Temperature elevation measured in a tissue-mimicking phantom for transvaginal ultrasound at clinical settings

INTRODUCTION: This paper reports the results of an audit to assess the possible thermal hazard associated with the clinical use of ultrasound scanners in UK Hospitals for transvaginal ultrasound imaging. METHODS: An anatomically relevant phantom composed of a block of agar-based tissue mimicking material with embedded thermal sensors was developed. Seventeen hospitals around the UK were visited and a total of 64 configurations were tested. A representative typical scanning protocol was adopted, which primarily used B-mode with 30 s periods of colour-flow and pulsed Doppler modes for both gynaecology and obstetrics pre-sets. RESULTS: The results confirmed that the highest temperature increase is always at the surface. The greatest temperature rise measured across all the systems was 3.6℃, with an average of 2.0℃ and 2.16℃ for gynaecology and obstetrics pre-sets, respectively. For some systems, the temperature increased rapidly when selecting one of the Doppler modes, so using them for longer than 30 s will in many cases lead to greater heating. It is also shown that, in agreement with previous studies, the displayed thermal index greatly underestimates the temperature rise, particularly close to the transducer face but even to distances approaching 2 cm. CONCLUSIONS: Overall, the results of the audit for the temperature rise during transvaginal ultrasound at clinical settings fell within the limits indicated by the national and international standards, for the pre-sets tested and following a representative typical scanning protocol. Only selected pre-sets were tested and the scanner outputs were not maximised (for example by using zoom, greater depth or narrow sector angles). Consequently, higher temperatures than those measured can certainly be achieved

Alveolar Osteitis: A Comprehensive Review of Concepts and Controversies

Alveolar osteitis, “dry socket”, remains amongst the most commonly encountered complications following extraction of teeth by general dentists and specialists. A great body of literature is devoted to alveolar osteitis addressing the etiology and pathophysiology of this condition. In addition numerous studies are available discussing methods and techniques to prevent this condition. To this date though great controversy still exists regarding the appropriate terminology used for this condition as well as the actual etiology, pathophysiology, and best methods of prevention and treatment. This article is a comprehensive critical review of the available literature addressing the concepts and controversies surrounding alveolar osteitis. We aim to assist the dental health care professional with patient preparation and management of this commonly encountered postoperative condition should be encountered

Establishing a Lung Model for Evaluation of Engineered Lung Microbiome Therapies

Benzene, a toxin and carcinogen found in air polluted by cigarette smoke, car exhaust, and industrial processes, is associated with the development of leukemia and lymphoma. Other than avoiding exposure, there is no current method to deter the effects of benzene. One potential strategy to prevent these effects is to engineer the bacteria of the human lung microbiome to degrade benzene. To evaluate this novel approach, we must verify that the bacteria remain viable within the lung microenvironment. To do so, lungs were harvested from rats and swabbed to determine the contents of the original lung microbiome. Then green fluorescent protein (GFP)-transformed E. coli were introduced to the lungs and the lungs were ventilated for five minutes before being swabbed again. The lungs were sliced with a vibratome and cultured for three days. They were analyzed under a microscope and swabbed daily to determine how the bacteria disperse upon delivery and detect changes within the lung microbiome. If results show that introduction of a new bacterial species does not significantly change the lung microbiome over time, the project can move forward to test the engineered bacteria’s viability in the lung environment and effectiveness in rescuing lung cells from benzene’s toxicity

Caratterizzazione parametrica delle prestazioni ed instabilita di induttori cavitanti

