Isometric Resolution Research Articles

Camera-based ultrasound-modulated optical tomography with isometric resolution

Ultrasound-modulated optical tomography (UOT) leverages the strengths of light and sound, enabling deep-tissue imaging with optical absorption contrast and acoustic resolution. Camera-based UOT, with its parallel detection capability, excels at handling weak light–sound interactions. However, the limited frame rate of the camera typically results in poor axial resolution and poses challenges for holographic measurements. In this study, we introduced intersected ultrasonic modulation to address these limitations, thereby achieving equal resolution in both lateral and axial dimensions through referenceless measurements. As a proof of concept, we constructed an imaging system and demonstrated two-dimensional imaging for absorptive targets buried inside a scattering medium. This approach opens avenues for improved imaging resolutions, showcasing the potential for future diagnostic endeavors.

Mixed reality-based technology to visualize and facilitate treatment planning of impacted teeth: Proof of concept.

We propose a method utilizing mixed reality (MR) goggles (HoloLens 2, Microsoft) to facilitate impacted canine alignment, as planning the traction direction and force delivery could benefit from 3D data visualization using mixed reality (MR). Cone-beam CT scans featuring isometric resolution and low noise-to-signal ratio were semi-automatically segmented in Inobitec software. The exported 3D mesh (OBJ file) was then optimized for the HoloLens 2. Using the Unreal Engine environment, we developed an application for the HoloLens 2, implementing HoloLens SDK and UX Tools. Adjustable pointers were added for planning attachment placement, traction direction, and point of force application. The visualization was presented to participants of a course on impacted teeth treatment, followed by a 10-question survey addressing potential advantages (5-point scale: 1 = totally agree, 5 = totally disagree). Out of 38 respondents, 44.7% were orthodontists, 34.2% dentists, 15.8% dental students, and 5.3% dental technicians. Most respondents (44.7%) were between 35 and 44 years old, and only 1 (2.6%) respondent was 55-64 years old. Median answers for six questions were 'totally agree' (25th percentile 1, 75th percentile 2) and for four questions 'agree' (25th percentile 1, 75th percentile 2). No correlation was found between age, profession, and responses. Our method generated substantial interest among clinicians. The initial responses affirm the potential benefits, supporting the continued exploration of MR-based techniques for the treatment of impacted teeth. However, the recommendation for widespread use awaits validation through clinical trials.

Pressure induced changes in endothelial cell morphology and Ca2+ signaling in ex vivo pressurized resistance arteries revealed using 4D diSPIM myography and AI deep-learning

The vascular endothelium is critical in promoting vasodilation of resistance-size arteries through Ca 2+ dependent pathways. Vascular endothelial cells (ECs) are exposed to mechanical stimulation through changing intravascular pressure and flow, yet it is unclear how these forces impact EC morphology and Ca 2+ signaling in pressurized arteries. Visualizing how the endothelium of an intact resistance-size vessel responds to changing physical forces requires isometric, sub-micron, resolution. Conventional confocal fluorescent microscope systems are limited by poor axial resolution. 4D dual inverted selective plane of illumination microscopy (diSPIM; 3i) uniquely provides isometric resolution at ~330 nm with high temporal resolution and minimal photobleaching or phototoxicity. We designed custom pressure myography chambers to allow simultaneous 4D diSPIM fluorescent imaging and vessel diameter tracking measurements via transmitted IR light (diSPIM Myography). We captured fluorescent images of ex vivo pressurized resistance-size mouse mesenteric arteries at 80, 60, 40, and 20 mm Hg before and after the generation of myogenic tone and in the absence of extracellular Ca 2+ . Representative images were annotated for ECs, nuclei, myoendothelial projections (MEPS), and Ca 2+ signals. Annotations were used as ground truth for CNN AI model generation and validation using Apeer (Zeiss). Arivis Vision4D (Zeiss) was used to run the AI model and quantify data. As static intravascular pressure is increased in arteries without tone (with or without Ca 2+ ), ECs increase in width as the vessel dilates. Myogenic tone minimizes pressure dilation and changes in EC width, however, ECs compress by up to 1 micron as pressure increases from 20 to 80 mm Hg. Additionally, increasing intravascular pressure in arteries with tone decreases local EC Ca 2+ signaling. The data demonstrate a relationship between intravascular pressure and EC shape and Ca 2+ signaling in intact resistance arteries under conditions of physiologic temperature, pressure, pH, and tone. diSPIM myography provides a method of studying the effects of physiologically relevant mechanical stimuli and the roles of various mechanosensitive mechanisms on vascular function. AI image annotation reduces analysis bias and increases the breadth of quantifiable microscopy data. DMC is supported by NIH R00HL133451 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Inter-subject stability and regional concentration estimates of 3D-FID-MRSI in the human brain at 7 T.

