Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada. Centre de recherche du CHU de Québec, Université Laval, Québec, Canada.
Published: August 2019
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Article Abstract
Recent studies have proposed that adding quinine to water while performing Cherenkov volumetric dosimetry improves the skewed percent depth dose measurement. The aim of this study was to quantify the ability of quinine to convert directional Cherenkov emission to isotropic fluorescence and evaluate its contribution to the total emitted light. Aqueous solutions of quinine were prepared with distilled water at various concentrations (0.01-1.2 g l). The solutions were irradiated with photon beams at 6 and 23 MV. The dependence of the light produced as a function of sample concentration was studied using a spectrometer with a fixed integration time. Spectral measurements of the luminescent solution and the blank solution (distilled water only) were taken to deconvolve the Cherenkov and quinine contribution to the overall emission spectrum. Using a CCD camera, intensity profiles were obtained for the blank and the 1.00 g l solutions to compare them with the dose predicted by a treatment planning system. The luminescent intensity of the samples was found to follow a logarithmic trend as a function of the quinine concentration. Based on the spectral deconvolution of the 1.00 g l solution, 52.4% ± 0.7% and 52.7% ± 0.7% of the signal in the visible range results from the quinine emission at 6 and 23 MV, respectively. The remaining fraction of the spectrum is due to the Cherenkov light that has not been converted. The fraction of the Cherenkov emission produced between 250 nm and 380 nm in the water and that was absorbed by the fluorophore reached 24.8% and 9.4% respectively at 6 and 23 MV. X-ray stimulated fluorescence of the quinine was then proven to be the principal cause to the increased total light output compared to the water-only signal. This new information reinforces the direct correlation of the solution intensity to the dose deposition.
Development of new scintillator materials is a continuous effort, which recently has been focused on materials with higher stopping power. Higher stopping power can be achieved if the compositions include elements such as Tl (Z=81) or Lu (Z=71), as the compounds gain higher densities and effective atomic numbers. In context of medical imaging this translates into high detection efficiency (count rates), therefore, better image quality (statistics, thinner films) or lower irradiation doses to patients in addition to lowering of cost.
. To develop a robust method for non-contact surface dosimetry during Total Body Irradiation (TBI) that uses an optimally paired choice of scintillator material with camera photocathode and can work insensitively to the normal ambient room lighting conditions (∼500 Lux)..
Positron emission tomography (PET) is the most sensitive biomedical imaging modality for non-invasively detecting and visualizing positron-emitting radiopharmaceuticals within a subject. In PET, measuring the time-of-flight (TOF) information for each pair of 511-keV annihilation photons improves effective sensitivity but requires high timing resolution. Hybrid materials that emit both scintillation and Cherenkov photons, such as bismuth germanate (BGO), recently offer the potential for more precise timing information from Cherenkov photons while maintaining adequate energy resolution from scintillation photons.
Department of Nuclear Medicine, Institute of Clinical Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China. Electronic address:
Molecular imaging of cancer is a collaborative endeavor, uniting scientists and physicians from diverse fields. Such collaboration is actively developing and translating cutting-edge molecular imaging approaches to enhance the diagnostic landscape of human malignancies. The advent of positron emission tomography (PET) and PET imaging tracers has realized non-invasive target annotation and tumor characterization at the molecular level.
