Cherenkov emissions for studying tumor changes during radiation therapy: An exploratory study in domesticated dogs with naturally-occurring cancer.



Real-time monitoring of physiological changes of tumor tissue during radiation therapy (RT) could improve therapeutic efficacy and predict therapeutic outcomes. Cherenkov radiation is a normal byproduct of radiation deposited in tissue. Previous studies in rat tumors have confirmed a correlation between Cherenkov emission spectra and optical measurements of blood-oxygen saturation based on the tissue absorption coefficients. The purpose of this study is to determine if it is feasible to image Cherenkov emissions during radiation therapy in larger human-sized tumors of pet dogs with cancer. We also wished to validate the prior work in rats, to determine if Cherenkov emissions have the potential to act an indicator of blood-oxygen saturation or water-content changes in the tumor tissue-both of which have been correlated with patient prognosis.


A DoseOptics camera, built to image the low-intensity emission of Cherenkov radiation, was used to measure Cherenkov intensities in a cohort of cancer-bearing pet dogs during clinical irradiation. Tumor type and location varied, as did the radiation fractionation scheme and beam arrangement, each planned according to institutional standard-of-care. Unmodulated radiation was delivered using multiple 6 MV X-ray beams from a clinical linear accelerator. Each dog was treated with a minimum of 16 Gy total, in ≥3 fractions. Each fraction was split into at least three subfractions per gantry angle. During each subfraction, Cherenkov emissions were imaged.


We documented significant intra-subfraction differences between the Cherenkov intensities for normal tissue, whole-tumor tissue, tissue at the edge of the tumor and tissue at the center of the tumor (p<0.05). Additionally, intra-subfraction changes suggest that Cherenkov emissions may have captured fluctuating absorption properties within the tumor.


Here we demonstrate that it is possible to obtain Cherenkov emissions from canine cancers within a fraction of radiotherapy. The entire optical spectrum was obtained which includes the window for imaging changes in water and hemoglobin saturation. This lends credence to the goal of using this method during radiotherapy in human patients and client-owned pets.





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Publication Info

Rickard, Ashlyn G, Hiroto Yoshikawa, Gregory M Palmer, Harrison Q Liu, Mark W Dewhirst, Michael W Nolan and Xiaofeng Zhang (2020). Cherenkov emissions for studying tumor changes during radiation therapy: An exploratory study in domesticated dogs with naturally-occurring cancer. PloS one, 15(8). p. e0238106. 10.1371/journal.pone.0238106 Retrieved from

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Gregory M. Palmer

Professor of Radiation Oncology

Greg Palmer obtained his B.S. in Biomedical Engineering from Marquette University in 2000, after which he obtained his Ph.D. in BME from the University of Wisconsin, Madison. He is currently an Associate Professor in the Department of Radiation Oncology, Cancer Biology Division at Duke University Medical Center. His primary research focus has been identifying and exploiting the changes in absorption, scattering, and fluorescence properties of tissue associated with cancer progression and therapeutic response. To this end he has implemented a model-based approach for extracting absorber and scatterer properties from diffuse reflectance and fluorescence measurements. More recently he has developed quantitative imaging methodologies for intravital microscopy to characterize tumor functional and molecular response to radiation and chemotherapy. His awards have included the Jack Fowler Award from the Radiation Research Society.

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Mark Wesley Dewhirst

Gustavo S. Montana Distinguished Professor Emeritus of Radiation Oncology

Mark W. Dewhirst, DVM, PhD is the Gustavo S. Montana Professor of Radiation Oncology and Vice Director for Basic Science in the Duke Cancer Institute. Dr. Dewhirst has research interests in tumor hypoxia, angiogenesis, hyperthermia and drug transport. He has spent 30 years studying causes of tumor hypoxia and the use of hyperthermia to treat cancer. In collaboration with Professor David Needham in the Pratt School of Engineering, he has developed a novel thermally sensitive drug carrying liposome that has been successfully translated to human clinical trials. He has utilized the thermal characteristics of this liposome to develop an MR imageable form that can accurately reflect drug concentrations in tumors, which then is related to the extent of anti-tumor effect in pre-clinical models. This property has been widely used by other investigators, world-wide, particularly in the area of high intensity focused ultrasound, where it would be possible to literally paint drug to a target zone and visualize this process in real time, during heating. For his work in this area, Dr. Dewhirst was named a Fellow in the AAAS. Dr. Dewhirst has well over 500 peer-reviewed publications, book chapters and reviews, with >20,000 citations and an H-index of 73. He has given named lectures at the University of Western Ontario, Thomas Jefferson University and the New Zealand Cancer Society. He was awarded the Failla Medal and Lecture at the Radiation Research Society in 2008, the Eugene Robinson award for excellence hyperthermia research in 1992 and a similar award from the European Society for Hyperthermic Oncology in 2009. He was named a fellow of ASTRO in 2009 and was awarded the prestigious Gold Medal from the same society in 2012. He is a Senior Editor of Cancer Research and Editor-in-Chief of the International Journal of Hyperthermia. He has mentored 24 graduate students, and many postdoctoral fellows, residents, junior faculty and medical students. He has been particularly skillful in assisting those he has mentored to obtain DOD and NIH fellowships, K awards and first R01 grants. His skill in mentoring has been recognized by the Duke Comprehensive Cancer Center, the Medical Physics Graduate Training programs and the School of Medicine, where he has received “Mentor of the Year” awards. In 2011 he was selected to become the first Associate Dean of Faculty Mentoring in the Duke School of Medicine. In this position, he is implementing a comprehensive program to enhance success in obtaining NIH funding. He graduated from the University of Arizona in 1971 with a degree in Chemistry and Colorado State University in 1975 and 1979 with DVM and PhD degrees, respectively.

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