Dr. Johnson attended Tulane University for his undergraduate education. He received his M.D. degree from the University of Texas at Galveston in 1963. After a surgical internship in Galveston and two years in the Army as a general duty medical officer, including service in Vietnam, Dr. Johnson trained in Diagnostic Radiology at Ochsner Foundation Hospital. He was Board certified by the American Board of Radiology in 1970.

Dr. Johnson was a co-founder and president of the American Society of Head and Neck Radiology. He was president of the New Orleans Radiology Society and has been awarded the gold-medal by the New Orleans Radiology Society, the American Society of Head and Neck Radiology and the Radiological Society of North America. Dr. Johnson has also served as president of the Louisiana State Medical Society, the American Medical Association and the World Medical Association.

Throughout his career, Dr. Johnson has felt that important changes in our healthcare financing system are necessary and has been a passionate advocate for change. He currently serves as a delegate from the American College of Radiology to the House of Delegates of the American Medical Association. He is a Visiting Fellow in Health Policy at the Heritage Foundation in Washington, DC and serves as chair of the Board of Directors of Consumers for Health Care Choices.