Water is a fundamental component of many biological systems. The ability to detect water therefore provides great insight into system functionality, particularly in the development of disease. In this work, the high interaction of terahertz radiation with water, paired with the dependence of the dynamics of water molecules with varying temperature, is utilised to monitor changes in the composition of bone tissue. Heterotopic ossification (HO) bone samples and deionised free water are measured using terahertz time-domain spectroscopy for varying environmental temperatures, for prospective use in disease diagnosis.
The realisation of hyperspectral terahertz imaging is a significant step towards understanding of the life sciences on all scales. A key to this understanding is the retrieval of dielectric properties from such images, a task which is plagued by experimental limitations, challenging the terahertz community for more than two decades. In this contribution, we propose a new combined retrieval methodology to overcome misalignments and Fabry-Pérot effects on the extraction of the dielectric properties of human bone samples through the combination of the Kramers-Kronig relations and Fabry-Pérot reflection modelling. Results extracted from ∼100 µm human bone slices composed largely of collagen are consistent with those measured for pristine collagen samples. This represents another stepping-stone towards the adoption of terahertz imaging into pre- and clinical practice.
In this contribution, we present the direct comparison between Ophir Pyrocam IV and Terasense Tera-1024 cameras used for imaging of terahertz (THz) and sub-THz signals. We compare general properties, such as frequency dependent and polarisation dependent sensitivity, angle dependent sensitivity essential for holographic and noncollinear interferometric measurements, and draw a conclusion about the most suitable camera for the discussed imaging approaches. Both cameras show acceptable performance and sensitivity at imaging both 0.14 THz and 0.3 THz signals. The Terasense camera, expectedly, shows stronger polarisation dependent properties, however, is significantly more angle independent, showing an acceptable performance at all tested incident angles up to 50 degrees. At the same time, although the angle dependence is stronger for the Ophir camera, it has smaller pixel pitch and more extended post-processing features, thus making it somewhat better suited for noncollinear interferometric and holographic sub THz imaging.
A swept-source optical coherence tomography (OCT) system is demonstrated in the mid-infrared region. A Michelson interferometric setup is illuminated by an external cavity quantum cascade laser (QCL), with a scanning frequency of 1 Hz. A-scans were collected using three different samples: a mirror, CaF2 coated with germanium on both of its surfaces, and CaF2 coated with germanium on the back side of the sample. These depth-profiles were used to mimic a tissue sample with multiple reflective boundaries. Fourier transformation of these interference fringes clearly showed the expected depths of reflection, allowing for the signal to noise ratio of the system to be determined.
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