Physics Informed Neural Networks for Estimation of Tissue Properties from Multi-echo Configuration State MRI.

This work investigates the use of configuration state imaging together with deep neural networks to develop quantitative MRI techniques for deployment in an interventional setting. A physics modeling technique for inhomogeneous fields and heterogeneous tissues is presented and used to evaluate the theoretical capability of neural networks to estimate parameter maps from configuration state signal data. All tested normalization strategies achieved similar performance in estimating and .

Characterizing dispersion in bovine liver using ARFI-based shear wave rheometry.

Dispersion presents both a challenge and a diagnostic opportunity in shear wave elastography (SWE).(SWR) is an inversion technique for processing SWE data acquired using an acoustic radiation force impulse (ARFI) excitation. The main advantage of SWR is that it can characterize the shear properties of homogeneous soft media over a wide frequency range.

Preliminary Experience with Three Alternative Motion Sensors for 0.55 Tesla MR Imaging.

Due to limitations in current motion tracking technologies and increasing interest in alternative sensors for motion tracking both inside and outside the MRI system, in this study we share our preliminary experience with three alternative sensors utilizing diverse technologies and interactions with tissue to monitor motion of the body surface, respiratory-related motion of major organs, and non-respiratory motion of deep-seated organs. These consist of (1) a Pilot-Tone RF transmitter combined with deep learning algorithms for tracking liver motion, (2) a single-channel ultrasound transducer with deep learning for monitoring bladder motion, and (3) a 3D Time-of-Flight camera for observing the motion of the anterior torso surface. Additionally, we demonstrate the capability of these sensors to simultaneously capture motion data outside the MRI environment, which is particularly relevant for procedures like radiation therapy, where motion status could be related to previously characterized cyclical anatomical data.

Different Leaf Anatomical Responses to Water Deficit in Maize and Soybean.

The stomata on leaf surfaces control gas exchange and water loss, closing during dry periods to conserve water. The distribution and size of stomatal complexes is determined by epidermal cell differentiation and expansion during leaf growth. Regulation of these processes in response to water deficit may result in stomatal anatomical plasticity as part of the plant acclimation to drought.

COVID-19 Vaccination reduced pneumonia severity.

Purpose: To investigate the effect of vaccinations and boosters on the severity of COVID-19 pneumonia on CT scans during the period of Delta and Omicron variants.

Methods: Retrospectively studied were 303 patients diagnosed with COVID-19 between July 2021 and February 2022, who had obtained at least one CT scan within 6 weeks around the COVID-19 diagnosis (-2 to +4 weeks). The severity of pneumonia was evaluated with a 6-point scale Pneumonia Score.

External Hardware and Sensors, for Improved MRI.

Complex engineered systems are often equipped with suites of sensors and ancillary devices that monitor their performance and maintenance needs. MRI scanners are no different in this regard. Some of the ancillary devices available to support MRI equipment, the ones of particular interest here, have the distinction of actually participating in the image acquisition process itself.

Ultrasound-based sensors for respiratory motion assessment in multimodality PET imaging.

Breathing motion can displace internal organs by up to several cm; as such, it is a primary factor limiting image quality in medical imaging. Motion can also complicate matters when trying to fuse images from different modalities, acquired at different locations and/or on different days. Currently available devices for monitoring breathing motion often do so indirectly, by detecting changes in the outline of the torso rather than the internal motion itself, and these devices are often fixed to floors, ceilings or walls, and thus cannot accompany patients from one location to another.

Ultrasound-based sensors to monitor physiological motion.

Purpose: Medical procedures can be difficult to perform on anatomy that is constantly moving. Respiration displaces internal organs by up to several centimeters with respect to the surface of the body, and patients often have limited ability to hold their breath. Strategies to compensate for motion during diagnostic and therapeutic procedures require reliable information to be available.

Expanding Applications of Pulmonary MRI in the Clinical Evaluation of Lung Disorders: Fleischner Society Position Paper.

Pulmonary MRI provides structural and quantitative functional images of the lungs without ionizing radiation, but it has had limited clinical use due to low signal intensity from the lung parenchyma. The lack of radiation makes pulmonary MRI an ideal modality for pediatric examinations, pregnant women, and patients requiring serial and longitudinal follow-up. Fortunately, recent MRI techniques, including ultrashort echo time and zero echo time, are expanding clinical opportunities for pulmonary MRI.

