Quality Assurance of Point and 2D Shear Wave Elastography through the Establishment of Baseline Data Using Phantoms.

Ultrasound elastography has been available on most modern systems; however, the implementation of quality processes tends to be ad hoc. It is essential for a medical physicist to benchmark elastography measurements on each system and track them over time, especially after major software upgrades or repairs. This study aims to establish baseline data using phantoms and monitor them for quality assurance in elastography. In this paper, we utilized two phantoms: a set of cylinders, each with a composite material with varying Young's moduli, and an anthropomorphic abdominal phantom containing a liver modeled to represent early-stage fibrosis. These phantoms were imaged using three ultrasound manufacturers' elastography functions with either point or 2D elastography. The abdominal phantom was also imaged using magnetic resonance elastography (MRE) as it is recognized as the non-invasive gold standard for staging liver fibrosis. The scaling factor was determined based on the data acquired using MR and US elastography from the same vendor. The ultrasound elastography measurements showed inconsistency between different manufacturers, but within the same manufacturer, the measurements showed high repeatability. In conclusion, we have established baseline data for quality assurance procedures and specified the criteria for the acceptable range in liver fibrosis phantoms during routine testing.

Non-chemical signatures of biological materials: Radio signals from Covid19?

All therapeutic methods dealing with coronavirus (past and present) are based on chemicals. We test for it (positive or negative) chemically and hope to cure it with a future vaccine (some complicated chemical preparation). If and when the virus mutates, another set of chemical protocols for its testing and a hunt for new chemicals as a vaccine shall begin again and again. But the history of modern (western) medicine tells us that our biotechnology is not so limited. Copious scientific evidence for sonic and low energy electromagnetic signals produced by all biological elements (DNA, cells, bacteria, parasites, virus) exists; in turn, the biological elements are affected by these non-chemical signals as well. A careful analysis and a catalogue of the spectrum of these non-chemical signals are proposed here as a unique biophysical signature.

Image quality evaluation of ultrasound imaging systems: advanced B-modes.

The Quality assurance of ultrasound clinical imaging systems is essential for maintaining their performance to the highest level and for complying with the requirements by various regulatory and accrediting agencies. Although there is no standardization yet, most of the quality assessment procedures available in literature are proposed for B-mode and Doppler imaging. However, ultrasound imaging systems offer a variety of advanced imaging modes, besides B-mode and Doppler, which are primarily aimed at improving image quality. This study presents computer-based methods for evaluating image quality for the advanced imaging modes of ultrasound imaging systems: harmonic imaging, spatial compounding imaging, adaptive speckle reduction, and tissue aberration correction. The functions and parameters proposed for evaluating image quality are: grayscale mapping function, image contrast, contrast-to-noise ratio (CNR), and high-contrast spatial resolution. We present our computer-based methods for evaluating image quality of these modes with a number of probe and scanner combinations, which were employed to image targets in ultrasound phantoms. The functions and parameters here proposed in image quality performance evaluation are: grayscale mapping function, image contrast, CNR, and high-contrast spatial resolution. We show that these quantities could be useful in developing standardized methods for evaluating the advanced ultrasound imaging modes, especially when the advanced mode resulted in subtle visual differences.

Breast Ultrasound Technology and Performance Evaluation of Ultrasound Equipment: B-Mode.

Ultrasound (US) has become increasingly important in imaging and image-guided interventional procedures. In order to ensure that the imaging equipment performs to the highest level achievable and thus provides reliable clinical results, a number of quality control (QC) methods have been developed. Such QC is increasingly required by accrediting agencies and professional organizations; however, these requirements typically do not include detailed procedures for how the tests should be performed. In this paper, a detailed overview of QC methods for general and breast US imaging using computer-based objective methods is described. The application of QC is then discussed within the context of a common clinical application (US-guided needle biopsy) as well as for research applications, where QC may not be mandated, and thus is rarely discussed. The implementation of these methods will help in finding early stage equipment faults and in optimizing image quality, which could lead to better detection and classification of suspicious findings in clinical applications, as well as improving the robustness of research studies.

