an experiment in computed tomography physics department portland state university, portland, or...
TRANSCRIPT
![Page 1: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/1.jpg)
An experiment in computed tomography
Physics DepartmentPortland State University, Portland, OR
Elliot Mylott ([email protected])Ryan KlepetkaJustin DunlapRalf Widenhorn ([email protected])
Buzug, Thorsten M. Computed Tomography: From Photon Statistics to Modern Cone-Beam CT
![Page 2: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/2.jpg)
Objectives
To design a lab that Introduces students to
CT Utilizes light instead of X-
rays Requires little setup Fast data collection and
analysis Reinforces concepts of
light/matter interaction Can highlight CT specific
issues
![Page 3: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/3.jpg)
An Example of X-rays and Projections for Students
X-ray tube
X-ray film Projecti
ons
![Page 4: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/4.jpg)
CT and Back Projection
X-ray source rotates around an object accumulating projection data
Projection data reflect the attenuation of the X-ray by the object
Projection data is spread back onto a reconstructed image
Multiple scans from different angles result in an image of the original object
Pro
jectio
n D
ata
X-ray Source
Pro
jec
tio
n
Dat
a
1
111
1
1
1
11
1
Projection Data
Back projection image
1
![Page 5: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/5.jpg)
An Example of Back Projection for StudentsThree light sources on a cylinder
Shadows (projections) converge at the cylinder
![Page 6: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/6.jpg)
Scanner Generations
3rd Generation
•Rotation Only•Large Fan Beam•Large Detector Array
1st Generation 2nd Generation 4th Generation
•Translation & Rotation•Pencil Beam•Single Detector
•Translation & Rotation•Small Fan Beam•Small Detector Array
•Rotation Only•Large Fan Beam•Stationary Detector Array
•Rotation Only•Pencil Beam (Simulated Fan Beam)•Single Detector (Simulated Large Detector Array)
![Page 7: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/7.jpg)
Hidden Objects
http://amasci.com/amateur/irgogg2.html
![Page 8: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/8.jpg)
Apparatus
![Page 9: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/9.jpg)
Comparison to X-ray CT Scanners
Rotate X-ray Source
Rotate Scanned Area
![Page 10: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/10.jpg)
Comparison to X-ray CT Scanners
Analog Projection Data
Attenuation0 1
Photogate Scan
X-ra
y tu
be Digital
Projection Data
![Page 11: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/11.jpg)
Focus-Center Distance (FCD)
Rotational Axis
Scanning line
y
x
IR Source
IR Detector
Scanner Geometry
Variables
•FCD – distance between the center of the grid and the rotary motion sensor
•θ - The angle between the rotary motion sensor and the x-axis
• φ – The angle between the focal length line and the scanning line
Output
Equation for the scanning line (y=mx+b)
![Page 12: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/12.jpg)
LabVIEW
•Displays data in real time•No programming experience needed•Can be adjusted for different computer speeds•Will be available as an .exe file
![Page 13: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/13.jpg)
Creating an Image
![Page 14: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/14.jpg)
Creating an Image
Original Positions Final Reconstruction
θ=180
θ=360
![Page 15: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/15.jpg)
CT Concepts - Artifacts
Back projection results in additional, unwanted data.
![Page 16: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/16.jpg)
CT Concepts -Windowing
Change in Gray Scale Value
![Page 17: An experiment in computed tomography Physics Department Portland State University, Portland, OR Elliot Mylott (emylott@pdx.edu) Ryan Klepetka Justin Dunlap](https://reader036.vdocuments.site/reader036/viewer/2022062804/56649ea05503460f94ba3e2d/html5/thumbnails/17.jpg)
Conclusion