Phased-array of microcoils allows MR microscopy ofex vivohuman skin samples at 9.4 T

Synergies between Hyperpolarized NMR and Microfluidics: A Review

Hyperpolarized nuclear magnetic resonance and lab-on-a-chip microfluidics are two dynamic, but until recently quite distinct, fields of research. Recent developments in both areas increased their synergistic overlap. By microfluidic integration, many complex experimental steps can be brought together onto a single platform. Microfluidic devices are therefore increasingly finding applications in medical diagnostics, forensic analysis, and biomedical research. In particular, they provide novel and powerful ways to culture cells, cell aggregates, and even functional models of entire organs. Nuclear magnetic resonance is a non-invasive, high-resolution spectroscopic technique which allows real-time process monitoring with chemical specificity. It is ideally suited for observing metabolic and other biological and chemical processes in microfluidic systems. However, its intrinsically low sensitivity has limited its application. Recent advances in nuclear hyperpolarization techniques may change this: under special circumstances, it is possible to enhance NMR signals by up to 5 orders of magnitude, which dramatically extends the utility of NMR in the context of microfluidic systems. Hyperpolarization requires complex chemical and/or physical manipulations, which in turn may benefit from microfluidic implementation. In fact, many hyperpolarization methodologies rely on processes that are more efficient at the micro-scale, such as molecular diffusion, penetration of electromagnetic radiation into a sample, or restricted molecular mobility on a surface. In this review we examine the confluence between the fields of hyperpolarization-enhanced NMR and microfluidics, and assess how these areas of research have mutually benefited one another, and will continue to do so.

Should We Scan Hidradenitis Suppurativa Patients? A Systematic Review of Radiologic Findings

OBJECTIVE

To bring awareness and close gaps between dermatologists and radiologists about the contribution of imaging techniques for diagnosis, treatment, and follow-up of hidradenitis suppurativa (HS).

DATA SOURCES

Investigators searched the PubMed database for articles on HS and radiology techniques.

STUDY SELECTION

Databases were searched up to December 2018. The query retrieved 257 publications, of which 103 were unique; of these, 7 were inaccessible. From the remaining 96, 33 were irrelevant (did not discuss HS lesion features). After applying the inclusion criteria, 63 studies were relevant to this study.

DATA EXTRACTION

A standardized form was constructed to extract data from eligible studies by two independent authors.

DATA SYNTHESIS

Imaging techniques are significant and useful tools in HS management. Imaging should be carried out to evaluate disease severity, subclinical features, treatment success, and intraoperative patient assessment. Providers should consider nonconventional radiology techniques, which are underused in clinical management of HS. Further, dermatology and radiology require a shared terminology of disease features to better understand patient status.

CONCLUSIONS

Publications on HS lesion imaging have increased over the years. Imaging techniques have proven useful for determining HS severity and treatment effectiveness, as well as intraoperative patient assessment. These authors strongly recommend the use of these techniques in routine clinical practice for patients with HS.

Ultrahigh-Field Quantitative MR Microscopy of the Chicken Eye In Vivo Throughout the In Ovo Period

PURPOSE

Ultrahigh-field MRI (UHF-MRI) with an in-plane spatial resolution of less than 100 μm is known as MR microscopy (MRM). MRM provides highly resolved anatomical images and allows quantitative assessment of different tissue types using diffusion-weighted imaging (DWI). The aim of the present study was to evaluate the feasibility of combined in vivo anatomical and quantitative assessment of the developing chicken eye in ovo.

PROCEDURES

Thirty-eight fertilized chicken eggs were examined at 7.1 T (ClinScan, Bruker Biospin, Germany) acquiring a dataset comprising T2-weighted anatomical images, DWI, and diffusion tensor imaging. To reduce motion artifacts, the eggs were moderately cooled before and during MR imaging. Two eggs were imaged daily for the entire developmental period, and 36 eggs were examined pairwise at only one time point of the embryonic period. Development of the eye was anatomically and quantitatively assessed.

RESULTS

From the D5 embryonic stage (116-124 h), MRM allowed differentiation between lens and vitreous body. The lens core and periphery were first identified at D9. DWI allowed quantification of lens maturation based on a significant decrease in apparent diffusion coefficient values and course of fractional anisotropy. Repeated moderate cooling had no influence on the development of the chicken embryo.

