The MRI probe can detect the amyloid beta brain toxins responsible for onset of the disease. The accumulated toxins show up as dark areas in MRI scans of the brain. "Non-invasive imaging by MRI of amyloid beta oligomers (toxins that damage the neurons) is a giant step forward towards diagnosis of this debilitating disease in its earliest form," said Vinayak Dravid, a professor at Northwestern University, US.