The image quality of a mammographic system is directly affected by the size of the focal spot and its measurement is very important for quality assurance evaluations. Modulation Transfer Function (MTF) is widely recognized as the best descriptor for spatial resolution evaluation of radiological equipment. However, focal spot size and MTF measurements have several complex technical procedures, such as the requirement of precise alignment and direct-exposure film, which have been making such measurements more difficult and time-consuming, besides sometimes less accurate. The purpose of this work is to present a new methodology to perform MTF and focal spot measurements from two focal spot projections at any position on the field acquired by using a pinhole camera and a CCD intraoral x-ray imaging device. Thus, it can allow those measurements in quality control procedures to be easier and faster, with no need of previous alignment.