Improving accuracy in small-animal cardiac SPECT/CT imaging

提高小动物心脏 SPECT/CT 成像的准确性

• 批准号: 261765-2011
• 负责人: Wells, Glenn
• 金额: $ 2.04万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=571143
• 关键词: Improving; accuracy; small; animal; cardiac

Small animal imaging with single-photon emission computed tomography (microSPECT) is central to the timely development of new radiotracers and to improving our understanding and treatment of important diseases like heart failure. It allows for in vivo 3D assessment of tracer distribution and organ function over multiple time points in the same animal. Work in this field to date has yielded very promising results, but further work is required to realize its full potential. Micro-imaging faces different challenges and demands than clinical imaging and this alters the emphasis of various aspects of the physics of the system. There is a strong emphasis on resolution due to the very small size of the subjects (mice and rats) which has led to a shift to pinhole SPECT imaging. The use of pinhole collimators results in variable resolution, magnification, and sensitivity across the field of view. In addition, the use of multiple pinholes to offset poor sensitivity can lead to overlap of the signals in the projections and thus introduce ambiguity in the data used for image reconstruction. The effects of photon attenuation and scatter are reduced in small-animals but not eliminated, and there remains a need to compensate for these effects in this more complex image-acquisition environment. Finally, one of the strengths of small-animal SPECT over competing technology is its ability to use different isotopes to probe multiple signals simultaneously. Nevertheless, the separation of these signals is not complete and correction for the remaining interference is required. While various methods exist from clinical imaging to correct for many of these effects, modification of these techniques to optimize them for micro-imaging is needed and the impact of these on the accuracy and precision of micro-imaging is presently unknown. This work is significant because the basic science nature of the tasks to which micro-imaging is devoted demand a high level of quantitative accuracy. Improvements in small-animal SPECT will enhance our ability to rapidly develop and evaluate new radiotracers and to study fundamental processes such as apoptosis and angiogenesis during the onset and progression of disease. My program is aimed at improving the quantitative accuracy and reproducibility of imaging with small-animal cardiac SPECT/CT. I am interested in understanding how different factors such as attenuation, scatter, partial-volume effects, and multi-isotope interference affect image quality and the impact of different methods of compensation for these effects during image reconstruction. I am exploring the means by which CT can further enhance microSPECT imaging, not only by providing a transmission image for correction methods, but also through direct integration into the reconstruction by, for example, anatomical priors and Bayesian reconstruction. My specific focus at this time is on understanding the accuracy and reproducibility of basic measures of cardiac function such as heart volume, ejection fraction, and perfusion homogeneity and on evaluating and developing compensation techniques which will enhance this precision. The methods employed by my laboratory include both Monte Carlo simulation, using anatomically realistic computer phantoms such as the MOBY phantom, as well as animal experiments in rats and mice with a multi-head microSPECT/CT camera. I hypothesize that image accuracy and precision will be significantly improved by using advanced reconstruction methods that integrate CT information and compensate for photon attenuation, scatter, and cross-talk. My lab provides a rich environment for undergraduate and graduate student education. We collaborate with radiochemists developing novel radiotracers as well as with basic scientists exploring the mechanisms underlying cardiac disease, in particular the role of apoptosis and the use of stem cells for heart repair. As part of the University of Ottawa Heart Institute, students are also exposed to the medical motivation that drives much of this field of research. As part of the Ottawa-Carleton joint program in medical physics, they also interact with students engaged in a wide variety of medical physics projects.

使用单光子发射计算机断层扫描（microSPECT）进行小动物成像对于及时开发新的放射性示踪剂以及提高我们对心力衰竭等重要疾病的理解和治疗至关重要。 它允许在同一动物的多个时间点内对示踪剂分布和器官功能进行体内3D评估。 迄今为止，这一领域的工作已经取得了非常有希望的成果，但要充分发挥其潜力，还需要开展进一步的工作。 显微成像面临着与临床成像不同的挑战和需求，这改变了系统物理学各个方面的重点。 由于受试者（小鼠和大鼠）的体积非常小，因此非常重视分辨率，这导致了向针孔SPECT成像的转变。 针孔准直器的使用导致整个视场的可变分辨率、放大率和灵敏度。 此外，使用多个针孔来抵消差的灵敏度可能导致投影中的信号重叠，从而在用于图像重建的数据中引入模糊性。 光子衰减和散射的影响在小动物中减少但没有消除，并且仍然需要在这种更复杂的图像采集环境中补偿这些影响。 最后，小动物SPECT相对于竞争技术的优势之一是它能够使用不同的同位素同时探测多个信号。 然而，这些信号的分离并不完全，需要对剩余的干扰进行校正。 虽然从临床成像中存在各种方法来校正许多这些效应，但需要修改这些技术以优化它们用于显微成像，并且这些对显微成像的准确性和精确度的影响目前是未知的。这项工作是重要的，因为基本的科学性质的任务，显微成像是专门要求高水平的定量精度。小动物SPECT的改进将提高我们快速开发和评估新的放射性示踪剂的能力，并研究疾病发生和进展过程中的细胞凋亡和血管生成等基本过程。 我的计划旨在提高定量准确性和重复性的小动物心脏SPECT/CT成像。 我感兴趣的是了解不同的因素，如衰减，散射，部分体积效应和多同位素干扰如何影响图像质量，以及在图像重建过程中补偿这些影响的不同方法的影响。 我正在探索CT可以进一步增强microSPECT成像的方法，不仅通过提供用于校正方法的透射图像，而且通过直接集成到重建中，例如，解剖先验和贝叶斯重建。 目前，我的重点是了解心脏功能基本指标的准确性和可重复性，如心脏容积、射血分数和灌注均匀性，以及评估和开发将提高这种精度的补偿技术。 我的实验室采用的方法包括蒙特卡洛模拟，使用解剖学上逼真的计算机模型，如MOBY模型，以及在大鼠和小鼠中使用多头microSPECT/CT相机进行的动物实验。我假设，图像的准确性和精度将显着提高，通过使用先进的重建方法，整合CT信息和光子衰减，散射和串扰补偿。 我的实验室为本科生和研究生教育提供了丰富的环境。 我们与放射化学家合作开发新型放射性示踪剂，并与基础科学家合作探索心脏疾病的潜在机制，特别是细胞凋亡的作用和干细胞用于心脏修复。 作为渥太华大学心脏研究所的一部分，学生们也接触到了推动这一领域研究的医学动机。 作为渥太华-卡尔顿医学物理联合项目的一部分，他们还与从事各种医学物理项目的学生进行互动。