im = phantom(256);
ang = [1:180];

R = radon(im,ang);
R = R+.1*randn(size(R));
backp = iradon(R,ang,'none');
recon = iradon(R,ang);

figure(1)
clf
imshow(im.^.5)
axis equal
colormap gray

figure(2)
clf
imagesc(R)
axis equal
colormap gray


figure(3)
clf
imshow(recon.^.5)
axis equal
colormap gray

figure(4)
clf
imagesc(backp)
axis equal
colormap gray