scholarly journals Real-Time High-Resolution MRI Endoscopy at up to 10 Frames per Second

BME Frontiers ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiaoyang Liu ◽  
Parag Karmarkar ◽  
Dirk Voit ◽  
Jens Frahm ◽  
Clifford R. Weiss ◽  
...  
Keyword(s):  
High Resolution ◽  
Soft Tissue ◽  
Real Time ◽  
Large Animal ◽  
Motion Sensitivity ◽  
X Ray ◽  
High Resolution Mri ◽  
Endoscopy Ultrasound ◽  
Tissue Sensitivity

Objective. Atherosclerosis is a leading cause of mortality and morbidity. Optical endoscopy, ultrasound, and X-ray offer minimally invasive imaging assessments but have limited sensitivity for characterizing disease and therapeutic response. Magnetic resonance imaging (MRI) endoscopy is a newer idea employing tiny catheter-mounted detectors connected to the MRI scanner. It can see through vessel walls and provide soft-tissue sensitivity, but its slow imaging speed limits practical applications. Our goal is high-resolution MRI endoscopy with real-time imaging speeds comparable to existing modalities. Methods. Intravascular (3 mm) transmit-receive MRI endoscopes were fabricated for highly undersampled radial-projection MRI in a clinical 3-tesla MRI scanner. Iterative nonlinear reconstruction was accelerated using graphics processor units connected via a single ethernet cable to achieve true real-time endoscopy visualization at the scanner. MRI endoscopy was performed at 6-10 frames/sec and 200-300 μm resolution in human arterial specimens and porcine vessels ex vivo and in vivo and compared with fully sampled 0.3 frames/sec and three-dimensional reference scans using mutual information (MI) and structural similarity (3-SSIM) indices. Results. High-speed MRI endoscopy at 6-10 frames/sec was consistent with fully sampled MRI endoscopy and histology, with feasibility demonstrated in vivo in a large animal model. A 20-30-fold speed-up vs. 0.3 frames/sec reference scans came at a cost of ~7% in MI and ~45% in 3-SSIM, with reduced motion sensitivity. Conclusion. High-resolution MRI endoscopy can now be performed at frame rates comparable to those of X-ray and optical endoscopy and could provide an alternative to existing modalities, with MRI’s advantages of soft-tissue sensitivity and lack of ionizing radiation.

scholarly journals A hydroxyapatite phantom material for the calibration of in vivo x-ray fluorescence systems of bone strontium and lead quantification

2021 ◽  
Author(s):  
Eric Da Silva
Keyword(s):  
Monte Carlo ◽  
Soft Tissue ◽  
Monte Carlo Simulations ◽  
Calibration Procedure ◽  
X Rays ◽  
X Ray ◽  
Total Phosphate Concentration ◽  
High Concentrations ◽  
Phantom Material

A hydroxyaptite [HAp; Ca5(PO4)3OH] phantom material was developed with the goal of improving the calibration protocol of the 125I-induced in vivo X-ray fluorescence (IVXRF) system of bone strontium quantification with further application to other IVXRF bone metal quantification systems, particulary those associated with bone lead quantification. It was found that calcium can be prepared pure of inherent contamination from strontium (and other elements) through a hydroxide precipitation producing pure Ca(OH)2, thereby, allowing for the production of a blank phantom which has not been available previously. The pure Ca(OH)2 can then be used for the preparation of pure CaHPO4 ⋅ 2H2O. A solid state pure HAp phantom can then be prepared by reaction of Ca(OH)2 and CaHPO4 ⋅ 2H2O mixed as to produce a Ca/P mole ratio of 1.67, that in HAp and the mineral phase of bone, in the presence of a setting solution prepared as to raise the total phosphate concentration of the solution by increasing the solubility CaHPO4 ⋅ 2H2O and thereby precipitating HAp. The procedure can only be used to prepare phantoms in which doping with the analyte does not disturb the Ca/P ratio substantially. In cases in which phantoms are to be prepared with high concentrations of strontium, the cement mixture can be modified as to introduce strontium in the form of Sr(OH)2 ⋅ 8H2O as to maintain a (Ca + Sr)/P ratio of 1.67. It was found by both X-ray diffraction spectrometry and Raman spectroscopy studies that strontium substitutes for calcium as in bone when preparing phantoms by this route. The necessity for the blank bone phantoms was assessed through the first blank bone phantom measurement and Monte Carlo simulations. It was found that for the 125I-induced IVXRF system of bone strontium quantification, the source, 125I brachytherapy seeds may be contributing coherently and incoherently scattered zirconium X-rays to the measured spectra, thereby requiring the use of the blank bone phantom as a means of improving the overall quantification methodology. Monte Carlo simulations were employed to evaluate any improvement by the introduction of HAp phantoms into the coherent normalization-based calibration procedure. It was found that HAp phantoms remove the need for a coherent conversion factor (CCF) thereby potentially increasing accuracy of the quantification. Further, it was found that in order for soft tissue attenuation corrections to be possible using spectroscopic information alone, HAp along with a suitable soft tissue surrogate material need to be employed. The HAp phantom material was used for the evaluations of portable X-ray analyzer systems for their potential for IVXRF quantification of lead and strontium with a focus on a comparison between tungsten, silver and rhodium target systems. Silver and rhodium target X-ray tube systems were found to be comparable for this quantification.

