When a sports team’s star millionaire takes a bad tumble, he is usually packed off to the nearest MRI clinic for a scan.
But if it weren’t for the research of Dr. Mark Henkelman, in the department of medical biophysics, that star might have to wait much longer, his medical diagnosis and playing career in limbo. Or else he might be burdened with heavy lead vests, and zapped with harmful x-rays.
Henkelman is one of the pioneers of magnetic resonance imaging (MRI). He completed his PhD in theoretical physics at U of T in 1973. After a stint at the University of British Columbia, he returned to U of T in 1981.
Back then, the entire MRI literature consisted of six published papers. “Companies were playing around trying to see whether these things could make good images,” Henkelman said.
He and colleagues at Princess Margaret Hospital, however, thought there were applications for this kind of imaging in detecting cancer. They were able to persuade the Canadian government of as much, and, in 1982, the hospital got hold of a very early prototype-the first such machine in Canada.
“The images were awful at the beginning,” said Henkelman. The patient’s motion would cause the image to splatter all over the screen. Another problem was boosting the brightness of objects against background noise-the so-called signal-to-noise ratio.
Henkelman and his team worked away to iron out the various kinks. They used mathematical algorithms and computing power to eliminate the motion artifacts. By 1985, MRI was good enough to use clinically, to look for cancer.
Although Canada lagged initially in adopting MRI, with only 20 machines in the country in 1990, there are now several hundred, according to Henkelman.
“I don’t think anybody really knew how far this was going to go,” he said, “and we still haven’t hit the end of it.”
The beauty of MRI is that it produces vivid three-dimensional views through bodies, using only strong magnetic fields and the magnetic properties of hydrogen atoms in water (read: protons). A proton in the body aligns its magnetic field with the powerful magnetic field from the MRI machine.
Kicks of energy from radio waves then throw the proton’s magnetic field off kilter, and as this realigns, the proton releases photons of energy that pinpoint its position. Since the denser the tissue, the more protons there are in it, tissues of different compositions come out in different shades of gray.
Cobbling all this information together produces an image of one’s innards. Despite the progress over the years, though, MRI machines still cost a couple of million dollars apiece, and about $1,000 per patient to operate.
For his pioneering MRI work, Henkelman was elected this year into the Royal Society of Canada. He is now imaging mice, at the Hospital for Sick Kids’ mouse imaging centre, which he started in 2002.
“We’re using imaging to phenotype based on … deliberate genetic changes,” Henkelman explained. They tinker with a gene, in other words, and then look for observable changes in the organism’s look. Through this, researchers are looking to gain insights into human diseases, by observing the effects of mutations. They use much stronger magnetic fields, which would be hazardous for human health, to produce crisper pictures-their subjects don’t complain much.
“It’s much better than cutting them up,” said Henkelman, “but probably a bit more expensive,” he added, with a chuckle.
