SLC5A5 and neoplasm: Regardless of the mechanism, the faster and more complete blood clearance contributes to higher target-to-background ratios in non-thyroidal NIS expressing tissues for [18F]BF4− than for [123I]iodide (18- to 30-fold better tumor-to-blood pool surrogate in the case of [18F]BF4− depending on the imaging time after tracer administration).