The T1-weighted image in Figure 5.60 represents a slice through the abdomen, with signals coming from liver, kidney, tumour and lipid. Given the following information: qliver 5 qkidney , qlipid , qtumour and the spectral density plot shown below: (a) Determine at which frequency (x1, x2, x3 or x4) the image was acquired, and give your reasons. (b) At which of these frequencies (x1, x2, x3 or x4) would the relative signal intensities of the four tissues be reversed, i.e. the highest becomes lowest and vice-versa?