Dr. Thomas E. Johnson practiced in the early days of what many doctors regard as a revolution in patient care.

Back in the 1960s, Johnson was among physicians who helped take into private practice a new medical specialty eventually called interventional radiology.

Unlike doctors who operate through "open" surgical incisions, interventional radiologists perform "minimally invasive" procedures in which doctors use technology to visualize the circulatory system and guide catheters to hard-to-reach treatment sites in the body.

After Johnson, 86, of Oakdale, died April 2, friends and family recalled the physician's generous nature, his leadership at two St. Paul hospitals and his contributions to medicine.

"They were making their own catheters at that time," recalled Dr. Allen Bergh, a retired physician in Woodbury who worked with Johnson at St. Paul Radiology, a large private practice in the east metro.

"They would get the raw material for the catheters, the tubes, and then they would shape them and do different things in order to guide them where they wanted to in the body," Bergh said. "As time went on, that now is all being done by large companies."

Johnson was born in La Crosse, Wis. He always was interested in science, recalled his wife, Ann Johnson, and knew from age 14 that he wanted to be a physician.

Johnson earned a bachelor of science degree from the University of Nebraska, where he also received his medical degree. He served as a captain in the U.S. Air Force Medical Corps until 1957, his family said, before completing a fellowship in radiology at the University of Minnesota. Among his mentors at the U was Dr. Kurt Amplatz, who went on to create a company that developed devices for use in minimally invasive procedures.

The website of St. Paul Radiology tracks the history of the practice's contribution to the field, and lists Johnson as the first radiologist to bring into private practice "percutaneous selective angiography" — a procedure for developing images of the artery system. Johnson would perform balloon angioplasty procedures, as well, inflating medical balloons inside blood vessels to clear blockages shown by imaging procedures.

Whether treating arteries or other parts of the body, doctors using the techniques "revolutionized medicine," Bergh said, because otherwise patients would require traditional surgeries that typically feature larger incisions and longer hospitalizations.

Johnson and other doctors helped the technology spread beyond university medical centers to a broader population of patients. Medical device manufacturers like Boston Scientific and Medtronic help outfit doctors with tools for minimally invasive procedures.

In 30 years of practice, Johnson treated patients at the old Miller Hospital in St. Paul, as well as at United Hospital, which is located near downtown.

"Although he had a lot of positions of authority and could lead very well, he was a very friendly person and well-liked by his colleagues," Bergh said.

Personal interests ranged from gardening, golf and Gophers football to watching the symphony and opera.

The tinkering with technology to create new tools for patient care, his wife said, fit with the numerous fix-it projects he pursued at the St. Paul home where they raised three children.

His son, Steve Johnson of St. Paul, remembers in high school learning from his dad about angioplasty procedures. His daughter, Leslie Darrell of Woodbury, recalls her dad coming home at night and routinely studying medical journals.

"He was a very quiet guy — very humble," his daughter said. "He was also very giving."

In addition to his wife, son and daughter, Johnson is survived by another daughter, Julia Larson, and several grandchildren.

Funeral services have been held.

Christopher Snowbeck • 612-673-4744