From X-Ray Interactions to Modern CT: A Physics-Centered Review

Computed Tomography (CT) has become a cornerstone of modern medical imaging, providing detailed cross-sectional visualization of internal anatomy. This review emphasizes the physics supporting CT, tracing its evolution from fundamental x-ray interactions to advanced imaging technologies. The discussion begins with the generation and detection of x-rays, highlighting how attenuation, scatter and energy dependence govern image formation. Mathematical reconstruction techniques including filtered back propagation and iterative methods are introduced as essential tools for converting projection data into interpretable images. Image quality metrics such as spatial resolution, noise, contrast and artifacts are analyzed through their physical determinants including attenuation coefficients, beam hardening and photon statistics. The progression of CT technology, from early single-slice systems to multi-slice and cone beam scanners is reviewed in the context of physics driven improvements in temporal resolution, coverage and detector performance. Radiation dose optimization is examined as a critical application of physics, where principles of photon flux, dose modulation and reconstruction algorithms are leveraged to enhance diagnostic accuracy while minimizing patient exposure.