DR offers.

Which factors help determine the detective quantum efficiency (DQE) of an image receptor? (1) Image receptor's capture layer thickness (2) Image receptor's capture layer atomic composition (3) Energy level of incoming x-ray photon 3 only 1, 2, and 3 1 and 2 only 2 and 3 only

1, 2, and 3 DQE is a measure of the image receptor's x-ray absorption efficiency. This is determined by three things: the thickness of an image receptor's capture layer and atomic composition along with the energy level of the incoming x-ray photon that is incident upon the image receptor.

Which part of the digital radiography system converts x-rays to light? A. Scintillator B. Photo detected C.TFT D. Substrate

A. Scintillator

What is the primary difference of Direct DR over indirect DR? A. Lacks the conversion of x-rays to light B. does not capture x-rays C. No difference D. Requires less exposure

A. lacks the conversion of x-rays to light.

what is the role of the charge coupled device in indirect DR? A. Converts x- ray to light B. Converts light to electrons C. Converts x-rays to electrons D. Converts electrons to x-rays

B. Converts lights to electrons

Which accreditation discovered that contrast resolution was mor beneficial that spar Rial resolution, thus concluding that digital mammography was an equal imaging counterpart to screen-film mammography. A. JCAHO B. DMIST C. American Collage of Radiology D. HIPPA

B. DMIST

What form of digital radiography is the use of a Csl phosphor plate with a charge-coupled device? a. Direct B. Indirect c. Computed D. Indifferent

B. Indirect

What component do the two forms of indirect DR have in common? A. Optics B. Scintillator C. CCD D. TFT

B. Scintillator Both us the scintillator to convert x-ray energy to light.

What term is defined as an image being produced by an x-ray beam intercepted by a phototstimuable phosphor plate or a direct- capture solid state device? A. Nuclear radiography B. Computed radiography C. Digital radiography D. Film screen radiography

C. Digital radiography Dr is defined as - an area x-ray beam intercepted by a photostimuable phosphor plate or direct capture solid state device.

What portion of the digital radiography flat plate is sensitive to x-rays and has an affect on the digital images spatial resolution? A. Scintillation B. Dynamic rage C. Fill Factor D. Couple device

C. Fill factor

Which ionizing radiation modality is the best for contrast resolution? Computed tomography (CT) Mammography Magnetic resonance imaging (MRI) Ultrasound

Computed Tomography (CT) The contrast detail curve can illustrate that mammography provides the best spatial (detail) resolution, while MRI has the best overall contrast resolution; however, CT is the best ionizing radiation-producing modality for contrast resolution.

On the contrast detail curve, which quality control is plotted along the vertical plane? MTF Noise Contrast Detail (spatial)

Contrast The vertical aspect of the curve plots the contrast, while the horizontal aspect plots the detail (spatial) resolution.

What imaging quality did DMIST state is equally as important as special resolution in digital mammography? A. Linearity B. Spatial Frequency C. Uniformity D. Contrast Resolution

D. Contrast Resolution

What area of a cesium iodide/amorphous silicon dR image receptor is sensitive to x-rays and contributes to the radio graphic image? A. Scintillator B. Capacitor Dynamic range D. fill factor

D. Fill Factor

Digital mammography spatial resolution is limited due to what feature? A. dynamic range B. Anatomy field of view C. Tomosynthesis D. Pixel Size

D. Pixel size

What aspect of the chest- dedicated SPR is responsible for collimating the beam to the corresponding scintillator phosphor? A. X-ray tube B. Prepayment collimation C. In-house filter D. Postpatient collimation

D. Post patient pollinators

DM tomosynthesis permits how many x-ray beam interactions with the image receptor? A. One in an anterior position B. Two perpendicular from one another C. Two parallel to one another D. several at varying angles

D. Several varying angles

As lp/mm increases, what effect does this have on MTF? Increase Decrease No effect lp/mm and MTF have no relationship.

Decrease As lp/mm increases, meaning spatial frequency of the object increases (smaller objects), blurring occurs. The blurring causes the imaged object to not appear as the actual object, resulting in a decreased MTF.

If image noise were to increase, what effect would occur to contrast resolution? Increase Decrease No change

Decrease As the noise that contributes to the radiographic is increased, it decreases the contrast resolution of that image.

As an imaged object becomes larger, what effect does this have on spatial frequency? Increase Decrease No effect

Decrease Depicting spatial frequency is how often an object fits within a given length. As an object becomes larger, less numbers are able to fit within a given measurement, thus decreasing spatial frequency.

Selecting an incorrect, overexposing technical factor does all of the following except: Increases patient dose Increases SNR Decreases contrast resolution Has no effect on spatial resolution

Decreases contrast Resolution An image receptor cannot be overexposed in digital radiography. Contrast resolution is preserved in digital imaging, regardless of the technique set by the radiographer. This can be dangerous because poor technical factor selection does not affect the image but may result in overexposure of the patient.

On the contrast detail curve, which quality control is plotted along the horizontal plane? Contrast MTF Detail (spatial) Noise

Detail (spatial) The vertical aspect of the curve plots the contrast, while the horizontal aspect plots the detail (spatial) resolution.

What are the varying size holes in a quality control test tool for contrast detail curve used to measure? Contrast resolution Focal spot size Noise Detail resolution

Detail Resolution Contrast detail curve quality control tools are made of a plastic or aluminum sheet that consists of holes in rows and columns. The rows consist of holes that will vary in size. The size of the hole is used to depict the spatial/detail aspect of the curve.

