Svein Ødegaard

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.

Antroduodenal motility and movements of luminal contents studied by duplex sonography

The motility of the gastroduodenal wall, movement of gastric contents, and velocity curves of transpyloric flow can be synchronously visualized by duplex sonography. In eight healthy individuals, 18 +/- 6 (mean +/- SD) peristaltic cycles per person in response to the ingestion of 500 mL of meat soup were recorded. Coordinated antroduodenal contractions were seen in 67% of the cycles. Two types of duodenogastric reflux were observed. One type occurred in the middle of the peristaltic cycle (midcycle reflux), whereas the other followed immediately after antegrade flow at the end of the cycle (end-cycle reflux). End-cycle reflux was significantly more frequent in conjunction with coordinated (70%) than with uncoordinated (17%) antroduodenal contractions (P less than 0.005). Thus, in the fed state, a short gush of duodenogastric reflux normally precedes the peristaltic closure of the pylorus.

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.

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.

Antroduodenal motility studied by real-time ultrasonography: Effect of enprostil

Transabdominal real-time ultrasonography was used to investigate antroduodenal motility effects of the prostaglandin E2 analogue enprostil. Ten healthy subjects were studied on two separate days, once after oral administration of one capsule of enprostil 35 micrograms 1 hour before the ingestion of 500 mL of meat soup and once without drug administration before the meal. The ultrasound probe was positioned at the level of the transpyloric plane to visualize the antrum, pylorus, and proximal duodenum simultaneously and thereafter vertically to visualize the antrum, superior mesenteric vein, and aorta simultaneously. The motility was videotaped for 15 minutes. The antroduodenal coordination, frequency and amplitude of antral contractions, and size of antral area were reduced, whereas the time during which the pylorus was wide open (greater than 5 mm) was increased after enprostil. It is concluded that antroduodenal motility can easily be visualized by ultrasonography. Therapeutic doses of enprostil impair antroduodenal peristalsis and coordination and open the pylorus in healthy subjects.

Three-Dimensional Ultrasonography of the Gastric Antrum in Patients with Functional Dyspepsia

BACKGROUND We have developed and validated a three-dimensional ultrasound system for transabdominal imaging. The aims of this study was to evaluate its applicability in scanning and volume estimation of the gastric antrum in humans. METHODS Twenty patients with functional dyspepsia and 20 healthy controls, comparable with regard to gender, age, and smoking habits, agreed to be scanned while ingesting 500 ml of meat soup. A mechanical scanner with a 3.25-MHz transducer coupled to a tilting motor provided in 3 sec multiple images of the antrum during fasting and 1, 10, and 30 min postprandially. On a Unix work station planar contours of the antrum were selected and drawn manually before organ reconstruction and volume computation. RESULTS Two volume scans of 160 could not be analyzed due to air in the antrum. Up to 5 cm proximal to the pylorus, volumes could be computed in 95% of fasting samples and in 98% of postprandial samples, versus 8% and 75%, respectively, up to 7 cm proximal to the pylorus. We found no significant differences in antral volumes between dyspeptic patients and controls, either fasting or postprandially. Fasting antral volumes in Helicobacter pylori-positive dyspeptics were smaller than in H. pylori-negative patients (P = 0.02). CONCLUSIONS Three-dimensional ultrasonography by use of a tilting motor makes non-invasive volume estimation of the gastric antrum possible without making assumptions about its geometry. In the present material no difference was found in antral volumes between patients with functional dyspepsia and controls. It is possible that fasting antral volumes in dyspeptic patients are dependent on H. pylori status.

Measurements of organ volume by ultrasonography.

Abstract In a clinical context, measurements of organ volume are often performed in the diagnosis and follow-up of patients with a variety of diseases. Ultrasonography is a cheap, widely available and non-hazardous imaging modality to use for estimation of volumes, and a range of two- and three-dimensional methods have emerged to accomplish this task. This paper reviews some of the ultrasound methods available in cardiology, gastroenterology, nephrology/urology and gynaecology/obstetrics. Using two-dimensional (2D) ultrasound, the simplest method of calculating the volume of an organ is based on the multiplication of three diameters perpendicular to each other. These 2D methods are often based on geometrical assumptions which may introduce significant errors in volume estimation. Therefore, volume estimation based on three-dimensional (3D) ultrasound has been developed to increase accuracy and precision. At present, the process of making 3D images based on ultrasonography is divided into five steps: data acquisition, data digitization, data storage, data processing and data display. In conclusion, ultrasonography is a useful and reliable tool to calculate volumes of organs. In particular, 3D ultrasonography seems promising in this respect and appears to be superior to 2D ultrasonography in accuracy and precision in volume measurements.

In vitro evaluation of three-dimensional ultrasonography based on magnetic scanhead tracking

The objective of this study was to evaluate the accuracy and precision of a magnetic position sensor system for acquisition of three-dimensional (3D) ultrasound images in volume estimation of phantoms in vitro. Installation of either 0.9% solution of saline at 37 degrees C or distilled water at 20 degrees C to a condom was performed. Scanning was performed either by a continuous or stepwise acquisition. This 3D ultrasound system demonstrated good correlation (r = 0.99-1.0, n = 8) between estimated (EV) and true volumes (TV). The errors were in the range 1.3%+/-0.3% (SEM) to 1.9%+/-0.6%, independent of sound velocity. Scanning through a porcine abdominal wall positioned at the fluid surface yielded a systematic underestimation of the volume: mean (EV - TV) = -7.2+/-0.8 ml. Eight repeated scans of the same volume yielded a coefficient of variation of 1.1%. Interobserver error of the tracing procedure was 2.6%+/-0.9%. This 3D ultrasound system gave high accuracy and precision in volume estimation in vitro, and yielded low interobserver error. A change in ultrasound velocity of approximately 60 m/s did not influence the accuracy significantly. Scanning through an abdominal wall underestimated volumes slightly.

Quantitative Contrast-Enhanced Ultrasound Comparison Between Inflammatory and Fibrotic Lesions in Patients with Crohn's Disease

The aim of this study was to determine whether there are differences in absolute blood flow between patients with Crohns disease with inflammation or fibrosis using contrast-enhanced ultrasound. Eighteen patients with fibrotic disease and 19 patients with inflammation were examined. Video sequences of contrast data were analyzed using a pharmacokinetic model to extract the arterial input and tissue residue functions with a custom software, enabling calculation of the absolute values for mean transit time, blood volume and flow. Feasibility of the examination was 89%. The fibrosis group had lower blood volume (0.9 vs. 3.4 mL per 100 mL tissue; p = 0.001) and flow (22.6 vs. 45.3 mL/min per 100 mL tissue; p = 0.003) compared with the inflammation group. There was no significant difference in mean transit time (3.9 vs. 5.5 s). In conclusion, absolute perfusion measurement in the gastrointestinal wall using contrast-enhanced ultrasound is feasible. There seems to be reduced blood volume and blood flow in patients with fibrotic disease.