Recently, a 3D-concentric ring trajectory (CRT)-based free induction decay (FID)-MRSI sequence was introduced for fast high-resolution metabolic imaging at 7 T. This technique provides metabolic ratio maps of almost the entire brain within clinically feasible scan times, but its robustness has not yet been thoroughly investigated. Therefore, we have assessed quantitative concentration estimates and their variability in healthy volunteers using this approach. We acquired whole-brain 3D-CRT-FID-MRSI at 7 T in 15 min with 3.4 mm nominal isometric resolution in 24 volunteers (12 male, 12 female, mean age 27 ± 6 years). Concentration estimate maps were calculated for 15 metabolites using internal water referencing and evaluated in 55 different regions of interest (ROIs) in the brain. Data quality, mean metabolite concentrations, and their inter-subject coefficients of variation (CVs) were compared for all ROIs. Of 24 datasets, one was excluded due to motion artifacts. The concentrations of total choline, total creatine, glutamate, myo-inositol, and N-acetylaspartate in 44 regions were estimated within quality thresholds. Inter-subject CVs (mean over 44 ROIs/minimum/maximum) were 9%/5%/19% for total choline, 10%/6%/20% for total creatine, 11%/7%/24% for glutamate, 10%/6%/19% for myo-inositol, and 9%/6%/19% for N-acetylaspartate. We defined the performance of 3D-CRT-based FID-MRSI for metabolite concentration estimate mapping, showing which metabolites could be robustly quantified in which ROIs with which inter-subject CVs expected. However, the basal brain regions and lesser-signal metabolites in particular remain as a challenge due susceptibility effects from the proximity to nasal and auditory cavities. Further improvement in quantification and the mitigation of B0 /B1 -field inhomogeneities will be necessary to achieve reliable whole-brain coverage.

A New 3-D Imaging Technique Integrating Ultrafast Compounding, Hadamard Encoding, and Reconfigurable Fresnel Lensing

Crossed electrode arrays address some of the challenges associated with 3-D ultrasound imaging because of the significant reduction in the number of elements ( 2N versus N2 ). However, creating a two-way focused 3-D image in real time is difficult with these arrays because azimuth and elevation dimensions cannot be beamformed at the same time. This work describes a new 3-D imaging technique that uses the flexibility of bias-sensitive substrates to create a high-quality elevation focus on a crossed electrode array. The principle behind this technique is to perform conventional compound imaging with an azimuth set of electrodes while implementing a bias controllable elevation lens with an elevation set of electrodes. On transmit, the biases are chosen to mimic a Fresnel lens. Then, on receive, the Hadamard coding is implemented along the elevation dimension. After decoding, we gain the RF data for each element across the elevation aperture even though there is effectively only one channel in that dimension. A 30-MHz, 128-element crossed electrode relaxor array was fabricated on a 1-3 electrostrictive composite substrate and was used to demonstrate the performance of the imaging technique. The on-axis -6-dB beamwidths were simulated to be 175 and [Formula: see text] in the azimuth and elevation directions, respectively, and the focus remained isotropic in the furthest elevation slice. Images were generated of a wire phantom to confirm the performance of the azimuth and elevational radiation patterns with good agreement between simulation and experiment. High-resolution 3-D volumetric images were generated of an ex vivo rat brain. Images of the cerebellum showed that the white and gray matter tracts could clearly be visualized with isometric resolution in both the azimuth and elevation dimensions.

P3.05-002 The Effect of Nodule Size on the Sensitivity of the LuCED® Test for Lung Cancer

The LuCED® test is based on analysis of sputum by the Cell-CT® platform that computes 3D images of cells with isometric resolution, allowing orientation-independent measurements of 704 3D structural biomarkers to generate a probabilistic score to identify abnormal cells. that was consistent by tumor histology and stage. Early stage tumors are generally smaller in size. One view is that smaller tumors might exfoliate fewer abnormal cells into sputum, making early stage tumor detection less likely.

