L12161 07

Pre-tests were performed with a standard laboratory X-ray source (RX Solutions, 3SR Lab, Grenoble, France) equipped with a conical polychromatic and divergent beam (Hamamatsu L12161-07 source), allowing absorption imaging mode. Corresponding imaging parameters are reported in Tables 1 and 2 (italic lines)^{30 (link),31 (link)}. The scans were obtained with a number n_p of X-ray 2D radiographs onto a 1914 × 1580 pixel² Varian flat panel detector, leading to a voxel size V_vox (varying from 12³ to 45³ μm³). Samples were exposed to a 360° rotation with respect to the X-ray source (step angle 360°/n_p varying from 0.07° to 0.25°), with an exposure time of 125 ms (respectively 400 ms) per radiograph for experiments on the whole laryngeal structures (respectively on dissected vocal tissues). To restrain the noise, an average of 6 radiographs per 2D image was used.

The microtomographic acquisition of SK 835 was performed in 2015 at the PLATINA platform of the IC2MP set at the (University of Poitiers, France), with the EasyTom XL Duo laboratory device (RX-solutions, France). A sealed microfocus X-ray source (L12161-07, Hamamatsu Photonics, Japan) was used coupled to a flat panel detector (PaxScan 2520DX, Varian, USA). The specimen was scanned at a spatial resolution of 25 µm according to the following acquisition parameters: 70 kV (tube voltage); 350 µA (tube current); 1184 projections; 9.3 frames per second; averaging of 15 frames per projection; filtration of the beam by a 1.2 mm aluminium filter; a source-to-detector distance and a source-to-object distance of 368 mm and 72.5 mm, respectively. We applied a procedure using random shifts of the detector to avoid the presence of ring artefacts on the reconstructed images. We also recorded 32 reference images at the end of the microtomographic scan to correct for possible beam drift. The data were reconstructed in 16 bits TIF images with the XAct software (RX-solutions). For the reconstruction, we applied a filtered back projection algorithm based on the Feldkamp method for cone beam geometry associated with a Tukey filter and beam hardening artefacts were corrected through linearization with a polynomial function.

X-ray irradiation
was performed with a Hamamatsu L12161-07. A tungsten target X-ray
tube was run at an accelerating voltage of 150 kV and a tube current
of 500 μA. The sample was placed at 9 cm distance from the tube,
resulting in a dose rate of 72 mGy/s, previously calibrated with a
commercial X-ray detector. Based on this value, the exposure time
was calculated in order to irradiate the sample with the desired dose.