Iodine-121: positron emission

Almeida, P., Ribeiro, M. J., Bottlaender, M. et al. Absolute quantitation of iodine-123 epidepride kinetics using single-photon emission tomography comparison with carbon-11 epidepride and positron emission tomography. Eur. J. Nucl. Med. 26 1580-1588,1999. 

Of the two isotopes of iodine, 1361 and 122I, one decays by (3 emission and one decays by positron emission. Which is which Explain. 

Glaser, M., Collingridge, D.R., Aboagye, E.O., Bouchier-Hayes, L., Hutchinson, O.C., Martin, S., Price, P., Brady, F., and Luthra, S.K. Iodine-124 labelled annexin-V as a potential radiotracer to study apoptosis using positron emission tomography. Appl. Radiat. Isot., 58 55-62, 2003. 

Robinson M K, Doss M, Shaller C, et al. (2005). Quantitative immuno-positron emission tomography imaging of HER2-positive tumor xenografts with an iodine-124 labeled anti-HER2 diabody. Cancer Res. 65 1471-1478. 

However, a body of evidence is being accumulated that if a halogen, such as a bromine or an iodine atom, is replaced by a beta-fluoroethyl group, the electronic and polar properties of the drug can be pretty much the same. So, what psychedelics have a bromo or an iodo group Obviously, DOB and DOI. Thus, DOEF is a natural candidate for fluorine-18 positron emission tomography, and also a natural candidate for clinical trials. And, voila, it is an active material. 

Each of the following nuclei undergoes either beta decay or positron emission. Predict the type of emission for each (a) tritium, fH, (b) fsSr, (c) iodine-120, (d) sUver-102. 

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