What post-processing procedure is indicated by the term 'Region-of-interest (ROI)'?

The term 'Region-of-interest (ROI)' specifically refers to a post-processing procedure where a particular area within an image is selected for further analysis. This procedure is commonly used in various imaging modalities, including computed tomography (CT), to focus on specific structures or abnormalities within the images.

When a technician or radiologist defines a ROI, they are essentially isolating a portion of the image to measure certain parameters or quantify features, such as density or enhancement. This facilitates detailed assessments without interference from surrounding areas. It is particularly useful in applications like evaluating tumors, assessing organ function, or measuring specific components such as volumes and area measurements.

In contrast, the other choices—histogram, calcium score, and ejection fraction—refer to different analytical or assessment techniques. A histogram provides a graphical representation of pixel values in an image, the calcium score quantifies calcifications within coronary arteries, and ejection fraction is a measure used in cardiology to assess the heart's pumping efficiency. Each of these serves distinct purposes, while the concept of ROI is inherently about selecting and analyzing a specific region within an image.