Methodology for Assessment of the Rat Jaw Bone Microstructure Using Ex-vivo Micro-computed Tomography

Objectives: Micro-computed tomography (microCT) can be applied in the maxillofacial bone region for assessment of the micro-architectural characteristics of the cortical and trabecular bone, alveolar bone (re)modelling, etc in either physiological or disease conditions. However, reports often lack a detailed description of the methodological steps used to analyse the microCT images, such as the considered regions of interest (ROIs), the algorithms used for image filtration, the approach used for image segmentation and the bone parameters quantified, thereby making it difficult to compare or reproduce the studies. This study addresses this critical need and aims to provide standardized assessment and consistent parameter reporting related to jaw bone image analysis. The proposed methodology is applied to the rat jaw bone for offering proof-of-concept.
Methods: Various regions of the rat jaw bones were screened for its potential for standardized microCT analysis. The ROIs that were anticipated to be most susceptible to bone structural changes in response to experimental interventions were defined. In the mandible, two ROIs were selected, namely the condyle (Fig.1A) and the alveolar bone surrounding the 3 molars (Fig.1B-C). In the maxilla, the maxillary tuber region (Fig.2A) and the intra-radicular septum of the second molar (Fig.2B-C) were considered as ROIs.
Results: The procedures for manual and automatic (ellipsoid/rectangle) delineation of the different ROIs, based on well-defined landmarks, and the quantified bone parameters are described. As a case study, the developed microCT protocol was applied for analyzing the jaw bone micro-architecture of osteoporotic rats (n=21), either untreated or treated with bisphosphonates.
Conclusions: The protocol developed in this work provides a standardized and reproducible methodology for microCT analysis of relevant jaw bone ROIs, and is intended to ensure global, accurate and consistent reporting of microCT-derived jaw bone morphometry. Furthermore, the proposed methodology holds potential as a variety of rodent animal models would benefit from its implementation.