Supporting data for "Advanced Application and Validation of a Phantom-less Quantitative Computed Tomography System on Site-specific Bone Density Assessment"
Abstract of thesis "Advanced Application and Validation of a Phantom-less Quantitative Computed Tomography System on Site-specific Bone Density Assessment"
Osteoporosis, as a silent epidemic, can lead to osteoporotic fractures in severe cases, resulting in a huge health and economic burden to the society. The diagnosis of osteoporosis and the assessment of its effects can play a role in its prevention and early intervention, which can minimize the risk it causes. Bone mineral density (BMD) is the primary indicator for the diagnosis of osteoporosis, and Quantitative computed tomography (QCT) is considered the most accurate and advanced BMD measurement tool. However, research about QCT applications on orthopaedic clinical diagnosis and applications is scarce. This thesis aims to apply the phantom-less QCT (PL-QCT) on clinically relevant sites like the spinal endplate, spinal pedicle, and proximal humerus of the shoulder. The second aim of this thesis is to validate the precision and accuracy of its measured BMD in aspects of cross-device and novel application sites.
PL-QCT was first applied to measure BMDs at different sites of the vertebral body to find their coordinate relevance to cage subsidence after interbody fusion, while the cross-device BMD measurement reliability of this PL-QCT was also examined. Endplate BMD was demonstrated as the most optimal risk factor of cage subsidence. The average intra-scanner and inter-brand precisions were 1.61 mg/cm3 and 2.64 mg/cm3, respectively, and the averages of L1~L3 vBMD measurements from all scanners met the ± 5 mg/cm3 bias criteria.
Screw planning for internal fixation based on the PL-QCT was also performed and evaluated based on comparison with the freehand outcomes. Results from the planning software based on PL-QCT (48.65 ± 5.99 mm/7.39 ± 0.42 mm) had better dimensions like larger length and thickness than that of the freehand method (44.78 ± 2.99 mm/6.1 ± 0.27 mm). The percentage of the highest surgical safety level of the software (85.1%) was also higher than that of the freehand method (64.9%).
Based on the relationship between endplate BMD and cage subsidence, a methodology was developed along an applicability study of the biomechanical customization interbody cage. Through the BMD-modulus relationship, the coordinate modulus for a patient-specific endplate BMD can be confirmed as a reference for cage modulus customization. Results of the simulation study indicated that the self-designed cage's optimal structural parameters for BMD-modulus customization were irregularity (IR) =1 and cage porosity (CP) = 43.86%~51.63%. Under such parameters, the modulus range of the self-designed cage can fit the modulus range of the endplate BMD.
On the proximal humerus of the shoulder, PL-QCT was applied to measure cancellous bone BMD, meanwhile, its validation was achieved based on the comparison with phantom-based QCT (PB-QCT). The mean BMD bias between these two QCTs was 1.0 mg/cm3 with P-value > 0.05. The correlation R-square between them was 0.9723. PL-QCT and PB-QCT were demonstrated with similar short-term reproductivity and repeatability.
In conclusion, studies in this thesis demonstrate the potential for expanding the range of orthopaedic application of the PL-QCT. The outcomes of this study have the potential to serve as valuable reference for advancing orthopaedic clinical practice.
