Abnormal Lung Uptake on In-111 WBC Scan

On this In-111 WBC scan, the lungs show prominent bilateral uptake. Why is this finding considered abnormal on delayed images?

1. AThe lungs always show high WBC uptake on In-111 studies because labeled cells are cleared by pulmonary capillaries, making any lung activity an expected and clinically insignificant finding
2. BLung activity indicates the labeling procedure was unsuccessful, as properly labeled cells accumulate only in the blood pool and should not localize in any organ at 24 hours
3. CProminent lung uptake is a known scatter artifact caused by the energy of In-111, which creates apparent pulmonary activity from adjacent high-uptake organs like the liver and spleen
4. DAfter the first few hours, labeled WBCs normally distribute to the liver, spleen, and bone marrow; persistent lung uptake on delayed images is abnormal and suggests active pulmonary infection or inflammation