Chapter 2 from the book
To decrease DI −1, decrease technique by _____%.
20%
with DI: −1 is ____% of the intended exposure
80%
T/F a digital image begins as an analog signal
True
T/F when it concerns DI, the technologist should continue to use image noise as the true determining factor of image acceptance, and these standard values should be used only as a guide
True
The term field of view (FOV) is synonymous with the _____ _____
X-ray field (In other words, it is the amount of body part or patient included in the image.)
how is brightness value measured?
by a photometer
DI is the acronym for
deviation index
Kind is the acronym for
indicated equivalent air kerma
picture element is also called a _____
pixel
Kstd is the acronym for
standardized radiation exposure
what is pixel bit depth
the number of bits within a pixel
maximum contrast resolution is defined as
the process of associating pixels with discrete values
If the DI is negative, the image has been underexposed/overexposed.
underexposed
A perfect image according to the deviation index has a DI value of _____.
0.0
Each pixel can have a gray level between __________________________-
1 (2to the power of 0) and 65,536 (2 to the power of 16)
the approximate size of cesium iodide AMFPI pixels are 125 to _____ µm
100um
with DI: +1 is approximately ____% of the intended exposure
125%
the approximate size of gadolinium AMFPI pixels are _____um
150 µm
If a pixel has a bit depth of 8, then the number of gray tones that pixel can produce is ____ to the power of the bit depth, or _____ shades of gray.
2 256
In 200___ the International Electrotechnical Commission (IEC) published a report titled "Medical Electrical Equipment—Exposure Index of Digital X-ray Imaging Systems—Part 1: Definitions and Requirements for General Radiography," and in 200___ the American Association of Physicists in Medicine (AAPM) released its "An Exposure Indicator for Digital Radiography" report.
2008 2009
The approximate size of a PSP pixel is _____ µm
200um
To raise the DI +1, increase technique by ____%.
25%
amorphous selenium pixels can be as small as ___ µm.
50 µm
The AAPM report expressed the clinical need to have this standardization, saying that standardization will give the technologist more confidence in adjusting technical factors while following the ______ (as low as reasonably achievable) principle.
ALARA
______ images are recorded as multiple numeric values and are divided into an array of small elements that can be processed in many different ways.
Digital
_______ images are formed through multiple samplings of the signal rather than the one single exposure of an analog image
Digital
T/F Changes in the FOV will affect the size of the matrix
False Changes in the FOV will not affect the size of the matrix
T/F Film/screen images are much more sensitive in recording scatter
False Digital systems are much more sensitive in recording scatter
T/F It is okay to rely on the DI as the sole determining factor of image quality.
False, Do not rely on the DI as the sole determining factor of image quality.
T/F changes in the matrix will not affect pixel size
False, changes in the matrix will affect pixel size
T/F the fact that digital imaging shows more soft tissue than film/screen, proves that there is additional detail in the image
False, digital image shows the soft tissue and the edge of the skin because of the wider dynamic recording range, this does not mean there is additional detail
the quantity kerma is expressed as _____.
J/kg
the median value of pixel values produced by the exposure on an IR is compared with the Kstd exposure to derive the ______ (its an acronym)
Kind
what is Kstd (standardized radiation exposure)?
Kstd is a standard exposure typical of that imaging receptor system. These standards for exposure are used to ensure the equipment is functioning appropriately
what is illuminance?
Light not only comes through the display but is also reflected from the surface of the display. this reflected ambient light will reflect from the surface of the display causing glare and blurring for the viewer. *measured by a photometer
MTF/spatial resolution/noise is a ratio of the image to the object; thus a perfect system would have 1% or 100%
MFT
MTF/spatial resolution/noise is a way to quantify the contribution of each system component to the overall efficiency of the entire system
MTF
what is spatial resolution?
The ability of the imaging system to demonstrate small details of an object is known as spatial resolution
T/F A pixel contains the smallest divisible component of a digital image.
True
T/F Most digital imaging systems have bit depths of 10 to 16
True
T/F The size of the matrix determines the size of the pixels.
True
T/F Thinner phosphor layers and smaller pixels produce images with higher resolution
True
T/F To reduce glare (illuminance), cathode ray tube (CRT) monitors are tinted so that the emitted light is decreased, and the faceplate glass is flat so that internal reflections are minimized.
True
T/F the digital image is digitized both by position (spatial location) and by intensity (gray level).
True
T/F the smaller the pixels, the higher the spatial resolution
True
T/F with MTF, the sum of the components in a recording system cannot be greater than the system as a whole
True
T/F The matrix size can be changed without affecting the FOV
True, For example, a 1024 × 1024 matrix has 1,048,576 pixels. If the FOV is collimated to 11 × 14, then all 1,048,576 pixels must fit in that field. If the same 1024 × 1024 matrix is used but the FOV is collimated to a 10 × 10 field, all 1,048,576 pixels must get smaller to fit in that field
T/F a change in either the matrix size and/or the FOV changes the size of the pixels
True, For example, a 1024 × 1024 matrix has 1,048,576 pixels. If the FOV is collimated to 11 × 14, then all 1,048,576 pixels must fit in that field. If the same 1024 × 1024 matrix is used but the FOV is collimated to a 10 × 10 field, all 1,048,576 pixels must get smaller to fit in that field
T/F the FOV can be changed without affecting the matrix size
True, For example, a 1024 × 1024 matrix has 1,048,576 pixels. If the FOV is collimated to 11 × 14, then all 1,048,576 pixels must fit in that field. If the same 1024 × 1024 matrix is used but the FOV is collimated to a 10 × 10 field, all 1,048,576 pixels must get smaller to fit in that field
target equivalent air kerma value (Ktgt) definition
a set of values, established by either the system manufacturer or the system user, that represents an optimal exposure for each specific body part and view. For example, there will be established perfect exposures for a posteroanterior (PA) chest, lateral chest, portable chest, pediatric chest, and so on
As humans, we experience the world through _______ vision. We see our surroundings as infinitely smooth gradients of shapes and colors.
