Ultrasound

The quantification of heating effects during exposure to ultrasound is usually based on laboratory experiments in water and is assessed using extrapolated parameters such as the thermal index. In our study, we have measured the temperature increase directly in a simulator of the maternal–fetal environment, the ‘ISUOG Phantom’, using clinically relevant ultrasound scanners, transducers and exposure conditions.

The study was carried out using an instrumented phantom designed to represent the pregnant maternal abdomen and which enabled temperature recordings at positions in tissue mimics which represented the skin surface, sub-surface, amniotic fluid and fetal bone interface. We tested four different transducers on a commercial diagnostic scanner. The effects of scan duration, presence of a circulating fluid, pre-set and power were recorded.

The highest temperature increase was always at the transducer–skin interface, where temperature increases between 1.4°C and 9.5°C were observed; lower temperature rises, between 0.1°C and 1.0°C, were observed deeper in tissue and at the bone interface. Doppler modes generated the highest temperature increases. Most of the heating occurred in the first 3 minutes of exposure, with the presence of a circulating fluid having a limited effect. The power setting affected the maximum temperature increase proportionally, with peak temperature increasing from 4.3°C to 6.7°C when power was increased from 63% to 100%.

Although this phantom provides a crude mimic of the in vivo conditions, the overall results showed good repeatability and agreement with previously published experiments. All studies showed that the temperature rises observed fell within the recommendations of international regulatory bodies. However, it is important that the operator should be aware of factors affecting the temperature increase.

Third trimester growth scans represent a significant proportion of the workload in obstetric ultrasound departments. The objective of these serial growth scans is to improve the antenatal detection of babies with fetal growth restriction. The aim of this paper is to describe a method of peer review for third trimester abdominal circumference measurements which is realistic within busy obstetric ultrasound departments in the UK.

Twenty-two, third trimester, measured abdominal circumference images were randomly selected. Images were assessed subjectively by 12 sonographers using the image Criteria Achieved Score. For quantitative assessment, termed the Inter-operator Variability Score, three of the abdominal circumference (AC) images were blindly remeasured. Following this, a questionnaire was used to ascertain which image criteria sonographers considered most important and to reach an agreement on correct caliper placement.

The least frequently met image criteria with the lowest Criteria Achieved Score related to an oblique abdominal circumference section. These included fetal kidney present (Criteria Achieved Score 24.6%), multiple oblique ribs (Criteria Achieved Score 39.4%) and oblique spine (Criteria Achieved Score 37.5%). Caliper placement was also identified as inconsistent.

This study demonstrates that the perfect AC section is not always possible and sonographers use their professional judgement to determine whether an image is acceptable. Seventy-three percent of the images reviewed were of an acceptable standard. There can be inconsistencies in sonographer opinion regarding what is an acceptable third trimester abdominal circumference image. These differences need to be addressed to maximise the effectiveness of the third trimester ultrasound examination.

Peer review can be used to monitor scan quality and identify areas of inconsistency.

To estimate the level of interobserver agreement in the calculation of placenta accreta index (PAI) as well as to evaluate the accuracy of PAI in prediction of morbidly adherent placenta.

This was a prospective study where 45 pregnant women (from 28 to 37 weeks of gestational age) with at least one previous Caesarean section and ultrasound-proven placenta previa were included. A known and previously published scoring system, the PAI, was evaluated independently by two radiologists and the cases were followed for the delivery and histopathology outcome. The accuracy of the PAI and the level of interrater agreement was analysed using cross-table analysis, intraclass correlation efficient and Cohen’s kappa as statistical variables.

Adherent placenta was found in 15 patients accounting for 33% of cases. The PAI showed nearly 90% sensitivity, specificity and the predictive values. Interrater agreement in calculation of PAI by the two radiologists was perfect with an intraclass correlation efficient of 0.959. An easy-to-use morbid adherent placenta score was also predicted to simplify the results of PAI, which showed moderate agreement (κ = 0.746).

The PAI can be helpful in stratifying the individual risk of placental invasion above the baseline risk. The PAI-derived, simplified scoring system called morbid adherent placenta score can be used as a simple tool to interpret and convey the results of PAI.

U-score ultrasound classification (graded U1-U5) is widely used to grade thyroid nodules based on benign and malignant sonographic features. It is well established that ultrasound is an operator-dependent imaging modality and thus more susceptible to subjective variances between operators when using imaging-based scoring systems. We aimed to assess whether there is any intra- or interobserver variability when U-scoring thyroid nodules and whether previous thyroid ultrasound experience has an effect on this variability.

A total of 14 ultrasound operators were identified (five experienced thyroid operators, five with intermediate experience and four with no experience) and were asked to U-score images from 20 thyroid cases shown as a single projection, with and without Doppler flow. The cases were subsequently rescored by the 14 operators after six weeks. The first and second round U-scores for the three operator groups were then analysed using Fleiss’ kappa to assess interobserver variability and Cochran’s Q test to determine any intraobserver variability.

