Abstract
Medicare's expenditures on medical imaging have grown dramatically in recent years, with spending on computed tomography, magnetic resonance imaging, and positron-emission tomography increasing from $3.6 billion in 2000 to $7.6 billion in 2006 — more rapid growth than in any other service billed by physicians. John Iglehart discusses recent changes in Medicare policies that have reduced payments for imaging studies and the ongoing debate about new policy proposals to reduce the use of expensive imaging studies.