Nel campo della propulsione chimica ad uso spaziale, le turbomacchine rivestono un ruolo di fondamentale importanza. Tutti i lanciatori esistenti, infatti, presentano almeno uno stadio con motore a propellente liquido ed alle turbopompe è affidato il compito di innalzare la pressione del fluido prima dell’ingresso in camera di combustione, in modo da aumentare l’efficienza della reazione, e, contemporaneamente, diminuire il valore della pressione all’interno del serbatoio con una conseguente diminuzione del peso di quest’ultimo. Gli obiettivi fondamentali della ricerca nel campo della propulsione sono, da un lato, diminuire il peso dei componenti e, dall’altro, avere la possibilità di lavorare con densità di potenze sempre più elevate. Questo consente di aumentare il rapporto di carico utile del lanciatore, tuttavia necessita di uno studio approfondito di fenomeni quali la cavitazione e le instabilità fluidodinamiche e rotodinamiche. Generalmente, a causa dei molteplici effetti deleteri che ha la cavitazione, si cerca di limitare l’insorgere di questo fenomeno introducendo a monte della pompa principale un ulteriore elemento denominato induttore. Un induttore è una pompa assiale con un numero limitato di pale (solitamente 3 o 4) che ha il compito di fornire una prima compressione al fluido di lavoro, evitando, o quantomeno ritardando, lo sviluppo della cavitazione sul componente principale. Nello svolgere questo lavoro, l’induttore è spesso costretto a lavorare in condizioni nelle quali è inevitabile lo sviluppo della cavitazione, che può portare al manifestarsi di instabilità fluidodinamiche e rotodinamiche che, oltre a peggiorare l’efficienza dell’intero lanciatore, rischiano di compromettere l’integrità strutturale del sistema. Lo studio teorico di questi fenomeni risulta quanto mai difficoltoso e spesso inaffidabile, data l’enorme complessità fisica del sistema. È perciò assolutamente necessaria una caratterizzazione sperimentale della turbomacchina, che può essere molto onerosa a causa della difficoltà di lavorare con componenti criogenici o comunque instabili e pericolosi. La possibilità di comprendere come alcuni fattori fondamentali, quali la portata, il numero di giri del motore e la temperatura, influenzino sia le prestazioni sia l’insorgere delle instabilità, può portare ad un notevole risparmio economico e di tempo, rendendo possibile studiare il comportamento della turbomacchina in condizioni di similitudine geometrica e fluidodinamica. Il seguente lavoro si concentra sulla caratterizzazione di due induttori sperimentali, il DAPAMITO3 ed il DAPAMITO4, rispettivamente a tre e quattro pale, disegnati grazie ad un modello di ordine ridotto realizzato dal Prof. Luca d’Agostino e dal suo team di lavoro. È stato inoltre caratterizzato un ulteriore induttore commerciale a tre pale. L’intero lavoro è stato svolto presso il laboratorio di cavitazione di ALTA S.p.A., con la supervisione del Prof. Luca d’Agostino e degli ingegneri Lucio Torre ed Angelo Pasini. Dopo una breve introduzione riguardante gli aspetti generali della propulsione chimica e della cavitazione (Capitolo 1), verranno analizzate più in dettaglio le turbopompe, introducendo i parametri che caratterizzano lo studio delle prestazioni degli induttori (Capitolo 2). Il Capitolo 3 offre una descrizione del laboratorio di cavitazione e del circuito di prova, con particolare attenzione alle modifiche apportate all’impianto per una migliore interfaccia con gli induttori caratterizzati ed un’analisi più approfondita di fenomeni il cui studio non era previsto nella configurazione originale. Nel Capitolo 4 si descriveranno gli induttori oggetto dello studio. Il Capitolo 5 è dedicato alle curve di prestazione non cavitante ed alle loro caratteristiche principali, evidenziando quali sono i fattori che ne influenzano la forma e l’andamento. Il Capitolo 6 riguarda invece le curve di prestazione cavitante; verrà descritta accuratamente la loro forma e si delineeranno le modalità di sviluppo della cavitazione al diminuire della pressione in ingresso agli induttori. Successivamente si analizzerà l’influenza del coefficiente di flusso e della temperatura, confrontando i risultati sperimentali con i metodi attualmente più diffusi di scalatura termica delle prestazioni. Lo studio delle instabilità fluidodinamiche è riportato al Capitolo 7, che si apre con una breve introduzione dei principali strumenti, perlopiù di origine statistica, utilizzati per l’analisi dei segnali rilevati dai trasduttori. I vari tipi di instabilità verranno trattati singolarmente, esaminando le circostanze che portano ad un loro sviluppo ed i fattori che ne influenzano la forma e l’ampiezza, con riferimenti agli articoli presenti in letteratura che riportano l’insorgere di fenomeni simili. Infine il Capitolo 8 riporta le conclusioni del lavoro e termina con un breve accenno agli argomenti oggetto di futuro lavoro presso il laboratorio di cavitazione di ALTA S.p.A

Magnetic resonance imaging of the brain and vocal tract:Applications to the study of speech production and language learning

The human vocal system is highly plastic, allowing for the flexible expression of language, mood and intentions. However, this plasticity is not stable throughout the life span, and it is well documented that adult learners encounter greater difficulty than children in acquiring the sounds of foreign languages. Researchers have used magnetic resonance imaging (MRI) to interrogate the neural substrates of vocal imitation and learning, and the correlates of individual differences in phonetic “talent”. In parallel, a growing body of work using MR technology to directly image the vocal tract in real time during speech has offered primarily descriptive accounts of phonetic variation within and across languages. In this paper, we review the contribution of neural MRI to our understanding of vocal learning, and give an overview of vocal tract imaging and its potential to inform the field. We propose methods by which our understanding of speech production and learning could be advanced through the combined measurement of articulation and brain activity using MRI – specifically, we describe a novel paradigm, developed in our laboratory, that uses both MRI techniques to for the first time map directly between neural, articulatory and acoustic data in the investigation of vocalisation. This non-invasive, multimodal imaging method could be used to track central and peripheral correlates of spoken language learning, and speech recovery in clinical settings, as well as provide insights into potential sites for targeted neural interventions

Vocal Tract Images Reveal Neural Representations of Sensorimotor Transformation During Speech Imitation

