Variability in circulating gas emboli after a same scuba diving exposure.

PURPOSE: A reduction in ambient pressure or decompression from scuba diving can result in ultrasound-detectable venous gas emboli (VGE). These environmental exposures carry a risk of decompression sickness (DCS) which is mitigated by adherence to decompression schedules; however, bubbles are routinely observed for dives well within these limits and significant inter-personal variability in DCS risk exists. Here, we assess the variability and evolution of VGE for 2 h post-dive using echocardiography, following a standardized pool dive in calm warm conditions. METHODS: 14 divers performed either one or two (with a 24 h interval) standardized scuba dives to 33 mfw (400 kPa) for 20 min of immersion time at NEMO 33 in Brussels, Belgium. Measurements were performed at 21, 56, 91 and 126 min post-dive: bubbles were counted for all 68 echocardiography recordings and the average over ten consecutive cardiac cycles taken as the bubble score. RESULTS: Significant inter-personal variability was demonstrated despite all divers following the same protocol in controlled pool conditions: in the detection or not of VGE, in the peak VGE score, as well as time to VGE peak. In addition, intra-personal differences in 2/3 of the consecutive day dives were seen (lower VGE counts or faster clearance). CONCLUSIONS: Since VGE evolution post-dive varies between people, more work is clearly needed to isolate contributing factors. In this respect, going toward a more continuous evaluation, or developing new means to detect decompression stress markers, may offer the ability to better assess dynamic correlations to other physiological parameters.

A comparison of 31P magnetic resonance spectroscopy and microbubble-enhanced ultrasound for characterizing hepatitis c-related liver disease.

We compared in vivo hepatic (31) P magnetic resonance spectroscopy ((31) P MRS) and hepatic vein transit times (HVTT) using contrast-enhanced ultrasound with a microbubble agent to assess the severity of hepatitis C virus (HCV)-related liver disease. Forty-six patients with biopsy-proven HCV-related liver disease and nine healthy volunteers had (31) P MRS and HVTT performed on the same day. (31) P MR spectra were obtained at 1.5 T. Peak areas were calculated for metabolites, including phosphomonoesters (PME) and phosphodiesters (PDE). Patients also had the microbubble ultrasound contrast agent, Levovist (2 g), injected into an antecubital vein, and time-intensity Doppler ultrasound signals of the right and middle hepatic veins were measured. The HVTT was calculated as the time from injection to a sustained rise in Doppler signal 10% greater than baseline. The shortest times were used for analysis. Based on Ishak histological scoring, there were 15 patients with mild hepatitis, 20 with moderate/severe hepatitis and 11 with cirrhosis. With increasing severity of disease, the PME/PDE ratio was steadily elevated, while the HVTT showed a monotonic decrease. Both imaging modalities could separate patients with cirrhosis from the mild and moderate/severe hepatitis groups. No statistical difference was observed in the accuracy of each test to denote mild, moderate/severe hepatitis and cirrhosis (Fisher's exact test P =1.00). (31) P MRS and HVTT show much promise as noninvasive imaging tests for assessing the severity of chronic liver disease. Both are equally effective and highly sensitive in detecting cirrhosis.

The governance of overseas surgical collaborations - BFIRST/BSSH.

Clinical governance is the structured approach to maintaining and improving the quality of patient care and is a vital part of global surgery. BFIRST and BSSH closely collaborate with local doctors on a number of overseas projects, seeking to strengthen and develop local knowledge and skills, aiming for an independent local practice in reconstructive and upper limb surgery. Thoughts on essential requirements, improvements and pitfalls in the ethical approach to global collaboratives are presented.

Hepatic vein transit times of a microbubble agent in assessing response to antiviral treatment in patients with chronic hepatitis C.

