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Phys Med Biol. 2014 Sep 21;59(18):5317-5328. doi: 10.1088/0031-9155/59/18/5317. Epub 2014 Aug 22.

Cherenkov excited phosphorescence-based pO2 estimation during multi-beam radiation therapy: phantom and simulation studies.

Author information

1
Department of Physics & Astronomy, Dartmouth College Hanover NH 03755.
2
Department of Biophysics & Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia PA 19104.
3
Thayer School of Engineering, Dartmouth College Hanover NH 03755.
4
Department of Medicine, Geisel School of Medicine, Lebanon NH 03756.
5
Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon NH 03756.
#
Contributed equally

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.

PMID:
25146556
PMCID:
PMC4259158
DOI:
10.1088/0031-9155/59/18/5317
[Indexed for MEDLINE]
Free PMC Article

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