A patient is being treated isocentrically for cervical cance…

A patient is being treated isocentrically for cervical cancer. The patient is in the 3rd week of treatment.  The patient is being treated on a machine that is calibrated at 100 SSD.  The tumor is 9.2 cm below the anterior surface of the patient.  The tumor is also located 10.2 cm medial from the patient’s left side. The patient is 26.4 cm thick (AP/PA) and from right to left lateral the patient is 34.6cm.  The doctor prescribes a total dose of 64.8 Gy to be delivered in fractions of 1.8 Gy.  The patient is being treated using a four field box technique. What is the PA SSD?