arXiv subjects

Quentin Grimal

Publications and source records attributed to Quentin Grimal.

5 recordsLinked to original sources

arXiv2026

Imaging of ultrasound specularity at cortical bone interfaces to detect unbalanced remodeling: A preliminary study

The region near the interface between cortical bone and the medullary cavity (the endosteal surface) is of particular interest for the early detection of osteoporosis. This region is typically the first to exhibit signs of unbalanced remodeling (enlarged pores and increased surface roughness). In this study, we analyze ultrasound reflection at the endosteal surface to introduce a novel potential biomarker of cortical bone health based on specularity. Our hypothesis is that increased pore size and surface roughness enhance ultrasound scattering, thereby reducing specular reflection. We reconstruct maps of specularity by combining a signal processing technique initially designed to enhance specular reflectors in soft tissues with a beamforming technique that accounts for refraction at bone soft tissue interfaces. Specularity values (between 0 and 1) quantify the similarity between received signals and signals from an ideal specular reflector. Using numerical simulations and ex vivo measurements with a 2.5 MHz phased array we highlight a strong relationship between specularity and bone microstructure, as assessed by high-resolution micro-computed tomography. Among 12 regions of interest (ROI) in the femoral bone of three donors, 8 ROIs without large pores showed high specularity (>0.5) in over 50% of pixels, in contrast to 4 ROIs with signs of extensive remodeling. Both pore volume fraction and pore size were strongly associated with specularity. In simple linear regression analyses, each parameter individually explained 84% of the variability in specularity. These findings suggest that specularity reflects bone microstructure and may potentially serve as a sensitive marker for identifying cortical bone degradation near the endosteal surface.

physics.med-ph↗

arXiv2025

Quantitative ultrasound imaging of bone: anatomical images, tissue structural quality, and pulsatile blood flow

We propose an ultrasound approach which provides, with one single examination and one single device, access to three bone biomarkers: anatomy, tissue quality and blood flow. It unlocks ultrasound imaging inside bone by accounting for ultrasound wave speed heterogeneity and anisotropic wave refraction. This study reports the first \emph{in vivo} evaluation with a comparison to peripheral Quantitative Computed Tomography (pQCT) and modulations of blood flow. Anatomical multi-layer bone-corrected reconstruction was validated at the tibia of healthy volunteers against pQCT and showed agreement on bone cortex interfaces. Estimation of axial and radial ultrasound wave speeds in cortical bone tissue (i.e. along the tissue symmetry axis and normal to it) demonstrated good reproducibility and positive correlation with bone mineral density measured by pQCT. Pulsatile blood flow was mapped and quantified in cortical and medullary regions. A directional ray selection method was developed to enhance blood signal extraction by reducing strong specular reflections originating from the outer and inner surfaces of the bone cortex. Physiological and non-physiological modulations of blood flow, namely head-up/head-down tilt table maneuvers and arterial occlusions, demonstrated the method sensitivity to blood flow variations. For the first time, reactive hyperemia was observed inside bone cortex. These results demonstrate the feasibility of a portable, non-ionizing, and quantitative ultrasound approach for structural, anatomical, and vascular characterization of bone tissue. This approach may offer new diagnostic capabilities for bone disorders, for instance osteoporosis, delayed fracture healing or osteonecrosis.

physics.med-ph↗

arXiv2025

Refraction corrected specular beamforming applied to cortical bone enhances interface visibility of bone-soft tissues interfaces

Ultrasound imaging of the cortex of long bones may enable the measurement of the cortical thickness and the ultrasound wave speed in cortical bone tissue. However, with bone loss, the cortical porosity and the size of the pores increase, resulting in strong ultrasound diffuse scattering whose magnitude can exceed that of the specular reflection from the bone-marrow (endosteal) interface. In this study we adapt to bone a specular beamforming technique proposed to better image a needle in soft tissue. Our approach takes into account both wave refraction and specular reflection physics to enhance the contrast of bone surfaces and reduce speckle from intracortical pores. In vivo ultrasound data were acquired at the center of the human tibia in a plane normal to the bone axis of 11 young healthy volunteeers. Ex vivo ultrasound data were acquired from 16 regions of interest from the femoral diaphysis of three elderly donors (donors 66-98 y.o.) using a 2.5 MHz US transducer. A single-element trans mission synthetic aperture imaging sequence was implemented on a research ultrasound system with a 2.5MHz phased array transducer. Image reconstruction was performed: (A) a delay-and-sum (DAS) algorithm with optimized f-number, correction of refraction at the soft tissue-bone interface and subject-specific ultrasound wave speed and (B) an adaptive algorithm using Snells law of reflection. The improvement of image quality was evaluated with contrast ratios of the average intensities: CEI between the endosteal surface and the center of the cortex. In vivo, specular beamforming improved the visibility of the endosteum (CEI ) by 1 to 13 dB while maintaining the relative contrast between the outer and inner surfaces of the cortex. These results suggest that the visualization of the intra-osseous anatomy can be enhanced if Snells law and wave refraction are taken into account during image reconstruction.

physics.med-ph↗

arXiv2025

Ultrasound imaging of cortical bone: cortex geometry and measurement of porosity based on wave speed for bone remodeling estimation

Intracortical US imaging extends B-mode imaging into bone using a dedicated image reconstruction algorithm that corrects for refraction at the bone-soft tissue interfaces. It has shown promising results in a few healthy, predominantly young adults, providing anatomical images of the cortex (periosteal and endosteal surfaces) along with estimations of US wave speed. However, its reliability in older or osteoporotic bones remains uncertain. In this study, we critically assessed the performance of intracortical US imaging ex vivo in bones with various microstructural patterns, including bones exhibiting signs of unbalanced intracortical remodeling. We analyzed factors influencing US image quality, particularly endosteal surface reconstruction, as well as the accuracy of wave speed estimation and its relationship with porosity. We imaged 20 regions of interest from the femoral diaphysis of five elderly donors using a 2.5 MHz US transducer. The reconstructed US images were compared to site-matched high-resolution micro-CT (HR-muCT) images. In samples with moderate porosity, the endosteal surface was accurately identified, and thickness estimates from US and HR-muCT differed by less than 10%. In highly remodeled bones with increased porosity, the reconstructed endosteal surface appeared less bright and was located above the cortex region containing resorption cavities. We observed a decrease in US wave speed with increasing cortical porosity suggesting that the method could discriminate between bones with low porosity (less than 5%) and those with moderate to high porosity (greater than ~10%). This study paves the way for the application of US imaging in diagnosing cortical bone health, particularly for detecting increased cortical porosity and reduced cortical thickness.

physics.med-ph↗

arXiv2025

Assessing ultrasonic and optical flow velocimetry in a millifluidic device using oil-in-water emulsions as blood mimicking fluid

Blood-mimicking fluids (BMFs) play a critical role in ultrasonic imaging and Doppler flow studies by replicating the physical and acoustic properties of blood. This study introduces a novel soybean oil-in-water emulsion as a BMF with particle size and deformability akin to red blood cells. Using a millifluidic device, we cross-validated flow profiles through both Doppler velocimetry and optical particle tracking, demonstrating compatibility with theoretical Poiseuille flow models. The millifluidic chip, fabricated via stereolithography, provided an optimized platform for dual optical and ultrasonic assessments. Results showed strong agreement between the two methods across a range of flow rates, affirming the suitability of the emulsion for velocimetry applications. Furthermore, the acoustic properties of soybean oil droplets support their potential as an echogenic and stable alternative to conventional BMFs.

physics.med-ph↗