University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
J Nucl Med. 2010 May 1;51 Suppl 1(0 1):18S-32S. doi: 10.2967/jnumed.109.068148.
The ability to trace or identify specific molecules within a specific anatomic location provides insight into metabolic pathways, tissue components, and tracing of solute transport mechanisms. With the increasing use of small animals for research, such imaging must have sufficiently high spatial resolution to allow anatomic localization as well as sufficient specificity and sensitivity to provide an accurate description of the molecular distribution and concentration.
Imaging methods based on electromagnetic radiation, such as PET, SPECT, MRI, and CT, are increasingly applicable because of recent advances in novel scanner hardware and image reconstruction software and the availability of novel molecules that have enhanced sensitivity in these methodologies.
Small-animal PET has been advanced by the development of detector arrays that provide higher resolution and positron-emitting elements that allow new molecular tracers to be labeled. Micro-MRI has been improved in terms of spatial resolution and sensitivity through increased magnet field strength and the development of special-purpose coils and associated scan protocols. Of particular interest is the associated ability to image local mechanical function and solute transport processes, which can be directly related to the molecular information. This ability is further strengthened by the synergistic integration of PET with MRI. Micro-SPECT has been improved through the use of coded aperture imaging approaches as well as image reconstruction algorithms that can better deal with the photon-limited scan data. The limited spatial resolution can be partially overcome by integrating SPECT with CT. Micro-CT by itself provides exquisite spatial resolution of anatomy, but recent developments in high-spatial-resolution photon counting and spectrally sensitive imaging arrays, combined with x-ray optical devices, hold promise for actual molecular identification by virtue of the chemical bond lengths of molecules, especially biopolymers.
Given the increasing use of small animals for evaluating new clinical imaging techniques and providing more insight into pathophysiologic phenomena as well as the availability of improved detection systems, scanning protocols, and associated software, the sensitivity and specificity of molecular imaging are increasing.
在特定解剖位置追踪或识别特定分子的能力可深入了解代谢途径、组织成分和溶质转运机制的追踪。随着小型动物在研究中的应用日益增多，此类成像必须具有足够高的空间分辨率，以实现解剖定位，并且具有足够的特异性和灵敏度，从而准确描述分子分布和浓度。
基于电磁辐射的成像方法，如 PET、SPECT、MRI 和 CT，由于新型扫描仪硬件和图像重建软件的最新进展以及这些方法中具有更高灵敏度的新型分子的可用性，应用越来越广泛。
通过开发提供更高分辨率的探测器阵列和允许标记新型分子示踪剂的正电子发射元素，小型动物 PET 得到了推进。通过增加磁场强度以及开发专用线圈和相关扫描协议，微 MRI 在空间分辨率和灵敏度方面得到了改善。特别有趣的是与局部机械功能和溶质转运过程成像相关的能力，这些过程可以直接与分子信息相关联。通过将 PET 与 MRI 协同集成，这种能力得到了进一步增强。通过使用编码孔径成像方法以及可以更好地处理光子受限扫描数据的图像重建算法，微 SPECT 得到了改进。通过将 SPECT 与 CT 集成，可以部分克服有限的空间分辨率。微 CT 本身提供了精细的解剖空间分辨率，但最近在高空间分辨率光子计数和光谱敏感成像阵列以及 X 射线光学器件方面的发展，结合分子的化学键长度，特别是生物聚合物，有望通过实际的分子识别。
鉴于小型动物在评估新的临床成像技术以及深入了解病理生理现象中的应用日益增多，以及改进的检测系统、扫描协议和相关软件的可用性，分子成像的灵敏度和特异性正在提高。
