Medical Imaging: Xrays to CT Zach Simmons UST Physics

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Medical ImagingX-rays to CTZach Simmons UST
Physics
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History

• X-Rays Wilhelm Conrad Röntgen, 1895
• Medical applications immediately apparent
• Safety concerns not immediately apparent
• Basically remained unchanged until CT
• Computerized Tomography (CT) first practical
  realization appeared in the 1970s
• First commercial CT scanner invented in 1971 by
  Godfrey Hounsfield, thanks to EMI and the Beatles

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X-RaysBremsstrahlung
cathode
anode
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OK, so

• Different types of tissue attenuate x-rays at
  different rates, causing there to be contrast in
  intensity transmitted to the resulting image
  depending on the tissue
• Beers law
• Some example attenuation coefficients
• µair 0, µbone .48/cm, µmuscle .180/cm
• -to give you an idea about 40 attenuation in
  1cm of bone

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X-Ray Radiography

• Projection of a 3D person onto a 2D film

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CT Scanner
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CT (Computerized Tomography) is where it gets
interesting
-Yields slices, instead of a shadow -This is
the simplest scanning configuration theres lots
more complicated geometries and this isnt how
modern CT scanners work.
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Projections
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Some Math
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But wait theres more
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Improvements/other

• 1980s Spiral CT and different geometries
• Fluoroscopy
• Higher resolution
• Faster scans also improves quality
• 3-D image reconstruction

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Questions?
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Sources

• Books
• Cho, Z.H. Foundations of Medical Imaging, New
  York John Wiley Sons, Inc. 1993.
• Webb, S. Ed. The physics of Medical Imaging, New
  York Adam Hilger, 1988.
• Pics
• Slide 1
• http//www.lgmsworld.de/de/downloads/hintergrundbi
  lder/homer/homer_1024.jpg
• Slide 3
• http//hyperphysics.phy-astr.gsu.edu/hbase/quantum
  /xtube.html
• Slide 5
• http//www.dmacgroup.com/Chest20X-ray.jpg
• http//www.le.ac.uk/pathology/teach/CA/Cases/exami
  nation8f1.htm
• Slide 6
• http//www.e-radiography.net/ibase5/5_Equipment/
• Slide 7
• Webb, p.100
• http//medinfo.ufl.edu/cme/geri/images/ct5.jpg
• Slide 8
• Webb, p.107
• Slide 12