X-Rays

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X-Rays
Wilhelm Roentgen
X-Ray Absorption Intensity I Io e-mx m
Absorption coefficient for this material
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CAT Scan (Computerized Axial Tomography)
Detect X-Rays passing through an object and use a
computer to reconstruct an image 1 10 mm
slices 360o rotation, 1000 scans
(profiles) Resolution 0.5 1 mm
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Nuclear Medicine, Radiotracers and SPECT
Single Photon Emission Computed Tomography
(SPECT) many different tracers, e.g. 99Tc (140
keV photon) directional information only with
collimator
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SPECT Resolution 10 mm
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The Physics of PET
Positron Emission Tomography flour
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Example of a Small Animal PET image
Rescan this picture Transgenic mouse showing
cells with albumin gene switched on
Resolution 3 - 4 mm
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Magnetic Resonance Imaging (MRI)
Protons just like electrons carry spin 1/2
or -1/2 Different energy states in a magnetic
field Photon transitions Eg E2-E1 kB
(Bmagnetic field) RF Signal with hf Eg
(typically around 10-7 eV) Gradient Coils change
B-field slightly -gt select different slices
E2 (spin parallel to B) E1 (spin opposite to B)
B0
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Resolution 0.5 mm