Image reconstruction Ch 3

back projection

called summation method. simple but produced star or blurring artifacts

what are the major components for image reconstruction?

hardware and software

example of interpolation

in spiral/ helical imaging, interpolation is used before filtered back projection because the patient is continually moving and will cause blur

what are the 3 principal types of memory?

1. Read- only memory (ROM) 2. Random-access memory (RAM) 3. Write-once read many times memory (WORM)

what are the 3 reconstruction algorithms

1. back projection 2. iterative 3. adaptive statistical iterative reconstruction

name 2 convolution filters

1. high- frequency convolution filter (low pass filter) 2. low- frequency convolution filter (high pass filter)

name some functions of mathematical filters

1. minimize streaks on the image from back projection 2.they use different algorithms

high- frequency convolution filter (low pass filter)

appear less noise with long scale of contrast. improvement in contrast resolution. it is used for imaging soft tissue such as brain and liver

noise vs detail

as detail increases, noise increases (edge enhancement) as noise decreases detail decreases (smoothing)

prospective reconstruction refers to?

automatically produced during scannig

explain SFOV

determine the area within the gantry, from which the raw data are required. SFOV selection determines the number of detectors cells collecting data. also SFOV is isocenter of the gantry

Explain DFOV

determines how much of the collected raw data are used to create an image. also called "zoom or target"

Interpolation

is a mathematical method of estimating the value of an unknown function using the known value on either side of the function

raw data

is all data collected from a detector array

what is the basic principle of image reconstruction?

it is based on the use of algorithm that uses the attenuated data measurements. scanners collect data for 360 degrees. "the more data collected the better quality images"

adaptive statistical iterative reconstruction

newer method of image reconstruction. reduce noise and shown to reduce the radiation dose to the patient by as much as 50%

iterative

not used today, it is to difficult to obtain accurate measurements

image data

occurs once the computer has processed the data into pixels. image data also require about 1/5th of the computer space as does raw data

Retrospective reconstruction refers to?

refers to using the same raw data later to create a new image

low- frequency convolution filter (high pass filter)

result in image with enhanced edges, short scale of contrast and much more noise. improvement in Spatial resolution. It is used for imaging bone ear inner

algorithm

uses a different mathematical formula for processing data , which will enhance certain features of CT image