Estrogen receptor scintigraphy

Radio-labeled estrogen receptor ligands are tracers that can be used for fu nctional receptor diagnosis. Their specificity towards receptors, together with the fact that only 50-70% of mammary carcinomas are receptor positive, renders them unsuitable for detection of primary tumors or metastases, and this means that estrogen receptor scintigraphy can be used neither for tum or screening nor for staging. However, both F-18-labeled and I-123-labeled estradiol derivatives are suitable for in vitro imaging of estrogen recepto rs. Their high specificity established in animal experiments and in vitro s tudies has been reproduced in in vivo applications in humans. Tracers with positron radiation emitters are, however, hardly suitable for broad applica tion owing to the short half-life of F-18, which would mean that users woul d need to be situated close to a cyclotron and a correspondingly equipped r adiochemical laboratory. The number of available PET scanners, on the other hand, has increased over the last few years, especially in Germany, so tha t this, at least, does not present a limiting factor. All the same, I-123-l abeled estradiol derivatives will find more widespread application, since t he number of gamma-cameras incorporating modern multi-head systems is sever al times greater. The results of studies with I-123-E-2-scintigraphy publis hed to date are very promising, even given the initial technical problems m entioned above. As a method of examination, it could be optimised by using improved tracers with a higher tumor contrast and less disturbance from ove rlapping in diagnostically relevant locations, for instance, by selecting t racers with higher activities whose excretion is more renal than hepatobili ary. The use of modern multi-head camera systems can also be expected to Im prove the photon yield.