Computer tomography has become a most important area in biomedical imaging system to reconstruct 3D image. Several exact CT reconstruction algorithms, such as the generalized filtered-back projection and back projection-filtration methods and fan beam reconstruction algorithm have been developed to solve the long object problem. Although the well-known 3D Shepp–Logan phantom is often used to validate these algorithms, it is deficient due to the discontinuity of the SLP. The need for a practical method of reconstruction gave rise to the back projection technique [1]. There are two method of filter back projection the first method back projection the measurements at each projection are projected or `smeared' back along the same line. The other method is filtered back projection is still the standard technique in commercial scanners used to correct the blurring encountered in back projection method. A basic difficulty in imaging with X-rays is that a two-dimensional image is obtained of a 3D object. This means that structures can overlap in the last image, even though they are completely separate in the object. This is particularly worrying in medical diagnosis where there are many anatomic structures that can interfere with what the physician is trying to see. Thus filter back projection algorithm is the easiest way to reconstruct the image. In this paper present Fan Beam projection data of Shepp-Logan head phantom was created using the arc fan sensor geometry with an angular beam spacing of 0. 05, 1. 75, 1 . 25, 2. 75 and 3 degrees using the Fan Beam algorithm. The results were implemented for the CT scan test image using MATLAB 7. 5. 0 (R2007b) software. The image quality was found to be dependent on the beam spacing. It was observed that the image reconstructed for lower angular beam spacing had a better visualization as compared to those for higher angular beam spacing. Further, the image quality was found to be optimum between the 2 angular beam spacing of 0. 15 and 0. 75. The image quality of test image was found appreciably degrade to higher values of angular beam spacing as well as lower values of angular beam spacing from optimum values.

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X-rays Computer Tomography Filter Back Projection Fan Beam Projection Histogram