Radioluminescence in biomedicine: physics, applications, and models

Abstract

The electromagnetic spectrum contains different frequency bands useful for medical imaging and therapy. Short wavelengths (ionizing radiation) are commonly used for radiological and radionuclide imaging and for cancer radiation therapy. Intermediate wavelengths (optical radiation) are useful for more localized imaging and for photodynamic therapy. Finally, longer wavelengths are the basis for magnetic resonance imaging and for hyperthermia treatments. Recently, there has been a surge of interest for new biomedical methods that synergize optical and ionizing radiation by exploiting the ability of ionizing radiation to stimulate optical emissions. These physical phenomena, together known as radioluminescence, are being used for applications as diverse as radionuclide imaging, radiation therapy monitoring, phototherapy, and nanoparticlebased molecular imaging. This review provides a comprehensive treatment of the physics of radioluminescence and includes simple analytical models to estimate the luminescence yield of scintillators and nanoscintillators, Cerenkov radiation, air fluorescence, and biologically endogenous radioluminescence. Examples of methods that use radioluminescence for diagnostic or therapeutic applications are reviewed and analyzed in light of these quantitative physical models of radioluminescence.

Mechanisms for Tuning Engineered Nanomaterials to Enhance Radiation Therapy of Cancer

“…[63][64][65] In vacuum CL has a broad spectrum that varies as a function of wavelength, , as −2 . [66] Due to light absorption and scattering in tissue and its components (water, hemoglobin, lipids), the effective CL spectrum in tissue has a complex shape, with a maximum around 650 nm. [67][68][69][70] The estimated photon yield of the Cherenkov process from clinical radionuclides is rather low, ≈1-50 photons per decay, corresponding to ≈12 000 photons per Bq for 18 F and ≈199 000 for 68 Ga. [66] The Cherenkov photon yield from 5 to 20 MeV X-ray photon beams is 60-100 photons per deposited MeV of energy.…”

“…[66] Due to light absorption and scattering in tissue and its components (water, hemoglobin, lipids), the effective CL spectrum in tissue has a complex shape, with a maximum around 650 nm. [67][68][69][70] The estimated photon yield of the Cherenkov process from clinical radionuclides is rather low, ≈1-50 photons per decay, corresponding to ≈12 000 photons per Bq for 18 F and ≈199 000 for 68 Ga. [66] The Cherenkov photon yield from 5 to 20 MeV X-ray photon beams is 60-100 photons per deposited MeV of energy. [66] The latter value can be related to the radiation dose where for 1 Gy radiation dose, ≈5 × 10 11 Cherenkov photons are generated per cm 3 of tissue.…”

Radiation Dose‐Enhancement Is a Potent Radiotherapeutic Effect of Rare‐Earth Composite Nanoscintillators in Preclinical Models of Glioblastoma

“…It has been demonstrated that the radioluminescence-yield of nanoscintillators can only enable low-dose PDT, [29][30][31][32] which hints toward the existence of other non-negligible therapeutic contributions of the nanoscintillators to explain the promising reported efficacies. First and foremost, as nanoscintillators are often composed of high-Z elements, we hypothesize that a radiation dose-enhancement effect exists when these materials are used for radiotherapeutic applications.…”

Single-cell radioluminescence microscopy with two-fold higher sensitivity using dual scintillator configuration

“…Once this process is repeated for the entire set of 10,000 images, the positions of all detected events are aggregated into a single image, where each pixel represents the number of radioactive decay events detected at that location. Detailed reconstruction procedures and radioluminescence imaging can also be found from our previous papers [ 14 , 16 , 17 ].…”