WASHINGTON (Reuters) - Using an experimental scanner and nanoparticles of gold, US researchers said they have found a way to identify the most dangerous types of blocked arteries.

The gold nanoparticles home in on blockages loaded with immune cells, which other studies have shown are the most likely to break off and cause a heart attack, said the researchers at Mount Sinai School of Medicine in New York.

The scanner made by Philips, using a method called multicolour computed tomography, or CT, showed the gold particles heading to the dangerous artery-clogging plaque, the team reported in the September issue of the journal Radiology.

"The use of multicolour CT and gold nanoparticles to visualize plaque will revolutionise cardiac imaging," radiology professor Zahi Fayad said in a statement.

The team hopes to test the method on people and will make the gold nanoparticle technology available for licensing, a university spokeswoman said.

Fayad's team found a way to make the tiny particles of gold attach to HDL, the high density lipoprotein or "good" cholesterol that carries away harmful cholesterol.

Scans on mice with blocked arteries showed these HDL-linked gold nanoparticles ended up in deposits of plaque that were also full of immune cells called macrophages.

"These mice had been on the Western high-fat, high-cholesterol diet for an average of 10 months," the researchers wrote.

Both HDL and macrophages help clear the blood of globs of harmful cholesterol, called LDL or low density lipoprotein. Macrophages try to consume these globs and often end up stuck in the artery walls when they are too fat to get all the way through with their load.

These deposits of overfed macrophages harden and are the main cause of artery clogging plaque. When they are unstable, they can break off and block arteries farther down the line, causing a heart attack or stroke.

Standard CT can show blockages but cannot tell doctors which particular blockages are unstable and in need of treatment with surgery or using a technique called angioplasty to stretch open the artery.

"There is a significant unmet need for imaging technology that visualizes plaque vulnerable to rupture," Mount Sinai's David Cormode said in a statement.

The technique may also work to improve imaging for including cancer, kidney disease, and bowel diseases, the researchers said.