The ROI-averaged Hb, HbO2, HbT, blood sO2 and ΔsO2 from 3 central slices per tumour, measured during air-breathing and oxygen-breathing, for the long term (6 day) variability study (total of 4 imaging sessions) are shown in Figs. S7–S9. The gene discussed is GSTM1; the disease is neoplasm.