X-ray computed tomography (CT) is a widely used non-invasive diagnostic tool for imaging tissues and organs in various medical settings. The technique, which involves rotating an X-ray source around an object and capturing projections to create 3D images, has seen significant advancements since its inception in the 1970s. CT imaging is particularly useful for visualizing tissues with high density or atomic number, such as bone and iodine or barium-based contrast agents. The development of CT contrast agents has been driven by the need to enhance image quality and differentiate between different tissues, with a focus on improving sensitivity, reducing toxicity, and minimizing adverse effects. Iodine-based contrast agents, particularly small-molecule iodinated compounds, have been the primary choice for CT imaging due to their high X-ray attenuation properties. However, these agents often exhibit high osmolality and viscosity, leading to potential renal toxicity and other physiological issues. Recent advancements include the development of low-viscosity, low-osmolality contrast agents, such as iosimenol and GE-145, which show promising results in reducing adverse effects while maintaining effective imaging performance. Nanoparticulate iodine-containing contrast agents, including liposomes, nanosuspensions, nanoemulsions, and polymeric nanoparticles, offer extended blood circulation times and reduced renal clearance, making them suitable for imaging solid tumors and other specific tissues. These agents can also be designed to target specific organs or tissues, such as the liver and spleen, by exploiting the enhanced permeation and retention effect. Lanthanide-based contrast agents, known for their high atomic numbers and luminescence properties, are also being explored for CT imaging. While they are primarily used in MRI, their potential in CT imaging is being investigated due to their high X-ray attenuation capabilities. Gadolinium chelates, such as gadoversetamide and gadopentetate dimeglumine, are commonly used in clinical settings for MRI but show promise for CT imaging as well. Overall, the field of CT contrast agent development continues to evolve, with a focus on improving imaging performance, reducing toxicity, and expanding the range of applications in medical diagnostics.X-ray computed tomography (CT) is a widely used non-invasive diagnostic tool for imaging tissues and organs in various medical settings. The technique, which involves rotating an X-ray source around an object and capturing projections to create 3D images, has seen significant advancements since its inception in the 1970s. CT imaging is particularly useful for visualizing tissues with high density or atomic number, such as bone and iodine or barium-based contrast agents. The development of CT contrast agents has been driven by the need to enhance image quality and differentiate between different tissues, with a focus on improving sensitivity, reducing toxicity, and minimizing adverse effects. Iodine-based contrast agents, particularly small-molecule iodinated compounds, have been the primary choice for CT imaging due to their high X-ray attenuation properties. However, these agents often exhibit high osmolality and viscosity, leading to potential renal toxicity and other physiological issues. Recent advancements include the development of low-viscosity, low-osmolality contrast agents, such as iosimenol and GE-145, which show promising results in reducing adverse effects while maintaining effective imaging performance. Nanoparticulate iodine-containing contrast agents, including liposomes, nanosuspensions, nanoemulsions, and polymeric nanoparticles, offer extended blood circulation times and reduced renal clearance, making them suitable for imaging solid tumors and other specific tissues. These agents can also be designed to target specific organs or tissues, such as the liver and spleen, by exploiting the enhanced permeation and retention effect. Lanthanide-based contrast agents, known for their high atomic numbers and luminescence properties, are also being explored for CT imaging. While they are primarily used in MRI, their potential in CT imaging is being investigated due to their high X-ray attenuation capabilities. Gadolinium chelates, such as gadoversetamide and gadopentetate dimeglumine, are commonly used in clinical settings for MRI but show promise for CT imaging as well. Overall, the field of CT contrast agent development continues to evolve, with a focus on improving imaging performance, reducing toxicity, and expanding the range of applications in medical diagnostics.