Some physical and mechanical property testing of main stalks of Lilium was conducted to provide information for future automatic machine design. Shear, compression and bending properties of Lilium stalks were determined with using a universal testing machine. The experiments were conducted at three rate of loading levels from 30 to 50 mm/min, three knife bevel angle levels from 30 to 60 degree and at two levels the stalk; upper and lower. The results showed that all the mentioned above parameters had significant effect on the measured mechanical properties (P<0.01). In all three loading rate, an increasing the shear strength and specific cutting energy were observed as the knife bevel angle increased. The highest compression strength and specific compressing energy were 6.86 MPa and 21.34 mJ/mm at the lower level, while the lowest 2 compression strength and specific compressing energy were 2.90 MPa and 10.69 mJ/mm at the upper level. As the loading rate of the stalk increased, the bending strength decreased, indicating a reduction in the brittleness of the stalk. The average values for modulus of elasticity were found to be 23.48 and 15.96 MPa for stalk regions of upper and lower, respectively.
Purpose: Photon-field shaping in radiation therapy with cerrobend block or Multi-Leaf Collimator (MLC) leads to an increase in the scattered dose to the out-of-field Organ At Risk (OAR). This study aimed to measure and compare the healthy organs absorbed dose outside the cerrobend block and MLC shielded field.
Materials and Methods: Computed Tomography (CT) images were taken of a heterogeneous Thorax phantom while the target volume and organ at risk, including the spinal cord, contralateral lung, and heart were contoured. Conformal Treatment planning was performed (POP fields, total dose 40 Gy, 5 fx/week, and 2 Gy/fx) on the Prowess Panter Treatment Planning System (TPS). Irradiation was performed with 6 and 18 Mv X-ray of Siemens Oncor medical linear accelerator, once for the block-shielded field and again for the MLC-shielded field. At each energy, the radiation dose to the contoured out-of-field organs was measured by an ionization chamber and compared.
Results: At both 6 and 18 MV energies, the out-of-field dose in the MLC-shielded fields was significantly lower than in the block-shielded ones (P < 0.001). The out-of-filed dose for contoured organ at risk was not significantly different at 18 MV compared with 6 MV. The dose calculated by the treatment planning system showed that the healthy organs absorbed doses in all conditions were significantly lower than the dosimetry results.
Conclusion: The use of MLC to shield the lung cancer treatment filed reduces the out-of-field OARs dose compared to cerrobend block. This reduction is greater at 18 MV photon beam but this difference is not statistically significant.
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