Supine craniospinal irradiation in children: patient position modification, dose uniformity and early adverse effects.

Thirty one patients were treated with CSI in the supine position. Custom-made Styrofoam was tailored for each patient to straighten the convexity and concavity of the spinal axis allowing better dose distribution uniformity during CSI technique. In the first 6 patients, CT simulation were performed twice: one time with the patient lying directly on the vacuum mattress without the foam (the conventional way) and the second while lying on the foam. Dose distribution was calculated using a 3D conformal planning. The gap between the fields was determined using isodose alignment method. All treatment portals were verified during the first 3 treatment sessions and once weekly thereafter using either cone-beam or portal image device. Weekly feathering (shifting of the junction between the 2 adjacent radiation fields) was routinely performed.