Method used to predict the transducer’s anterior-posterior home position in a registered-referral imaging dataset. The treatment dataset magnetic isocentre is known because the registered-referral imaging dataset had been registered to the treatment imaging dataset. A line was drawn downwards from the treatment dataset isocentre and intersected the skin at the skin point. From this skin point, the home position was calculated using the average compressed gel-pad thickness, the average membrane bowing distance, and the calibrated distance between undeformed membrane and home position of 67.5 mm (see Figure 3).