We found no significant interobserver variability on combined assessment of all operators with fair agreement in round 1 (Fleiss’ kappa = 0.30, p <0.0001) and slight agreement in round 2 (Fleiss’ kappa = 0.19, p < 0.0001). Cochran’s Q test revealed no significant intraobserver variability in all 14 operators between round 1 and round 2 (all p>0.05).

We found no statistically significant inter- or intraobserver variability in the U-scoring of thyroid nodules between all participants reinforcing the validity of this scoring method in clinical practice, allaying concerns regarding potential subjective biases in reporting.

Although transrectal ultrasound is routinely performed for imaging prostate lesions, colour Doppler imaging visualizing vascularity is not commonly used for diagnosis. The goal of this study was to measure vascular and echogenic differences between malignant and benign lesions of the prostate by quantitative colour Doppler and greyscale transrectal ultrasound.

Greyscale and colour Doppler ultrasound images of the prostate were acquired in 16 subjects with biopsy-proven malignant or benign lesions. Echogenicity and microvascular flow velocity of each lesion were measured by quantitative image analysis. Flow velocity was measured over several cardiac cycles and the velocity–time waveform was used to determine microvascular pulsatility index and microvascular resistivity index. The Wilcoxon rank sum test was used to compare the malignant and benign groups.

Median microvascular flow velocity of the malignant lesions was 1.25 cm/s compared to 0.36 cm/s for the benign lesions. Median pulsatility and resistive indices of the malignant lesions were 1.55 and 0.68, respectively versus 6.38 and 1.0 for the benign lesions. Malignant lesions were more hypoechoic relative to the surrounding tissue, with median echogenicity of 0.24 compared to 0.76 for the benign lesions. The differences between the malignant and benign groups for each measurement were significant (p < 0.01).

Marked differences were observed in flow velocity, microvascular pulsatility, microvascular resistance, and echogenicity of prostate cancer measured with quantitative colour Doppler and greyscale ultrasound imaging. Vascular differences measured together with echogenicity have the combined potential to characterize malignant and benign prostate lesions.

Diagnosing pleural tuberculosis can be difficult in patients with ambiguous presentation, especially in resource-limited health centres. Thus, lung ultrasound had been studied as a novel method in helping clinicians to diagnose this condition.

A 48-year-old woman presented with worsening dyspnoea and orthopnoea for one week. She had also experienced weight loss, minimal dry cough and right-sided pleuritic chest pain for several weeks. A chest radiograph showed a right lower zone pleural effusion with no apparent lung consolidation. Lung ultrasound showed a right apical consolidation and right lower zone septated pleural effusion. Pleural fluid investigations showed exudative features of mixed lymphocytic, mesothelial and neutrophilic cellular components. Tuberculin skin test was strongly positive. She was subsequently treated for pleural tuberculosis. One month after treatment, her symptoms had improved considerably.

Lung ultrasound has been found to be more effective than chest radiograph in detecting consolidation and diagnosing pneumonia. The portability and efficacy of today’s ultrasound machines, including the handheld types, show that lung ultrasound is a practical, reliable and valuable diagnostic tool in managing pulmonary conditions including tuberculosis, provided that the operators are adequately trained.

Lung ultrasound in tuberculosis is the next frontier for clinicians and researchers.

Focal nodular hyperplasia, a benign liver tumour, is the second most common focal benign liver lesion, after a cavernous haemangioma. Contrast-enhanced ultrasound is used increasingly for the diagnostic work up and follow-up of focal liver lesions in adults, but is particularly valuable in the paediatric population, with the ability to reduce radiation and the nephrotoxic contrast agents used in computed tomography or magnetic resonance imaging. Confident recognition of focal nodular hyperplasia is important; it is benign, usually asymptomatic, of no clinical significance, of no clinical consequence or malignant potential. We present a case of focal nodular hyperplasia of the liver with its characteristic findings on conventional ultrasound, contrast-enhanced ultrasound with quantitative analysis and correlated with magnetic resonance imaging.

Case presentation: A 15-year-old female with right upper quadrant abdominal pain was referred for liver ultrasound. A focal liver lesion was detected on B-mode ultrasound examination, and colour Doppler demonstrated no specific features. Contrast-enhanced ultrasound examination demonstrated early arterial enhancement, with a characteristic spoke-wheel pattern, centrifugal uniform filling of the lesion on the late arterial phase and sustained enhancement on the portal venous phase. Quantitative contrast-enhanced ultrasound has been performed, showing a typical curve of enhancement, as well as characteristic parametric images, supporting the interpretation of contrast-enhanced ultrasound and assisting the diagnosis. Magnetic resonance imaging demonstrated a central T2 hyperintense scar and similar enhancement characteristics as contrast-enhanced ultrasound on T1 gadolinium-enhanced sequences.

Contrast-enhanced ultrasound is a useful technique for the differentiation of benign from malignant liver lesions and has the potential to establish the diagnosis of focal nodular hyperplasia, based on the enhancement pattern, which is similar to that observed on magnetic resonance imaging but can be better appreciated with superior temporal, contrast and spatial resolution of contrast-enhanced ultrasound.