Table 1.

Reference standard criteria for target lesions for each diagnostic task in this study

Cohort of cases	Reference Standard
	Hepatic Metastasis	Detection of Indeterminate Pulmonary Nodules	Cause of potential acute neurologic deficit
Positive cases	For each case proven malignancy at least one hepatic lesion that meets criteria below For each lesion hepatic metastasis by histopathology (surgical extirpation or biopsy) progression (increase in size) over serial cross-sectional exams regression (decrease in size) over serial cross-sectional exams while on medical treatment	Two chest radiologists, not participating as readers in this study, independently evaluate routine dose CT images, unblinded to prior and subsequent exams Both chest radiologists circumscribe every indeterminate nodule 5–15 mm in size Nodules circled by both radiologists are reference nodules	Head CT findings visible in retrospect by diagnostic task leader, and (one of the following)… Neurologist or attending physician or neurosurgical note indicating clinical findings that correspond to CT findings, or Subsequent confirmation on MRI, or Subsequent progression on serial CT exams, or Confirmation of CT findings at neurosurgery and/or histology
Negative cases without other findings	Agreement between individual assessment by 2 GI radiologists that no liver lesions are present A subsequent CT or MRI performed ≥ 6 months later also showing absence of liver lesions	Two non-reader chest radiologists verify absence of indeterminate pulmonary nodules comparing to prior and subsequent CT exams	2 non-reader neuro-radiologists to agree on absence of CT findings on routine dose images that would indicate acute neurologic deficit, as well as corresponding neurological assessment prior to discharge
Negative cases with benign findings	Characteristic imaging features 19 plus stability on separate CT or MR exam performed ≥ 5 months from index CT	Not applicable (granulomas are not marked or tracked)	Leukoaraiosis was confirmed and noted when present on subsequent MRI exam