Abstract
We investigated the effects of low-dose multi detector computed tomography (MDCT) in combination with statistical iterative reconstruction algorithms on trabecular bone microstructure parameters. Twelve donated vertebrae were scanned with the routine radiation exposure used in our department (standard-dose) and a low-dose protocol. Reconstructions were performed with filtered backprojection (FBP) and maximum-likelihood based statistical iterative reconstruction (SIR). Trabecular bone microstructure parameters were assessed and statistically compared for each reconstruction. Moreover, fracture loads of the vertebrae were biomechanically determined and correlated to the assessed microstructure parameters. Trabecular bone microstructure parameters based on low-dose MDCT and SIR significantly correlated with vertebral bone strength. There was no significant difference between microstructure parameters calculated on low-dose SIR and standard-dose FBP images. However, the results revealed a strong dependency on the regularization strength applied during SIR. It was observed that stronger regularization might corrupt the microstructure analysis, because the trabecular structure is a very small detail that might get lost during the regularization process. As a consequence, the introduction of SIR for trabecular bone microstructure analysis requires a specific optimization of the regularization parameters. Moreover, in comparison to other approaches, superior noise-resolution trade-offs can be found with the proposed methods.
Highlights
Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength predisposing an individual to an increased risk for fracture [1]
Comparing all parameters to the values assessed with SD-filtered backprojection (FBP) using the Wilcoxon rank sum test showed significant differences for the following values (p < 0.05; Table 2): trabecular number (TbN), fractal dimension (FD) for low-dose protocol (LD)-FBP; TbN, trabecular separation (TbSp), trabecular thickness (TbTh), FD for LD-statistical iterative reconstruction (SIR) with β = 0.1, δ = 0.0001
It was shown that trabecular bone microstructure parameters as assessed by LD-SIR significantly correlated with vertebral bone strength
Summary
Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength predisposing an individual to an increased risk for fracture [1]. Low-Dose CT and IR for Trabecular Bone Microstructure Assessment considerably reduce quality of life but are associated with an increased mortality. Due to the aging population, the prevalence of osteoporosis and the incidence of osteoporotic fractures are expected to increase. Osteoporosis is classified as a public health problem. The socio-economic burden is expected to rise dramatically, e.g. in the United States from $17 billion in 2005 by almost 50% until 2025 [2]
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