Comparing linear and nonlinear finite element models of vertebral strength across the thoracolumbar spine: a benchmark from density-calibrated computed tomography.

Background: Opportunistic assessment of vertebral strength from clinical computed tomography (CT) scans holds substantial promise for fracture risk stratification, yet variability in calibration methods and finite element (FE) modeling approaches has led to limited comparability across studies. In this work, we provide a publicly available benchmark dataset that supports standardized biomechanical analysis of the thoracic and lumbar spine using density-calibrated CT data. We extended the VerSe 2019 dataset to include phantomless quantitative CT calibration, automated vertebral substructure segmentation, and vertebral strength estimates derived from both linear and nonlinear FE models.

Recovery of bone microarchitecture and density four years after spaceflight: two case studies.

Spaceflight is known to negatively impact bone health, but the duration of these effects remains unclear. These two case studies investigated bone microarchitecture, density, and remodelling up to 4 years after long-duration spaceflight, aiming to inform countermeasure development and guide future research efforts. High-resolution peripheral quantitative computed tomography (HR-pQCT) and dual X-ray absorptiometry (DXA) scans were conducted on two crew members at pre-flight and up to 48-months post-spaceflight.

Using solid-state MRI and a double-tuned RF coil to quantify bone matrix and mineral densities in rat bones.

Quantitative information on the composition of bone, specifically the content of calcium phosphate mineral and organic matrix, is essential for accurate diagnosis of metabolic bone diseases such as osteoporosis, osteomalacia, and renal osteodystrophy, as well as for differentiating among these conditions. Conventional MRI fails to provide this information because these substances are solid and, therefore, yield no signal in conventional MRI scans, which typically employ spin or gradient echoes. In this report, we show how phosphorus and proton solid-state MRI yield the desired compositional information in bone specimens with ZTE and WASPI pulse sequences, respectively, coupled with the use of a two-port double-tuned solenoidal RF coil.

Quantifying localized bone loss in clinical computed tomography using void spaces.

Unlabelled: Localized bone loss, known as void spaces, is not captured using standard measures in clinical computed tomography (CT). This study validated the use of CT to systemically assess void spaces throughout the skeleton. We found that void spaces were localized to skeleton regions (e.

Structural alterations during fracture healing lead to void spaces developing in surrounding bone microarchitecture.

Distal radius fractures are among the most common fracture sites, with a high incidence across all age groups. High-resolution peripheral quantitative computed tomography (HR-pQCT) has enabled assessment of bone microarchitecture in vivo at the distal radius, providing new insights into the healing process. However, we have observed structural bone loss that is not captured by standard analysis.

Tracking of spaceflight-induced bone remodeling reveals a limited time frame for recovery of resorption sites in humans.

Mechanical unloading causes bone loss, but it remains unclear whether disuse-induced changes to bone microstructure are permanent or can be recovered upon reloading. We examined bone loss and recovery in 17 astronauts using time-lapsed high-resolution peripheral quantitative computed tomography and biochemical markers to determine whether disuse-induced changes are permanent. During 6 months in microgravity, resorption was threefold higher than formation.

A graph model to describe the network connectivity of trabecular plates and rods.

The trabecular network is perceived as a collection of interconnected plate- (P) and rod-like (R) elements. Previous research has highlighted how these elements and their connectivity influence the mechanical properties of bone, yet further work is required to elucidate better the deeply interconnected nature of the trabecular network with distinct element formations conducting forces per their mechanical boundary conditions. Within this network, forces act through elements: a rod or plate with force applied to one end will transmit this force to a component connected to the other end, defining the boundary conditions for the loading of each element.

Quantitative H Magnetic Resonance Imaging on Normal and Pathologic Rat Bones by Solid-State H ZTE Sequence with Water and Fat Suppression.

Background: Osteoporosis (OP) and osteomalacia (OM) are metabolic bone diseases characterized by mineral and matrix density changes. Quantitative bone matrix density differentiates OM from OP. MRI is a noninvasive and nonionizing imaging technique that can measure bone matrix density quantitatively in ex vivo and in vivo.

Bone remodeling and responsiveness to mechanical stimuli in individuals with type 1 diabetes mellitus.

Type 1 diabetes mellitus (T1DM) has been linked to increased osteocyte apoptosis, local accumulation of mineralized lacunar spaces, and microdamage suggesting an impairment of the mechanoregulation network in affected individuals. Diabetic neuropathy might exacerbate this dysfunction through direct effects on bone turnover, and indirect effects on balance, muscle strength, and gait. However, the in vivo effects of impaired bone mechanoregulation on bone remodeling in humans remain underexplored.