analog
_____ refers to a device or system that captures or measures a continuously changing signal
analog
Contrast resolution in digital imaging is directly related to the _____ _____ of the pixels in the image.
bit depth
with Ktgt each _____ _____ and view will have its own unique optimal exposure.
body part
Changing the window level makes the image _____ or _____
brighter or darker
define brightness
brightness of a digital image refers to its appearance on the display monitor of the computer and is a function of the monitor's ability to emit light through the surface of the display.
to reduce scatter, use of tight _______ and the correct ____ size will allow higher kVp values to be used without compromising contrast resolution.
collimation grid
in Analog images: what we are seeing are the various levels of brightness and colors. The images are _______; that is, they are not broken into their individual pieces.
continuous
The gray level will be a factor in determining the image _____ _____
contrast resolution.
___ ____ and _____ of the phosphor layer determine resolution in film/screen radiography
crystal size thickness
Higher-contrast resolution means that the differences between adjacent _______ are enhanced
densities
In _____ radiography, analog signals are converted into numbers that are recorded.
digital
dynamic range AP knee film/screen vs digital image _______ image shows soft tissue and the edge of the skin more than the film/screen? why is this?
digital because of the wider dynamic recording range
The size of the pixel is indirectly/directly related to the amount of spatial resolution or detail in the image.
directly
Kind is the amount of _______ on the IR
exposure
Ktgt uses a table that shows the unique optimal _____ for each body part and view.
exposure *These exposures are listed in a table within the system by body part (b) and view (v), Ktgt (b,v)
The _____ _____ refers to the amount of exposure received by the image receptor (IR), not by the patient
exposure index
In an analog system such as ________ radiography, X-ray energy is converted to light, and the light waves are recorded just as they are.
film/screen
higher-contrast resolution means more shades of ____ may be demonstrated, resulting in the ability to differentiate between small differences in densities
gray
Each box within the matrix corresponds to a specific location in the ______ and corresponds to a specific area of the patient's _____
image tissue
as the matrix decreases/increases and the FOV remains the same size, the pixel size must decrease to fit into the matrix, and vice versa, if the FOV decreases and the matrix remains the same, the pixels must get smaller/larger to fit within the field.
increases smaller
With digital imaging, higher _______ values and lower ________ values can be used, lowering patient dose without affecting contrast nearly as much as was seen in film/screen radiography
kilovoltage peak (kVp) milliampere-seconds (mAs)
Air kerma (______ energy released per unit mass [of air]) is the measurement of ________ energy (joules or J) absorbed in a unit of air (kg).
kinetic radiation
The smaller/larger the FOV, the more area is imaged.
larger
Also of note, the larger the matrix, the smaller/larger the file size of the image
larger -This fact will be important when discussing the size of archive storage needed for these images.
window width, the displayed tones are varied toward a _____ or _____ scale
longer or shorter
brightness can also be called ______
luminance
Pixel size may change when the size of the _____ or the _____ changes.
matrix field of view (FOV)
MTF acronym
modulation transfer function
Kind helps determine whether the IR was _______ or ______ for a particular body part
over/underexposed
If the DI is positive, the image has been underexposed/overexposed.
overexposed
A matrix is a square arrangement of numbers (pixel values) in columns and rows, and in digital imaging, the numbers correspond to discrete _____ values.
pixel
indicated equivalent air kerma (Kind) measurement is derived from reading the _____ values produced by the exposure on an IR.
pixel
phosphor layer thickness and _____ _____ determine resolution in PSP systems, and pixel size and capture technique in active matrix flat panel imagers (AMFPI)
pixel size
The standardized radiation exposure (Kstd) is a standard exposure typical of that imaging _______ system
receptor system
what is contrast resolution?
refers to the ability of the digital system to display subtle changes in the shade of gray.
However, contrast resolution in digital imaging is affected by the amount of _____ caused during the image production process
scatter
if you have a 10 × 12 and a 14 × 17 photostimulable phosphor (PSP) plate and both have a 512 × 512 matrix, then the 10 × 12 cassette will have smaller/larger pixels.
smaller
a pixel is the _______ element in digital image
smallest
what are the 4 critical characteristics of a digital image
spatial resolution contrast resolution noise dose efficiency
(Ktgt) is an acronym for
target equivalent air kerma value
The DI can be used to adjust _______ factors if the image must be repeated.
technical
what is MTF
the ability of a system to record available spatial frequencies * there is a methematical theorem that breaks down spatial resolution into individual components and the quality of each component affects the total resolution which is how we can see a "gain" or "loss" in resolution
dynamic range definition
the ability to respond to varying levels of exposure
what is deviation index (DI)?
the difference between the actual exposure (K ind) and the target exposure (Ktgt) expressed in a logarithmic fashion
what is indicated equivalent air kerma (Kind)?
the measurement of radiation that was incident on the IR for that particular exposure
The DI is intended to help the technologist determine whether the image has been ______ or _____
underexposed or overexposed
When viewing images on any display, the technologist can adjust the brightness of the image within the viewing software using a technique called ____ _____
window level.
Display contrast resolution can be controlled by a technique called _____ _____
window width
name 4 variances that could cause the reading of the pixel values (Q) to be off (info found under DI section)
• A prostheses within the image • Gonadal shielding within the image • Failure of the system to recognize the collimated border • An unexpected body part in the image *Any of these factors will cause the DI to fluctuate
