Tomography is an imaging technique that allows one to reconstruct object sections by analyzing particular penetrating waves; this method finds applications in different areas of science. The mathematical procedure used to reconstruct images is generally called tomographic reconstruction; when X-rays are exploited, the overall procedure is called Computed Tomography scan (CT scan). Historically, this technique was first idealized by Johann Radon in 1917, when he introduced the so-called Radon transform: he showed that a cross-section of an image can be reconstructed in a single step through an infinite set of its projections. The first practical application in CT scan dates back to 1971, more than fifty years later.