Today it means: A specific type of clinicoradiopathologic conference that was used in the early decades of radiography (circa 1900 until World War I), whereby practitioners would make a radiologic diagnosis and then systematically compare it with the subsequent clinical course and any surgery, intraoperative or postoperative radiography or fluoroscopy, and/or autopsy. This method helped advance radiology, given that it is inherently a field of discerning clinicoradiological and clinicoradiopathological correlations. It is no longer codified under this name, because it is no longer necessary in routine practice. Full definition →
From retrospect + -o- + -graphy in both senses. The radiologic sense (from the early 20th century) was developed by radiology technicians and radiologists (who were not yet differentiated from each other at the time). The sense of reviewing photographs and learning additional insights about their subjects/contents was developed in 2017 by Jeffrey Ross of the website JBRish.com.
Etymology from Wiktionary, CC BY-SA 4.0.