Ultrasound Vascular Elastography as a Tool for Assessing Atherosclerotic Plaques - A Systematic Literature Review

Atherosclerosis is a widespread disease that accounts for nearly 3-quarters of deaths due to cardiovascular disease. Ultrasound elastography might be able to reliably identify characteristics associated with vulnerable plaques. There is a need for the evaluation of elastography and its ability to distinguish between vulnerable and stable plaques. The aim of this paper is to provide an overview of the literature on vascular elastography. A systematic search of the available literature for studies using elastography for assessing atherosclerotic plaques was conducted using the MEDLINE, Embase, Cochrane Library and Web of Science databases. A standardized template was used to extract relevant data following the PRISMA 2009 checklist. 20 articles were included in this paper. The studies were heterogeneous. All studies reported that elastography was a feasible technique and provided additional information compared to B-mode ultrasound alone. Most studies reported higher strain values for vulnerable plaques. Ultrasound elastography has potential as a clinical tool in the assessment of atherosclerotic plaques. Elastography is able to distinguish between different plaque types, but there is considerable methodological variation between studies. There is a need for larger studies in a clinical setting to determine the full potential of elastography.

EFSUMB Statement on Medical Student Education in Ultrasound [long version]

The European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) recommends that ultrasound should be used systematically as an easy accessible and instructive educational tool in the curriculum of modern medical schools. Medical students should acquire theoretical knowledge of the modality and hands-on training should be implemented and adhere to evidence-based principles. In this paper we report EFSUMB policy statements on medical student education in ultrasound that in a short version is already published in Ultraschall in der Medizin 1.

Simulation-Based Abdominal Ultrasound Training - A Systematic Review

PURPOSE

The aim is to provide a complete overview of the different simulation-based training options for abdominal ultrasound and to explore the evidence of their effect.

MATERIALS AND METHODS

This systematic review was performed according to the PRISMA guidelines and Medline, Embase, Web of Science, and the Cochrane Library was searched. Articles were divided into three categories based on study design (randomized controlled trials, before-and-after studies and descriptive studies) and assessed for level of evidence using the Oxford Centre for Evidence Based Medicine (OCEBM) system and for bias using the Cochrane Collaboration risk of bias assessment tool.

RESULTS

Seventeen studies were included in the analysis: four randomized controlled trials, eight before-and-after studies with pre- and post-test evaluations, and five descriptive studies. No studies scored the highest level of evidence, and 14 had the lowest level. Bias was high for 11 studies, low for four, and unclear for two. No studies used a test with established evidence of validity or examined the correlation between obtained skills on the simulators and real-life clinical skills. Only one study used blinded assessors.

CONCLUSION

The included studies were heterogeneous in the choice of simulator, study design, participants, and outcome measures, and the level of evidence for effect was inadequate. In all studies simulation training was equally or more beneficial than other instructions or no instructions. Study designs had significant built-in bias and confounding issues; therefore, further research should be based on randomized controlled trials using tests with validity evidence and blinded assessors.

Ultrasound Elastography in Breast Cancer Diagnosis

Ultrasound elastography is an established method for characterization of focal lesions in the breast. Different techniques and analyses of the images may be used for the characterization. This article addresses the use of ultrasound elastography in breast cancer diagnosis. In the first part of the article the techniques behind both strain- and shear-wave-elastography are explained and followed by a section on how to obtain adequate elastography images and measurements. In the second part of the article the application of elastography as an adjunct to B-mode ultrasound in clinical practice is described, and the potential diagnostic gains and limitations of elastography are discussed.

EFSUMB Guidelines on Interventional Ultrasound (INVUS), Part I. General Aspects (long Version)

This is the first part of the Guidelines on Interventional Ultrasound of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) and covers all general aspects of ultrasound-guided procedures (long version).

EFSUMB Guidelines on Interventional Ultrasound (INVUS), Part I. General Aspects (Short Version)

This is the first part of the Guidelines on Interventional Ultrasound of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) and covers all general aspects of ultrasound-guided procedures (short version; the long version is published online).

Strain Elastography for Prediction of Malignancy in Soft Tissue Tumours--Preliminary Results

PURPOSE

To evaluate the ability of strain elastography to predict malignancy in patients with soft tissue tumors, and to compare three evaluation methods of strain elastography: strain ratios, strain histograms and visual scoring.

MATERIALS AND METHODS

60 patients with 61 tumors were analyzed in the study. All patients were referred due to suspicion of malignant soft tissue tumors after diagnostic imaging (contrast-enhanced MRI, CT or PET-CT). Ultrasound-guided biopsy was preceded by the recording of strain elastography video clips, which were evaluated in consensus between three investigators. Strain ratio, strain histogram analysis and visual scoring using a five-point visual scale were compared with the final pathology from either biopsy or resection of the tumors.

RESULTS

The difference between the mean strain ratio for malignant and benign tumors was significant (p = 0.043). The mean strain ratios for malignant and benign tumors were 1.94 (95% CI [0.37; 10.21]) and 1.35 (95% CI [0.32; 5.63]), respectively. There were no significant differences for strain histograms or visual scoring. Liposarcomas had lower mean strain ratio, strain histogram values, and visual scoring than other malignant tumors. When analyzing a subgroup of patients without fat-containing tumors (n = 46), based on appearance on MRI or CT, the difference between the mean strain ratios for malignant and benign tumors increased (p = 0.014).

CONCLUSION

The mean strain ratios of malignant tumors were significantly higher than the mean strain ratios of benign tumors. There was no significant difference for strain histograms and visual scoring. Strain ratios may be used as an adjunct in soft tissue tumor diagnosis, possibly minimizing the number of biopsies.

