By Peter Weiss
Radioactivity-detecting medical scanners, such as positron emission tomography (PET) imagers, are becoming so sharp-eyed that it’s more challenging than ever to find the limits of the machines’ vision. Doing this requires uniform radiation sources smaller than the minimum-size object the scanners are supposed to discern. Without such verification, uncertainty about the resolution of the machines’ detectors could lead to misinterpretations of scans.
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Medical physicists have made test items for scanners by irradiating fine metal wires or other objects in nuclear reactors or particle accelerators, but that’s not cheap or convenient.