The differentiation of normal and radioresistant tumour potentially allows the tailoring of cancer treatment to the patient. DU145 prostate cancer cells from normal and radioresistant cell lines were injected in mouse hind limb and allowed to grow into tumours. The tumours were imaged within 48 h before and after x-ray therapy using CEST. The magnetization transfer ratio (MTR) was compared between tumours grown from each cell line and at both time points. The MTR was significantly different at a frequency offset of –3.3 ppm at both time points. T1 and T2 values were not found to be significantly different.