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3)Late 20th century to date: Including the launch of university courses for radiological technolo-gists (1987)contrast media are associated with the evolution of contrast radiography15). In the 1950s and 1960s, iodine-based contrast media were used, causing many side effects, including pain, dizziness, and occasional death21). Non-ionic contrast media were introduced in the 1970s, initially applied to myelog-raphy21). As alternatives to these hyperosmolar contrast media, low-osmolar contrast media were developed in the 1980s, significantly reducing the incidence of side effects21).Another historically important clinical applica-tion of contrast radiography is double-contrast radiography using barium22). In Japan, routine examinations for the early detection of gastric cancer using an X-ray fluoroscopy were intro-duced in the 1950s23, 24), with nationwide examina-tions continuing for decades25). At present, routine screening for early gastric diseases involves double- contrast radiographic examinations combined with gastrointestinal tract examinations by endoscopy24).The number of institutions is retrieved according to the institutions that are currently active. There may have been institutions that existed in the past but were not included because of the lack of records.Figure 1　Transition in the education systems in radiological technologists from 1927 to 2021The introduction of CT and MRI into clinical practice in the late 20th century was one of the biggest paradigm shifts in radiological examina-tions. X-ray CT was introduced by an English elec-trical engineer, Godfrey Hounsfield, who received a Nobel Prize in 1979 for the development of this remarkable technology26). To accrue data, an X-ray tube and a detector are arrayed on the opposite sides of a circle, which spins around the patient’s body26). In Japan, the first CT was installed in Tokyo Women’s Medical University Hospital in 197527). The initial CT machines were only for the head, with each scan taking 4 minutes28). The scan-ning method evolved to shorten the time required to scan the entire body. Shifting from a pencil beam to a narrow fan beam shortened the scanning time to 20 seconds, after which the technique was altered from translate/rotate to rotate/rotate methods28). In the late 1980s, a helical scan was introduced, which moves the bed while rotating 47