DWI and complex brain network analysis predicts vascular cognitive impairment in spontaneous hypertensive rats undergoing executive function tests.

The identification of biomarkers of vascular cognitive impairment is urgent for its early diagnosis. The aim of this study was to detect and monitor changes in brain structure and connectivity, and to correlate them with the decline in executive function. We examined the feasibility of early diagnostic magnetic resonance imaging (MRI) to predict cognitive impairment before onset in an animal model of chronic hypertension: Spontaneously Hypertensive Rats. Cognitive performance was tested in an operant conditioning paradigm that evaluated learning, memory, and behavioral flexibility skills. Behavioral tests were coupled with longitudinal diffusion weighted imaging acquired with 126 diffusion gradient directions and 0.3 mm3 isometric resolution at 10, 14, 18, 22, 26, and 40 weeks after birth. Diffusion weighted imaging was analyzed in two different ways, by regional characterization of diffusion tensor imaging (DTI) indices, and by assessing changes in structural brain network organization based on Q-Ball tractography. Already at the first evaluated times, DTI scalar maps revealed significant differences in many regions, suggesting loss of integrity in white and gray matter of spontaneously hypertensive rats when compared to normotensive control rats. In addition, graph theory analysis of the structural brain network demonstrated a significant decrease of hierarchical modularity, global and local efficacy, with predictive value as shown by regional three-fold cross validation study. Moreover, these decreases were significantly correlated with the behavioral performance deficits observed at subsequent time points, suggesting that the diffusion weighted imaging and connectivity studies can unravel neuroimaging alterations even overt signs of cognitive impairment become apparent.

Resolution improvement in optical projection tomography by the focal scanning method

Optical projection tomography (OPT) requires the depth of field (DOF) of the lens to cover at least half of the sample. There is a trade-off between obtaining high resolution with a high-NA lens and obtaining large DOF with a low-NA lens. The DOF of a high-NA objective lens can be extended by scanning its focal plane through the sample. We call this extended DOF image a "pseudoprojection." Images reconstructed from these pseudoprojections have isometric resolution, which can be the same as the lateral resolution of the high-NA objective. The focal scanning method produces an over 10× improvement in OPT resolution.

MicroCT-Based Virtual Histology Evaluation of Preclinical Medulloblastoma

The purpose of this paper is to validate a rapid and cost-effective ex vivo technique, microCT-based virtual histology, as an alternative to MRI imaging for assessing the therapeutic response in genetically engineered mouse models of cancer. All animal procedures were conducted in accordance with the Guidelines for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Texas Health Science Center at San Antonio. MRI imaging was performed on 6-week-old, bortezomib-treated genetically engineered Patched1, p53 mice that recapitulate the characteristics of human medulloblastoma. After MRI scans, the same mice were euthanized to collect brain or spine samples for virtual histology staining followed by microCT scanning. Nine-micrometer resolution ex vivo micro X-ray computed tomography (microCT)-based virtual histology images were qualitatively reflective of high-field live animal images obtained with magnetic resonance imaging (MRI) and histopathology. Cerebellar volumes on microCT-based virtual histology correlated closely with MRI cerebellar volumes (R = 0.998). MRI and microCT-based virtual histology both indicated a significant difference between cerebellar volumes of untreated and treated mice (p = 0.02 and p = 0.04, respectively). The ex vivo microCT method also allowed a 7,430-fold improvement in voxel resolution (voxel volume of 729 μm³ for 9-μm isometric resolution microCT vs. 5,416,800 μm³ for 400 × 111 × 122 μm resolution MRI) at a 28% cost savings ($400 vs. $555 per animal). The ex vivo, en bloc technique of microCT-based virtual histology matched MRI in reflecting histopathology. MicroCT-based virtual histology proved to be a more cost-effective technique and less labor-intensive. On the other hand, MRI provides ability to perform in vivo imaging, faster scanning and lower radiation dose by sacrificing the spatial resolution. Thus, both in vivo MRI and ex vivo microCT-based virtual histology are effective means of quantitatively evaluating therapeutic response in preclinical models of cerebellar tumors including the childhood cancer, medulloblastoma.