title: Cherenkov excited phosphorescence-based pO2 estimation during multi-beam radiation therapy: phantom and simulation studies.
abstract: Megavoltage radiation beams used in External Beam Radiotherapy (EBRT) generate Cherenkov light emission in tissues and equivalent phantoms. This optical emission was utilized to excite an oxygen-sensitive phosphorescent probe, PtG4, which has been developed specifically for NIR lifetime-based sensing of the partial pressure of oxygen (pO2). Phosphorescence emission, at different time points with respect to the excitation pulse, was acquired by an intensifier-gated CCD camera synchronized with radiation pulses delivered by a medical linear accelerator. The pO2 distribution was tomographically recovered in a tissue-equivalent phantom during EBRT with multiple beams targeted from different angles at a tumor-like anomaly. The reconstructions were tested in two different phantoms that have fully oxygenated background, to compare a fully oxygenated and a fully deoxygenated inclusion. To simulate a realistic situation of EBRT, where the size and location of the tumor is well known, spatial information of a prescribed region was utilized in the recovery estimation. The phantom results show that region-averaged pO2 values were recovered successfully, differentiating aerated and deoxygenated inclusions. Finally, a simulation study was performed showing that pO2 in human brain tumors can be measured to within 15 mmHg for edge depths less than 10-20 mm using the Cherenkov Excited Phosphorescence Oxygen imaging (CEPhOx) method and PtG4 as a probe. This technique could allow non-invasive monitoring of pO2 in tumors during the normal process of EBRT, where beams are generally delivered from multiple angles or arcs during each treatment fraction.
authors.affiliation: Department of Physics & Astronomy, Dartmouth College Hanover NH 03755.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Holt
authors.affiliation: Department of Physics & Astronomy, Dartmouth College Hanover NH 03755.
authors.forename: Rongxiao
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Biophysics & Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia PA 19104.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Esipova
authors.affiliation: Department of Biophysics & Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia PA 19104.
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Vinogradov
authors.affiliation: Thayer School of Engineering, Dartmouth College Hanover NH 03755.
authors.forename: Adam K
authors.initials: AK
authors.lastname: Glaser
authors.affiliation: Department of Medicine, Geisel School of Medicine, Lebanon NH 03756.|Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon NH 03756.
authors.forename: David J
authors.initials: DJ
authors.lastname: Gladstone
authors.affiliation: Department of Physics & Astronomy, Dartmouth College Hanover NH 03755.|Thayer School of Engineering, Dartmouth College Hanover NH 03755.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Pogue
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy*; D003198:Computer Simulation; D060733:Electromagnetic Radiation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008163:Luminescent Measurements / Q000379:methods*; D009010:Monte Carlo Method; D010100:Oxygen / Q000737:chemistry*; D010313:Partial Pressure; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D014054:Tomography / Q000295:instrumentation / Q000379:methods*
chemical_list: D010100:Oxygen