NOTA is a bifunctional chelate which acts as the framework to construct PET imaging tools. NOTA also can be used for probe design and signal amplification via the multivalent effect[1][2].
[1]. Singh AN, et al. Multivalent bifunctional chelator scaffolds for gallium-68 based positron emission tomography imaging probe design: signal amplification via multivalency. Bioconjug Chem. 2011;22(8):1650-1662. [2]. Liao AH, et al. Evaluation of 18F-labeled targeted perfluorocarbon-filled albumin microbubbles as a probe for microUS and microPET in tumor-bearing mice. Ultrasonics. 2013;53(2):320-327.