Cherenkov radiation fluence estimates in tissue for molecular imaging and therapy applications

Abstract

Cherenkov radiation has recently emerged as an interesting phenomenon for a number of applications in the biomedical sciences. Its unique properties, including broadband emission spectrum, spectral weight in the ultraviolet and blue wavebands, and local generation of light within a given tissue, have made it an attractive new source of light within tissue for molecular imaging and phototherapy applications. While several studies have investigated the total Cherenkov light yield from radionuclides in units of [photons/decay], further consideration of the light propagation in tissue is necessary to fully consider the utility of this signal in vivo. Therefore, to help further guide the development of this novel field, quantitative estimates of the light fluence rate of Cherenkov radiation from both radionuclides and radiotherapy beams in a biological tissue are presented for the first time. Using Monte Carlo simulations, these values were found to be on the order of 0.01 – 1 nW/cm2 per MBq/g for radionuclides, and 1 – 100 µW/cm2 per Gy/sec for external radiotherapy beams, dependent on the given waveband, optical properties, and radiation source. For phototherapy applications, the total light fluence was found to be on the order of nJ/cm2 for radionuclides, and mJ/cm2 for radiotherapy beams. The results indicate that diagnostic potential is reasonable for Cherenkov excitation of molecular probes, but phototherapy may remain elusive at such exceedingly low fluence values. The simulation tools of this study are available upon request.

Nanoparticle-aided external beam radiotherapy leveraging the Čerenkov effect

“…In any case, normal tissue toxicity is minimized and should not be a concern when applying this new method to improve EBRT results. Previous studies [2] have indicated that the use of CR for therapy is highly unlikely without the use of appropriate photosensitizers delivered to tumor. This study proposes an innovative approach with potential benefits of enhancing therapeutic efficacy during radiotherapy, which could improve survival and quality of life for cancer patients.…”

“…It has a broad-band spectrum with a large percentage falling in the ultraviolet region [2]. Radiotherapy beams produce CR within tissue, which has been widely studied recently for imaging purposes [3, 4].…”

“…Much less research has been done on utilizing CR for therapy partially due to its lack of penetration. Previous studies [2] have indicated that the use of CR for therapy is highly unlikely without the use of appropriate photosensitizers successfully delivered to the tumor.…”

“…A much larger population of patients would benefit from this approach if it could be applied in external beam radiotherapy (EBRT). Monte Carlo simulations show that the CR energy fluence is in the order of nJ/cm 2 for radionuclides, and mJ/cm 2 for radiotherapy beams [2]. We therefore propose that the greater CR present in EBRT could be leveraged to substantially amplify damage to cancer cells using titania nanoparticles (NPs) targeted to the tumor.…”

Cherenkov imaging method for rapid optimization of clinical treatment geometry in total skin electron beam therapy

“…16,18,22 In addition, recent studies have looked at using this Cherenkov emission as an excitation source for molecular imaging applications directly on the medical linear accelerator treatment bed. [23][24][25] Applying Cherenkov imaging to unique treatments such as TSET could ensure more homogeneous dose delivery and provide a new method for TSET protocol commissioning.…”