To use the CT/Radon transform Matlab routines (for demo use only!).

First, the attenuation function is defined in the subroutine "lambda(x,y)". You can alter it
as you see fit, but right now it's just a zero attenuation background with a small "inclusion".
There's blocks of code commented out for other attenuation possibilities.

Once you've got a "lambda" attenuation function, a typical calling sequence is

1. Execute plotlambda(300). This plots the attenuation function
(grayscale) on a 301 by 301 grid. Change 300 if you like.

2. Execute "sinodat = sino(200,200);" This computes the
sinogram using using 200 angles and 2*200=400 radial offsets
for the line integrals. Of course you can change the 200 to get
more or less resolution.

3. Execute "plotsino(sinodat)" to plot the sinogram (grayscale)

4. Execute "lambdaest = backproject(sinodat, 200, 200, f);"
where f is 0 or 1. This backprojects the sinogram data onto a
radial 200 by 200 grid (change the 200's if you like). The flag
f=0 gives unfiltered backprojection, f=1 applies a ramp filter
before backprojecting to give sharp reconstructions.

5. Execute "plotlamest(lambdaest, 300)" to plot the
reconstruction.
