Irwin I Tendler1, Alan Hartford2, Michael Jermyn3, Ethan LaRochelle1, Xu Cao1, Victor Borza1, Daniel Alexander1, Petr Bruza1, Jack Hoopes4, Karen Moodie5, Brian P Marr6, Benjamin B Williams2, Brian W Pogue7, David J Gladstone8, Lesley A Jarvis9. 1. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire. 2. Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. 3. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; DoseOptics LLC, Lebanon, New Hampshire. 4. Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire. 5. Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. 6. Department of Ophthalmic Oncology, Columbia University Medical Center, New York, New York. 7. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; DoseOptics LLC, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire. 8. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. 9. Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. Electronic address: lesley.a.jarvis@hitchcock.org.
Abstract
PURPOSE: Patients have reported sensations of seeing light flashes during radiation therapy, even with their eyes closed. These observations have been attributed to either direct excitation of retinal pigments or generation of Cherenkov light inside the eye. Both in vivo human and ex vivo animal eye imaging was used to confirm light intensity and spectra to determine its origin and overall observability. METHODS AND MATERIALS: A time-gated and intensified camera was used to capture light exiting the eye of a patient undergoing stereotactic radiosurgery in real time, thereby verifying the detectability of light through the pupil. These data were compared with follow-up mechanistic imaging of ex vivo animal eyes with thin radiation beams to evaluate emission spectra and signal intensity variation with anatomic depth. Angular dependency of light emission from the eye was also measured. RESULTS: Patient imaging showed that light generation in the eye during radiation therapy can be captured with a signal-to-noise ratio of 68. Irradiation of ex vivo eye samples confirmed that the spectrum matched that of Cherenkov emission and that signal intensity was largely homogeneous throughout the entire eye, from the cornea to the retina, with a slight maximum near 10 mm depth. Observation of the signal external to the eye was possible through the pupil from 0° to 90°, with a detected emission near 2500 photons per millisecond (during peak emission of the ON cycle of the pulsed delivery), which is over 2 orders of magnitude higher than the visible detection threshold. CONCLUSIONS: By quantifying the spectra and magnitude of the signal, we now have direct experimental observations that Cherenkov light is generated in the eye during radiation therapy and can contribute to perceived light flashes. Furthermore, this technique can be used to further study and measure phosphenes in the radiation therapy clinic.
PURPOSE:Patients have reported sensations of seeing light flashes during radiation therapy, even with their eyes closed. These observations have been attributed to either direct excitation of retinal pigments or generation of Cherenkov light inside the eye. Both in vivo human and ex vivo animal eye imaging was used to confirm light intensity and spectra to determine its origin and overall observability. METHODS AND MATERIALS: A time-gated and intensified camera was used to capture light exiting the eye of a patient undergoing stereotactic radiosurgery in real time, thereby verifying the detectability of light through the pupil. These data were compared with follow-up mechanistic imaging of ex vivo animal eyes with thin radiation beams to evaluate emission spectra and signal intensity variation with anatomic depth. Angular dependency of light emission from the eye was also measured. RESULTS:Patient imaging showed that light generation in the eye during radiation therapy can be captured with a signal-to-noise ratio of 68. Irradiation of ex vivo eye samples confirmed that the spectrum matched that of Cherenkov emission and that signal intensity was largely homogeneous throughout the entire eye, from the cornea to the retina, with a slight maximum near 10 mm depth. Observation of the signal external to the eye was possible through the pupil from 0° to 90°, with a detected emission near 2500 photons per millisecond (during peak emission of the ON cycle of the pulsed delivery), which is over 2 orders of magnitude higher than the visible detection threshold. CONCLUSIONS: By quantifying the spectra and magnitude of the signal, we now have direct experimental observations that Cherenkov light is generated in the eye during radiation therapy and can contribute to perceived light flashes. Furthermore, this technique can be used to further study and measure phosphenes in the radiation therapy clinic.
Authors: Jennifer A Soter; Ethan P M LaRochelle; Brook K Byrd; Irwin I Tendler; Jason R Gunn; Boyu Meng; Rendy R Strawbridge; Dennis J Wirth; Scott C Davis; David J Gladstone; Lesley A Jarvis; Brian W Pogue Journal: Phys Med Biol Date: 2020-04-28 Impact factor: 3.609
Authors: Irwin I Tendler; Petr Bruza; Michael Jermyn; Jennifer Soter; Gregory Sharp; Benjamin Williams; Lesley A Jarvis; Brian Pogue; David J Gladstone Journal: J Appl Clin Med Phys Date: 2020-04-19 Impact factor: 2.102