The relevant section from the ECC's Employer's Written Procedure EP2\ ECC\3422 'RadCalc instructions' for parallel opposed pair at 100cm FSD calculations
For patients with POP calculation at 100cm FSD:
- A new calculation point must be created that sits midway between the 2 isocentres.
- In Points & Off Axis Assistance, copy the IsoCenter_1 point by clicking on the middle button "copy point".
- Tick "Enter 3D coordinates for point" and look at the x, y, and z coordinates for Isocentre_1 and Isocentre_2 to find out which value differs. If they are lateral fields, the x value will be different. If they are ant/post fields, the y value will be different.
- Set whichever value differs to zero for IsoCenter_3.
- With IsoCenter_3 selected, set the SSD for both beams to 100cm and then enter the prescribed dose per fraction in RTP Dose.
- On the photon beams tab, select Calc Pt as IsoCenter_3 for both beams.