The present invention relates to a thermoplastic composition suitable for manufacturing a thermoplastic sheet for producing a medical cast such as a radiation mask. The composition has a polymeric component comprising a mixture of a styrene acrylonitrile copolymer and polycaprolactone optionally together with a cross linker and/or a filler wherein the polymeric component comprises 20 to 40 weight% of a styrene acrylonitrile copolymer and 80 to 60 weight% of a polycaprolactone expressed in weight% of the polymeric component wherein the thermoplastic composition has a glass transition temperature of 35 °C 80 °C. The invention further relates to a thermoplastic sheet and to a medical cast in particular a radiation mask obtainable from said composition. In a final aspect the invention relates to a method for producing said sheet and said radiation mask.
