Exploration of melanoma metastases in mice brains using endogenous contrast photoacoustic imaging

B16F10 murine skin melanoma cells were implanted orthotopically into the mouse brain.
Imaging of melanoma cells in tissue mimicking phantoms showed a linear correlation between PA signal and cell concentration, with a detection limit of 625 cells.
3D ultrasound and spectroscopic PA imaging were performed, looking at melanin, oxy and deoxy-hemoglobin.
Both total hemoglobin content (HbT) and Oxygen saturation (SO2) were assessed.
Higher HbT values were observed in tumors compared to heathy brain of the same volume, whereas SO2 values were much lower in the tumors.
A clear presence of melanin was detected, with 3 times higher PA signal compared to surround brain tissue.
Further regional analysis showed much higher HbT and SO2 signals at the tumor periphery that decrease when moving towards the core.

Photoacoustic (PA) imaging combines the advantages of high optical contrast and high ultrasound resolution at depth, to allow for non-invasive evaluations of endogenous contrasts. This enables non-invasive, contrast agent-free characterization of tumor vasculature and hypoxia, providing new opportunities for understanding cancer progression and treatment response.

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