In vivo characterization of the child rib mechanical properties using quantitative computed tomography

12th International symposium Computer Methods in Biomechanics and Biomedical Engineering, Amsterdam, PAYS-BAS, 13-/10/2014 - 15/10/2014The mechanical properties of the rib cortical bone have been poorly explored on children due to difficulties to obtain specimens to perform ex vivo tests. Some recent studies have used cadaveric bones or bone tissues collected during surgery but are limited by the number of collected samples. A non-invasive technique could be extremely valuable to overcome this limitation. It has been shown that a relationship exists between the mechanical properties (apparent Young's modulus and ultimate strength) and the bone mineral density (assessed using Quantitative Computed Tomography, QCT), for the femur and recently by our group for the adult ribs ex vivo.Thus, the aim of this study was to assess the mechanical properties of the child rib cortical bone using in vivo QCT images and the relationship between bone mineral density and mechanical properties of the rib cortical bone. Twenty-eight children were included in this study. Seven age-groups have been considered (1, 1.5, 3, 6, 10, 15, 18 years old). The QCT images were prescribed for various cardio thoracic pathologies at the pediatric hospital in Lyon. A calibration phantom was added to the clinical protocol without any modification for the patient. The protocol was approved by the local ethical committee. A 3D reconstruction of each thorax was performed using the QCT images. A custom software was then used to obtain cross-sections to the rib midline.The mean bone mineral density was then computed by averaging the Hounsfield Units in a specific cross-section and by converting the mean value (Hounsfield Units) in bone mineral density using the calibration phantom. This bone mineral density was assessed for the 6th rib of each subject.The relationship between the bone mineral density and the mechanical properties of the rib cortical bone (assessed previously on adult specimens) was used to derive the mechanical properties of the child ribs in vivo. The results give values for the apparent Young's modulus and the ultimate strength. The mechanical properties increase with growth. As an example the apparent Young's modulus in the lateral region ranges from 7 GPa +/-3 at 1 year old up to 13 GPa +/-2 at 18 years old. These data are in agreement with the few previous values obtained from child tissues (e.g. Agnew et al. 2013). This methodology opens the way to in vivo measurement of the mechanical properties of the child cortical bone based on calibrated QCT image

Caractérisation in vivo des propriétés mécaniques des côtes de l'enfant, à partir de tomodensitométrie

Séminaire du Groupe de Recherche en Biomécanique des Chocs (GRBC), PARIS, FRANCE, 27-/11/2014 - 27/11/2014Caractérisation in vivo des propriétés mécaniques des côtes de l'enfant, à partir de tomodensitométri

In vivo assessment of elasticity of child rib cortical bone using quantitative computed tomography

Elasticity of the child rib cortical bone is poorly known due to the difficulties in obtaining specimens to perform conventional tests. It was shown on the femoral cortical bone that elasticity is strongly correlated with density for both children and adults through a unique relationship. Thus, it is assumed that the relationships between the elasticity and density of adult rib cortical bones could be expanded to include that of children. This study estimated in vivo the elasticity of the child rib cortical bone using quantitative computed tomography (QCT). Twenty-eight children (from 1 to 18y.o.) were considered. Calibrated QCT images were prescribed for various thoracic pathologies. The Hounsfield units were converted to bone mineral density (BMD). A relationship between the BMD and the elasticity of the rib cortical bone was applied to estimate the elasticity of children's ribs in vivo. The estimated elasticity increases with growth (7.1±2.5GPa at 1y.o. up to 11.6±1.9GPa at 18y.o.). This data is in agreement with the few previous values obtained using direct measurements. This methodology paves the way for in vivo assessment of the elasticity of the child cortical bone based on calibrated QCT images

Individual radiation exposure from computed tomography: a survey of paediatric practice in French university hospitals, 2010–2013

International audienc

Multicentre chest computed tomography standardisation in children and adolescents with cystic fibrosis : The way forward

Progressive cystic fibrosis (CF) lung disease is the main cause of mortality in CF patients. CF lung disease starts in early childhood. With current standards of care, respiratory function remains largely normal in children and more sensitive outcome measures are needed to monitor early CF lung disease. Chest CT is currently the most sensitive imaging modality to monitor pulmonary structural changes in children and adolescents with CF. To quantify structural lung disease reliably among multiple centres, standardisation of chest CT protocols is needed. SCIFI CF (Standardised Chest Imaging Framework for Interventions and Personalised Medicine in CF) was founded to characterise chest CT image quality and radiation doses among 16 participating European CF centres in 10 different countries. We aimed to optimise CT protocols in children and adolescents among several CF centres. A large variety was found in CT protocols, image quality and radiation dose usage among the centres. However, the performance of all CT scanners was found to be very similar, when taking spatial resolution and radiation dose into account. We conclude that multicentre standardisation of chest CT in children and adolescents with CF can be achieved for future clinical trials