Microbubble measurement of hepatic vein transit times (HVTT) may have the potential to assess severity of hepatitis C virus (HCV)-related liver disease, where there is a shorter HVTT with more severe disease. We investigated the utility of this test as a marker of response to antiviral treatment. Thirty-seven patients with biopsy-proven HCV-related disease undergoing antiviral treatment were studied. All had baseline scans and then repeat scans 6 months after the end of treatment. HVTT using Levovist were obtained from the right and middle hepatic veins, and the shorter time was used for analysis. The aspartate aminotransferase to platelet ratio index (APRI) scores were calculated retrospectively. There were seven patients with mild hepatitis, 23 with moderate/severe hepatitis and seven with cirrhosis. The mean baseline HVTT in responders ± SE increased from 27.3 ± 2.29 s to 33.5 ± 2.8 s posttreatment (P = 0.01). In the 10 nonresponders, the HVTT remained the same; 43.3 ± 9 s baseline compared to 44 ± 7.8 s posttreatment (P = 0.84). This trend was also seen with the APRI score where in responders, the mean score decreased from 1.1 ± 0.2 to 0.74 ± 1 (P = 0.03) and in nonresponders, the score remained unchanged; 0.88 ± 0.2 compared to 0.84 ± 0.2 (P = 0.31). HVTT measurement lengthened, while APRI scores decreased in patients who responded to antiviral treatment while both remained the same, shortened (HVTT) or increased (APRI), respectively, in patients who were nonresponders. These results are encouraging and indicate that these tests could be potentially used as markers of response to treatment and could obviate the need for serial biopsies in antiviral future treatment studies.

Photoacoustics, thermoacoustics, and acousto-optics for biomedical imaging.

Recently there have been significant advances in developing hybrid techniques combining electromagnetic waves with ultrasound for biomedical imaging, namely photoacoustic, thermoacoustic, and acousto-optic (or ultrasound modulated optical) tomography. All three techniques take advantage of tissue contrast offered by electromagnetic (EM) waves, while achieving good spatial resolution in deeper tissue facilitated by ultrasound. In this review the principles of the three techniques are introduced. A description of existing experimental and image reconstruction techniques is provided. Some recent key developments are highlighted and current issues in each of the areas are discussed.

Partial wrist denervation versus total wrist denervation: A systematic review of the literature.

The aim of this systematic review was to understand which procedure-total or partial wrist denervation-provides better results in terms of pain relief and function. This review was registered on PROSPERO (CRD42018088856). We searched the Medline (PubMed), Web of Science and Scopus databases. Twenty-one studies were included in this review. We assessed the quality of the studies using the Coleman Methodological Score. Data on demographics, surgical indications, diagnostic methods, follow-up periods, type and rates of complications, survivorship of the procedure, return to work, and outcome measures were recorded. A total of 1065 patients were included in this review; the mean quality of the studies included was considered poor. The outcomes could not be analyzed because none of the studies had reliable outcome data reported, but both procedures were effective in terms of pain relief and range of motion. Partial wrist denervation has an average subsequent procedure rate of 19%. Total wrist denervation had an average subsequent procedure rate of 4.7%. No complications were reported in any patient who underwent partial wrist denervation versus 20 patients who underwent total wrist denervation. Both partial and total wrist denervation are safe and reliable procedures that can provide good pain relief and preserve wrist range of motion. Total wrist denervation offers better long-term outcomes in term of pain relief, with fewer subsequent procedures being needed compared to partial denervation, and with a low complication rate. LEVEL OF EVIDENCE: Level III, Systematic review, Therapeutic.

Motion Artifacts and Correction in Multipulse High-Frame Rate Contrast-Enhanced Ultrasound.

High-frame-rate (HFR) ultrasound (US) imaging and contrast-enhanced US (CEUS) are often implemented using multipulse transmissions, to enhance image quality. Multipulse approaches, however, suffer from degradation in the presence of motion, especially when coherent compounding and CEUS are combined. In this paper, we investigate this effect on the intensity of HFR CEUS in deep tissue imaging using simulations and in vivo contrast echocardiography (CE). The simulation results show that the motion artifact is much higher when the flow is in an axial direction than a lateral direction. Using a pulse repetition frequency suitable for cardiac imaging, a motion of 35 cm/s can cause as much as 28.5 dB decrease in image intensity, where compounding can contribute up to 18.7 dB of intensity decrease (11 angles). These motion effects are also demonstrated for in vivo cardiac HFR CE, where the large velocities of both the myocardium and the blood are present. Intensity reductions of 10.4 dB are readily visible in the chamber. Finally, we demonstrate how performing motion-correction before pulse inversion compounding greatly reduces such motion artifact and improve image signal-to-noise ratio and contrast.

