Although MRI is widely used for detecting breast cancer, its ability in assessing functional responses to chemotherapy prior to surgery has not been fully exploited. Dynamic contrast enhanced (DCE) MRI has a sensitivity around 90% and provides quantitative measurements of blood volume and flow. Other functional techniques detect variation in tissue oxygenation: this is called the blood oxygen level-dependent (BOLD) mechanism. The BOLD technique uses a special magnetic resonance (MR) sequence called T2* to measure the weakly magnetic effect of deoxygenated haemoglobin. The investigators wish to develop and validate T2* measurements which relate to oxygenation of a tumour. The investigators also want to validate other MR sequences including diffusion weighted (DW) MRI, which quantifies microcirculation of blood in the capillary network and the diffusion of water within tissues.