The Jacobian of the deformation field of elastic registration between images taken during radiotherapy is a measure of inter-fraction local deformation. The histogram of the Jacobian values (Jac) within an organ was introduced (JVH-Jacobian-volume-histogram) and first applied in quantifying parotid shrinkage. MVCTs of 32 patients previously treated with helical tomotherapy for head-neck cancers were collected. Parotid deformation was evaluated through elastic registration between MVCTs taken at the first and last fractions. Jac was calculated for each voxel of all parotids, and integral JVHs were calculated for each parotid; the correlation between the JVH and the planning dose-volume histogram (DVH) was investigated. On average, 82% (±17%) of the voxels shrinks (Jac < 1) and 14% (±17%) shows a local compression >50% (Jac < 0.5). The best correlation between the DVH and the JVH was found between V10 and V15, and Jac < 0.4-0.6 (p < 0.01). The best constraint predicting a higher number of largely compressing voxels (Jac0.5<7.5%, median value) was V15 ≥ 75% (OR: 7.6, p = 0.002). Jac and the JVH are promising tools for scoring/modelling toxicity and for evaluating organ/contour variations with potential applications in adaptive radiotherapy.

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The colour shade quality control scenario is ubiquitous within the cosmetic hair colouring industry. Visual inspection is nowadays the go-to standard for the evaluation of dye application outcomes, even although the increased availability of easily operated spectrophotometers has favoured the introduction of colorimeters in the manufacturing process. Human hairs, however, are very efficient scatterers, and this makes their instrumental measurements more difficult and less consistent. To as-

Colour science has had a very long history, dotted over the millennia with many contributions from the most diverse fields of human knowledge. At the beginning of the 20th century, Albert Henry Munsell, an artist formally trained in academia, and Friedrich Wilhelm Ostwald, Nobel prize for chemistry in 1909 and amateur painter, each envisioned and developed a colour system with a related colour atlas. Both authors recognized the importance of the visual relationship between colours, which they conceived as sensations stemming from, but not merely confined to, pigments and light. We hereby describe the salient features of these colour spaces, their strengths and weaknesses, the authors' analogy of intents and divergence in execution. The contribution of this paper is a discussion on how these are employed both in Italian educational facilities, and salon practice, as well as a suggestion about their use within the industry of human hair cosmetics.

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