Employing photoluminescence to rapidly follow aggregation and dispersion of cellulose nanofibrils

Multichannel confocal spectroscopy enables tracking of time dependent, spatially resolved changes in the physicochemical environment of cellulose nanofibrils due to variation in emission intensity ratios.

Does pixel/voxel-size limit the measurement of distances in CBCT-tomography?

The necessity to obtain relevant structural information from tomographic images is an all-pervasive step in a host of clinical and research-areas. Cone Beam Computed Tomography (CBCT) is the imaging modality often used among the many available. Currently approaches to extract structural properties from raw CBCT-images, involve some manual intervention by experts to measure their properties, such as size and displacements of their geometrical structures. Regarding the factors limiting the precision of these measurements, such as voxel-size and image contrast, we find conflicting statements in the literature. It is therefore useful to provide accurate data under well-defined experimental conditions. Here we present a method and associated software to measure displacements of geometrical structures. We also determined the minimum measureable displacement and minimum detectable defect in terms of voxel size. We select as our geometrical structure a sample of bovine bone and to provide a set of defects, we drilled a pattern of holes into it. We determined the hole's three-dimensional structures using confocal spectroscopy. In order to obtain the minimum measurable displacement, we acquired CBCT-radiographies containing a stationary reference and micro-metrically cnc controlled displacements of the sample. We then process these images with our software to extract the distances and compare them with the cnc displacements. All our processing includes a computational interpolation from the voxel-size of $0.35$ mm corresponding to our CBCT-radiographies, down to $0.05$ mm. We find that sample-displacements can be measured with a precision of $\sim 20 \mu$, 17 times smaller than the voxel-size of $0.35$ mm. To measure the size of the holes using our CBCT-radiographies, we first register the holes onto a hole-free region of the sample with our software, then overlay the result with the three-dimensional structure obtained from confocal spectroscopy. We find the minimum detectable hole-size to be $0.7$ mm, twice the voxel-size.