scholarly journals A multi-center comparison of dual energy X-ray absorptiometers: In vivo and in vitro soft tissue measurement

1997 ◽  
Vol 51 (5) ◽  
pp. 312-317 ◽  
Author(s):  
CD Economos ◽  
ME Nelson ◽  
MA Fiatarone ◽  
GE Dallal ◽  
SB Heymsfield ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Dual Energy ◽  
X Ray

ITVT-10. Using functional Ultrasound (fUS) for real-time, depth-resolved functional and vascular delineation of brain tumors with micrometer-millisecond precision

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi230-vi230
Author(s):  
Sadaf Soloukey ◽  
Luuk Verhoef ◽  
Frits Mastik ◽  
Bastian Generowicz ◽  
Eelke Bos ◽  
...  
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Cerebral Blood Volume ◽  
Imaging Technique ◽  
Power Doppler ◽  
Ease Of Use ◽  
Frame Rate ◽  
Neurosurgical Procedures ◽  
Vascular Morphology

Abstract BACKGROUND Neurosurgical practice still relies heavily on pre-operatively acquired images to guide tumor resections, a practice which comes with inherent pitfalls such as registration inaccuracy due to brain shift, and lack of real-time functional or morphological feedback. Here we describe functional Ultrasound (fUS) as a new high-resolution, depth-resolved, MRI/CT-registered imaging technique able to detect functional regions and vascular morphology during awake and anesthesized tumor resections. MATERIALS AND METHODS fUS relies on high-frame-rate (HFR) ultrasound, making the technique sensitive to very small motions caused by vascular dynamics (µDoppler) and allowing measurements of changes in cerebral blood volume (CBV) with micrometer-millisecond precision. This opens up the possibility to 1) detect functional response, as CBV-changes reflect changes in metabolism of activated neurons through neurovascular coupling, and 2) visualize in-vivo vascular morphology of pathological and healthy tissue with high resolution at unprecedented depths. During a range of anesthetized and awake neurosurgical procedures we acquired vascular and functional images of brain and spinal cord using conventional ultrasound probes connected to a research acquisition system. Building on Brainlab’s Intra-Operative Navigation modules, we co-registered our intra-operative Power Doppler Images (PDIs) to patient-registered MRI/CT-data in real-time. RESULTS During meningioma and glioma resections, our co-registered PDIs revealed fUS’ ability to visualize the tumor’s feeding vessels and vascular borders in real-time, with a level of detail unprecedented by conventional MRI-sequences. During awake resections, fUS was able to detect distinct, ESM-confirmed functional areas as activated during conventional motor and language tasks. In all cases, images were acquired with micrometer-millisecond (300 µm, 1.5–2.0 ms) precision at imaging depths exceeding 5 cm. CONCLUSION fUS is a new real-time, high-resolution and depth-resolved imaging technique, combining favorable imaging specifications with characteristics such as mobility and ease of use which are uniquely beneficial for a potential image-guided neurosurgical tool.

From local to global matrix organization by fibroblasts: a 4D laser-assisted bioprinting approach

2021 ◽  
Author(s):  
Camille Douillet ◽  
Marc Nicodeme ◽  
Loïc Hermant ◽  
Vanessa Bergeron ◽  
Fabien Guillemot ◽  
...  
Keyword(s):  
High Resolution ◽  
Soft Tissue ◽  
Dynamic Properties ◽  
Unmet Need ◽  
Specific Pattern ◽  
Matrix Remodeling ◽  
Collagen Gels ◽  
Lattice Contraction

