有望诊治癌症的切伦科夫冷光成像技术

导读：新技术有望帮助人们诊治癌症和其他疾病，以及更快和更有效地开发放射性药物。

美国核医学学会7月1日表示，新出版的《核医学杂志》报道了名为切伦科夫冷光成像（Cerenkov luminescence imaging）的新型光学成像技术。据文章作者介绍，新技术有望帮助人们诊治癌症和其他疾病，以及更快和更有效地开发放射性药物。

研究负责人、斯隆-凯特灵纪念癌症中心教授简·格林姆博士表示，新型多通道显影剂和技术属于医学成像科学领域的研究前沿，它可能为新的光学成像进入临床应用开辟新途径。格林姆小组认为，自己的研究属于那些首次探讨将切伦科夫辐射应用于医学成像的工作。据悉，加州大学和斯坦福大学科学家参与了研究。

当光在水中传播时，其速度会减慢。而此时速度超过光速的粒子如同突破声障的音爆，会产生 “震波”（或“冲击波”）发出蓝色可见光，该现象被称为切伦科夫辐射。

光学成像是一种分子成像过程。在此过程中，设计出来用于附着在特殊细胞和分子上的发光分子被注入人体血液中，并可为光学成像仪探测到。通常，为便于光学成像仪工作，这些发光分子需要通过体外光源或生物手段进行激活。

在新型光学成像技术中，由于切伦科夫成像产生的光来源于辐射，因此不再需要用体外光源照明。格林姆认为，这种将光学成像与核医学的结合代表了医学成像的新途径。他同时表示，目前多种核示踪物被批准用于医学临床，它们与光学成像组成的切伦科夫冷光成像系统能够很快得到应用，这与荧光染料截然不同。

在研究中，科学家对有可能用于切伦科夫冷光成像系统的几种放射性核素进行了评估。他们用切伦科夫冷光成像系统和正电子断层扫描仪（PET）对患有肿瘤的实验鼠进行了视觉化处理，结果表明，切伦科夫冷光成像系统能够将摄入到体内的放射性示踪物可视化。生物谷新域名www.bioon.net

研究人员表示，切伦科夫冷光成像技术采用了过去无法可视化的轻同位素，也就是说它能够对既不发射正电子又不发射伽玛射线的放射性示踪物进行成像，这个能力是目前核成像法所不具备的。此外，光学成像技术将有助于内窥检查和外科手术，原因是它能将肿瘤的损害实现可视化，为手术等提供实时信息。(生物谷Bioon.net)

生物谷推荐原文出处：

Journal of Nuclear Medicine doi: 10.2967/jnumed.110.076521

Cerenkov Luminescence Imaging of Medical Isotopes
Alessandro Ruggiero*,1, Jason P. Holland*,2, Jason S. Lewis2,3 and Jan Grimm1,3

1 Nuclear Medicine Service, Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York; 2 Radiochemistry Service, Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York; and 3 Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York

The development of novel multimodality imaging agents and techniques represents the current frontier of research in the field of medical imaging science. However, the combination of nuclear tomography with optical techniques has yet to be established. Here, we report the use of the inherent optical emissions from the decay of radiopharmaceuticals for Cerenkov luminescence imaging (CLI) of tumors in vivo and correlate the results with those obtained from concordant immuno-PET studies. Methods: In vitro phantom studies were used to validate the visible light emission observed from a range of radionuclides including the positron emitters 18F, 64Cu, 89Zr, and 124I; β-emitter 131I; and -particle emitter 225Ac for potential use in CLI. The novel radiolabeled monoclonal antibody 89Zr-desferrioxamine B [DFO]-J591 for immuno-PET of prostate-specific membrane antigen (PSMA) expression was used to coregister and correlate the CLI signal observed with the immuno-PET images and biodistribution studies. Results: Phantom studies confirmed that Cerenkov radiation can be observed from a range of positron-, β-, and -emitting radionuclides using standard optical imaging devices. The change in light emission intensity versus time was concordant with radionuclide decay and was also found to correlate linearly with both the activity concentration and the measured PET signal (percentage injected dose per gram). In vivo studies conducted in male severe combined immune deficient mice bearing PSMA-positive, subcutaneous LNCaP tumors demonstrated that tumor-specific uptake of 89Zr-DFO-J591 could be visualized by both immuno-PET and CLI. Optical and immuno-PET signal intensities were found to increase over time from 24 to 96 h, and biodistribution studies were found to correlate well with both imaging modalities. Conclusion: These studies represent the first, to our knowledge, quantitative assessment of CLI for measuring radiotracer uptake in vivo. Many radionuclides common to both nuclear tomographic imaging and radiotherapy have the potential to be used in CLI. The value of CLI lies in its ability to image radionuclides that do not emit either positrons or -rays and are, thus, unsuitable for use with current nuclear imaging modalities. Optical imaging of Cerenkov radiation emission shows excellent promise as a potential new imaging modality for the rapid, high-throughput screening of radiopharmaceuticals.