Functional ultrasound methods in oncological imaging.

The real time nature of ultrasound and functional methods such as Doppler ultrasound mean that ultrasound can claim to have always been a functional imaging method, but recent developments in quantitation, dramatic improvement in Doppler performance and now microbubbles have created many exciting new applications. These include methods for assessing the neovascularity of tumours, for following the effects of therapy and for predicting the likelihood of development of metastatic disease at the staging of primary tumours.

Segmentation and analysis of colour Doppler images of tumour vasculature.

A technique has been developed to segment (separate), from a digitized colour Doppler video image, the colour and greyscale information and then to estimate from the colour information the original mean Doppler frequency shift data from which the image was created. The remapped velocity image is then analysed to extract numerical features of the tumour vasculature. The present version of the software is set-up to work for an Acuson 128 colour Doppler system using the V4 colour scale, although it should work well with any system which modulates only two colours for each flow direction and displays a colour calibration scale at the side of the image. Accuracy of classification of greyscale, colour and flow direction was estimated as being in the region of 95% for typical breast tumour images. The degree of agreement between the remapped colour velocity values and those stated by the scanner at the same image locations was evaluated in terms of the linearity of the relationship (> 99%), precision (better than +/- 5%) and accuracy (better than 7.6%). We investigated the value, for diagnosis and assessment of response of, a variety of characteristics of the displayed vascularity. At present, the software calculates the following vascular image features within any region of interest defined by the operator: mean displayed velocity, maximum displayed velocity, standard deviation of displayed velocity, total area occupied by colour signal, percentage area occupied by colour signal, area integral of displayed velocity and the total displayed velocity per unit area.

Stimulated acoustic emission to image a late liver and spleen-specific phase of Levovist in normal volunteers and patients with and without liver disease.

Quantitative studies were performed to investigate liver- specific uptake of the microbubble Levovist, using stimulated acoustic emission (SAE), which can detect microbubbles even when stationary or slow-moving. These comprised studies of biodistribution comparing the liver and kidney in five normal volunteers, reproducibility in 34 patients, comparison between cirrhotics and controls (n = 9 each) and maximal depth of effect at different frequencies (180 measurements in 31 patients). Stimulated acoustic emission lasted beyond 30 min, with strongly liver-specific properties in each volunteer and was highly reproducible. No difference in the amount of SAE in the superficial liver was seen between cirrhotic and normal livers, but attenuation was higher in cirrhotics. This demonstrates a frequency-dependent effect on liver SAE penetration. We conclude that the liver uptake of Levovist lasts over 30 min, is reproducible, occurs even where diffuse liver disease is present and can be used to assess tissue attenuation in a novel fashion.

[Stimulated acoustic emissions with the ultrasound contrast medium levovist: a clinically useful contrast effect with liver-specific properties]. / Stimulierte akustische Emission mit dem Ultraschall-Kontrastmittel Levovist: Ein klinisch nutzbarer Kontrasteffekt mit leberspezifischen Eigenschaften.

PURPOSE: The purpose of this study was systematically to investigate stimulated acoustic emission (SAE) with the microbubble contrast agent Levovist (Schering AG, Berlin) in vivo with regards to reproducibility, distribution in various organs over time, dependence on technical factors, and influence on the delineation of focal liver lesions. PATIENTS AND METHODS: 2 intravenous injections of 1 g of Levovist were given to 2 dogs and 1-6 injections of 2.5 g Levovist to 5 healthy volunteers and 37 patients. The liver, spleen, large abdominal vessels, and kidney were intermittently scanned for up to 30 min. Studies were evaluated for the presence of SAE signals by 2 observers. In 20 patients with focal liver lesions (15 with metastases, 4 haemangiomata, 1 hepatocellular carcinoma, and 1 cyst) the influence on lesion visualization was also assessed. RESULTS: SAE effects, lasting up to 30 minutes, were seen in all subjects in the liver and spleen. Vascular and renal SAE signals were noted shortly after injection, lasting up to 6 minutes. SAE was absent or markedly reduced in focal liver lesions, which were seen as colour voids. This increased the conspicuity of focal lesions, and in 5 patients additional metastases were detected that could not be delineated on B-mode alone. CONCLUSION: A liver- and spleen-specific late phase of Levovist can be consistently demonstrated using SAE and the effect increases the conspicuity of focal liver lesions.

