الفهرس 
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Abstract
The linear accelerator is a device that uses high-frequency electromagnetic waves to accelerate charged particles such as electrons to high energies through a linear tube. There are several types of linear accelerator designs, but the ones used in radiotherapy accelerate electrons either by traveling or stationary electromagnetic waves is Elekta linear accelerator which have been used in this study. Radiotherapy patient may be exposed to different doses of x-ray. Therefore, the main interest was to find out whether do exposures to these doses of x-ray can affect bones structure and function.
This study aimed to investigate the effect of different doses of x-ray from linear accelerator (6MV) on some biochemical (calcium concentration and collagen concentration) and some biophysical (stress – strain behavior, breakpoint and hysteresis loop) parameters of rat bone.
In this work the following materials and methods were used:
In the presence work 60 male albino rats, each of average weight 170±15 gm divided into five main groups, namely group A, B, C, D, and E. Animals of group A are used as a control group and didn’t receive any treatment and housed at normal environmental conditions. Animals of group B, C, D, and E were whole body exposed to X-rays 1, 3, 5 and 7Gy. doses respectively from a clinical therapeutic(6 MV) linear accelerator. Animals of group B, C, D and E were housed at normal environmental conditions similar to control group A. At the end of the exposure period, animals of groups B, C, D and E each were then equally divided into two subgroups, namely B1, C1, D1 and E1. Animals of the groups B1, C1, D1 and E1 were sacrificed after 3 days and bone samples from each animal were collected for experimental investigation. Animals of the groups B2, C2, D2 and E2 were sacrificed after 10 days and bone samples from each animal were collected to determine:
- Calcium and collagen concentrations.
- Stress – strain behavior.
- Breakpoint.
- Hysteresis loop
The results of the present work are:
1- Significant decrease in calcium concentration in all experimental groups as compared by control group.
2- Significant decrease in collagen concentration in all experimental groups as compared by control group.
3- Significant decrease in breakpoint values in all experimental groups as compared by control group.
4- Significant decrease in tensile strain values in all experimental groups as compared by control group.
5- Significant increase in area enclosed load-unload curve values in all experimental groups as compared by control group.
6- Significant decrease in elasticity of bone in all experimental groups as compared by control group.
II- Conclusion
Depending on the present work results, we can conclude that all x-ray doses in this study have direct and clear effect on:
• Calcium concentration in bone.
• Collagen concentration in bone.
• Bone structure and function.
• Elasticity of bone.