Quantitative P magnetic resonance imaging on pathologic rat bones by ZTE at 7T.

Background: Osteoporosis is characterized by low bone mineral density (BMD), which predisposes individuals to frequent fragility fractures. Quantitative BMD measurements can potentially help distinguish bone pathologies and allow clinicians to provide disease-relieving therapies. Our group has developed non-invasive and non-ionizing magnetic resonance imaging (MRI) techniques to measure bone mineral density quantitatively.

A multi-stack registration technique to improve measurement accuracy and precision across longitudinal HR-pQCT scans.

Background: Recent applications of high-resolution peripheral quantitative computed tomography (HR-pQCT) have demonstrated that changes in local bone remodelling can be quantified in vivo using longitudinal three-dimensional image registration. However, certain emerging applications, such as fracture healing and joint analysis, require larger multi-stack scan regions that can result in stack shift image artifacts. These artifacts can be detrimental to the accurate alignment of the bone structure across multiple timepoints.

Mechanostat parameters estimated from time-lapsed micro-computed tomography data of mechanically driven bone adaptation are logarithmically dependent on loading frequency.

Mechanical loading is a key factor governing bone adaptation. Both preclinical and clinical studies have demonstrated its effects on bone tissue, which were also notably predicted in the mechanostat theory. Indeed, existing methods to quantify bone mechanoregulation have successfully associated the frequency of (re)modeling events with local mechanical signals, combining time-lapsed micro-computed tomography (micro-CT) imaging and micro-finite element (micro-FE) analysis.

Meta-analysis of Diabetes Mellitus-Associated Differences in Bone Structure Assessed by High-Resolution Peripheral Quantitative Computed Tomography.

Purpose Of Review: Diabetes mellitus is defined by elevated blood glucose levels caused by changes in glucose metabolism and, according to its pathogenesis, is classified into type 1 (T1DM) and type 2 (T2DM) diabetes mellitus. Diabetes mellitus is associated with multiple degenerative processes, including structural alterations of the bone and increased fracture risk. High-resolution peripheral computed tomography (HR-pQCT) is a clinically applicable, volumetric imaging technique that unveils bone microarchitecture in vivo.

Bone Mechanoregulation Allows Subject-Specific Load Estimation Based on Time-Lapsed Micro-CT and HR-pQCT .

Patients at high risk of fracture due to metabolic diseases frequently undergo long-term antiresorptive therapy. However, in some patients, treatment is unsuccessful in preventing fractures or causes severe adverse health outcomes. Understanding load-driven bone remodelling, i.

Application of subject-specific adaptive mechanical loading for bone healing in a mouse tail vertebral defect.

Methods to repair bone defects arising from trauma, resection, or disease, continue to be sought after. Cyclic mechanical loading is well established to influence bone (re)modelling activity, in which bone formation and resorption are correlated to micro-scale strain. Based on this, the application of mechanical stimulation across a bone defect could improve healing.

Two Colour Photoflow Chemistry for Macromolecular Design.

We report a photochemical flow setup that exploits λ-orthogonal reactions using two different colours of light (λ =350 nm and λ =410 nm) in sequential on-line irradiation steps. Critically, both photochemically reactive units (a visible-light reactive chalcone and a UV-activated photo-caged diene) are present in the reaction mixture. We demonstrate the power of two colour photoflow by the wavelength-selective end group modification of photo-caged polymer end groups and the subsequent polymer ring closure driven by a [2+2] cycloaddition.

Targeted and modular architectural polymers employing bioorthogonal chemistry for quantitative therapeutic delivery.

There remain several key challenges to existing therapeutic systems for cancer therapy, such as quantitatively determining the true, tissue-specific drug release profile , as well as reducing side-effects for an increased standard of care. Hence, it is crucial to engineer new materials that allow for a better understanding of the pharmacokinetic/pharmacodynamic behaviours of therapeutics. We have expanded on recent "click-to-release" bioorthogonal pro-drug activation of antibody-drug conjugates (ADCs) to develop a modular and controlled theranostic system for quantitatively assessing site-specific drug activation and deposition from a nanocarrier molecule, by employing defined chemistries.

To what extent are psychiatrists aware of the comorbid somatic illnesses of their patients with serious mental illnesses? - a cross-sectional secondary data analysis.

Background: Somatic comorbidities are a serious problem in patients with severe mental illnesses. These comorbidities often remain undiagnosed for a long time. In Germany, physicians are not allowed to access patients' health insurance data and do not have routine access to documentation from other providers of health care.