Novel applications of pQCT in a Paediatric Diagnostic Setting

Abstract

There is considerable interest in the clinical use of peripheral quantitative computed tomography (pQCT) to assess paediatric bone density (BMD). Peripheral QCT’s volumetric measurement of trabecular and cortical BMD is less dependent on stature, making pQCT advantageous when monitoring bone health during growth, and in disorders of growth. Peripheral QCT can also assess bone parameters like geometry, strength indices, and more recently, density distribution.

Despite the advantages offered by pQCT, there are shortcomings with its current use in paediatrics. There is no standard acquisition and analysis methodology, and the analysis methodologies used for paediatric reference populations are frequently inappropriate for clinical subjects. In addition, there is no widely accepted reference dataset that includes both tibia and radius data. Notably, there is limited assessment of the utility of novel pQCT data, like density distribution.

To address some of these issues, this thesis evaluates the clinical application of data produced by an open-source image analysis programme (ImageJ, plus pQCT plugin). The plugin was modified to generate novel density frequency descriptives, in addition to its ‘standard’ density distribution data. Peripheral QCT images of the tibia and radius were analysed using parameters suitable for most paediatric clinical subjects and the agreement between the ImageJ and the manufacturer-provided ‘generic’ data (Stratec) was assessed. Focusing on the cortical bone sites, normal predictive equations for height and gender were produced for all novel parameters, and their application tested in a variety of clinical cohorts.

As it is currently implemented, pQCT does not improve diagnosis over DXA alone in many paediatric clinical conditions. However, with improved analysis methodology, and the utilisation of novel measures, it has the potential to become a valuable diagnostic tool.