Final - Part 2 Flashcards
The % of the pixel in a digital IR that is sensitive to x-rays is known as?
Fill factor
How is fill factor related to spatial resolution?
Increased fill factor = increased spatial resolution.
How do you determine pixel sixe?
FOV / Matrix
What is bit depth?
of grey shades available. Total # of brightness levels
The digital image is composed of rows & columns called a?
Matrix
Each ___ in a matrix represents a visual brightness or density level. This brightness is reflective of the tissue characteristics.
pixel
Steps of digitatl imaging:
1st step: ___ - the image is broken down into pixels.
2nd step: ____ - pixel brightness is measured.
3rd step: ____ - brightness levels are assigned a numerical value.
1 - scanning
2 - sampling
3 - quantization
Each pixel corresponds to a 3D volume of tissue known as?
Voxel
The # of pixels per mm in the image is known as?
Pixel density
A greyscale bit depth of 12 produces how many levels or shades of grey?
4096
To determine the # of pixels, multiply the # of rows by the # of columns. A matrix size of 512 x 512 has how many pixels?
262,144
The overall dimension of a matrix is known as ___ which represents how much anatomy is included in the matrix.
FOV (Field of View)
If the FOV stays the same & the matrix size increases, the pixel size?
Decreases
If the matrix stays the same & the FOV decreases, the pixel size?
Decreases
The smaller the pixel size the better the image quality, therefore the pixel size determines?
Spatial resolution
A histogram is a representation of the imaged area broken down into pixels based on the min & max values.
The x (horizontal) axis represents _____.
The y (vertical) axis represents _____.
The system will determine the VOI or ____.
The S1 is the ____ signal & the S2 is the _____ signal.
x - specific exposure values captured by receptor.
y - frequency of specific exposure values.
VOI = values of interest
S1 - minimum
S2 - maximum
The shape of the histogram corresponds to the specific anatomy & the technique that was used. The computer will try to “shift’ or rescale the histogram to be closer to the original or reference histogram. This is known as?
Histogram modification/stretching/rescaling.
The histogram of the processed image is compared to a pre-existing histogram for the same body part in the ____. This applies the proper grayscale to the image by adjusting the contrast to the reference contrast levels to provide consistent images.
Look up table
Histogram errors can be caused by the histogram not matching the parameters of the reference histogram, ____ recognition errors, inaccurate exposure #s caused by too much or too little ____, & increased or decreased attenuation by body parts.
field
collimation
During pre-processing the system tries to determine the density values of densities w/i the collimated field versus outside of the collimated field for the correct histogram. This is known as?
Exposure Field Recognition
Spatial resolution is increased w/
____ matrix size,
____ pixel size,
decreased (smaller) phosphor size,
____ laser beam,
____ pixel pitch,
____ DEL size,
____ fill factor, and
____ PSP.
increased (larger)
decreased (smaller)
smaller
decreased
smaller
increased
thinner
The range of exposures that can be captured by a detector is known as?
Dynamic range
A radiograph produced w/ an extreme level of overexposure might have an error known as ___.
While a radiograph produced in the lowest portion of the dynamic range might exhibit ____.
saturation artifact
quantum mottle
The range of exposures that produce a quality image at an appropriate dose is known as?
Exposure latitude
The dynamic range is ___ that the exposure latitude.
wider
