- In vivo evaluation of 99mTc-DTPA and 99mTc-sulphur colloid as tracers in colonic drug delivery systems using gamma scintigraphy in volunteers. Krishnaiah, Y.S., Satyanarayana, S., Prasad, Y.V., Rao, S.N. Journal of pharmacy & pharmaceutical sciences [electronic resource] : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques. (2002)