Medical Imaging:Medical Imaging:X-rays to CTX-rays to CT

Zach Simmons UST PhysicsZach Simmons UST Physics

HistoryHistory

X-Rays: Wilhelm Conrad RX-Rays: Wilhelm Conrad Röntgen, 1895öntgen, 1895– Medical applications immediately apparentMedical applications immediately apparent– Safety concerns not immediately apparentSafety concerns not immediately apparent– Basically remained unchanged until CTBasically remained unchanged until CT

Computerized Tomography (CT) : first practical Computerized Tomography (CT) : first practical realization appeared in the 1970’srealization appeared in the 1970’s

First commercial CT scanner: invented in 1971 First commercial CT scanner: invented in 1971 by Godfrey Hounsfield, thanks to EMI and the by Godfrey Hounsfield, thanks to EMI and the BeatlesBeatles

X-Rays:Bremsstrahlung

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OK, so:OK, so:

Different types of tissue attenuate x-rays Different types of tissue attenuate x-rays at different rates, causing there to be at different rates, causing there to be contrast in intensity transmitted to the contrast in intensity transmitted to the resulting image depending on the tissueresulting image depending on the tissue– Beer’s law:Beer’s law:– Some example attenuation coefficients: Some example attenuation coefficients:

µµair air =0, =0, µµbone bone =.48/cm, =.48/cm, µµmuscle muscle =.180/cm=.180/cm-to give you an idea: about 40% attenuation in 1cm of bone-to give you an idea: about 40% attenuation in 1cm of bone

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X-Ray RadiographyX-Ray Radiography

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

CT Scanner CT Scanner

CT (Computerized Tomography)CT (Computerized Tomography) is where it gets interesting: is where it gets interesting:

-Yields slices, instead of a “shadow”-This is the simplest scanning configuration; there’s lots more complicated geometries and this isn’t how modern CT scanners work.

Projections:Projections:

Some Math:Some Math:

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But wait there’s more:But wait there’s more:

Improvements/other:Improvements/other:

1980’s Spiral CT and different geometries1980’s Spiral CT and different geometries

FluoroscopyFluoroscopy

Higher resolutionHigher resolution

Faster scans also improves qualityFaster scans also improves quality

3-D image reconstruction3-D image reconstruction

Questions?Questions?

Sources:Sources:Books:Books:Cho, Z.H. Cho, Z.H. Foundations of Medical Imaging, Foundations of Medical Imaging, New York: John Wiley & Sons, Inc. 1993.New York: John Wiley & Sons, Inc. 1993.Webb, S. Ed. Webb, S. Ed. The physics of Medical Imaging, The physics of Medical Imaging, New York: Adam Hilger, 1988.New York: Adam Hilger, 1988.Pics:Pics:Slide 1:Slide 1:http://www.lgmsworld.de/de/downloads/hintergrundbilder/homer/homer_1024.jpghttp://www.lgmsworld.de/de/downloads/hintergrundbilder/homer/homer_1024.jpgSlide 3:Slide 3:http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xtube.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xtube.htmlSlide 5:Slide 5:http://www.dmacgroup.com/Chest%20X-ray.jpghttp://www.dmacgroup.com/Chest%20X-ray.jpghttp://www.le.ac.uk/pathology/teach/CA/Cases/examination8f1.htmhttp://www.le.ac.uk/pathology/teach/CA/Cases/examination8f1.htmSlide 6:Slide 6:http://www.e-radiography.net/ibase5/5_Equipment/http://www.e-radiography.net/ibase5/5_Equipment/Slide 7:Slide 7:Webb, p.100 Webb, p.100 http://medinfo.ufl.edu/cme/geri/images/ct5.jpghttp://medinfo.ufl.edu/cme/geri/images/ct5.jpgSlide 8:Slide 8:Webb, p.107Webb, p.107Slide 12:Slide 12:http://147.163.65.155/mambo/index.php?option=content&task=view&id=42http://147.163.65.155/mambo/index.php?option=content&task=view&id=42