Effect of the Air Gap Between Skin and Bolus Material on the Surface Dose

• Main Authors: LIN, HUNG-CHENG, 林宏澄
• Other Authors: CHEN, HSIN-HSIUNG
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/pn9v2w

碩士 === 中臺科技大學 === 醫學影像暨放射科學系暨研究所 === 106 === Bolus material is frequently adopted in the radiotherapy treatment planning. It can help to uplift the surface skin dose in practical setting. This is essential for some carcinomas that falls in the buildup region and the inappropriate arrangement may cause low dose to form a cold spot in the clinical therapy. To effectively suppress the situation, it is usually recommended to add bolus materials to increase the surface dose around skin. However, it is important to ensure the seal tightness between bolus material and real skin. If the covered area is close to the nose, ear or any irregular skin surface, the sealed function may decrease, and thus the given dose also reduce significantly to affect the clinical results. The topic of this work tries to evaluate the air gap between bolus material and the surface of skin, further, the discrepancy between assigned and surveyed dose is also explored. There are two major sections included in this work : (a) to measure the skin dose using RW3 solid water phantom and markus planner ionization chamber ; (b) verify the surveyed dose using EBT2 film. The film was randomly collected 10 points of data then scanned to obtain the dose. The dose is given by the linac (Elekta, synergy) under 6, 10 MV X-rays or 6, 9 MeV electron beam, respectively. The surveyed condition were preset as various field size, thicknesses of bolus material, or air gaps between bolus material and surface of measure and so on. All of the surveyed readings were normalized and analyzed. The results indicated that all the preset conditions influenced the reading significantly. Small field size, shallow position, thick bolus materials or larger air gap reduced the reading dramatically. The survey also can provide greatly the referred index for future clinical of treatment planning.