3D melanoma spheroid model for the development of positronium biomarker

Melanoma spheroids (lWM 115 WM 266-4)were irradiated by positrons emitted from the 22Na radionuclide (with activity of about 1 MBq) placed in Kapton foil. A dedicated aluminum chamber was used as a container for spheroids and a holder which was connected to a heater to keep cells at 370C. Exemplary experimental lifetime spectrum (black histogram) with superimposed histograms resulting from the fit of the sum of the exponential function convoluted with the detector resolution, performed by means of the PALS Avalanche program. First component (yellow line) shows the contribution from p-Ps (mean lifetime: 0.125 ns), second component (green line) originates from annihilations in source (Kapton foil) (0.374 ns), third component (light blue) shows free annihilation lifetime (0.395 ns), forth component (dark blue) illustrates the contribution from o-Ps. A sum of all contributions resulting from the fit is shown as a red curve.