Simultaneous dislocations of the radiocapitellar and distal radioulnar joints.

Posttraumatic instability of the distal radioulnar joint (DRUJ), occurring in isolation or in association with fractures of the radius, is well-documented. Few reports have identified simultaneous ipsilateral DRUJ instability and elbow dislocation. The authors of the present study describe a case of persistent radiocapitellar subluxation after closed reduction of an elbow dislocation, secondary to irreducible volar subluxation of the DRUJ.

Kirschner wire pin tract infection rates: a randomized controlled trial between percutaneous and buried wires.

This prospective, randomized trial compares the infection rates of Kirschner wires left percutaneously and those buried deep to the skin in a group of patients with isolated distal radial fractures. Percutaneous wires had a significantly greater infection rate than wires which were buried deep to the skin.

Prophylactic decompression of extensor pollicis longus to prevent rupture.

We present a case of a patient with spontaneous rupture of right extensor pollicis longus (EPL) tendon, who had also developed left wrist pain and weakness in his left EPL that MRI studies confirmed to be caused by tendinosis. Subsequently, decompression of left EPL and reconstruction of right EPL with palmaris longus tendon graft was undertaken. In this case, decompression of the left EPL tendon led to resolution of the patient's symptoms as well as preventing tendon rupture. We advocate the use of ultrasound imaging to evaluate EPL in these cases and prophylactic decompression of EPL tendon to avoid rupture in those patients found to have tendinosis.

Acoustic super-resolution with ultrasound and microbubbles.

Ultrasound (US) is a widely used clinical imaging modality that offers penetration depths in tissue of >10 cm. However, the spatial resolution in US imaging is fundamentally limited by diffraction to approximately half the wavelength of the sound wave employed. The spatial resolution of optical microscopy is limited by the same fundamental physics, but in recent years super-resolution imaging techniques have been developed that overcome the diffraction limit through the localization of many spatially separated photo-switchable or photo-activatable fluorophores. In this paper, we apply a related approach to demonstrate super-resolution imaging with US. We imaged dilute suspensions of microbubble contrast agents flowing through narrow tube-based phantoms. By spatially localizing multiple spatially isolated microbubbles, we constructed super-resolved microbubble location density maps that clearly resolve features 5.1-2.2 times smaller than the US system point spread function full width half maximum in the lateral and axial directions respectively. Our initial characterization experiment using a fixed 100 µm diameter brass wire and a US frequency of 2 MHz suggests that for an ideal stationary point scatterer the ultimate resolution of the unmodified clinical US system used could be in the range of 2-4 µm.

Quantitative contrast-enhanced ultrasound imaging: a review of sources of variability.

Ultrasound provides a valuable tool for medical diagnosis offering real-time imaging with excellent spatial resolution and low cost. The advent of microbubble contrast agents has provided the additional ability to obtain essential quantitative information relating to tissue vascularity, tissue perfusion and even endothelial wall function. This technique has shown great promise for diagnosis and monitoring in a wide range of clinical conditions such as cardiovascular diseases and cancer, with considerable potential benefits in terms of patient care. A key challenge of this technique, however, is the existence of significant variations in the imaging results, and the lack of understanding regarding their origin. The aim of this paper is to review the potential sources of variability in the quantification of tissue perfusion based on microbubble contrast-enhanced ultrasound images. These are divided into the following three categories: (i) factors relating to the scanner setting, which include transmission power, transmission focal depth, dynamic range, signal gain and transmission frequency, (ii) factors relating to the patient, which include body physical differences, physiological interaction of body with bubbles, propagation and attenuation through tissue, and tissue motion, and (iii) factors relating to the microbubbles, which include the type of bubbles and their stability, preparation and injection and dosage. It has been shown that the factors in all the three categories can significantly affect the imaging results and contribute to the variations observed. How these factors influence quantitative imaging is explained and possible methods for reducing such variations are discussed.