Focused Assessment with Sonography for Trauma in patients with confirmed liver lesions

BACKGROUND AND AIMS

The objective was to determine the sensitivity and specificity of Focused Assessment with Sonography for Trauma (FAST) in patients with confirmed liver lesions and also to compare results from surgeons trained in FAST with results from radiologists trained in general abdominal ultrasound as part of the specialist training. Explorative laparotomy or CT served as gold standard.

MATERIALS AND METHODS

This retrospective study included all patients admitted to our institution from 2003 to 2010 registered with the diagnosis "Injury of the liver or gallbladder". Of 405 patients, 135 patients were eligible for analysis. Seventy-two patients were examined by radiologists and 63 by surgeons.

RESULTS

We found FAST to have a sensitivity, specificity, PPV, and NPV of 79.6%, 100%, 100%, and 68.9%. There was no statistically significant difference between FAST performed by radiologists and surgeons trained in FAST.

CONCLUSION

FAST remains an important screening tool in abdominal trauma including liver lesions, and can be performed at a satisfactory level by surgeons trained in the FAST procedure only.

Freehand biopsy guided by electromagnetic needle tracking: a phantom study

PURPOSE

To evaluate the overall accuracy and time spent on biopsy guided by electromagnetic needle tracking in a phantom compared with the standard technique of US-guided biopsy with an attached steering device. Furthermore, to evaluate off-plane biopsy guided by needle tracking.

MATERIALS AND METHODS

Three different series of biopsy were performed in a phantom: one with a steering device attached to the transducer without needle tracking, simulating the standard ultrasound-guided biopsy procedure (series 1), one freehand in the scan plane using electromagnetic needle tracking (series 2), and one freehand off-the-scan plane using electromagnetic needle tracking (series 3). The phantom contained spheres of 1  cm in diameter filled with red dye. Each time of the phantom surface was perforated counted as an attempt.

RESULTS

180 biopsies were performed. The mean time spent on each biopsy in series one was 19.9 seconds (SD: 9.1), in series two 34.1 seconds (SD: 17.9) and in series three 34.4 seconds (SD: 14.0). The overall rate of success was: 88 % for in-plane needle-guided biopsy, 87 % for in-plane needle tracking, and 92 % for off-plane needle tracking. No statistically significant difference between the methods was shown.

CONCLUSION

Needle navigation is a potentially valuable tool for image-guided biopsy with an equal rate of success compared with conventional image-guided biopsy. Furthermore, it enables off-plane image-guided biopsy.

Characterization by biopsy or CEUS of liver lesions guided by image fusion between ultrasonography and CT, PET/CT or MRI

PURPOSE

The aim of this study was to show the number of cases in which the use of fusion-guided ultrasonography (US) provided conclusive diagnosis of lesions in the liver seen on CT or MRI or PET/CT. A lesion is defined as a region that has suffered damage due to injury or disease.

MATERIALS AND METHODS

Forty patients of whom 34 had confirmed neoplastic disease, referred to US evaluation or US-guided biopsy of liver lesions seen on CT (n = 35), MRI (n = 2) or PET/CT (n = 3), were prospectively included in the study. We used a LOGIQ prototype system with incorporated software for fusion imaging, and a convex-array 4 MHz transducer (GE Healthcare, Chalfont St. Giles, UK). All patients were initially examined with B-mode US, then by fusion-guided US and for some patients also with CEUS. All patients received follow-up after at least one year.

RESULTS

Twenty-six lesions were initially indistinguishable with US. Of these, 9 became visible with fusion-guided US and another 4 became visible with CEUS, which facilitated a final diagnosis in 11 of these 13 patients. The median tumor size for all lesions included in the study was 1.5 cm (interquartile range: 1.0 - 2.4). There was no statistically significant difference in tumor size between the groups.

CONCLUSION

We have successfully demonstrated an increase in the characterization of liver lesions by using fusion-guided US compared with conventional B-mode US.

Comparison of two co-registration methods for real-time ultrasonography fused with MRI: a phantom study

PURPOSE

To test the accuracy of spatial registration of real-time ultrasonography (US) fused with MRI in a phantom.

MATERIALS AND METHODS

An US prototype system (LOGIQ, GE Healthcare) with incorporated software for fusion imaging was used to test two methods of co-registration in a phantom: co-registration from specific points, where common reference points identifiable on both MRI and US images were marked, and plane registration, where common planes identifiable on both MRI and US images were marked. In two series we performed co-registration from points and in one series we performed co-registration from planes. The accuracy of the co-registration was measured at 3 measuring points, defined before initiation of the study, and it was calculated as the root mean square deviation (RMSD), which corresponds to the standard deviation. It was measured in millimeters. Two observers each performed 30 co-registrations for each series, totaling 180 co-registrations. The difference between the methods and the observers was calculated using analysis of variance (two-way ANOVA).

RESULTS

Co-registration was significantly more accurate when using the measuring points as co-registration points than when using points covering a different area of the phantom (p < 0.0001). The mean calculated RMSD when using the measuring points as co-registration points was 1.3 mm (95 % CI: 1.1 - 1.5 mm), when using points away from the measuring points: 4.0 mm (95 % CI: 3.2 - 4.8 mm), and when using planes for the co-registration: 3.8 mm (95 % CI: 3.2 - 4.4 mm).

CONCLUSION

Image fusion involving real-time US has high accuracy and is easy to use in a phantom. Working within the area given by the co-registration points optimizes the accuracy. Image fusion is a promising tool for clinical US, since it provides the potential of benefiting from different imaging modalities in one examination.