baseline flt imaging in this patient with metastatic malignant melanoma demonstrated splenic ( s ) , peritoneal ( p ) and bm metastases . after 14 days of treatment with a novel antiangiogenesis agent the upper abdominal peritoneal deposit ( vertical arrow ) had substantially decreased activity while the lower abdominal focus could no longer be visualised . uptake at sites of baseline abnormality in the spleen ( horizontal arrow ) and right femoral bm ( oblique arrow ) were relatively photopaenic compared to adjacent normal tissues . fdg  pet scanning ( not shown ) demonstrated no change over the same period . most clinical studies of hypoxia imaging have utilized the nitroimadozole , [ f]fluoromisonidazole ( fmiso ) . slow blood pool clearance and high lipophilicity contribute to significant background activity and relatively low contrast between hypoxic and normal tissues . a new agent [ f]fluoro - azomyacinarabinofuranoside ( faza ) has lower lipophilicity as demonstrated by low brain uptake in the left panel . more rapid blood clearance with similar absolute uptake in hypoxic tissue leads to higher contrast as demonstrated in this comparative study of faza ( left ) and fmiso ( right ) scans in a patient with locally advanced retropharyngeal cancer .
despite the excellent clinical performance of fluorodeoxyglucose ( fdg ) as a cancer - imaging agent for positron emission tomography ( pet ) , false positive and false negative results can be problematic in some clinical settings . 
 radiopharmaceutical development has recently focussed on the search for new pet tracers that could complement or replace fdg in such settings . due to the general availability and favourable physical properties of fluorine-18 
 , much effort has been directed to fluorinated compounds . 
 the most promising of these are discussed .