Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, CA 94158-2330, USA.
Neoplasia. 2011 Feb;13(2):81-97. doi: 10.1593/neo.101102.
A major challenge in cancer biology is to monitor and understand cancer metabolism in vivo with the goal of improved diagnosis and perhaps therapy. Because of the complexity of biochemical pathways, tracer methods are required for detecting specific enzyme-catalyzed reactions. Stable isotopes such as (13)C or (15)N with detection by nuclear magnetic resonance provide the necessary information about tissue biochemistry, but the crucial metabolites are present in low concentration and therefore are beyond the detection threshold of traditional magnetic resonance methods. A solution is to improve sensitivity by a factor of 10,000 or more by temporarily redistributing the populations of nuclear spins in a magnetic field, a process termed hyperpolarization. Although this effect is short-lived, hyperpolarized molecules can be generated in an aqueous solution and infused in vivo where metabolism generates products that can be imaged. This discovery lifts the primary constraint on magnetic resonance imaging for monitoring metabolism-poor sensitivity-while preserving the advantage of biochemical information. The purpose of this report was to briefly summarize the known abnormalities in cancer metabolism, the value and limitations of current imaging methods for metabolism, and the principles of hyperpolarization. Recent preclinical applications are described. Hyperpolarization technology is still in its infancy, and current polarizer equipment and methods are suboptimal. Nevertheless, there are no fundamental barriers to rapid translation of this exciting technology to clinical research and perhaps clinical care.
癌症生物学的一个主要挑战是在体内监测和了解癌症代谢，目标是改善诊断，也许还能改善治疗效果。由于生化途径的复杂性，需要示踪剂方法来检测特定的酶促反应。(13)C 或 (15)N 等稳定同位素通过核磁共振提供关于组织生物化学的必要信息，但关键代谢物的浓度很低，因此超出了传统磁共振方法的检测阈值。解决方法是通过在磁场中暂时重新分配核自旋的群体，将灵敏度提高 10,000 倍或更高，这个过程称为极化。尽管这种效果是短暂的，但可以在水溶液中产生超极化分子，并在体内输注，在体内代谢会产生可以成像的产物。这一发现消除了磁共振成像监测代谢时的主要限制——低灵敏度——同时保留了生化信息的优势。本报告的目的是简要总结癌症代谢的已知异常、当前代谢成像方法的价值和局限性，以及极化的原理。描述了最近的临床前应用。极化技术仍处于起步阶段，当前的极化器设备和方法并不理想。然而，将这项令人兴奋的技术快速转化为临床研究，甚至临床护理，并没有根本的障碍。
