Fall 2004 Volume 16, Number 4	Combine and Conquer Pooling two MR techniques may uncover tumor boundaries.
	"With malignant brain tumors such as gliomas," says neuroradiologist Dima Hammoud, M.D., "you're always trying to buy a few more months for the patient." Eventually, she says, the right combination of approaches may shift the balance in life's favor. That's what drives Hammoud's new study to point out brain tumor boundaries with greater precision.
Hammoud monitors molecules whose changes in concentration are a tip-off for high malignancy-an approach that relies on magnetic resonance spectroscopy (MRS). Choline, for example, a typical building block of myelin in white matter, shoots up concentration-wise as crumbling brain cells release it. But for extra measure, Hammoud seeks to combine MRS with a second technique, magnetic resonance perfusion. Because perfusion imaging is sensitive to blood flow in the brain, it highlights areas of increased vascular supply. So tumors-well-known for their ability to recruit blood vessels-show up as unusually bright areas on a monitor. In pairing spectroscopy with perfusion imaging, Hammoud hopes to get a handle on infiltrating tumors, those that present surgeons with a large, frustrating gray area that shades from frank tumor to healthy tissue. Traditionally, standard MRI gives the first glimpse of tumors. Radiologists spot an "area of enhancement," a bright zone reflecting pooled gadolinium, a common contrast agent. Anything that destroys the blood-brain barrier-infection, trauma, tumor-causes gadolinium to seep into the brain. The enhanced areas spell "tumor" to neurosurgeons. "But we know tumors can extend far beyond that," says Hammoud. Studies show that, in most patients, infiltrating cells edge an inch or more beyond the enhancement. Too sparse to injure the blood-brain barrier, malignant cells in that area can still seed new tumors. So far, Hammoud's combining of the techniques is experimental. But nearly a dozen patients have shown its value: their MRS and perfusion images support pathologists' reports on tissue that's been sampled from the brain prior to tumor operations. One day, she suspects, radiologists will read brain maps that meld the two techniques. That should cut tumor surgery's guesswork down to size. For more information, call 410-955-2835.