RT Journal Article SR Electronic T1 Cerenkov Luminescence Endoscopy: Improved Molecular Sensitivity with β−-Emitting Radiotracers JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP jnumed.114.139105 DO 10.2967/jnumed.114.139105 A1 Carpenter, Colin M. A1 Ma, Xiaowei A1 Liu, Hongguang A1 Sun, Conroy A1 Pratx, Guillem A1 Wang, Jing A1 Gambhir, Sanjiv S. A1 Xing, Lei A1 Cheng, Zhen YR 2014 UL http://jnm.snmjournals.org/content/early/2014/10/06/jnumed.114.139105.abstract AB Cerenkov luminescence endoscopy (CLE) is an optical technique that captures the Cerenkov photons emitted from highly energetic moving charged particles (β+ or β−) and can be used to monitor the distribution of many clinically available radioactive probes. A main limitation of CLE is its limited sensitivity to small concentrations of radiotracer, especially when used with a light guide. We investigated the improvement in the sensitivity of CLE brought about by using a β− radiotracer that improved Cerenkov signal due to both higher β-particle energy and lower γ noise in the imaging optics because of the lack of positron annihilation. Methods: The signal-to-noise ratio (SNR) of 90Y was compared with that of 18F in both phantoms and small-animal tumor models. Sensitivity and noise characteristics were demonstrated using vials of activity both at the surface and beneath 1 cm of tissue. Rodent U87MG glioma xenograft models were imaged with radiotracers bound to arginine-glycine-aspartate (RGD) peptides to determine the SNR. Results: γ noise from 18F was demonstrated by both an observed blurring across the field of view and a more pronounced fall-off with distance. A decreased γ background and increased energy of the β particles resulted in a 207-fold improvement in the sensitivity of 90Y compared with 18F in phantoms. 90Y-bound RGD peptide produced a higher tumor-to-background SNR than 18F in a mouse model. Conclusion: The use of 90Y for Cerenkov endoscopic imaging enabled superior results compared with an 18F radiotracer.