Fig. 3

Characterising Oncological Heterogeneity through Multiplexed PET Imaging. The figure demonstrates the potential of multiplexed PET imaging technique on a patient with coexistent malignancies: ⁶⁸Ga-PSMA-positive/ ¹⁸F-FDG- negative prostate cancer (refer to PET/CT axial slice) highlighted in green and ¹⁸F-FDG-avid metastatic melanoma (refer to coronal slice with prominent ¹⁸F-FDG uptake and mild ⁶⁸Ga-PSMA uptake), highlighted with red arrows. Separate scans using ¹⁸F-FDG and ⁶⁸Ga-PSMA tracers reveal distinct metabolic and molecular patterns corresponding to melanoma and prostate cancer, respectively. The composite image results from diffeomorphic algorithmic synthesis, assigning discrete chromatic channels—red for ¹⁸F-FDG and green for ⁶⁸Ga-PSMA—to each radiotracer, thereby creating a composite image. This multiplexed image merges the two separate datasets into a single, integrated visual field. Manifestations of sole ¹⁸F-FDG uptake are visualized in red, ⁶⁸Ga-PSMA uptake in green, and concomitant tracer accumulation is rendered in shades of yellow, indicating co-expression. ¹⁸F-FDG dominant malignancies in the multiplexed images are highlighted with red arrows, while ⁶⁸Ga-PSMA dominant malignancies are highlighted with green arrows. This technique of image multiplexing, akin to multiplex histopathology, allows for a nuanced characterization of tumoural heterogeneity, providing an intuitive and single-image synopsis of the distinct pathophysiological processes at play