Fig. 3

The Chou tests for the comparison of the diffusion curves of CT, MRI and PET. *X axis: months after been reimbursed by the NHI; Y axis: cumulative service volume divided by the volume of the first month. **Blue line (intercept=-4.015, slope=1.425) : The diffusion curve of CT; Black line (intercept=-12.318, slope=1.962): The diffusion curve of MRI; Red line (intercept=-20.294, slope=1.935): The diffusion curve of PET. ***Results of Chow test: between CT and MRI: P=0.59; between MRI and PET: P=0.39;between CT and PET: P=0.76