title: Cerenkov luminescence endoscopy: improved molecular sensitivity with β--emitting radiotracers.
abstract: 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 (90)Y was compared with that of (18)F 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 (18)F 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 (90)Y compared with (18)F in phantoms. (90)Y-bound RGD peptide produced a higher tumor-to-background SNR than (18)F in a mouse model.
  
  
  CONCLUSIONS
  The use of (90)Y for Cerenkov endoscopic imaging enabled superior results compared with an (18)F radiotracer.
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Colin M
authors.initials: CM
authors.lastname: Carpenter
authors.affiliation: Canary Center at Stanford for Cancer Early Detection, Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, Stanford, California; and Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China zcheng@stanford.edu lei@stanford.edu.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Ma
authors.affiliation: Canary Center at Stanford for Cancer Early Detection, Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, Stanford, California; and.
authors.forename: Hongguang
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Conroy
authors.initials: C
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Guillem
authors.initials: G
authors.lastname: Pratx
authors.affiliation: Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Canary Center at Stanford for Cancer Early Detection, Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, Stanford, California; and.
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California zcheng@stanford.edu lei@stanford.edu.
authors.forename: Lei
authors.initials: L
authors.lastname: Xing
authors.affiliation: Canary Center at Stanford for Cancer Early Detection, Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, Stanford, California; and zcheng@stanford.edu lei@stanford.edu.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001610:Beta Particles; D045744:Cell Line, Tumor; D003952:Diagnostic Imaging / Q000379:methods; D004724:Endoscopy / Q000379:methods*; D005462:Fluorine Radioisotopes / Q000737:chemistry; D006801:Humans; D049449:Luminescence; D051379:Mice; D009368:Neoplasm Transplantation; D009842:Oligopeptides / Q000737:chemistry; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D015021:Yttrium Radioisotopes / Q000737:chemistry
chemical_list: D005462:Fluorine Radioisotopes; D009842:Oligopeptides; D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes; C047981:arginyl-glycyl-aspartic acid
keywords: Cerenkov luminescence endoscopy; Cerenkov luminescence imaging; radionuclides; β-emitter