Odd Helge Gilja

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

EFSUMB guidelines and recommendations on the clinical use of ultrasound elastography. Part 1: Basic principles and technology.

The technical part of these Guidelines and Recommendations, produced under the auspices of EFSUMB, provides an introduction to the physical principles and technology on which all forms of current commercially available ultrasound elastography are based. A difference in shear modulus is the common underlying physical mechanism that provides tissue contrast in all elastograms. The relationship between the alternative technologies is considered in terms of the method used to take advantage of this. The practical advantages and disadvantages associated with each of the techniques are described, and guidance is provided on optimisation of scanning technique, image display, image interpretation and some of the known image artefacts.

EFSUMB Guidelines and Recommendations on the Clinical Use of Ultrasound Elastography. Part 2: Clinical Applications

The clinical part of these Guidelines and Recommendations produced under the auspices of the European Federation of Societies for Ultrasound in Medicine and Biology EFSUMB assesses the clinically used applications of all forms of elastography, stressing the evidence from meta-analyses and giving practical advice for their uses and interpretation. Diffuse liver disease forms the largest section, reflecting the wide experience with transient and shear wave elastography . Then follow the breast, thyroid, gastro-intestinal tract, endoscopic elastography, the prostate and the musculo-skeletal system using strain and shear wave elastography as appropriate. The document is intended to form a reference and to guide clinical users in a practical way.

Impaired accommodation of proximal stomach to a meal in functional dyspepsia

In patients with functional dyspepsia, scanning by a novel ultrasonographic method was carried out to investigate postprandial accommodation of the proximal stomach. Twenty patients with functional dyspepsia and 20 controls were scanned fasting in a sitting position after drinking 500 ml meat soup. Images were recorded up to 25 min after the ingestion period using an ultrasound sector scanner with a 3.25-MHz transducer. The area in a sagittal section and the maximal diameter in an oblique frontal section were chosen as the main variables for calculating the emptying fraction of the proximal stomach, defined as: (aV2.5min-aVactual/aV2.5min. All subjects were asked to score total symptoms (1–9) provoked by the meal. From 7.5 to 25 min after the ingestion period the patients exhibited both smaller area in the sagittal section (P<0.018) and shorter diameter in the frontal section (P<0.046) compared with healthy controls, and they suffered more symptoms in response to the meal (P=0.002). Dyspeptic patients revealed higher emptying fractions (P=0.0005, ANOVA), andH. pylori status did not influence the emptying fractions. Diagnostic sensitivity of the method at 20 min postprandially was 70% and the specificity was 65%. Patients with functional dyspepsia have impaired accommodation of the proximal stomach to a meal, temporarily related to symptom induction.

In vitro evaluation of three-dimensional ultrasonography in volume estimation of abdominal organs

The purpose of this study was to evaluate the accuracy and precision of a three-dimensional (3D) ultrasound system in volume estimation of abdominal organs in vitro. A mechanical sector scanner coupled to a stepping motor recorded images of porcine stomach and kidneys. The transducer was tilted through 88 degrees yielding 81 frames, and volume estimation was performed digitally after interactive manual contour indication and organ reconstruction in 3 dimensions. This 3D system showed good correlation (r = 0.998) between estimated and true volumes. Volume estimation of stomach and kidneys using 3.25 MHz probe demonstrated limits of agreement of 0.877 to 1.146 and 1.007 to 1.125, respectively, depicting estimated volumes as a proportion of true volumes in 95% of the examinations. Intra- and interobserver variation of the tracing procedure revealed low values. We conclude that this 3D ultrasound system performs high accuracy and precision in volume estimation.

Intragastric distribution and gastric emptying assessed by three- dimensional ultrasonography

BACKGROUND & AIMS Three-dimensional (3D) ultrasound imaging of the total stomach volume has not yet been achieved. The aim of this study was to investigate whether a magnetic position sensor system for acquisition of 3D ultrasonograms could be used to determine gastric emptying rates and intragastric distribution. METHODS A system for position and orientation measurement was interfaced to an ultrasound scanner. In vitro accuracy was evaluated by scanning a porcine stomach. Fourteen volunteers, with a median age of 35 years, were scanned fasting and postcibally by two-dimensional (2D) and 3D ultrasound after ingesting a 500-mL soup meal. RESULTS This 3D system yielded a strong correlation (r = 0.997) between true and estimated volumes in vitro. The limits of agreement were -9.1:70.1 mL in the volume range 1200-1900 mL. The intersubject variability of the total gastric volumes ranged from 12.5% to 46.0%, less than for antral area variability. The average half-emptying time was 22.1 +/- 3.8 minutes. Intragastric distribution of the meal, expressed as proximal distal volume, varied on average from 3.6 +/- 2.1 (5 minutes postpradially) to 2.7 +/- 1.9 (30 minutes postprandially). CONCLUSIONS This 3D ultrasound system using magnetic scanhead tracking showed excellent in vitro accuracy, calculated gastric emptying rates more precisely than by 2D ultrasound, and enabled estimation of intragastric distribution of a soup meal.

