Radiographic Exposures Flashcards
Radiographic image obtained through continuous scanning by a light source transmitted through an image onto a photomultiplier tube that generates an analog output signal.
analog image
Computer processing of digital data into a numerical representation of the patient that must be converted to an analog image.
digital processing
Numerical representation of computer processing of digital data.
digital image
Domain in which the X-Y coordinate (right-handed) explains an image.
Spatial location domain
Domain in which images are acquired and described according to the wavelength of the signal used to acquire the image.
Spatial frequency domain
Generate an image that is more pleasing to the observer.
image enhancement
Improve quality of images that have distortions or degradations.
image restoration
Allow measurements and statistics to be performed; image segmentation, feature extraction, classification of objects.
image analysis
Reduce the size of the image in order to decrease transmission time and reduce image storage space.
image compression
“create images from other images from other images,” or non-image data.
image synthesis
A two-dimensional array of numbers that makes up a digital image.
Matrix
(picture element) small square regions in an image matrix containing a discrete value that represents a brightness level reflecting the tissue characteristics being imaged.
pixel
(volume element) the information contained in a volume of tissue that is converted into numerical values expressed in pixels.
Voxel
Number of bits per pixel.
Bit depth
Matrix, pixel, Voxel , and Bit depth are the major features of_?
digital image characteristics
What is the relationship between pixel size, FOV, and matrix size?
The larger the matrix size, the smaller the pixel size (for the same FOV) and the better spatial resolution.
What physical characteristics of tissues does the pixel number represent?
Atomic number and mass density of the tissues
What is the main controlling factor for the spatial resolution of a digital image?
matrix size
What are the three steps in digitizing an image?
Scanning; Sampling; and Quantization
The image is first divided into an array of pixels.
Scanning
Measures the brightness level of each of the pixels using special devices such as a photomultiplier tube (PMT).
sampling
the brightness levels obtained are assigned an integer (gray level)
quantization
What is the goal of the four digital image processing operations: point processing; global processing; and geometric processing?
To suit the needs of the observer in order to enhance diagnosis.
A graph of the number of pixels in the entire image or part of the image having the same gray levels (density values) plotted as a function of gray levels.
histogram
