Dual modality neutron and x-ray tomography for enhanced image analysis of the bone-metal interface

Abstract

The bone tissue formed at the contact interface with metallic implants, particularly its 3D microstructure, plays a pivotal role for the structural integrity of implant fixation. X-ray tomography is the classical imaging technique used for accessing microstructural information from bone tissue. However, neutron tomography has shown promise for visualising the immediate bone-metal implant interface, something which is highly challenging with x-rays due to large differences in attenuation between metal and biological tissue causing image artefacts. To highlight and explore the complementary nature of neutron and x-ray tomography, proximal rat tibiae with titanium-based implants were imaged with both modalities. The two techniques were compared in terms of visualisation of different material phases and by comparing the properties of the individual images, such as the contrast-to-noise ratio. After superimposing the images using a dedicated image registration algorithm, the complementarity was further investigated via analysis of the dual modality histogram, joining the neutron and x-ray data. From these joint histograms, peaks with well-defined grey value intervals corresponding to the different material phases observed in the specimens were identified and compared. The results highlight differences in how neutrons and x-rays interact with biological tissues and metallic implants, as well as the benefits of combining both modalities. Future refinement of the joint histogram analysis could improve the segmentation of structures and tissues, and yield novel information about specimen-specific properties such as moisture content.

Effect of collagen fibril orientation on the anisotropic properties of peri-implant bone

“…Xray micro-tomography is frequently used to obtain the degree of tissue mineralization as the grey levels obtained in the reconstructed images are linked to the local content of minerals. However, such a technique is difficult to conduct close to metallic implants due to frequent imaging artifacts (Barrett and Keat, 2004;Törnquist et al, 2021). Previous numerical work has shown an increase in bone tissue stiffness with the increase of the mineralization on cortical bone (Sansalone et al, 2010).…”

The Hydration State of Bone Tissue Affects Contrast in Neutron Tomographic Images

“…Visibility of internal structures in neutron tomography images is comparable to X-ray tomography images when the specimens are dried (Figures 1C,D) (Törnquist et al, 2021). Hence, a new exchange protocol was devised in this study where the specimens were first dried to remove as much H 2 O as possible before being rehydrated in D 2 O, thereby improving the exchange compared to the previous diffusion-driven protocol, whilst also allowing for a FIGURE 1 | Study motivation.…”

“…Thus, studying the integration of metallic implants into bone using X-rays are challenging (Le Cann et al, 2019). Neutron tomography has recently been shown to be a promising alternative technique to X-ray tomography for the evaluation of bone tissue in close proximity to a metallic implant (Isaksson et al, 2017;Le Cann et al, 2017;Guillaume et al, 2021;Törnquist et al, 2021). Neutrons interact differently with matter compared to X-rays, which translates into an alternative contrast between materials, that is, not correlated with X-ray attenuation values (Bilheux et al, 2009;Roubin et al, 2019;Tengattini et al, 2021).…”