الفهرس 
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Abstract
Radiation therapywas soon being used in the treatment of a wide variety of
malignant tumorsusing ionizing radiation as high energy electron beam. Linear
accelerators have become the most widely used machines in radiation therapy centers
to produce electron beams. Theclinical dosimertry for electron beams is of great
importance for new and modern devices characterized by both quality and high
precision.
Due to the variation of the dosimetry parameters of electron beams energy
between different LINACS,the aim of the present study was to make a comparison
between the dosimetric parametersofmutualhigh electron beam energies 8, 10 and 12
MeV betweentwo type of linear accelerator machines one at Mohamed Rashid center
for cancer treatment and nuclear medicine, Alexandria faculty of medicine and the
other at EL Qabbary` hospital center, Alexandriaby using 10x10, 15x15 and 20x20
cm2 applicators at source to surface distance (SSD) = 100 cm.
Water is recommended as a standard medium because the dose distribution in the
water and human tissue are equivalents forexposed ionization radiation as electron
beams. Sometimes water was replaced by slab phantom made fromPoly Methyl
Methacrylate (PMMA) has the properties of water.