Purpose
In this study, we aimed to develop a new technique, ultrashort echo time Cones double echo steady state (UTE‐Cones‐DESS), for highly efficient morphological imaging of musculoskeletal tissues ...with short T2s. We also proposed a novel, single‐point Dixon (spDixon)‐based approach for fat suppression.
Methods
The UTE‐Cones‐DESS sequence was implemented on a 3T MR system. It uses a short radiofrequency (RF) pulse followed by a pair of balanced spiral‐out and spiral‐in readout gradients separated by an unbalanced spoiling gradient in‐between. The readout gradients are applied immediately before or after the RF pulses to achieve a UTE image (S+) and a spin/stimulated echo image (S−). Weighted echo subtraction between S+ and S− was performed to achieve high contrast specific to short T2 tissues, and spDixon was applied to suppress fat by using the intrinsic complex signal of S+ and S−. Six healthy volunteers and five patients with osteoarthritis were recruited for whole‐knee imaging. Additionally, two healthy volunteers were recruited for lower leg imaging.
Results
The UTE‐Cones‐DESS sequence allows fast volumetric imaging of musculoskeletal tissues with excellent image contrast for the osteochondral junction, tendons, menisci, and ligaments in the knee joint as well as cortical bone and aponeurosis in the lower leg within 5 min. spDixon yields efficient fat suppression in both S+ and S− images without requiring any additional acquisitions or preparation pulses.
Conclusion
The rapid UTE‐Cones‐DESS sequence can be used for high contrast morphological imaging of short T2 tissues, providing a new tool to assess their association with musculoskeletal disorders.
A relationship between an acidic pH in the joints, osteoarthritis (OA), and pain has been previously demonstrated. Acidosis Chemical Exchange Saturation Transfer (acidoCEST) indirectly measures the ...extracellular pH through the assessment of the exchange of protons between amide groups on iodinated contrast agents and bulk water. It is possible to estimate the extracellular pH in the osteoarthritic joint using acidoCEST MRI. However, conventional MR sequences cannot image deep layers of cartilage, meniscus, ligaments, and other musculoskeletal tissues that present with short echo time and fast signal decay. Ultrashort echo time (UTE) MRI, on the other hand, has been used successfully to image those joint tissues. Here, our goal is to compare the pH measured in the knee joints of volunteers without OA and patients with severe OA using acidoCEST-UTE MRI. Patients without knee OA and patients with severe OA were examined using acidoCEST-UTE MRI and the mean pH of cartilage, meniscus, and fluid was calculated. Additionally, the relationship between the pH measurements and the Knee Injury and Osteoarthritis Outcome Score (KOOS) was investigated. AcidoCEST-UTE MRI can detect significant differences in the pH of knee cartilage, meniscus, and fluid between joints without and with OA, with OA showing lower pH values. In addition, symptoms and knee-joint function become worse at lower pH measurements.
Bone is comprised of mineral, collagenous organic matrix, and water. X-ray-based techniques are the standard approach for bone evaluation in clinics, but they are unable to detect the organic matrix ...and water components in bone. Magnetic resonance imaging (MRI) is being used increasingly for bone evaluation. While MRI can non-invasively assess the proton pools in soft tissues, cortical bone typically appears as a signal void with clinical MR techniques because of its short T2*. New MRI techniques have been recently developed to image bone while avoiding the ionizing radiation present in x-ray-based methods. Qualitative bone imaging can be achieved using ultrashort echo time (UTE), single inversion recovery UTE (IR-UTE), dual-inversion recovery UTE (Dual-IR-UTE), double-inversion recovery UTE (Double-IR-UTE), and zero echo time (ZTE) sequences. The contrast mechanisms as well as the advantages and disadvantages of each technique are discussed.
Chemically functional hydrogel microspheres hold significant potential in a range of applications including biosensing, drug delivery, and tissue engineering due to their high degree of flexibility ...in imparting a range of functions. In this work, we present a simple, efficient, and high-throughput capillary microfluidic approach for controlled fabrication of monodisperse and chemically functional hydrogel microspheres via formation of double emulsion drops with an ultra-thin oil shell as a sacrificial template. This method utilizes spontaneous dewetting of the oil phase upon polymerization and transfer into aqueous solution, resulting in poly(ethylene glycol) (PEG)-based microspheres containing primary amines (chitosan, CS) or carboxylates (acrylic acid, AA) for chemical functionality. Simple fluorescent labelling of the as-prepared microspheres shows the presence of abundant, uniformly distributed and readily tunable functional groups throughout the microspheres. Furthermore, we show the utility of chitosan's primary amine as an efficient conjugation handle at physiological pH due to its low pKa by direct comparison with other primary amines. We also report the utility of these microspheres in biomolecular conjugation using model fluorescent proteins, R-phycoerythrin (R-PE) and green fluorescent protein (GFPuv), via tetrazine-trans-cyclooctene (Tz-TCO) ligation for CS-PEG microspheres and carbodiimide chemistry for AA-PEG microspheres, respectively. The results show rapid coupling of R-PE with the microspheres' functional groups with minimal non-specific adsorption. In-depth protein conjugation kinetics studies with our microspheres highlight the differences in reaction and diffusion of R-PE with CS-PEG and AA-PEG microspheres. Finally, we demonstrate orthogonal one-pot protein conjugation of R-PE and GFPuv with CS-PEG and AA-PEG microspheres via simple size-based encoding. Combined, these results represent a significant advancement in the rapid and reliable fabrication of monodisperse and chemically functional hydrogel microspheres with tunable properties.
