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The Weizmann Institute of Science in Rehovot, Israel, has devised a
noninvasive technique for diagnosing whether a tumour is benign or malignant. A
contrast-enhancing dye is injected into the patient’s bloodstream and magnetic
resonance imaging is used to watch it pass through the tumour. The spaces
between cells and the presence or absence of blood vessels determine the rate at
which the dye passes through. In benign tumours the dye accumulates and washes
out slowly, but in malignant cancers it passes straight through.