Oxygen in cancer tumors is known to be a major factor that helps radiation therapy be successful. Hypoxia, or starvation of oxygen, in solid tumors is also thought to be an important factor in resistance to therapy. However, it is difficult to monitor tumor oxygenation without invasive sampling of oxygen distributions throughout the tissue, or without averaging across the whole tumor, whereas oxygen is highly heterogenous within a tumor.
A research team at Dartmouth's and Dartmouth-Hitchcock's Norris Cotton Cancer Center led by Brian Pogue, PhD, has developed the first non-invasive way to directly monitor oxygen distributions within the tumor right at the time when radiation therapy is happening. With injection of an oxygen probe drug, PtG4, they are able to image the distribution of oxygen from within the tumor. The method measures the luminescence lifetimes of PtG4 while it is excited by the Cherenkov light emitted by the radiation therapy. The drug, PtG4, stays in the tumor for at least a week, and works for imaging repeatedly.
The imaging is all done without any additional radiation, simply by using a camera to monitor the emissions during radiotherapy treatment. Following two tumor lines, one which is known to be responsive to radiation and one which is known to be resistant, we could see differences in the oxygenation of the tumor which are reflective of their differences in response." Brian Pogue, PhD, Dartmouth-Hitchcock's Norris Cotton Cancer Center
The team's findings, "Tissue pO2 Distributions in Xenograft Tumors Dynamically Imaged by Cherenkov-Excited Phosphorescence during Fractionated Radiation Therapy," are newly published in Nature Communications , by lead author, Xu Cao.
Pogue's team is able to capture oxygenation imaging through special technology. "We have a unique set of time-gated cameras in our radiation therapy department that were designed for Cherenkov-based radiation dosimetry, but we have used them for this additional purpose of monitoring oxygen in the tumors under treatment," says Pogue. "So access to these specialized Cherenkov cameras made the measurements possible." Pogue's team also collaborated with Professor Sergei Vinogradov and his team at the University of Pennsylvania Perelman School of Medicine, who produced the PtG4 and supported the work with drug characterization and co-supervision of the study. Related Stories
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