For many years, MRI of the musculoskeletal system has relied mostly on conventional sequences with qualitative analysis. More recently, using quantitative MRI applications to complement qualitative ...imaging has gained increasing interest in the MRI community, providing more detailed physiologic or anatomic information.
In this article, we review the current state of quantitative MRI, technical and software advances, and the most relevant clinical and research musculoskeletal applications of quantitative MRI.
Bone possesses a highly complex hierarchical structure comprised of mineral (~45% by volume), organic matrix (~35%) and water (~20%). Water exists in bone in two forms: as bound water (BW), which is ...bound to bone mineral and organic matrix, or as pore water (PW), which resides in Haversian canals as well as in lacunae and canaliculi. Magnetic resonance (MR) imaging has been increasingly used for assessment of cortical and trabecular bone. However, bone appears as a signal void on conventional MR sequences because of its short T2
. Ultrashort echo time (UTE) sequences with echo times (TEs) 100-1,000 times shorter than those of conventional sequences allow direct imaging of BW and PW in bone. A series of quantitative UTE MRI techniques has been developed for bone evaluation. UTE and adiabatic inversion recovery prepared UTE (IR-UTE) sequences have been developed to quantify BW and PW. UTE magnetization transfer (UTE-MT) sequences have been developed to quantify collagen backbone protons, and UTE quantitative susceptibility mapping (UTE-QSM) sequences have been developed to assess bone mineral.
The COVID-19 pandemic is marked by a wide range of clinical disease courses, ranging from asymptomatic to deadly. There have been many studies seeking to explore the correlations between COVID-19 ...clinical outcomes and various clinical variables, including age, sex, race, underlying medical problems, and social habits. In particular, the relationship between smoking and COVID-19 outcome is controversial, with multiple conflicting reports in the current literature. In this study, we aim to analyze how smoking may affect the SARS-CoV-2 infection rate. We analyzed sequencing data from lung and oral epithelial samples obtained from The Cancer Genome Atlas (TCGA). We found that the receptor and transmembrane protease necessary for SARS-CoV-2 entry into host cells, ACE2 and TMPRSS2, respectively, were upregulated in smoking samples from both lung and oral epithelial tissue. We then explored the mechanistic hypothesis that smoking may upregulate ACE2 expression through the upregulation of the androgen pathway. ACE2 and TMPRSS2 upregulation were both correlated to androgen pathway enrichment and the specific upregulation of central pathway regulatory genes. These data provide a potential model for the increased susceptibility of smoking patients to COVID-19 and encourage further exploration into the androgen and tobacco upregulation of ACE2 to understand the potential clinical ramifications.
We report a simple and rapid microfluidic approach to produce core–shell hydrogel microspheres in a single step. We exploit triple emulsion drops with sacrificial oil layers that separate two ...prepolymer phases, forming poly(ethylene glycol)-based core–shell microspheres via photopolymerization followed by spontaneous removal of the oil layer. Our technique enables the production of monodisperse core–shell microspheres with varying dimensions of each compartment by independently and precisely controlled flow rates. This leads to stable and uniform incorporation of functional moieties in the core compartment with negligible cross-contamination into the shell layer. Selective conjugation of biomolecules is enabled through a rapid bioorthogonal reaction with functional groups in the core compartment with minimal non-specific adsorption. Finally, in-depth protein conjugation kinetics studies using microspheres with varying shell porosities highlight the capability to provide tunable size-selective diffusion barriers by simple tuning of prepolymer compositions for the shell layer. Combined, these results illustrate a significant step forward for programmable high-throughput fabrication of multifunctional hydrogel microspheres, which possess substantial potential in a large array of biomedical and biochemical applications.
Areal bone mineral density (aBMD) from dual-energy x-ray absorptiometry (DEXA) and volumetric bone mineral density (vBMD) have demonstrated limited capabilities in the evaluation of bone mechanical ...competence and prediction of bone fracture. Predicting the macroscopic mechanical behavior of the bone structure has been challenging because of the heterogeneous and anisotropic nature of bone, such as the dependencies on loading direction, anatomical location, and sample dimensions. Magnetic resonance imaging (MRI) has been introduced as a promising modality that can be coupled with finite element analysis (FEA) for the assessment of bone mechanical competence. This review article describes studies investigating MRI-based micro-FEA as a potential non-invasive method to predict bone mechanical competence and facilitate bone fracture risk estimation without exposure to ionizing radiation. Specifically, the steps, applications, and future potential of FEA using indirect and direct bone imaging are discussed.
We have investigated the concurrence of sleep apnea and pulmonary hypertension in a Veteran population. We retrospectively reviewed 142 patients who underwent chest CT scans and had a dilated main ...pulmonary artery, defined as a width exceeding 29 mm on axial images. Approximately 40% of patients with pulmonary hypertension had associated sleep apnea. No significant difference in pulmonary artery diameters could be found between the group without sleep apnea and the group with sleep apnea (34.5 ± 4.2 mm vs. 34.7 ± 4.4 mm,
= 0.373).
Summary Purpose To investigate the effect of sample orientation on T1rho and T2 values of articular cartilage in histologically confirmed normal and abnormal regions using a whole-body 3T scanner, ...providing information on the angular dependence of T1rho and T2 in clinical imaging. Materials and Methods Eight human cadaveric patellae were evaluated using a 2D CPMG sequence for T2 measurement as well as a 2D spin-locking prepared spiral sequence and a 3D magnetization-prepared angle-modulated partitioned-k - space spoiled gradient echo snapshots (3D MAPSS) sequence for T1rho measurement. Each sample was imaged at six angles from 0° to 100° relative to the B0 field. T2 and T1rho values were measured for three regions (medial, apex and lateral) with three layers (10% superficial, 60% middle, 30% deep). Multiple histopathologically confirmed normal and abnormal regions were also used to evaluate the angular dependence of T2 and T1rho relaxation in articular cartilage. Results Our study demonstrated a strong magic angle effect for T1rho and T2 relaxation in articular cartilage, especially in the deeper layers of cartilage. On average over eight patellae, T2 values were increased by 231.8% (72.2% for superficial, 237.6% for middle, and 187.9% for deep layers) while T1rho values were increased by 92% (31.7% for superficial, 69% for middle, and 140% for deep layers) near the magic angle. Both normal and abnormal cartilage showed similar T1rho and T2 magic angle effect. Conclusions Changes in T1rho and T2 values due to the magic angle effect can be several times more than that caused by degeneration, and this may significantly complicate the clinical application of T1rho and T2 as an early surrogate marker for degeneration.
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