M. Bachmann Nielsen

The EFSUMB guidelines and recommendations on the clinical practice of contrast enhanced ultrasound (CEUS): Update 2011 on non-hepatic applications

Authors F. Piscaglia1, C. Nolsøe2, C. F. Dietrich3, D. O. Cosgrove4, O. H. Gilja5, M. Bachmann Nielsen6, T. Albrecht7, L. Barozzi8, M. Bertolotto9, O. Catalano10, M. Claudon11, D. A. Clevert12, J. M. Correas13, M. D’Onofrio14, F. M. Drudi15, J. Eyding16, M. Giovannini17, M. Hocke18, A. Ignee19, E. M. Jung20, A. S. Klauser21, N. Lassau22, E. Leen23, G. Mathis24, A. Saftoiu25, G. Seidel26, P. S. Sidhu27, G. ter. Haar28, D. Timmerman29, H. P. Weskott30

In-vivo examples of flow patterns with the fast vector velocity ultrasound method.

PURPOSE Conventional ultrasound methods for acquiring color flow images of the blood motion are limited by a relatively low frame rate and are restricted to only giving velocity estimates along the ultrasound beam direction. To circumvent these limitations, the Plane Wave Excitation (PWE) method has been proposed. MATERIAL AND METHODS The PWE method can estimate the 2D vector velocity of the blood with a high frame rate. Vector velocity estimates are acquired by using the following approach: The ultrasound is not focused during the ultrasound transmission, and a full speckle image of the blood can be acquired for each pulse emission. The pulse is a 13 bit Barker code transmitted simultaneously from each transducer element. The 2D vector velocity of the blood is found using 2D speckle tracking between segments in consecutive speckle images. Implemented on the experimental scanner RASMUS and using a 100 CPU linux cluster for post processing, PWE can achieve a frame of 100 Hz where one vector velocity sequence of approximately 3 sec, takes 10 h to store and 48 h to process. In this paper a case study is presented of in-vivo vector velocity estimates in different complex vessel geometries. RESULTS The flow patterns of six bifurcations and two veins were investigated. It was shown: 1. that a stable vortex in the carotid bulb was present opposed to other examined bifurcations, 2. that retrograde flow was present in the superficial branch of the femoral artery during diastole, 3. that retrograde flow was present in the subclavian artery and antegrade in the common carotid artery during diastole, 4. that vortices were formed in the sinus pockets behind the venous valves in both antegrade and retrograde flow, and 5. that secondary flow was present in various vessels. CONCLUSION Using a fast vector velocity ultrasound method, in-vivo scans have been recorded where complex flow patterns were visualized in greater detail than previously visualized by conventional color flow imaging techniques.

Ultrasound guided electrocoagulation in patients with chronic non-insertional Achilles tendinopathy: a pilot study

Background: High resolution colour Doppler ultrasound shows intratendinous Doppler activity in patients with chronic Achilles tendinopathy. Treatment of this neovascularisation with sclerosing therapy seems to relieve the pain. However, the procedure often has to be repeated. Objective: To investigate the effect of electrocoagulation of the neovessels on tendon pain and tendon vascularity in patients with chronic Achilles tendinopathy. Methods: Colour Doppler ultrasound guided electrocoagulation was used on vessels in the ventral portion of the Achilles tendon in 11 patients (seven men, four women, mean age 41 years) with painful chronic mid-portion Achilles tendinosis. A unipolar coagulation device was used. Results: One patient dropped out after two months (dissatisfied with the results). The remaining 10 patients (91%) were satisfied. These 10 patients were still satisfied at six months of follow up and had returned to their previous level of activity. All 10 patients were “cured” after one treatment. The patient who dropped out received two treatments because of lack of progress. There was significantly reduced pain (Likert pain scale, 0–10) during activity, from a median of 7 (range 4 to 10) at baseline to 0 (0 to 8) at six months’ follow up (p<0.005); and at rest, from 1.5 (1 to 5) to 0 (0 to 8) (p = 0.005). In all patients, vascularisation was unchanged at the six months follow up, with no significant change in semiquantitative or quantitative colour scoring. Conclusions: Coagulation in the area with vessels entering the tendon appears to be effective treatment for painful chronic mid-tendinous Achilles tendinopathy. No effect on the intratendinous Doppler activity could be detected, suggesting that the effect is independent of changes in blood flow. Localisation of hyperaemia appears to be the key to the pathology and for targeting the treatment. One explanation could be that the effect is obtained by destruction of nerves accompanying the vessels.