Imitating speech necessitates the transformation from sensory targets to vocal tract motor output, yet little is known about the representational basis of this process in the human brain. Here, we address this question by using real-time MR imaging (rtMRI) of the vocal tract and functional MRI (fMRI) of the brain in a speech imitation paradigm. Participants trained on imitating a native vowel and a similar nonnative vowel that required lip rounding. Later, participants imitated these vowels and an untrained vowel pair during separate fMRI and rtMRI runs. Univariate fMRI analyses revealed that regions including left inferior frontal gyrus were more active during sensorimotor transformation (ST) and production of nonnative vowels, compared with native vowels; further, ST for nonnative vowels activated somatomotor cortex bilaterally, compared with ST of native vowels. Using test representational similarity analysis (RSA) models constructed from participants' vocal tract images and from stimulus formant distances, we found that RSA searchlight analyses of fMRI data showed either type of model could be represented in somatomotor, temporal, cerebellar, and hippocampal neural activation patterns during ST. We thus provide the first evidence of widespread and robust cortical and subcortical neural representation of vocal tract and/or formant parameters, during prearticulatory ST

The effect of curing temperature and time on the acoustic and optical properties of PVCP

Polyvinyl chloride plastisol (PVCP) has been increasingly used as a phantom material for photoacoustic and ultrasound imaging. As one of the most useful polymeric materials for industrial applications, its mechanical properties and behaviour are well-known. Although the acoustic and optical properties of several formulations have previously been investigated, it is still unknown how these are affected by varying the fabrication method. Here, an improved and straightforward fabrication method is presented and the effect of curing temperature and curing time on PVCP acoustic and optical properties, as well as their stability over time, is investigated. Speed of sound and attenuation were determined over a frequency range from 2 to 15 MHz, while the optical attenuation spectra of samples was measured over a wavelength range from 500 to 2200 nm. Results indicate that the optimum properties are achieved at curing temperatures between 160 °C and 180 °C, while the required curing time decreases with increasing temperature. The properties of the fabricated phantoms were highly repeatable, meaning the phantoms are not sensitive to the manufacturing conditions provided the curing temperature and time are within the range of complete gelation-fusion (samples are optically clear) and below the limit of thermal degradation (indicated by the yellowish appearance of the sample). The samples’ long term stability was assessed over 16 weeks and no significant change was observed in the measured acoustic and optical properties

Measurement of the ultrasound attenuation and dispersion in 3D-printed photopolymer materials from 1 to 3.5 MHz

Over the past decade, the range of applications in biomedical ultrasound exploiting 3D printing has rapidly expanded. For wavefront shaping specifically, 3D printing has enabled a diverse range of new, low-cost approaches for controlling acoustic fields. These methods rely on accurate knowledge of the bulk acoustic properties of the materials; however, to date, robust knowledge of these parameters is lacking for many materials that are commonly used. In this work, the acoustic properties of eight 3D-printed photopolymer materials were characterised over a frequency range from 1 to 3.5 MHz. The properties measured were the frequency-dependent phase velocity and attenuation, group velocity, signal velocity, and mass density. The materials were fabricated using two separate techniques [PolyJet and stereolithograph (SLA)], and included Agilus30, FLXA9960, FLXA9995, Formlabs Clear, RGDA8625, RGDA8630, VeroClear, and VeroWhite. The range of measured density values across all eight materials was 1120–1180 kg · m−3, while the sound speed values were between 2020 to 2630 m · s−1, and attenuation values typically in the range 3–9 dB · MHz−1· cm−1

Characterisation of hydrophone sensitivity with temperature using a broadband laser-generated ultrasound source

In this work, we present a novel method for characterising the relative variation in hydrophone sensitivity with temperature, addressing a key aspect of measurements in the field of ultrasound metrology. Our study focused on a selection of miniature ultrasonic hydrophones commonly used in medical applications. The method is based on using water as a temperature-sensitive laser-generated ultrasound (LGUS) source for calibration, allowing for flexible characterisation across a wide temperature range. The measurements were performed using both the LGUS method and the established self-reciprocity method. Our results demonstrate good agreement within 5% between the two methods, validating the effectiveness of the LGUS approach. We found that the sensitivity of the tested hydrophones exhibited low temperature dependence less than −0.2% per ∘C within the studied temperature range from 17 ∘C up to 50 ∘C. The presented LGUS method offers greater flexibility than current approaches as it allows for characterisation of membrane hydrophones with small element sizes and non-electrical transducers. By combining the relative sensitivity variation obtained through the LGUS method with the standard calibration at room temperature, absolute values of hydrophone sensitivity can be determined. The expanded uncertainty of our measurements, which was evaluated at temperature intervals of 8 ∘C, was determined to be on average 10%. Our work provides valuable insights into the temperature dependence of hydrophone sensitivity and lays the foundation for further investigations in this area. The LGUS method holds promise for future enhancements, such as increased bandwidth of the LGUS source and frequency domain analysis, to explore the frequency dependency of sensitivity variation with temperature