Detection of proteoglycan loss from articular cartilage using Brillouin microscopy, with applications to osteoarthritis

© 2019, OSA - The Optical Society. All rights reserved. The degeneration of articular cartilage (AC) occurs in osteoarthritis (OA), which is a leading cause of pain and disability in middle-aged and older people. The early diseaserelated changes in cartilage extra-cellular matrix (ECM) start with depletion of proteoglycan (PG), leading to an increase in tissue hydration and permeability. These early compositional changes are small (<10%) and hence difficult to register with conventional non-invasive imaging technologies (magnetic resonance and ultrasound imaging). Here we apply Brillouin microscopy for detecting changes in the mechanical properties and composition of porcine AC. OA-like degradation is mimicked by enzymatic tissue digestion, and we compare Brillouin microscopy measurements against histological staining of PG depletion over varying digestion times and enzyme concentrations. The non-destructive nature of Brillouin imaging technology opens new avenues for creating minimally invasive arthroscopic devices for OA diagnostics and therapeutic monitoring

Laser beam deflection-based perimeter scanning of integrated circuits for local overheating location

4 páginas, 2 figuras.In integrated circuits, local overheating (hot spots) can be detected by monitoring the temperature gradients present in the silicon substrate at a given depth, laterally accessing the die with an infra-red laser beam probe. The sensed magnitude is the laser beam deflection, which is proportional to the temperature gradients found along the beam trajectory (mirage effect). Biasing the devices with periodic electrical functions allows employing lock-in detection strategies (noise immunity) and thermally isolating the analysed chip substrate thermal behaviour from the external boundary conditions by setting the excitation frequency (control of the thermal energy penetration depth). Measuring the first harmonic of the deflection signal components (vertical and horizontal) allows performing a fast and accurate location of devices, interconnects or circuits dissipating relatively high power levels without any calibration procedure. It has been concluded that the horizontal component of the beam deflection provides a higher spatial resolution than the vertical one when measurements are performed beyond the thermal energy penetration depth.This work has been partially supported by the Spanish Ministerio de Educación y Ciencia (under contracts TEC2005- 087392 SPACESIC Project and TEC2005-02739), FEDER funds and the Consejo Superior de Investigaciones Científicas (CSIC) (under contract ‘Junta para la Ampliación de Estudios’, JAE-Doc).Peer reviewe