Today’s computer tomography (CT) imaging methods in clinical settings workpoorly in detecting defects such as cancer tumors in soft tissues. In this thesis,we use phase contrast imaging, a new approach that has been found that usesthe phase shifting properties of the X-ray beam instead of the attenuating ones,and performs better in softer tissues. This report aims to investigate how usefulphase contrast imaging in clinical X-ray CT scans in detecting tumors.A simulation of an X-ray beam propagating through a tumor embedded in differ-ent bodily materials was created and the signal distance to noise ratio (SDNR)was calculated and used to determining the visibility of the tumor.We found that tumors inside human tissues with a diameter of 0.1 mm, are vis-ible for higher photon fluences than used in clinical cases, using our simulationparameters. However, using clinical photon fluences, tumors become visible at adiameter of 0.25-0.45 mm.