Reproducibility of ultrasound and magnetic resonance imaging measurements of tendon size

Purpose: To investigate the intra- and inter-tester reproducibility of measurements of the Achilles tendon, tibialis anterior tendon, and the tibialis posterior tendon in football players using ultrasound (US) and magnetic resonance imaging (MRI). Material and Methods: Eleven asymptomatic football players were examined. Using a standardized US scanning protocol, the tendons were examined by two observers with US for thickness, width, and cross-sectional area. One observer conducted the procedure twice. The subjects also underwent an MRI examination, and the assessment of tendon size was conducted twice by two observers. Results: The best reproducibility judged by coefficient of variation (CV) and 95% confidence interval was determined for the Achilles tendon on both US and MRI. The variability of US on measurements on the tibialis anterior and tibialis posterior tendons was less than that when using MRI. In 12 out of 18 measurements, there were systematic differences between observers as judged by one-sided F-test. Conclusion: The reproducibility of the three tendons was limited. Precaution should be taken when looking for minor quantitative changes, i.e., training-induced hypertrophy, and when doing so, the Achilles tendon should be used.

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.

EFSUMB statement on medical student education in ultrasound [short 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 summarise EFSUMB policy statements on medical student education in ultrasound.

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.

Sentinel Node Detection in Melanomas Using Contrast-Enhanced Ultrasound

Background: Sentinel node (SN) biopsy has proven to be a useful clinical method based on the combination of radionuclide tracer principles and the dye technique. Contrast-enhanced ultrasound (CEUS) has been used successfully for detection of SN in animals, but the use of CEUS has not been reported in humans. Purpose: To investigate the possible use of CEUS in detecting SN in patients with malignant melanomas (MM), and to improve the method by using different concentrations of contrast agent and various positions of the extremity. Material and Methods: Ten patients with MM on an extremity and one healthy volunteer were included. One milliliter of a contrast agent (Sonovue; Bracco, Milan, Italy) was injected subcutaneously on both sides of the scar from the excised tumor. Contrast-enhanced lymph channels and lymph nodes (LNs) were searched for using low-mechanical-index CEUS and by stimulated acoustic emission. Afterward, lymphoscintigraphy was performed and the patient operated. During surgery, the SNs were located via scintigraphic findings, gamma-probe signals, and blue-dye visualization of lymph channels and LNs. Before the human study, a study of 10 mice was performed to exclude possible tissue damage, as the contrast agent was not registered for subcutaneous administration. Results: In one patient, two contrast-enhanced inguinal LNs were visualized by CEUS, corresponding to two inguinal SNs found by scintigraphic imaging. No contrast-enhanced lymph channels or LNs were visualized in any other patients or in the volunteer. No tissue damage was observed in the 10 mice. Conclusion: This study does not support the use of CEUS for detection of SNs in humans. However, the application of CEUS for the investigation of SNs is still not fully explored in humans, and an alternative setup and/or contrast agent might provide better results.

Contrast-enhanced ultrasound in renal transplants: applications and future directions.

