Petersson Johan, Sánchez-Crespo Alejandro, Larsson Stig A, Mure Margareta
Department of Anesthesiology and Intensive Care, Karolinska University Hospital, Solna, 171 76 Stockholm, Sweden.
J Appl Physiol (1985). 2007 Jan;102(1):468-76. doi: 10.1152/japplphysiol.00732.2006. Epub 2006 Sep 21.
Emission tomography provides three-dimensional, quantitative images of the distribution of radiotracers used to mark physiological, metabolic, or pathological processes. Quantitative single photon emission computed tomography (SPECT) requires correction for the image-degrading effects due to photon attenuation and scatter. Phantom experiments have shown that radioactive concentrations can be assessed within some percentage of the true value when relevant corrections are applied. SPECT is widely spread, and radiotracers are available that are easy to use and comparably inexpensive. Compared with other methods, SPECT suffers from a lower spatial resolution, and the time required for image acquisition is longer than for some alternative methods. In contrast to some other methods, SPECT allows simultaneous imaging of more than one process, e.g., both regional blood flow and ventilation, for the whole lung. SPECT has been used to explore the influence of posture and clinical interventions on the spatial distribution of lung blood flow and ventilation. Lung blood flow is typically imaged using macroaggregates of albumin. Both radioactive gases and particulate aerosols labeled with radioactivity have been used for imaging of regional ventilation. However, all radiotracers are not equally suited for quantitative measurements; all have specific advantages and limitations. With SPECT, both blood flow and ventilation can be marked with radiotracers that remain fixed in the lung tissue, which allows tracer administration during conditions different from those at image registration. All SPECT methods have specific features that result from the used radiotracer, the manner in which it is administered, and how images are registered and analyzed.
发射断层扫描可提供放射性示踪剂分布的三维定量图像，这些示踪剂用于标记生理、代谢或病理过程。定量单光子发射计算机断层扫描（SPECT）需要校正由于光子衰减和散射导致的图像质量下降效应。模体实验表明，当应用相关校正时，放射性浓度可以在真实值的一定百分比范围内进行评估。SPECT应用广泛，有易于使用且成本相对较低的放射性示踪剂。与其他方法相比，SPECT的空间分辨率较低，图像采集所需时间比某些替代方法更长。与其他一些方法不同，SPECT允许对多个过程进行同时成像，例如对整个肺部的区域血流和通气进行同时成像。SPECT已被用于探索姿势和临床干预对肺血流和通气空间分布的影响。肺血流通常使用白蛋白大聚合体进行成像。放射性气体和标记有放射性的颗粒气溶胶都已用于区域通气成像。然而，并非所有放射性示踪剂都同样适用于定量测量；它们都有各自的优点和局限性。使用SPECT时，血流和通气都可以用固定在肺组织中的放射性示踪剂进行标记，这允许在与图像配准条件不同的情况下给予示踪剂。所有SPECT方法都有其特定的特征，这些特征源于所使用的放射性示踪剂、其给药方式以及图像的配准和分析方式。
