Computed Tomography Technologist Practice Exam 2025 - Free CT Technologist Practice Questions and Study Guide

During the bolus phase of imaging, a positive contrast agent is used primarily to enhance the visibility of structures in the body during imaging techniques like CT scans. Positive contrast agents, such as iodine-based compounds, increase the contrast between different tissues, making it easier to distinguish between various anatomical structures. This is particularly important in the bolus phase, where rapid injection of the contrast agent highlights blood vessels and specific organs, allowing for clearer visualization of perfusion or abnormalities.

Negative contrast agents, on the other hand, are used to create a contrast effect against dense structures but do not enhance visibility in the same way as positive agents during the bolus phase. Isotonic saline is generally used for hydration or as a flushing agent, but it does not serve the primary purpose of enhancing imaging contrast. Radiopaque materials, while they do provide contrast, are not the standard agents used during the bolus phase; positive contrast agents are specifically designed for this purpose, making them the ideal choice for optimal imaging results.