We attempted to test the applicability of the polymethyl metacrylate (Acrylite) as a body phantom for the deep radiotherapy. We measured the attenuation curves of the Acrylite and the percentage depth dose curves in the Acrylite phantom for the X-rays of the half value layer 0.146 mm Cu, 0.26 mm Cu, 0.57 mm CU, 0.82 mm Cu and 2.07 mm Cu. The attenuation curves of the Acrylite for these X-ray qualities were compared with the zezo field percentage depth dose data of the Quimby's table, and also the effective mass absorption coefficients of the Acrylite for various X-ray qualities were determined from the attenuation curves. We found that the effective mass absorption coefficient of the Acrylite for the 0.1 Å X-rays was equal to that of water. On the other hand, it was found that the percentage depth dose. curves in the Acrylite phantom for these X-ray qualities coincided with those in water phantom, in spite of the difference of density between the Acrylite and water. Then we concluded that this circumstance was caused by the scattering in the Acrylite phantom.