The role of contrast-enhanced ultrasound (CEUS) in the detection and characterisation of focal liver lesions is well established 1 . The renal applications of ultrasound contrast agents (UCAs) have increased and diversified since their introduction 2 3 4 5 6 7 and recent guidelines have underlined their importance in the renal transplantation 4 . Ultrasound contrast agents are simple to use and are well tolerated by patients 8 . They can be safely used in renal impairment and obstruction unlike computed tomography (CT) and magnetic resonance (MR) agents. The imaging methods operate in real-time, often allowing a diagnosis to be promptly attained without exposure to ionising radiation, the fear of claustrophobia and at a lower cost than CT or MR imaging. Normally, B-mode and Doppler ultrasonography are the modality of choice for imaging the transplant kidney; excellent at assessing graft vascularity, diagnosing obstruction, detecting peri-nephric collections, focal masses and cysts. B-mode and Doppler ultrasonography have limitations in the assessment of the renal transplant microcirculation, cortical perfusion and deciphering focal masses or complex cysts. Before the introduction of UCAs focal lesions would be further characterised by contrast-enhanced CT and magnetic resonance (MR) imaging and there was no reliable non-invasive method of assessing the microcirculation. The application of CEUS in renal transplants highlights its versatility in immediate problem solving, without recourse to other potentially nephrotoxic agents. In addition CEUS can uniquely provide additional information not available from other modalities about the microcirculation. This is elegantly illustrated in the article by Fernandez et al. 9 , where renal cortical necrosis is clearly depicted, allows immediate clinical management and adds to the knowledge in this expanding field. It is important to have a clear understanding of the background, current applications and potential for UCAs in the evaluation of the renal transplant to appreciate the value of CEUS in this domain. Microbubbles 10 11 consist of a complex gas (e.g perfluorocarbon gas) stabilized by a phospholipid, or polymer shell and are of the size of a red blood cell, small enough to cross capillary beds but are too large to enter the interstitial fluid and therefore serve as pure intravascular agents. Renal ultrasound contrast agent dynamics differ from CT and MR contrast agents; UCAs remain entirely intravascular, are not excreted by the kidneys and therefore have no nephrographic or excretory phase. Following an intravenous bolus of UCAs the cortical phase (90 % of renal perfusion) begins 10 – 15 s after injection and lasts 20 – 40 s followed by a slower medullary phase lasting 45 – 120 s. The whole CEUS examination lasts about 3 min. CEUS allows imaging of vessels down to 100 μm in diameter which is well below the 1 mm resolution limit of conventional Doppler techniques. Therefore, CEUS is excellent at assessing the vascular complications of renal transplants, can exquisitely image the microcirculation and is very sensitive in the detection of infarction (which shows as a defect on all phases of enhancement). The defect on CEUS appears smaller than on the corresponding Doppler study because of this ability to depict flow in the microcirculation. Perfusion defects appear as focal wedge shaped areas of absent, decreased or delayed contrast enhancement compared with the adjacent renal parenchyma 12 . As Fernandez et al. 9 confirm cortical necrosis is rendered more conspicuous by CEUS, making this an exquisite tool for bedside assessment of transplant vascularity. Quantitative methods can be applied to the kidney (native or transplant) using low or high acoustic power techniques 13 . Since microbubbles are pure blood pool agents their transit through a region of interest can be followed using a low acoustic power technique. A time intensity curve (TIC) can be generated and a number of indices can be derived such as arrival time, time to peak intensity, area under the curve and rate of washout. Alternatively a high energy reperfusion technique can be used to measure perfusion 14 . This may play a role in the assessment of transplant perfusion and the early detection of complications. B-mode ultrasound is poor at discriminating between the important causes of early graft dysfunction, especially acute tubular necrosis, rejection, and drug toxicity: these important distinctions still rely on biopsy. Recent work with UCAs has provided hope that functional data from microbubble contrast agent dynamics might produce useful information for their detection and differentiation, thus directing management and possibly avoiding the need for biopsy. Recent studies using microbubbles to measure renal flow in renal transplants have shown promising results in terms of monitoring graft function and directing anti-rejection therapy 15 16 17 18 19 . CEUS can be helpful in the characterisation of focal tumours in the native and transplant kidney, with typical differential hyper or hypo enhancement compared to the adjacent cortex. Cystic or avascular necrotic components can be distinguished from viable tumour as they appear as conspicuous signal voids. However, current CEUS guidelines 4 indicate that there are no specific patterns which reliably differentiate benign from malignant renal tumours. Although tumours are uncommon in renal transplants, cysts are frequently encountered and the superior spatial and temporal resolution of CEUS, real-time imaging allows visualisation of flow within septa, nodules and cyst wall which cannot be imaged on conventional US techniques, contrast-enhanced CT or contrast-enhanced MR 20 21 22 23 . A CEUS Bosniak classification is likely more sensitive than a CT classification 23 when adapted for ultrasonography 21 , and should be more accurate in the evaluation of cystic structures in the superficially located renal transplant. CEUS is usually unnecessary in the diagnosis of renal artery thrombosis or stenosis but can be used in difficult cases. CEUS is also excellent in assessing venous patency in renal transplants in problem cases and also distinguishing bland from tumour thrombus. In conclusion CEUS is a safe and excellent method for assessing the renal transplant vasculature and can be used in the diagnosis of renal infarction, renal arterial/venous thrombosis, as well as the non-invasive quantification of cortical perfusion and the microcirculation. CEUS provides unique functional data in grafts with promising results in terms of monitoring graft function and directing anti-rejection therapy. CEUS may characterise indeterminate renal lesions, complex cysts and focal inflammatory lesions to rival CT and MR imaging. The possibility of visualising and diagnosing acute cortical necrosis adds to the already formidable armamentarium of the physician who uses CEUS in assessing the renal transplant. All of this without any nephrotoxicity!

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.