Acrylic & Polystyrene

Phantom Materials

A typical acrylic or polystyrene phantom is a 25cm cube consisting of one of each fractional thickness, eight 1" thick sections and one 1" thick section which has an ion chamber cavity drilled at 1cm from the nearest surface.  This allows the calibration depth to be adjusted in 0.8mm (1/32") increments over 1cm for photon beams.  A section for a plane-parallel chamber is machined to position the chamber flush with one surface.  In this manner, depths can be achieved for calibrating electron beams in 0.8mm (1/32") steps.

Economy is achieved by using standard thickness material in English System dimensions.  Although the thickness tolerance can vary ±5%, the thickness of each section is individually measured and marked with permanent ink in metric units.

Separate sections are available for adding to an existing phantom or to assemble a phantom with custom dimensions.

Polystyrene plastic (PS), also known as polystyrol, has a density of 1.05g/cm³, which makes it lighter than acrylic.  Historically supplied in clear sheets, polystyrene is currently only supplied in milky white sheets.  It is available in 25 x 25cm sections of varying thickness.

Acrylic phantom material is a clear plastic with the chemical formula (C-5/H-8/O-2)n, polymethylmethacrylate (PMMA).  It is also known under the trade names Lucite, Plexiglas and Perspex.  Acrylic has a density of 1.185g/cm³.  It is available in 25 x 25cm sections of varying thickness.

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