A computed axial tomography (CAT) scan is a medical imaging method that uses many X-ray measurements taken from different angles to produce tomographic (cross-sectional) images of specific areas of the part of the body that was scanned. It allows for restructuring images in various planes and even as a three-dimensional (3D) or volumetric representation of body structures.
A CAT scan is one of the most accurate and fastest tools for examining the head, neck, chest, abdomen and pelvis. While different types of tissues and organs can exhibit a “natural” contrast, imaging and identifying the interface between two adjacent tissues/organs (for example, the liver and a tumor) or imaging soft tissues in contact with blood or other physiological fluids (like a clot) can be challenging. Greater differences in attenuation will ease the process and improve quality of images, so the use of contrast imaging agents is frequently used for better visualization of the tissue/organ of interest.
Contrast agents allow evaluation of tissue/organ performance or function, increase sensitivity and enhance differentiation between two tissues, and provide specific biochemical information of the tissue/organ. Iodine-containing and barium-based compounds are the contrast-agents of choice for CT imaging. These agents are given orally (both barium-based and iodine-containing compounds) and intravenously (iodine-containing agents) and allow identification of blood vessels (useful in embolisms, especially pulmonary embolism), tumors and cysts, cancer staging, digestive diseases (pancreatitis, appendicitis, and diverticulitis), among several other diseases.