If you ever had any doubts about whether Medicare rules were designed to benefit doctors or patients, the following tale about hospital radiological payments may offer some guidance.

The centerpiece of this instructive little story is ultrasound, a new diagnostic technique that uses sound waves to find abnormalities within the human body. Radiologists, who normally stick to X-rays and other types of radioactive materials for their work, have begun employing ultrasound, but so have several other medical specialists.

Radiologists, however, benefit from special rules in the Medicare payment program. And, according to their medical colleagues, radiologists attempted to have these rules changed so that radiologists working through hospitals would have cornered the ultra-sound business.

You may remember that when Congress possed the Medicare and Medicaid legislation, it did not define specifically what hospital and physician services the federal government would pay for. This key job was left to the bureaucracy and the inevitable special interests that develop around a program that pays out almost $7 billion a year.

"Whole groups of people have emerged who spend their lives in difinitional policy," one official observed.

Under Medicare, the patient has been required to pay 20 percent of the "reasonable charge" made by a physician. In 1967, however, the American Hospital Association requested and got a special law passed that allows Medicare to pay 100 percent of the costs of radiological services in hospitals.

Some time ago, according to the Aug. 22 Federal Register (page 56060), radiologists went to the administrators of the Health Care Financing Administration -- the section of the Department of Health and Human Services that handles Medicare payments -- and asked the government to reimburse them for performing the new ultra-sound technique.

When the word got out, other specialists went through the roof.

Cardiologists complained, claiming according to one official, that they had pioneered ultrasound. So did ophthalmologists, gynecologists and internists. Some of them went to their members of Congress.

They contended that if the federal government decided to reimburse radiologists for this new service, nonradiologists would be shut out ot the ultrasound business.

A patient would naturally choose to have a radiologist diagnose his ills if the government would pick up the entire tab instead of choosing, say, an internist, and having to pay part of the cost himself -- or so the reasoning went.

"It was a turf battle among medical specialties," said an official, and in the end, the Medicare administrators dropped the notion of including ultrasound in the category of fully reimbursed radiological services. The official noted, "We are not referees in such disputes."

"Had we included benefits to patients in our consideration," he added, "it might have been different. But that was not the intent of the 1967 amendment."

The 100 percent reimbursement law was promoted and passes, he explained, to benefit hospitals by simplifying their billing, not the help people by lowering their bills.