A panel of health experts recommended yesterday that strong measures be adopted to prevent overbuying and overuse of a sophisticated, expensive X-ray device known as the CT Scanner.

The report, prepared by a committee of the National Academy of Science's Institute of Medicine, was given added emphasis by the president of the Blue Cross Association - the nation's largest private health insurer - who said his organization may restrict or withhold reimbursement of charges for CT scanning if the report's recommendations are not adopted.

The Institute of Medicine's report is the most complete and authoriative study yet made public on the efficacy of the CT scanner and potential problems the device poses. A study by the congressional Office of Technology Assessment, more limited in scope, is still in draft form and has not been formally made public.

The CT (for computed tomography) scanner uses a thin beam of X-rays coupled with a computer to present a reconstructed view on a television screen of cross sections of internal body organs.

A scanner costs anywhere from $300,000 to $700,000 to purchase and patients are charged from $150 to $5 for a series of scans, according to the Institute's report. The report estimates that 76 scanners are already being used or on order.

According to studies of the CT scanner and estimates by health experts, the annual bill for scans is already from $200 million to $300 million annually and could reach $1 billion by the end of the decade.

The CT scanner has been hailed by some physcians as a device that could revolutionize medicine. Its critics charge, however, that the scanner has come into widespread use without sufficient attention to its usefulness, that too many have been bought and that the opportunity for medical profiteering with the device is enormous.

The institute study was done under the sponsorship of the national Blue Cross Association, which has roughly 107 million subscribers across the country.

The report, while acknowledging the scanners' efficiency in certain cases, recommends that insurance companies should pay for CT scans only when these standards are followed:

CT scanners used should have been installed with the approval of a local health planning agency under a certificate of need program.

Scans should not be performed until a request for the test is reviewed by a physician responsible for controlling access to the device.

A utilization review program should be established to make sure that tests performed were appropriate.

Scanners should perform a minimum of 2,500 tests a year. Amortization of the purchase cost of scanners should be spread over at least five years to limit costs.

A uniform professional fee of $35 per patient on top of the cost of the test should be established except where local conditions warrant a higher or lower fee.

Use of scanners in doctors' offices and private clinics should be permitted "only when placement in full-service hospitals is not practical."

"New units should be approved until there is full and appropriate use of existing scanners."

Walter J. McNerney, president of Blue Cross, said that the next step for his organization is to study the panel's recommendations to decide which should be implemented by local Blue Cross Organizations.

McNerney was asked at one point during a press conference called to discuss the report if Blue Cross might refuse to pay charges generated by machines that did not meet the study's recommendations. "If we follow the recommendations of the report," McNerney said, "we would be doing precisely that.We would not be pay.

McNerney indicated that the report will provide Blue Cross with a lever to limit the spread of scanners.