ABSTRACT
To paraphrase Andrew Carnegie, there is nothing more important to business than quality. In modern radiation therapy (RT), quality assurance (QA) is ubiquitous; every organization devotes a significant amount of effort to QA, numerous papers are published on the topic each month, and various advisory or regulatory bodies have issued QA guidelines. Two terms that are used less frequently are quality control (QC) and quality improvement (QI). Formal distinctions between QA, QC, and QI are discussed in the next section; for the present purposes, it is sufficient to understand that there is more to the pursuit of quality than QA.
