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Low Z target optimization for spatial resolution improvement in planar imaging and cone-beam CT.

机译：低Z目标优化可提高平面成像和锥束CT的空间分辨率。

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摘要

Recent studies in medical physics have focused on the application of low atomic number (Z) targets for their effect on contrast in megavoltage portal imaging and cone-beam computed tomography (CBCT). This work seeks to compliment those studies by investigating the effects of varying different target parameters including atomic number, thickness and incident electron energy on spatial resolution in megavoltage planar imaging and CBCT. Target materials of beryllium (Be, Z = 4), aluminum (Al, Z = 13) and tungsten (W, Z = 74) were investigated over a variety thicknesses between 10% and 100% of the continuous slowing down approximation range. Incident electron kinetic energies of 4.5 MeV and 7.0 MeV were used along with custom targets installed into the carousel of a Varian 2100EX linear accelerator (Varian Medical, Inc.) to produce the experimental beams of interest. Monte Carlo simulated results were compared to measured data and it was shown that thinner targets are generally superior to thicker targets and that higher incident electron energies produce better results. Due to a dependence of the MTF of the detector system on photon energy, it was shown that low Z targets produced superior spatial resolution. Simulations also showed a 14.5% and 21.5% increase in spatial frequency in which the modulation transfer function dropped to half of its maximum ( f50) for the 7.0 MeV and 4.5 MeV targets, respectively, when moved from the carousel to the location of the clinical target. The f50 values of the custom targets were compared to the clinical 6 MV beam and were found to be between 10.4% lower and 15.5% higher than the 6 MV value. Low-Z CBCT sets were acquired using the CATphan phantom and compared to the clinical 6 MV beam and kilovoltage CBCT sets. Using the low-Z targets it was possible to resolve the 0.5 lp/mm, compared to 0.4 lp/mm and 1.0 lp/mm for the clinical 6 MV and kilovoltage sets respectively.
机译：医学物理学方面的最新研究集中于低原子序数（Z）靶标的应用，因为它们对兆伏门成像和锥束计算机断层扫描（CBCT）中的对比度有影响。这项工作旨在通过研究改变不同目标参数（包括原子序数，厚度和入射电子能量）对兆电压平面成像和CBCT中的空间分辨率的影响来补充这些研究。研究了铍（Be，Z = 4），铝（Al，Z = 13）和钨（W，Z = 74）的目标材料，其厚度在连续减慢近似范围的10％至100％之间。使用4.5 MeV和7.0 MeV的入射电子动能，以及安装在Varian 2100EX线性加速器（Varian Medical，Inc.）的转盘中的定制靶，以产生感兴趣的实验束。将蒙特卡罗模拟结果与测量数据进行了比较，结果表明，较薄的靶通常优于较厚的靶，并且较高的入射电子能产生更好的结果。由于探测器系统的MTF依赖于光子能量，因此表明低Z目标可产生出众的空间分辨率。模拟还显示，当从转盘传送带移到临床位置时，对于7.0 MeV和4.5 MeV目标，调制传递函数分别降至其最大频率（f50）的一半，空间频率增加了14.5％和21.5％。目标。将自定义目标的f50值与临床6 MV光束进行比较，发现其比6 MV值低10.4％至15.5％。使用CATphan幻影获取低Z CBCT集，并将其与临床6 MV束和千伏CBCT集进行比较。使用低Z靶标，可以分辨出0.5 lp / mm，而临床6 MV和千伏特电压分别为0.4 lp / mm和1.0 lp / mm。

著录项

  • 作者

    Connell, Tanner.;

  • 作者单位

    McGill University (Canada).;

  • 授予单位 McGill University (Canada).;
  • 学科 Physics Radiation.
  • 学位 M.Sc.
  • 年度 2009
  • 页码 99 p.
  • 总页数 99
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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