Micro-CT systems are used to obtain high-resolution CT images of small animals in vivo. The physical principals of x-ray CT require that the radiation dose delivered to the subject increase rapidly to achieve finer resolution while maintaining image quality. The effect of micro-CT imaging dose on tumour growth in mice was investigated in longitudinal imaging study. Four groups of tumour bearing mice were used: a control group that received no radiation, and three unique imaging groups that received low, medium and high dose scans respectively. The mice underwent their imaging protocols four times, once every four days starting the fourth day post inoculation. The results of an ANOVA test indicate the serial imaging did not cause a statistically significant difference in tumour growth among the four groups. The notion that serial imaging causes an effect equivalent to radiotherapy treatment can confidently be rejected (α + 0.1, β = 0.1).