A phantom study of terahertz spectroscopy and imaging of micro-and nano-diamonds and nano-onions as contrast agents for breast cancer

Terahertz (THz) imaging is effective in distinguishing between cancerous, healthy, and fatty tissues in breast tumors, but a challenge remains in the contrast between cancerous and fibroglandular ( healthy) tissues. This work investigates carbon-based nanoparticles as potential contrast agents for THz imaging of breast cancer. Microdiamonds, nanodiamonds (NDs), and nanometer-scale onion-like carbon (OLC) are characterized with THz transmission spectroscopy in low-absorption backgrounds of polydimethylsiloxane or polyethylene. The refractive index and absorption coefficients are calculated based on the measured electric fields. NDs show little effect on the THz signal, microdiamonds express resonance-like, size-dependent absorption peaks, and OLC provides a uniform increase in the optical properties even at low concentration. Due to its strong interaction with THz frequencies and ability to be activated for selective binding to cancer cells, OLCis implemented into engineered three-dimensional breast tumor models composed of phantom tissue mimicking infiltrating ductal carcinoma surrounded by a phantom mimicking healthy fibroglandular tissue. This model is imaged using the THz reflection mode to examine the effectiveness of contrast agents for differentiation between the two tissue types. In both spectroscopy and imaging, a 10% concentration of OLC shows the strongest impact on the THz signal and holds promise as a THz contrast agent.