Computed Tomography

DANGER DETECTOR production

Typical CT scanner

So how old is the CT scanner?

http://www.impactscan.org/slides/impactcourse/basic_principles_of_ct/img24.html

2nd generation

http://www.impactscan.org/slides/impactcourse/basic_principles_of_ct/img25.html

3rd generation

http://www.impactscan.org/slides/impactcourse/basic_principles_of_ct/img26.html

4th generation

http://www.impactscan.org/slides/impactcourse/basic_principles_of_ct/img27.html

Projected X-Rays

F1

Tomographic Reconstruction

• Projection at each θ is made up of line integrals

• Each line integral represents total X-ray attenuation

• We can relate the attenuation to the original image

• Infinite 1D projections at infinite angles perfect reconstruction

Projection-Slice Theorem

Filtered Back Projection

• Only have finite number of projections• Approximate the original by “back projecting”• Run ray sums back through to simulate

original• Krithika forbade me from discussing this

further

Uses of CT scanners

• Non-invasive medical imaging• Examine examine chest, abdomen, and pelvis

areas by imaging blood, bone, and soft tissue• radiation exposure of 2 – 10 mSv = 3 years of

background radiation

Why do we care?

• CT scanners are used to detect explosives in checked baggage

• Can create detailed, cross-sectional slices of the baggage

• The slices are the input to our program

Pan Am Bomb Slice