The donut hole.
Hodgson
John McB
JM
D002309:Cardiology / Q000592:standards / Q000639:trends; D017023:Coronary Angiography; D005544:Forecasting; D006801:Humans; D015641:Radiography, Interventional / Q000592:standards* / Q000639:trends; D012680:Sensitivity and Specificity; D012955:Societies, Medical / Q000592:standards / Q000639:trends; D018084:Ultrasonography, Interventional / Q000592:standards* / Q000639:trends