Abstract
In the clinical field of diagnosis and monitoring of bone diseases, high-resolution peripheral quantitative computed tomography (HR-pQCT) is an important imaging modality. It provides a resolution where quantitative bone morphometry can be extracted in vivo on patients. It is known that HR-pQCT provides slight differences in morphometric indices compared to the current standard approach micro-computed tomography (micro-CT). The most obvious reason for this is the restriction of the radiation dose and with this a lower image resolution. With advances in micro-CT evaluation techniques such as patient-specific remodeling simulations or dynamic bone morphometry, a higher image resolution would potentially also allow the application of such novel evaluation techniques to clinical HR-pQCT measurements. Virtual supersampling as post-processing step was considered to increase the image resolution of HR-pQCT scans. The hypothesis was that this technique preserves the structural bone morphometry. Supersampling from 82 μm to virtual 41 μm by trilinear interpolation of the grayscale values of 42 human cadaveric forearms resulted in strong correlations of structural parameters (R2: 0.96–1.00). BV/TV was slightly overestimated (4.3%, R2: 1.00) compared to the HR-pQCT resolution. Tb.N was overestimated (7.47%; R2: 0.99) and Tb.Th was slightly underestimated (-4.20%; R2: 0.98). The technique was reproducible with PE%CV between 1.96% (SMI) and 7.88% (Conn.D). In a clinical setting with 205 human forearms with or without fracture measured at 82 μm resolution HR-pQCT, the technique was sensitive to changes between groups in all parameters (p < 0.05) except trabecular thickness. In conclusion, we demonstrated that supersampling preserves the bone morphometry from HR-pQCT scans and is reproducible and sensitive to changes between groups. Supersampling can be used to investigate on the resolution dependency of HR-pQCT images and gain more insight into this imaging modality.
Highlights
Quantitative assessment of the trabecular bone microstructure is a valuable tool in bone research because a number of bone diseases act directly on the trabecular bone surface which causes alterations in the bone microstructure
HR-pQCT provides an image resolution where single trabeculae can be resolved and the bone microstructure can be quantified using the techniques originally developed for micro-CT [1,2]
Trabecular and cortical microstructural and biomechanical parameters gained from HR-pQCT scans have been validated in comparison to scans obtained using micro-CT at distal radius, tibia and calcaneus [1,3,4,5,6,7]
Summary
Quantitative assessment of the trabecular bone microstructure is a valuable tool in bone research because a number of bone diseases act directly on the trabecular bone surface which causes alterations in the bone microstructure.The current standard technology to quantify human three-dimensional bone morphology is micro-computed tomography (micro-CT) ex vivo where no radiation issues have to be respected. With advances in in vivo imaging technologies, the quantitative determination of the bone morphology has entered the clinical setting. High-resolution, peripheral quantitative computed tomography (HR-pQCT) is a promising clinical tool for the monitoring of the microstructure in bone diseases and their treatments in vivo in patients. HR-pQCT provides an image resolution where single trabeculae can be resolved and the bone microstructure can be quantified using the techniques originally developed for micro-CT [1,2]. Metcalf et al [3] found, comparing trabecular structural parameters of HR-pQCT with micro-CT, very strong correlations of BV/TV, and moderate correlations for Tb.Th and Tb.N. Christen et al [4] developed a biomechanical analysis tool for micro-CT resolutions [5] which provides detailed insight into the reasons for a certain form of the bone microstructure. Christen et al investigated the tool’s voxel size dependency, reproducibility, and sensitivity on HR-pQCT data and showed with this that their tool can be applied at HR-pQCT resolutions
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