What does the term "subtraction" refer to in fluoroscopy?

The term "subtraction" in fluoroscopy specifically refers to the technique of removing or eliminating overlying structures from the image to enhance the visibility of a particular area of interest. This process allows the radiologist or clinician to highlight vascular structures or other details by subtracting the background or unrelated anatomical features that might obscure the target area.

This technique is especially useful in studies involving dynamic processes, such as angiography, where it is crucial to isolate blood vessels from surrounding tissues to evaluate blood flow and identify any abnormalities without interference from adjacent organs or structures.

While enhancing contrast, reducing noise, and improving resolution are important aspects of imaging, they do not define the specific function of subtraction in fluoroscopy, which is all about isolating the area of interest by eliminating overlapping structures.