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ENGG 167 - F02MEDICAL IMAGING

Wednesday, Oct. 27

Chapter 14: Computed Tomography

Reference: Chapters 12 & 13, The Essential Physics of Medical Imaging, BushbergComputed Tomography, Kalender, Verlag, 2000.Chapter 12, Intermediate Physics for Medicine and Biology, 3rd Ed., Hobbie.Chapter 3, Principles of Computerized Tomographic Imaging, Kak and Slaney, IEEE Press

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X-ray imaging with digital subtraction

Ref: Bushberg

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Dual energy imaging

Ref: Bushberg

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Dual energy subtraction imaging

Ref: Bushberg

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Chapter 12 – Tomosynthesis – approaching computed tomography

Ref: Bushberg

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Computed Tomography – READ Chapter 13

Ref: Bushberg

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Computed Tomography: reconstruct pixelated images

Ref: Bushberg

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Computed Tomography – detection geometries

Ref: Bushberg

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Image Reconstruction : projection data

Ref: Kalendar

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Reconstruction

Ref: Kalendar

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CT – History

Ref: Kalendar

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CT – 5th generation system - fast cardiac imaging

Ref: Bushberg

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CT – 6th generation - helical or spiral CT

Ref: Bushberg

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CT – 7th generation – multiple detector slice arrays

Ref: Bushberg

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CT – slip ring input and output of voltage/current

Ref: Kalendar

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CT detectors – xenon gas – old style

Ref: Bushberg

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CT detectors – solid state detectors

Ref: Bushberg

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CT detectors – solid state multiple detector arrays

Ref: Bushberg

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CT slice thickness

Ref: Bushberg

Increasing slice thickness increasesSNR by square root of thickness ratio.This provides better contrast resolution but decreased spatial resolution in slice thickness dimension.Alternatively, the mAs can be increased for thin slices to keep the number of counts detected high.

Slice thickness is actually a sensitivity distribution

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CT slice thickness & collimators

Ref: Bushberg

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Pitch -Major factor influencing patient dose, image quality and scan time

Ref: Bushberg

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Interpolation of data in spiral CT

Ref: Bushberg

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Reconstruction - increasing # rays increases resolution

Ref: Bushberg

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Reconstruction - increasing # views increases resolution

Ref: Bushberg

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Reconstruction - effect of frequency filters

Ref: Bushberg

rampfilter

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Hounsfield units / CT Numbers

Ref: Bushberghttp://www.nobel.se/medicine/laureates/1979/hounsfield-lecture.pdf

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Hounsfield units / CT Numbers

Ref: Kalender

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Hounsfield units / CT Numbers

Ref: Kalender

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CT Numbers – windowing for display

Ref: Bushberg

CT images – 12 bitHuman vision – 6-8 bitDigital display – 8 bit

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CT geometry

Ref: Bushberg

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Radiation Dose in CT

Ref: Bushberg

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Radiation Dose in CT

Ref: Bushberg

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Radiation Dose in CT – effect of pitch

Ref: Bushberg

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Radiation Dose in Helical CT

Ref: Bushberg

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Dose versus SNR, pixel size & slice thickness

Ref: Bushberg

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Contrast Resolution vs Spatial Resolution

Ref: Bushberg

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Computed Tomography – improved contrast over projection x-ray imaging with loss of spatial resolution

Ref: Bushberg

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Contrast - Resolution analysis

Ref: Kalender

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Contrast - Resolution analysis

Ref: Kalender

40Ref: Bushberg

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II

Ref: Bushberg

42Ref: Bushberg

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Artifacts – beam hardening

Ref: Bushberg

energy

Inte

nsity

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Artifacts – beam hardening

Ref: Bushberg

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Artifacts – beam hardening

Ref: Bushberg

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Artifacts – partial volume effects

Ref: Bushberg

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Artifacts –

Ref: Bushberg

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Projects – schedule…

Talk to me to define project BEFORE Oct 28

Report on outline of your project BEFORE Nov 12Including – outline of literature search

(words used in search, papers found, etc)- endnote print out of all papers in search

(you read all abstracts of those listed)- list of papers skimmed in more detail.- list of papers read completely

Plan – papers to read in next two weeks- work with B. Pogue on strategic changes.

Final report written by Dec 8 or before.