CONCLUSIONS

MRM allows in vivo assessment of embryonic development of the chicken eye in ovo without affecting normal development. The method provides anatomical information supplemented by quantitative evaluation of lens development using DWI. With increasing availability of ultrahigh-field MR systems, this technique may provide a noninvasive complementary tool in the field of experimental ophthalmology.

Tracking protein function with sodium multi quantum spectroscopy in a 3D-tissue culture based on microcavity arrays

The aim of this study was to observe the effects of strophanthin induced inhibition of the Na-/K-ATPase in liver cells using a magnetic resonance (MR) compatible bioreactor. A microcavity array with a high density three-dimensional cell culture served as a functional magnetic resonance imaging (MRI) phantom for sodium multi quantum (MQ) spectroscopy. Direct contrast enhanced (DCE) MRI revealed the homogenous distribution of biochemical substances inside the bioreactor. NMR experiments using advanced bioreactors have advantages with respect to having full control over a variety of physiological parameters such as temperature, gas composition and fluid flow. Simultaneous detection of single quantum (SQ) and triple quantum (TQ) MR signals improves accuracy and was achieved by application of a pulse sequence with a time proportional phase increment (TQTPPI). The time course of the Na-/K-ATPase inhibition in the cell culture was demonstrated by the corresponding alterations of sodium TQ/SQ MR signals.

MR microscopy of the human fetal upper extremity - a proof-of-principle study

BACKGROUND

Current knowledge of the human fetal and embryonic development relies on early descriptive studies of humans and from experimental studies of laboratory animals and embryos. Taking the upper extremity as an example, this study explores the potential of magnetic resonance microscopy (MRM) for the assessment of the development of the fetal upper extremity and discusses its correlation with histological findings.

METHODS

Ex vivo MRM at 7.1 T (Clin Scan, Bruker Biospin, Germany) was performed in 10 human specimens at 8 to 12 weeks of gestational age (GA). In-plane resolution was 20 μm with a slice thickness of 70 μm. MRM was followed by histological work-up of the specimens. MRM images were then correlated with conventional histology with a focus on the presence of chondrification and ossification.

RESULTS

Ossification of the upper human extremity is detectable at 8 weeks GA in the humerus and the long bones of the forearm. There is excellent correlation for location and size of ossification between MRM and conventional histology. MRM imaging is in accordance with historical studies.

CONCLUSION

Ex vivo MRM for the non-invasive assessment of the embryonic and fetal development of the upper human extremity is feasible. It may provide an accurate complementary tool for the evaluation of embryological development.

An optimised detector for in-situ high-resolution NMR in microfluidic devices

Integration of high-resolution nuclear magnetic resonance (NMR) spectroscopy with microfluidic lab-on-a-chip devices is challenging due to limited sensitivity and line broadening caused by magnetic susceptibility inhomogeneities. We present a novel double-stripline NMR probe head that accommodates planar microfluidic devices, and obtains the NMR spectrum from a rectangular sample chamber on the chip with a volume of 2μl. Finite element analysis was used to jointly optimise the detector and sample volume geometry for sensitivity and RF homogeneity. A prototype of the optimised design has been built, and its properties have been characterised experimentally. The performance in terms of sensitivity and RF homogeneity closely agrees with the numerical predictions. The system reaches a mass limit of detection of 1.57nmols, comparing very favourably with other micro-NMR systems. The spectral resolution of this chip/probe system is better than 1.75Hz at a magnetic field of 7T, with excellent line shape.

DLA based compressed sensing for high resolution MR microscopy of neuronal tissue

In this work we present the implementation of compressed sensing (CS) on a high field preclinical scanner (17.2 T) using an undersampling trajectory based on the diffusion limited aggregation (DLA) random growth model. When applied to a library of images this approach performs better than the traditional undersampling based on the polynomial probability density function. In addition, we show that the method is applicable to imaging live neuronal tissues, allowing significantly shorter acquisition times while maintaining the image quality necessary for identifying the majority of neurons via an automatic cell segmentation algorithm.