Radiologists recognized the need for properly trained medical physicists as early as the 1920s. In the absence of formal medical physics education, physicists were trained largely in radiation therapy facilities. In 1947, the ABR began certifying medical physicists.
Initially, most medical physicists were certified in radiological physics, which allowed them to practice clinically in both diagnostic radiology and radiation therapy, as it was then termed. The medical physics board certification eventually became specialized, with the ABR issuing three primary certificates: therapeutic, diagnostic and nuclear . Most states in the U.S. register, rather than license, medical physicists, although licenses are available in Florida, Texas, Hawaii, and New York. Hence, ABR certification helps recognize medical physicists as qualified for clinical service.
The ABR physics certification is issued to candidates who meet the training requirements specified by the board and pass the part one and part two computer-based examinations and the part three oral certifying examination. In 1987, a new American Board of Medical Physics (ABMP)  began certifying medical physicists in the traditional disciplines of radiation therapy physics and diagnostic imaging physics. Therefore, from 1987 to 2001, two boards were certifying medical physicists. However, in 2001, an agreement with the ABR was signed, with the ABMP discontinuing new certifications in radiation therapy physics and diagnostic imaging physics . Medical physicists who held ABMP certification were given a letter of certification equivalency from the ABR prior to Dec. 31, 2002. Currently, ABMP certifies in the field of MRI physics and medical health physics . Those who received a letter of certification equivalency from the ABR are required to participate in the MOC examinations, as are other ABR-certified physicists with time-limited certificates, which the ABR began issuing for medical physics in 2002. Anyone certified prior to 2002 had lifetime certification. The ABR’s MOC program changed from a 10-year cycle to continuous certification in 2012, then requiring diplomates to participate in the MOC program. Medical physicists who hold lifetime certificates may voluntarily participate in the MOC program. In 2020, ABR-OLA replaced the 10-year MOC examination.
Starting in 2012, the ABR began requiring successful completion of a Commission on Accreditation of Medical Physics Education Programs (CAMPEP)-accredited graduate program as a prerequisite to sit for the ABR medical physics examination. Prior to that, anyone with an MS or PhD in physics, engineering or other science was eligible to take the medical physics certifying examination. With the limited number of CAMPEP-approved programs, there are a substantial number of potential candidates who are no longer allowed to seek ABR certification. Previously, most practicing medical physicists had degrees in physics or engineering or were postdoctoral fellows in physics and became eligible to take the certifying examination after acquiring satisfactory clinical experience. There does remain a pathway for a limited number of such candidates to take a short CAMPEP-approved certification course to qualify for the ABR examination.
Those who graduate from CAMPEP-approved graduate programs with an MS or PhD must also enroll in a CAMPEP-approved medical physics residency program to qualify for the certification test. With a limited number of residency programs available, especially in diagnostic radiology and nuclear medicine physics, programs tend to choose PhD graduates, making it difficult for those with MS degrees to be accepted to these residency programs. These two requirements limit the number of people entering the field, which may lead to a long-term shortage in certified medical physicists.