Acoustic neuromodulation from a basic science prospective.

We present here biophysical models to gain deeper insights into how an acoustic stimulus might influence or modulate neuronal activity. There is clear evidence that neural activity is not only associated with electrical and chemical changes but that an electro-mechanical coupling is also involved. Currently, there is no theory that unifies the electrical, chemical, and mechanical aspects of neuronal activity. Here, we discuss biophysical models and hypotheses that can explain some of the mechanical aspects associated with neuronal activity: the soliton model, the neuronal intramembrane cavitation excitation model, and the flexoelectricity hypothesis. We analyze these models and discuss their implications on stimulation and modulation of neuronal activity by ultrasound.

Transient photothermal spectra of plasmonic nanobubbles.

The photothermal efficacy of near-infrared gold nanoparticles (NP), nanoshells, and nanorods was studied under pulsed high-energy optical excitation in plasmonic nanobubble (PNB) mode as a function of the wavelength and duration of the excitation laser pulse. PNBs, transient vapor nanobubbles, were generated around individual and clustered overheated NPs in water and living cells. Transient PNBs showed two photothermal features not previously observed for NPs: the narrowing of the spectral peaks to 1 nm and the strong dependence of the photothermal efficacy upon the duration of the laser pulse. Narrow red-shifted (relative to those of NPs) near-infrared spectral peaks were observed for 70 ps excitation laser pulses, while longer sub- and nanosecond pulses completely suppressed near-infrared peaks and blue shifted the PNB generation to the visual range. Thus, PNBs can provide superior spectral selectivity over gold NPs under specific optical excitation conditions.

Estimation of thermal dose from MR thermometry during application of nonablative pulsed high intensity focused ultrasound.

PURPOSE: To evaluate whether MR thermometry is sufficiently fast, accurate, and spatially resolved for monitoring the thermal safety of nonablative pulsed high intensity ultrasound (pHIFU) treatments. MATERIALS AND METHODS: A combination of real MR thermometry data and modeling was used to analyze the effects of temporal and spatial averaging as well as noise on the peak temperatures and thermal doses that would be measured by MR thermometry. RESULTS: MR thermometry systematically underestimates the temperature and thermal doses during pHIFU treatment. Small underestimates of peak temperature can lead to large underestimates of thermal dose. Spatial averaging errors are small for ratios of pixel dimension to heating zone radius less than 0.25, which may be achieved by reducing the voxel size or steering the acoustic beam. Thermal dose might also be underestimated for very short, high power pulses due to temporal averaging. A simple correction factor based on the applied power and duty cycle may be applied to determine the upper bound of this effect. CONCLUSION: The temperature and thermal dose measured using MR thermometry during pulsed HIFU treatment is probably sufficient in most instances. Simple corrections may be used to calculate an upper bound where this is a critical factor.

Cavitation threshold of microbubbles in gel tunnels by focused ultrasound.

The investigation of inertial cavitation in micro-tunnels has significant implications for the development of therapeutic applications of ultrasound such as ultrasound-mediated drug and gene delivery. The threshold for inertial cavitation was investigated using a passive cavitation detector with a center frequency of 1 MHz. Micro-tunnels of various diameters (90 to 800 microm) embedded in gel were fabricated and injected with a solution of Optison(trade mark) contrast agent of concentrations 1.2% and 0.2% diluted in water. An ultrasound pulse of duration 500 ms and center frequency 1.736 MHz was used to insonate the microbubbles. The acoustic pressure was increased at 1-s intervals until broadband noise emission was detected. The pressure threshold at which broadband noise emission was observed was found to be dependent on the diameter of the micro-tunnels, with an average increase of 1.2 to 1.5 between the smallest and the largest tunnels, depending on the microbubble concentration. The evaluation of inertial cavitation in gel tunnels rather than tubes provides a novel opportunity to investigate microbubble collapse in a situation that simulates in vivo blood vessels better than tubes with solid walls do.