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On-board single photon emission computed tomography (SPECT) for biological target localization.

机译：机载单光子发射计算机断层扫描（SPECT）用于生物目标定位。

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摘要

On-board imaging is useful for guiding radiation to patients in the treatment position however, current treatment-room imaging modalities are not sensitive to physiology---features that may differentiate tumor from nearby tissue or identify biological targets, e.g., hypoxia, high tumor burden, or increased proliferation. Single photon emission computed tomography (SPECT) is sensitive to physiology. We propose on-board SPECT for biological target localization.Localization performance was studied in computer-simulated and scanner-acquired parallel-hole SPECT images. Numerical observers were forced to localize hot targets in limited search volumes that account for uncertainties common to radiation therapy delivery. Localization performance was studied for spherical targets of various diameters, activity ratios, and anatomical locations. Also investigated were the effects of detector response function compensation (DRC) and observer normalization on target localization. Localization performance was optimized as a function of iteration number and degree of post-reconstruction smoothing. Localization error patterns were analyzed for directional dependencies and were related to the detector trajectory. Localization performance and the effect of the detector trajectory were investigated in a hardware study using a whole-body phantom.Typically targets of 6:1 activity were localized as accurately using 4-minute scans as those of 3:1 activity using 20-minute scans. This trend is consistent with the relationship between contrast and noise in the contrast-to-noise ratio (CNR) and implies that higher contrast targets are better candidates for on-board SPECT because of time constraints in the treatment room. Using 4-minute scans, mean localization errors were within 2 mm for superficial targets of 6:1 activity that were proximal to the detector trajectory and of at least 14 mm in diameter. Localization was significantly better (p0.05, Wilcoxon signed-rank test) with than without observer normalization and DRC at 5 of 6 superficial tumor sites. Observer normalization improved localization substantially for a target proximal to the much hotter heart. Localization error patterns were shown to be anisotropic and dependent on target position relative to the detector trajectory. Detector views of close approach and of minimal attenuation were predictive of directions with the smallest (magnitude) localization bias and precision. The detector trajectory had a substantial effect on localization performance. In scanner-acquired SPECT images, mean localization errors of a 22-mm-diameter superficial target were 0.8, 1.5, and 6.9 mm respectively using proximal 180°, 360°, and distal 180° detector trajectories, thus demonstrating the benefits of using a proximal 180° detector trajectory.In conclusion, the potential performance characteristics of on-board SPECT were investigated using computer-simulation and real-detector studies. Mean localization errors 2 mm were obtained for proximal, superficial targets with diameters >14 mm and of 6:1 activity relative to background using scan times of approximately 5 minutes. The observed direction-dependent localization errors are related to the detector trajectory and have important implications for radiation therapy. This works shows that parallel-hole SPECT could be useful for localizing certain biological targets.
机译：机载成像对于将放射线引导至治疗位置的患者很有用，但是，当前的治疗室成像方式对生理学并不敏感-这些特征可能会将肿瘤与附近的组织区分开来或识别生物学目标，例如缺氧，高肿瘤负担，或扩散增加。单光子发射计算机断层扫描（SPECT）对生理敏感。我们提出了机载SPECT用于生物目标定位的方法。在计算机模拟和扫描仪获取的平行孔SPECT图像中研究了定位性能。数值观察员被迫将热目标定位在有限的搜索范围内，这是放射治疗实施中常见的不确定因素。研究了各种直径，活度比和解剖位置的球形目标的定位性能。还研究了探测器响应函数补偿（DRC）和观察者归一化对目标定位的影响。优化了本地化性能，作为迭代次数和重建后平滑程度的函数。分析了定位误差模式的方向依赖性，并与探测器的轨迹有关。使用全身模型在硬件研究中研究了定位性能和探测器轨迹的影响。通常使用4分钟扫描精确定位6：1活动的目标，而使用20分钟扫描精确定位3：1活动的目标。这种趋势与对比度与噪声之间在对比度与噪声比（CNR）中的关系一致，并暗示由于治疗室中的时间限制，较高的对比度目标更适合用于机载SPECT。使用4分钟扫描，对于6：1活动的表面目标，最接近探测器轨迹且直径至少14 mm的平均定位误差在2 mm以内。与没有观察者归一化和DRC相比，在6个浅表肿瘤部位中有5个部位的定位要好得多（p <0.05，Wilcoxon符号秩检验）。观察者归一化大大改善了对较热心脏近端的目标的定位。定位误差模式显示为各向异性，并取决于相对于探测器轨迹的目标位置。接近方法和最小衰减的检测器视图可预测具有最小（幅度）定位偏差和精度的方向。探测器的轨迹对定位性能有很大影响。在扫描仪获取的SPECT图像中，使用近端180°，360°和远端180°探测器轨迹，直径为22 mm的浅表目标的平均定位误差分别为0.8、1.5和6.9 mm，因此证明了使用近端180°探测器的好处总之，使用计算机仿真和真实探测器研究了机载SPECT的潜在性能特征。使用约5分钟的扫描时间，对于直径> 14 mm且相对于背景的活性为6：1的近端浅表目标，获得了平均定位误差<2 mm。所观察到的与方向有关的定位误差与探测器的轨迹有关，并且对放射治疗具有重要意义。这项工作表明平行孔SPECT可能有助于定位某些生物学目标。

著录项

  • 作者

    Roper, Justin R.;

  • 作者单位

    Duke University.;

  • 授予单位 Duke University.;
  • 学科 Engineering Biomedical.Health Sciences Radiology.Health Sciences Oncology.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 154 p.
  • 总页数 154
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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