In vivo comparison of 3D ultrasonography and magnetic resonance imaging in volume estimation of human kidneys

The objective of this study was to evaluate the accuracy of a three-dimensional ultrasound system (3D-US) compared with Magnetic Resonance Imaging (MRI) in volume estimation of human kidneys in vivo. Twenty healthy volunteers were scanned fasting in supine position with MRI and with a 3D-US. An ultrasound sector scanner with a mechanical transducer coupled to a tilting motor provided images of multiple sections of kidneys. A 3.25-MHz transducer was tilted through 88 degrees yielding 81 frames, and volume estimation was performed on a Unix workstation after manual contour indication. Data acquisition with MRI was performed by using a 1-T magnet. Eighteen included kidneys [mean +/- standard deviation (SD)] measured 155.7 +/- 26.4 mL (range 110.0-205.0 mL) by 3D ultrasound and 171.8 +/- 24.6 mL (range 127.5-211.0 mL) by MRI, yielding a good correlation (r = 0.82, p < 0.001) between the two methods. The mean difference was -16.1 +/- 15.6 mL (SD) and the limits of agreement were -49.0 mL. We conclude that this 3D-US is accurate in volume estimation of human kidneys in vivo.

Freehand Real-Time Elastography: Impact of Scanning Parameters on Image Quality and In Vitro Intra- and Interobserver Validations

Real-time elastography is a method for visualization of the elastic properties of soft tissue and may potentially enable differentiation between malignant and benign pathologic lesions. Our aim was to validate the method on a tissue-mimicking (TM) phantom and to evaluate the influence of different scanning parameters and investigator variability. A TM-phantom containing eight spherical inclusions with known storage modulus was examined using two different transducers on an ultrasound (US) scanner equipped with software for real-time elasticity imaging. The ultrasound transducers were moved vertically in a repetitive manner to induce strain. Two investigators performed series of standardized elastography scans applying a 0-4 categorical quality scale to evaluate the influence of seven parameters: dynamic range of elasticity, region-of-interest, frequency of transducer movement, rejection of elastogram noise, frame rate, persistence and smoothing. Subsequently, repeated examinations of four selected inclusions were performed using a visual analog scale (VAS) where investigators marked a 100 mm horizontal line representing the span in image quality based on experience from the first examination. The hardest and softest inclusions were imaged more clearly than the inclusions with elasticity more similar to the background material. Intraobserver agreement on elastogram quality was good (kappa: 0.67 - 0.75) and interobserver agreement average (kappa: 0.55 - 0.56) when using the categorical scale. The subsequent VAS evaluation gave intraclass-correlation coefficients for the two observers of 0.98 and 0.93, respectively, and an interclass-correlation coefficient of 0.93. Real-time elastography adequately visualized isoechoic inclusions with different elastic properties in a TM-phantom with acceptable intra- and interobserver agreement. Dynamic range of elasticity was the parameter with most impact on the elastographic visualization of inclusions.

Contrast-enhanced and targeted ultrasound

Ultrasonic imaging is becoming the most popular medical imaging modality, owing to the low price per examination and its safety. However, blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit frequencies. For perfusion imaging, markers have been designed to enhance the contrast in B-mode imaging. These so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable shells. In this review, the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are described. Furthermore, an outline of clinical imaging applications of contrast-enhanced ultrasound is given. It is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition, and how these phenomena may be utilized in ultrasonic imaging. Aided by high-speed photography, our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery techniques. More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves, and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage occurs. These are beginning to be accepted into clinical practice. In the long term, targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested.

Monitoring postprandial size of the proximal stomach by ultrasonography.

The purpose of this study was to develop a sonographic method to monitor postprandial size of the proximal stomach. Twenty‐three healthy persons were scanned in a sitting position with a 3.25 MHz transducer after ingestion of 500 ml meat soup. The area in a sagittal section and the maximal diameter in an oblique frontal section were chosen as standard measurements. The soup emptied from the proximal stomach in a linear manner (r = 0.99) and at a rate of 2.0 +/‐ 1.3%/min. Intraobserver error of the scans (mean +/‐ SD) was 5.6% +/‐ 2.3% and 9.5% +/‐ 4.5% for sagittal area and frontal diameter, respectively, and the corresponding interobserver error was 5.3% +/‐ 4.0% and 8.3% +/‐ 5.3%, respectively. This sonographic method demonstrated a moderate day‐to‐day variation, had low intra‐ and interobserver error, and allowed estimation of initial emptying fractions of the proximal stomach.