Durian Seed As A Potential Substrate For Bolus In Radiotherapy
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Date
2015-06
Authors
Ahmad Lothfy, Fairuzdzah
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Abstract
Three types of bolus were fabricated using three types of composition with different ratios of polyvinyl alcohol (PVA) to durian seed gums. The ratio of PVA to durian seed gum were 1:9; 3:7 and 5:5. The fabricated bolus was characterized based on the mechanical properties such as tensile strength, strain, and flexibility. Eventually, all bolus composition that were prepared had low tensile strength. The maximum tensile strength for bolus 1:9 was 0.083 MPa, bolus 3:7 was 0.323 MPa and bolus 5:5 was 0.786 MPa. The strain of every type of fabricated bolus fulfilled the minimum requirement which was more than 50%. All types of bolus had less than 100 MPa value of Young‟s Modulus which fulfilled one of the requirements for bolus to be used in radiotherapy. This value was important to produce bolus with good flexibility. The fabricated bolus had tissue equivalent properties. Hence, physical density, relative electron density and transmission factor were measured. Physical densities for bolus 1:9 was 1.07 ± 0.01 g cm-3, bolus 3:7 was 1.00 ± 0.01 g cm-3 and bolus 5:5 was 1.00 ± 0.01 g cm-3. The density bolus 1:9 differed from water density by 7 %. However, density bolus 3:7 and bolus 5:5 had no significant difference with water density. All types of fabricated bolus density were compared with a list of commercial bolus density. The values did not show significant difference towards the density. Relative electron density for bolus 1:9 was 1.028 ± 0.019, bolus 3:7 was 1.002 ± 0.003 and bolus 5:5 was 1.002 ± 0.002. There was a significant difference in electron density between bolus 1:9 and water. However, bolus 3:7 and bolus 5:5 showed no significant differences. Transmission factor was measured by calculating the percentage depth dose (PDD) of the maximum depth dose.. PDD of the maximum depth dose for bolus 1:9 was 85.63%, bolus 3:7 was 98.13%, and bolus 5:5 was 98.88%. The comparison of transmission factor for bolus 3:7 and bolus 5:5 with water phantom type 2967 showed no significant difference, and transmission factor of with bolus 1:9 and water type 2967 showed significant difference.
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Physics (General)