Dose distribution of high energy electron by shielding material

We studied for the shielding materials of normal tissue in high energy election irradiation. The lead plate has being chosen as the appropriate shielding material and the dose distribution is transformed into following: 1) The thickness of lead for complete shielding of high energy election is 3.2 mm Pb for 8 MeV 4.3 mm Pb for 10 MeV 5.0 mm Pb for 12 MeV 2) Surface dose is increased about 3 to 10 percent of maximum dosage, if the lead plate is used for electron beam shielding. 3) The Bremsstrahlung is occurred from shielding lead plate from above 4 to 6 percent of maximum dosage, yet this dosage is not above the practical error of radiotherapy.