Controversial scan used on patients

By MARTIN JOHNSTON health reporter

Two Auckland clinics are checking patients' hearts with a test which experts say delivers as much radiation as 100 to 400 chest x-rays.

The controversial technique, computer tomography (CT) scanning to detect calcium in heart arteries, was introduced in April by Ascot Radiology, which says the risk has been exaggerated. The Ascot test costs $490.

A second clinic, Salus Health, started offering the service yesterday for $685.

The Cardiac Society of Australia and New Zealand says it has "grave reservations" about use of the test on patients who have no symptoms of diseased heart arteries.

Calcium is linked to the fatty deposits which can cause the narrowing of arteries leading to heart disease. Calcium's role in heart disease is unclear, but its quantity can be used to predict disease risk.

Ascot Radiology aims the test at people who are at risk of heart disease through factors such as smoking, high cholesterol or a family history of heart trouble.

It has used the test on about 100 patients and says it has already saved the life of one.

Radiologist Dr David Rogers said the man was in his early 50s and had no heart disease symptoms. The test found a high level of calcium and he went on to have treatment to overcome narrowed heart arteries.

The Radiation Protection Advisory Council, which advises the Government, initially opposed the test. But it later softened its position, saying the test could be used on individuals referred by a doctor.

A report of the decision in a National Radiation Laboratory newsletter says the council found that when the radiation dose was compared with the potential benefit, the test was not justified as a screening tool. The dose is equivalent to about 100 to 400 chest x-rays, it says.

But Dr Rogers said this was misleading because chest x-rays taken from the front were among the lowest-dose x-rays.

He estimated that each of the heart scans delivered a dose equivalent to five to eight chest x-ray series. A series usually involved a front and a side x-ray.

A Green Lane Hospital radiologist, Dr Chris Occleshaw, said that if patients had seven of the heart scans they faced a risk of up to one in 250 of developing a fatal cancer.

Dr Rogers dismissed this as "grossly exaggerating the risk." He was unable to state what the risk was, but he added that the dose was lower than for CT scans of other parts of the body.

Salus Health principal cardiologist Dr Gerald Lewis said the dose was similar to a mammogram and patients should not need more than two calcium scans in a lifetime.

The Cardiac Society's New Zealand chairman, Green Lane cardiologist Professor Harvey White, said a low calcium score could falsely reassure some people who might continue unhealthy habits like smoking.