The following thermal devices are used to photoablate hepatic tissue with a water mass fraction of 0.55. (i) Estimate the depth of the ablated lesion created for each device if the energy delivered for each device is as follows: Thermal device CO laser Argon laser YAG laser Contact spot radius (mm) Energy delivered (J) 0.75 9 1.1 15 2.6 80 Outline any necessary approximations that you feel are justified. [13 marks] (ii) If the actual depth of the photoablated lesions created are measured and are as follows: Thermal device CO laser Argon laser YAG laser Lesion Depth 2 mm (vaporised) 5.5 mm (ablated but not vaporised) 4 mm (ablated but not vaporised) Comment on the reasons for the difference between these values and those calculated in (1) above and outline the most suitable therapeutic application of each laser type giving reasons to support your answer.