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.
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.