In vivo beam localization by positron activation in pion therapy

L. F. Mausner, M. A. Moinester, J. D. Knight, S. Cochavi, S. S. Friedland

Research output: Contribution to journalArticlepeer-review


Measurements have been made of the absolute yield of the positron emitters 11C and 13N produced by 76-MeV negative pions stopped in thick 'stacked-foil' targets of C (as graphite), N (as boron nitride), O (as water), and a tissue-equivalent mixture. The depth distribution of radioactivity exhibits a distinct peak in the water, boron nitride, and tissue-equivalent targets which correlates well with the position and width of the pion stopping distribution and with the high-LET component of dose. There are 0.0186 11C nuclei and 0.0085 13N nuclei produced per pion stopped in water, and 0.0484 11C nuclei produced per pion stopped in nitrogen. These yields are compared to predictions of an intranuclear cascade calculation. The yields of 11C and 13N in the stopping region from secondary particle-induced reactions are low, and do not significantly limit the ability to localize the pion star region. The activities measured from the tissue-equivalent target agree with the predictions based on the measurements for carbon, nitrogen, and oxygen targets and are similar to the yields for water. The utilization of a positron camera to image the radioactivity distribution in the pion stopping region is discussed.

Original languageEnglish
Pages (from-to)10-23
Number of pages14
JournalRadiation Research
Issue number1
StatePublished - 1979
Externally publishedYes


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