Abstract Fibroblasts and myofibroblasts play a central role in skin homeostasis through dermal organization and maintenance. Nonetheless, the dynamic interactions between (myo)fibroblasts and the extracellular matrix (ECM) remain poorly exploited in skin repair strategies. Indeed, there is still an unmet need for soft tissue models allowing to study the spatial-temporal remodeling properties of (myo)fibroblasts. In vivo, wound healing studies in animals are limited by species specificity. In vitro, most models rely on collagen gels reorganized by randomly distributed fibroblasts. But biofabrication technologies have significantly evolved over the past ten years. High-resolution bioprinting now allows to investigate various cellular micropatterns and the emergent tissue organizations over time. In order to harness the full dynamic properties of cells and active biomaterials, it is essential to consider “time” as the 4th dimension in soft tissue design. Following this 4D bioprinting approach, we aimed to develop a novel model that could replicate fibroblast dynamic remodeling in vitro. For this purpose, (myo)fibroblasts were patterned on collagen gels with laser-assisted bioprinting (LAB) to study the generated matrix deformations and reorganizations. First, distinct populations, mainly composed of fibroblasts or myofibroblasts, were established in vitro to account for the variety of fibroblastic remodeling properties. Then, LAB was used to organize both populations on collagen gels in even isotropic patterns with high resolution, high density and high viability. With maturation, bioprinted patterns of fibroblasts and myofibroblasts reorganized into dispersed or aggregated cells, respectively. Stress-release contraction assays revealed that these phenotype-specific pattern maturations were associated with distinct lattice tension states. The two populations were then patterned in anisotropic rows in order to direct the cell-generated deformations and to orient global matrix remodeling. Only maturation of anisotropic fibroblast patterns, but not myofibroblasts, resulted in collagen anisotropic reorganizations both at tissue-scale, with lattice contraction, and at microscale, with embedded microbead displacements. Following a 4D bioprinting approach, LAB patterning enabled to elicit and orient the dynamic matrix remodeling mechanisms of distinct fibroblastic populations and organizations on collagen. For future studies, this method provides a new versatile tool to investigate in vitro dermal organizations and properties, processes of remodeling in healing, and new treatment opportunities.

scholarly journals Real-time in vivo imaging of regional lung function in a mouse model of cystic fibrosis on a laboratory X-ray source

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rhiannon P. Murrie ◽  
Freda Werdiger ◽  
Martin Donnelley ◽  
Yu-wei Lin ◽  
Richard P. Carnibella ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Lung Function ◽  
Mouse Model ◽  
Real Time ◽  
In Vivo Imaging ◽  
X Ray ◽  
Regional Lung Function ◽  
Regional Lung

scholarly journals Automatic Segmentation of the Dorsal Claustrum in Humans Using in vivo High-Resolution MRI

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Shai Berman ◽  
Roey Schurr ◽  
Gal Atlan ◽  
Ami Citri ◽  
Aviv A Mezer
Keyword(s):  
High Resolution ◽  
Automatic Segmentation ◽  
Thin Sheet ◽  
Brain Regions ◽  
Reproducible Research ◽  
Human Connectome Project ◽  
High Resolution Mri ◽  
Magnetic Resonance Imaging Mri ◽  
And Function

Abstract The claustrum is a thin sheet of neurons enclosed by white matter and situated between the insula and the putamen. It is highly interconnected with sensory, frontal, and subcortical regions. The deep location of the claustrum, with its fine structure, has limited the degree to which it could be studied in vivo. Particularly in humans, identifying the claustrum using magnetic resonance imaging (MRI) is extremely challenging, even manually. Therefore, automatic segmentation of the claustrum is an invaluable step toward enabling extensive and reproducible research of the anatomy and function of the human claustrum. In this study, we developed an automatic algorithm for segmenting the human dorsal claustrum in vivo using high-resolution MRI. Using this algorithm, we segmented the dorsal claustrum bilaterally in 1068 subjects of the Human Connectome Project Young Adult dataset, a publicly available high-resolution MRI dataset. We found good agreement between the automatic and manual segmentations performed by 2 observers in 10 subjects. We demonstrate the use of the segmentation in analyzing the covariation of the dorsal claustrum with other brain regions, in terms of macro- and microstructure. We identified several covariance networks associated with the dorsal claustrum. We provide an online repository of 1068 bilateral dorsal claustrum segmentations.

High-resolution real-time X-ray topography of dislocation generation in silicon

1982 ◽  
Vol 46 (6) ◽  
pp. 1009-1013 ◽  
Author(s):  
Shih-Lin Chang ◽  
Hans-Joachim Queisser ◽  
Helmut Baumgart ◽  
Werner Hagen ◽  
Werner Hartmann
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Dislocation Generation ◽  
X Ray
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