Radiotherapy has become the most important modality in treating cancer with approximately 50% of
cancer patient undergo the treatment. However, more improvement to the radiotherapy treatment
efficacy is required to deprive cancer. Assessment of tumor progress during treatment is important, to
accommodate the changes that occur during the fractionation course. The objective of this study is to
assess tumor cell damage after external beam radiotherapy by using technetium-99m
pertechnetate (99mTcOf) as a tracer. In this study, HeLa cells were irradiated with 6 MVphoton beam
with different radiation dose ranging from 0.5 Gy to 10 Gy. The irradiated cells were recultured in 6-
well plates and incubated for 10 days. After that, 2 mCi of 99mTcOf were prescribed to each cell
colonies. The viable cells were separated from the rest, and measured for 99mTcOf uptake using singlehead
gamma camera with LEHR collimation. As results, the cells survival, fractions clearly indicate
diminishing effect, to the cells at, higher dose of irradiation. Good correlation were observed between
mmTcGi uptake and survival, fraction for cells irradiated at, lower dose and less significant, correlation
were indicated at higher dose. In conclusion, there is potential for the efficacy of external beam
radiotherapy in treating cancer to be assessed by using radioisotope as a non-invasive tracer. In this
case, technetium-99m, pertechnetate (99mTcOjt) could be attached to the specific antibody so that, better
correlation, between, the cells uptake and possible cell damages could be observed.