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Med Phys. 2011 Jul;38(7):4127-32.

Cerenkov emission induced by external beam radiation stimulates molecular fluorescence.

Author information

  • 1Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA. johan.axelsson@dartmouth.edu

Abstract

PURPOSE:

Cerenkov emission is induced when a charged particle moves faster than the speed of light in a given medium. Both x-ray photons and electrons produce optical Cerenkov photons in everyday radiation therapy of tissue; yet, this phenomenon has never been fully documented. This study quantifies the emissions and also demonstrates that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms.

METHODS:

In this study, Cerenkov emission induced by radiation from a clinical linear accelerator is investigated. Biological mimicking phantoms were irradiated with x-ray photons, with energies of 6 or 18 MV, or electrons at energies 6, 9, 12, 15, or 18 MeV. The Cerenkov emission and the induced molecular fluorescence were detected by a camera or a spectrometer equipped with a fiber optic cable.

RESULTS:

It is shown that both x-ray photons and electrons, at MeV energies, produce optical Cerenkov photons in tissue mimicking media. Furthermore, we demonstrate that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms.

CONCLUSIONS:

The results here indicate that molecular fluorescence monitoring during external beam radiotherapy is possible.

PMID:
21859013
[PubMed - indexed for MEDLINE]
PMCID:
PMC3139507
Free PMC Article
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