Improved PRF-based MR thermometry using k-space energy spectrum analysis.

Purpose: Proton resonance frequency (PRF) thermometry encodes information in the phase of MRI signals. A multiplicative factor converts phase changes into temperature changes, and this factor includes the TE. However, phase variations caused by B and/or B inhomogeneities can effectively change TE in ways that vary from pixel to pixel.

Multi-pathway multi-echo acquisition and neural contrast translation to generate a variety of quantitative and qualitative image contrasts.

Purpose: Clinical exams typically involve acquiring many different image contrasts to help discriminate healthy from diseased states. Ideally, 3D quantitative maps of all of the main MR parameters would be obtained for improved tissue characterization. Using data from a 7-min whole-brain multi-pathway multi-echo (MPME) scan, we aimed to synthesize several 3D quantitative maps (T and T ) and qualitative contrasts (MPRAGE, FLAIR, T -weighted, T -weighted, and proton density [PD]-weighted).

Relative Magnetic Force Measures and Their Potential Role in MRI Safety Practice.

Background: Magnetic field markings are occasionally used at MRI sites to provide visual feedback of magnetic field strength at locations within the MRI scan room for safety purposes. In addition to magnetic field line markings, relative magnetic force, or ratio of magnetic to gravitational forces on an object, may be considered a useful complementary metric to quantify the risk associated with bringing objects containing ferromagnetic material into the magnetic field.

Purpose: To develop and validate methods for deriving useful relative magnetic-force measures including a simple force index for application to MRI safety.

Accelerated Segmented Diffusion-Weighted Prostate Imaging for Higher Resolution, Higher Geometric Fidelity, and Multi-b Perfusion Estimation.

Purpose: The aim of this study was to improve the geometric fidelity and spatial resolution of multi-b diffusion-weighted magnetic resonance imaging of the prostate.

Materials And Methods: An accelerated segmented diffusion imaging sequence was developed and evaluated in 25 patients undergoing multiparametric magnetic resonance imaging examinations of the prostate. A reduced field of view was acquired using an endorectal coil.

Dispersion in Tissue-Mimicking Gels Measured with Shear Wave Elastography and Torsional Vibration Rheometry.

Dispersion, or the frequency dependence of mechanical parameters, is a primary confounding factor in elastography comparisons. We present a study of dispersion in tissue-mimicking gels over a wide frequency band using a combination of ultrasound shear wave elastography (SWE), and a novel torsional vibration rheometry which allows independent mechanical measurement of SWE samples. Frequency-dependent complex shear modulus was measured in homogeneous gelatin hydrogels of two different bloom strengths while controlling for confounding factors such as temperature, water content and material aging.

Multipathway multi-echo (MPME) imaging: all main MR parameters mapped based on a single 3D scan.

Purpose: Quantitative parameter maps, as opposed to qualitative grayscale images, may represent the future of diagnostic MRI. A new quantitative MRI method is introduced here that requires a single 3D acquisition, allowing good spatial coverage to be achieved in relatively short scan times.

Methods: A multipathway multi-echo sequence was developed, and at least 3 pathways with 2 TEs were needed to generate T , T , T , B , and B maps.

Application of a forward model of axisymmetric shear wave propagation in viscoelastic media to shear wave elastography.

A simple but general solution of Navier's equation for axisymmetric shear wave propagation in a homogeneous isotropic viscoelastic medium is presented. It is well-suited for use as a forward model for some acoustic radiation force impulse based shear wave elastography applications because it does not require precise knowledge of the strength of the source, nor its spatial or temporal distribution. Instead, it depends on two assumptions: (1) the source distribution is axisymmetric and confined to a small region near the axis of symmetry, and (2) the propagation medium is isotropic and homogeneous.

Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis.

On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.

Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger.

On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until 8.

Electromagnetic evidence that SSS17a is the result of a binary neutron star merger.

Eleven hours after the detection of gravitational wave source GW170817 by the Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers, an associated optical transient, SSS17a, was identified in the galaxy NGC 4993. Although the gravitational wave data indicate that GW170817 is consistent with the merger of two compact objects, the electromagnetic observations provide independent constraints on the nature of that system. We synthesize the optical to near-infrared photometry and spectroscopy of SSS17a collected by the One-Meter Two-Hemisphere collaboration, finding that SSS17a is unlike other known transients.