A novel methodology for analysis and data visualisation of T1 weighted MRIs of the distal end of the femur

Introduction: In recent studies, MRIs have shown to be of value for evaluating the osteological maturation of different skeletal areas. However, numerous limitations exist regarding reproducibility and comparison of these studies and available information concerning the development of the distal end of the femur is limited. One of the largest issues with these studies is the lack of methodology in relation to identifying where and on which slice of the MRI maturation is happening and how this compares to other MRIs.
Aims: This study aims to develop a new method for the analysis of T1 weighted Magnetic Resonance Images (MRIs) in the coronal plane that can be used to visualise, describe and compare the osteological maturation of the distal end of the femur.
Material & methods: The T1 weighted MRIs used for this study were acquired using a 1.5 T scanner, with a slice thickness of 3mm, TE: 10-12 and TR: 466-553. MRIs were accessed from the radiology department of Ninewells hospital in Dundee (Scotland)through the Pictures Archiving and Communication System (PACS) and included both male and female individuals with an age between 10 and 20 years. To develop the new method, all slices in each MRI set were taken into consideration at all times, and the MRIs used included individuals from both sexes and from all age groups. Initially, 37 MRIs were ordered and analysed youngest to oldest, and the main morphological changes within the growth plate were recorded. The morphological changes observed were then classified into different stages which took into account the morphology of metaphyseal end plate and epiphyseal plate, signal intensity of the growth plate, presence/absence of bone bridges and presence/absence of an epiphyseal scar. The classification system was applied to 30 further MRIs and 7 final stages were determined. For each stage, an image, a drawing and a written description is provided. To apply this new classification method, in each slice within each set of MRI, the distal epiphysis of the femur has to be divided into nine equal sections that are kept constant in width in all slices. Section width is determined using the MRI slice where the distal femoral epiphysis is the widest, in the coronal plane. Each section is then scored according to the classification system.
Conclusion: These scoring and data collection systems allow the creation of a maturational map which is intuitive and provides a direct way to visualise and describe the osteological maturation of the distal end of the femur growth plate allowing comparison between individuals. This new classification system and the maturational map could be used to develop a new method for age assessment in the living individuals as the morphological changes observed at the growth plate can be related to chronological age.