Which characteristic that defines an image receptor's x-ray absorption efficiency allows digital radiography to result in lower patient dose? Modulation transfer function (MTF) Postprocessing Detective quantum efficiency (DQE) Contrast detail curve

Detective quantum Efficiency (DQE)

Which IR has the widest dynamic range? Digital or Film Screen

Digital systems have a very long gray scale, referred to as dynamic range

A digital image's contrast resolution is still optimal at too-low exposure technique. True False

False

Digital imaging was applied to mammography to amend screen -films short comings in spatial resolution. True or False

False

Postprocessing is possible in screen-film imaging. True False

False

The human eye can see more shades of gray in digital radiography than screen-film radiography due to dynamic range. True False

False One benefit of digital imaging over screen-film is the very long gray scale that can be displayed; however, as the gray scale may be more vast and visible in digital, the human eye is limited in only being able to view and depict 30 shades of gray regardless of the imaging method.

Increasing the SNR, more photons interacting with the image receptor, will cause a decrease in contrast resolution. True False

False Signal-to-noise ratio (SNR) compares the level of desired signal to level of noise, and the two concepts are inversely related. If signal is increased, then noise is decreased. Image noise shares an inverse relationship with contrast resolution. So if noise is decreased, then contrast resolution is increased.

A 150-mm pixel digital radiographic system will display an improved spatial resolution over an 80-mm pixel system according to the contrast detail curve. True False

False The contrast detail curve is commonly used to compare the effect changing technical factors has on the spatial and contrast resolution of an x-ray image. *The system with the smaller pixel size will have better spatial resolution, but the contrast resolution of both will be the same because all the other technical factors remained the same.

Scanned projection radiography was developed. By nuclear medicine vendors to asses the human organan functionality in a quick fashion. True or False

False - scanned projection radiography (SPR) was developed by CT vendors to assist in patient positioning.

Postprocessing allows all of the following except: Extraction of more anatomic information Improved image signal-to-noise ratio Improved contrast in areas of poor subject contrast Manipulation of an image to display various portions of the gray scale

Improved image signal-to-noise ratio A principal advantage of digital imaging is the ability to postprocess the image for the purpose of extracting even more information. This is done by manipulating the gray scale to see any portion of the 16,384 distinct gray values. This proves especially beneficial in regions of similar tissue densities and poor subject contrast.

In digital imaging, overexposing an image receptor has what effect(s)? (1) Increased patient dose (2) Decreased contrast resolution (3) Repeating the exam

Increased patient dose

Which term is defined as one bar and its interspace of equal width? Line pair Modulation transfer function Pixel Dynamic range

Line Pair One line pair consists of the high-contrast line and an interspace of the same width as the line.

What factor is responsible for the cutoff that occurs in a digital radiography MTF curve? kVp mAs Pixel size Focal spot size

Pixel Size In DR, the MTF curve has the distinctive feature of a cutoff. Remember that in DR imaging, the smallest object visualized cannot be smaller than the pixel size.

Which side of the contrast detail curve is noise limited? Left Right Anterior Posterior

Right The far right portion of the contrast detail curve shows contrast resolution at its least and detail at its greatest. This area is noise limiting because noise reduces contrast resolution but has no effect on spatial (detail) resolution.

Computed radiography has higher detective quantum efficiency than what form of radiographic imaging? Direct digital radiography Digital fluoroscopy Indirect digital radiography Screen-film radiography

Screen Film Radiology

What compares the level of x-rays transmitted through a patient unattenuated and interacting with the image receptor to the level of graininess or scatter present? Contrast Signal-to-noise ratio (SNR) Dynamic range Postprocessing

Signal to noise ratio (SNR)

What quality control is defined as an imaging system's ability to depict small objects in an image? Contrast resolution SNR Postprocessing Spatial resolution

Spatial Resolution

What term is defined as an imaging system's ability to depict small objects in a given image? SNR Spatial resolution Contrast resolution Detective quantum efficiency

Spatial Resolution

All of the following would be affected by changing an image's dynamic range except: The image's gray scale The amount of anatomical information Optical density The number of shades of gray depicted by the human eye

The number of shades of gray depicted by the human eye *Changing the dynamic range will affect the gray scale of the image, which ultimately affects the anatomical information and the optical density.

Direct DR does not use a scintillator. True or False

True

Increasing mAs in digital radiography will depict an improved contrast resolution on the contrast detail curve. True False

True If the mAs is increased during DR, spatial resolution remains the same, but contrast resolution is improved at the higher mAs. This is can be illustrated on a contrast detail curve.

In a contrast detail curve quality control test tool, the variation in hole depth is used to measure which image quality factor? Focal spot size Detail resolution Noise Contrast resolution

contrast resolution

Which part of a flat panel DR system is made up of lates on a glass substrate? A. Scintillator B. Photodetector C. PSP D.TFT

d. TFT

Decreasing the number of objects in a given measurement has what effect on spatial frequency? Decrease No effect Increase

increase

Increasing the size of an object has what effect on MTF? No effect Increase Decrease

increase Increasing the size of an object reduces the image blurring that may occur. A larger object's image is more likely to resemble the actual. This increases the MTF.

In digital imaging, which technical factor should be increased by the radiologic technologist first to improve image quality? Exposure time Focal spot size kVp mAs

kVp Digital imaging techniques must be approached differently than in screen-film radiography. Because digital image contrast is unrelated to dose, kVp becomes less important. When digital examination of specific anatomy is conducted, the kVp should start to be increased and result in an accompanying reduction in mAs. The result will be adequate contrast resolution, constant spatial resolution, and reduced patient radiation dose.

Digital imaging's contrast resolution is less kVp dependent. True False

true