A study published in the New England Journal of Medicine reports that newer CT scans that use multiple X-rays to produce spectacular 3-D images for the heart are beneficial in identifying patients who need treatment, but they aren’t ready to replace the standard procedure of coronary angiography.

The gold standard for diagnosing heart disease is coronary angiography, which requires inserting a thin catheter into an artery in the groin and running it up to the arteries near the heart. Once the catheter reaches the area being examined, a contrast material is injected through the tube and images are captured using a small dose of ionizing radiation. It is a minimally invasive medical test that helps doctors diagnose and treat medical conditions. The procedure may be performed in less than an hour; however, it may last several hours.

CT scans of the heart are less invasive than angiograms. They use a contrast dye and multiple radiation-generating X-rays, which a computer assembles into a high-resolution, three-dimensional image of the heart. In a statement, Johns Hopkins cardiologist Dr. Joao Lima, one of the researchers, said CT scans are "an alternative diagnostic tool" that doctors can use to rule in or rule out coronary blockages when other, more indirect tests for reduced blood flow, such as cardiac stress testing, are unclear or unsafe for a particular patient.

Researchers at John Hopkins University in Baltimore looked at 291 patients who were scheduled for an angiogram but also had a 64-slice CT scan. A total of 56% had heart disease. They found the newer test was 93 percent as precise as conventional cardiac catheterization without subjecting a patient to an invasive procedure. The CT scans cost about $700 and angiograms cost about $1,500, according to Johns Hopkins.

At the same time, researchers compared data from nine medical centers and found that, of those patients with a significantly clogged artery, the scan failed to detect blockages 15% of the time; of those who didn't have a blockage, the device incorrectly said the patient did have one in 10% of cases.

Based on these results, the researchers concluded that "CT angiography cannot replace conventional coronary angiography at present." However, they suggest that CT scans can help doctors "rule in or rule out" blocked arteries when patients aren’t able to undergo other indirect tests, such as stress tests.

The study conducted by John Hopkins researchers was funded by Toshiba, which makes one of the 64-row CT devices used in the study.

The newer tests are controversial because there are concerns about their accuracy and worries about their exposure of patients to high doses of radiation. Previous studies have shown that overuse of CT scans and the subsequent exposure to dangerous radiation from the potent X-rays could raise the risk of cancer. Children are more susceptible to radiation, because their tissues are more sensitive to it. Researchers said that doctors should be more selective when ordering a CT scan and not rely exceedingly on this technique.