This technical note presents our experience with the additional prone examination of patients during low dose CT lung cancer screening. The prone examination adds only a minor amount of radiation and ...time to the study and can reduce false positive findings that are gravity-dependent.
Pain is a common complication in patients following spinal cord injury (SCI), with studies citing up to 80% of patients reporting some form of pain. Neuropathic pain (NP) makes up a substantial ...percentage of all pain symptoms in patients with SCI and is often complex. Given the high prevalence of NP in patients with SCI, proper identification and treatment is imperative. Indeed, identification of pain subtypes is a vital step toward determining appropriate treatment. A variety of pharmacological and non-pharmacological treatments can be undertaken including antiepileptics, tricyclic antidepressants, opioids, transcranial direct current stimulation, and invasive surgical procedures. Despite all the available treatment options and advances in the field of SCI medicine, providing adequate treatment of NP after SCI continues to be challenging. It is therefore extremely important for clinicians to have a strong foundation in the identification of SCI NP, as well as an understanding of appropriate treatment options.
Here, we highlight the definitions and classification tools available for NP identification, and discuss current treatment options. We hope that this will not only provide a better understanding of NP for physicians in various subspecialties, but that it will also help guide future research on this subject.
•This review includes discussion about current classifications and tools for identification of neuropathic pain in individuals with SCI.•Discussion of current pharmacological and non-pharmacological treatment for NP in SCI are provided.•Recommendations on what tools to use for NP identification in SCI patients, and a “decision tree” for NP treatment is included.•This is the first review to pair identification with treatment recommendations.
This review article summarizes recent technical developments in ultrashort echo time (UTE) magnetic resonance imaging of musculoskeletal (MSK) tissues with short‐T2 relaxation times. A series of ...contrast mechanisms are discussed for high‐contrast morphological imaging of short‐T2 MSK tissues including the osteochondral junction, menisci, ligaments, tendons, and bone. Quantitative UTE mapping of T1, T2*, T1ρ, adiabatic T1ρ, magnetization transfer ratio, MT modeling of macromolecular proton fraction, quantitative susceptibility mapping, and water content is also introduced. Met and unmet needs in MSK imaging are discussed.
Evidence Level
1
Technical Efficacy
Stage 3
Purpose
To develop a deep learning‐based method for knee menisci segmentation in 3D ultrashort echo time (UTE) cones MR imaging, and to automatically determine MR relaxation times, namely the T1, ...T1ρ, and T2∗ parameters, which can be used to assess knee osteoarthritis (OA).
Methods
Whole knee joint imaging was performed using 3D UTE cones sequences to collect data from 61 human subjects. Regions of interest (ROIs) were outlined by 2 experienced radiologists based on subtracted T1ρ‐weighted MR images. Transfer learning was applied to develop 2D attention U‐Net convolutional neural networks for the menisci segmentation based on each radiologist's ROIs separately. Dice scores were calculated to assess segmentation performance. Next, the T1, T1ρ, T2∗ relaxations, and ROI areas were determined for the manual and automatic segmentations, then compared.
Results
The models developed using ROIs provided by 2 radiologists achieved high Dice scores of 0.860 and 0.833, while the radiologists’ manual segmentations achieved a Dice score of 0.820. Linear correlation coefficients for the T1, T1ρ, and T2∗ relaxations calculated using the automatic and manual segmentations ranged between 0.90 and 0.97, and there were no associated differences between the estimated average meniscal relaxation parameters. The deep learning models achieved segmentation performance equivalent to the inter‐observer variability of 2 radiologists.
Conclusion
The proposed deep learning‐based approach can be used to efficiently generate automatic segmentations and determine meniscal relaxations times. The method has the potential to help radiologists with the assessment of meniscal diseases, such as OA.
To measure T
relaxations for the major tissues in whole knee joints on a clinical 3T scanner.
The 3D UTE-Cones actual flip angle imaging (AFI) method was used to map the transmission radiofrequency ...field (B
) in both short and long T
tissues, which was then used to correct the 3D UTE-Cones variable flip angle (VFA) fitting to generate accurate T
maps. Numerical simulation was carried out to investigate the accuracy of T
measurement for a range of T
values, excitation pulse durations, and B
errors. Then, the 3D UTE-Cones AFI-VFA method was applied to healthy volunteers (N = 16) to quantify the T
of knee tissues including cartilage, meniscus, quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), marrow, and muscles at 3T.
Numerical simulation showed that the 3D UTE-Cones AFI-VFA technique can provide accurate T
measurements (error <1%) when the tissue T
is longer than 1 ms and a 150 μs excitation RF pulse is used and therefore is suitable for most knee joint tissues. The proposed 3D UTE-Cones AFI-VFA method showed an average T
of 1098 ± 67 ms for cartilage, 833 ± 47 ms for meniscus, 800 ± 66 ms for quadriceps tendon, 656 ± 43 ms for patellar tendon, 873 ± 38 ms for ACL, 832 ± 49 ms for PCL, 379 ± 18 ms for marrow, and 1393 ± 46 ms for muscles.
The 3D UTE-Cones AFI-VFA method allows volumetric T
measurement of the major tissues in whole knee joints on a clinical 3T scanner.
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