Determination of experimental Cherenkov spectrum (200–1050 nm) of ¹⁸F and its implications on optical dosimetry: murine model

Abstract

Cherenkov luminescence imaging modality takes advantage of optical Cherenkov photons since this light could be used for photoactivation, photodynamic therapy, photothermal therapy, excited fluorophores, etc. The aim of this work is to experimentally determine ¹⁸F Cherenkov spectrum from 200 to 1050 nm. By Monte Carlo simulation in a mouse modeled, the number of absorbed photons and those ballistic and scattered that left the mouse were computed to determine its implications on optical dosimetry. An ¹⁸F-FDG source was used to measure the Cherenkov emission of ¹⁸F by placing it inside the 6” integrating sphere. Light was measured 100 times for two different activities with a Cherenkov spectrophotometer and all spectra with similar form and central moment were selected. In this group, the average Cherenkov spectrum was generated from 200 to 1050 nm, then the amount of Cherenkov photons emitted in the 200–1050-nm range was computed. The mouse body was set up in the MCLTmx code using an ellipsoidal figure, with dimensions and mass corresponding to the average size of a 10-to-12-weeks-old male mouse that is the optimal age for experimentation. A Cherenkov light (CL) isotropic point-source was also simulated; it was placed at the origin of the ellipsoid, moving on the y-axis from 0 to 1.2 cm in 0.2 cm increments. As a result, the Cherenkov spectra absorbed and leaving the ellipsoid were obtained. The average experimental Cherenkov spectrum of ¹⁸F for 200–1050 nm was obtained. ¹⁸F emits 3.28 photons per decay in 200–1050 nm range if the beta is emitted in a medium with a 1.33 refractive index, that corresponds to water. The number of photons per decay emerging from the ventral and dorsal sides of the murine model was computed by Monte Carlo Simulation. Preclinical dosimetry will be more accurately ascertained as the relation between activity in a target region and the amount of CL leaving a volume such as that of a mouse. On the other hand, adequate internal dosimetry will help to predict with greater certainty whether the energy deposited in a volume of interest will be able to induce therapeutic effects.

KEYWORDS:

• Cherenkov radiation
• optical dosimetry
• Fluor-18
• Cherenkov spectrum

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Universidad Autonoma del Estado de México: [Grant Number 6163/2020CIB].

Notes on contributors

Eugenio Torres-García

Eugenio Torres-García, Bachelor's Degree in Physics. PhD Research in medical physics in Autonomous University of Mexico State (UAEMéx), México State, México. College Professor at UAEMéx. Researcher in radiation dosimetry, nuclear medicine, medical imaging, optical imaging, Monte Carlo Simulation, etc.

Hansel Torres-Velazquez

Fís. Hansel Torres-Velazquez, Physics undergraduate student, Autonomous University of Mexico State.

Luis E. Díaz-Sánchez

Dr. Luis E. Díaz-Sánchez, Bachelor's Degree in Physics. PhD Research in quantum physics. College Professor at Autonomous University of Mexico State. Researcher in big data, Monte Carlo Simulation, Nanotecnology, supercomputing, medical imaging, etc.

Liliana Aranda-Lara

Dr. Liliana Aranda-Lara, Bachelor's Degree in Biology and MSc specialized in Medical Physics at The Autonomous University of Mexico State. Doctorate of Health Sciences in the research area of radiopharmaceutical science. College Professor. Expert in targeted therapy, radionuclide imaging and therapy, optical imaging, etc.

Keila Isaac-Olivé

Dr. Keila Isaac-Olivé, BSc in Radiochemistry, MSc and PhD in Radioanalytical techniques. Full professor at UAEMex. Researcher in the study of material and compounds with potential use in theragnostic nanosystems where radioactive, fluorescence or photothermal properties are used for imaging and/or therapy purposes.