G. Weijers

Quantitative gray-scale analysis in skeletal muscle ultrasound: a comparison study of two ultrasound devices.

Muscle ultrasound is a useful technique to detect neuromuscular disorders. Quantification of muscle echo intensity (EI) using gray‐scale analysis is more reliable and more sensitive compared with visual evaluation of the images. We devised a method to reliably use EI normal values established with one ultrasound device for use with another device. Based on measurements in a dedicated phantom and in 7 healthy subjects, a conversion equation was calculated to convert the mean EI. The reliability of this equation was next evaluated in a follow‐up study of 22 healthy children. Mean muscle EI could be reliably converted from one ultrasound device to another. This allows for normal values obtained with one device to be used with other devices, which is an important step forward toward the use of quantitative muscle ultrasound in daily clinical care. Muscle Nerve, 2009

Interobserver, Intraobserver and Intrapatient Reliability Scores of Myocardial Strain Imaging with 2-D Echocardiography in Patients Treated with Anthracyclines

Myocardial strain imaging with 2-D echocardiography is a relatively new noninvasive method to assess myocardial deformation. To determine the interobserver, intraobserver and intrapatient reliability scores, we evaluated myocardial strain measurements of 10 asymptomatic survivors of childhood cancer. Ten patients were selected randomly out of a follow-up cohort of childhood cancer survivors. All 10 patients underwent a transthoracic echocardiographic examination. Two-dimensional gray scale images were made in parasternal apical four-chamber, apical two-chamber, midcavity short-axis and basal short-axis views. Offline analysis was performed using software for echocardiographic quantification (Echopac 6.1.0, GE Medical Systems, Horten, Norway). All echocardiographic studies were analyzed offline by three observers, separately (A.M., G.W., M.P.). A custom-made software package was designed for averaging the strain curves of three consecutive cardiac cycles. Values of peak systolic strain, time-to-peak strain and time-to-end systole of the different segments of the left ventricle were used for statistical analysis. Interobserver, intraobserver and intrapatient reliability were expressed as intraclass correlation coefficients (ICCs). Interobserver ICCs of peak strain, time to peak strain and time to aortic valve closure (AVC) were generally good to very good in all views and segments, except for in the two-chamber view. Intraobserver ICCs were rated as very good for almost all segments, except for the longitudinal peak strain values of the two-chamber view. Intrapatient ICCs were generally good for the two-chamber, four-chamber and midcavity short-axis views, but fair to moderate for the segments of the basal short-axis view (SaxMV). We recommend use of the four-chamber view for longitudinal peak strain values, and the basal and midcavity short-axis views for radial and circumferential peak strain values. Furthermore, we strongly recommend using the average of three cardiac cycles for peak strain values in clinical studies.

Transcutaneous vs. Intraoperative Quantitative Ultrasound for Staging Bovine Hepatic Steatosis

The aim of this study was to test the hypothesis that the Computer Aided UltraSound (CAUS) method developed by the authors [1-4] for the estimation of UltraSound Tissue Characteristics (UTC) parameters on transcutaneous (Transc) ultrasound (US) images can predict the liver fat content with similar accuracy and precision as with intraoperative (Intraop) US. A large animal study in post partum dairy cows (N=151) was performed to test these hypotheses. Five Transc B-Mode US liver image were acquired before surgery. During abomasal displacement surgery five Intraop US B-Mode liver images and a liver biopsy was taken. In liver tissue samples, triacylglycerol (TAG) content was measured by biochemical analysis. Firstly the equipment preset, which was kept fixed during whole study time, was carefully calibrated[5]. For the echo level calibration a TMP was used, and all UTC parameters were expressed relatively to those of the phantom. Prior to UTC parameters estimation several pre-processing steps were performed: Back-Scan Conversion (BSC); Look Up Table (LUT) correction; superficial tissue layers (Fat layer) attenuation correction and Automatic Gain Correction (AGC) were performed. Also several postprocessing steps were incorporated like: Automatic segmentation and residual attenuation correction were performed. Stepwise multiple linear regression analysis on a training set (N=76) was performed. In all cases the Residual Attenuation coefficient (ResAtt, R=0.81) was the only selected parameter. The results were tested on the residual cows (test set N=75) to predict the TAG content in the liver. Receiver Operating Characteristics (ROC) analysis then was applied to estimate the Area Under the Curve (AUC) and the sensitivity and specificity of the CAUS method. Equivalent high predictive values for AUC (95%), sensitivity(87%) and specificity (83%) for Intraop and Transc applications were found. Consequently, it can be concluded, applied Fat layer attenuation correction to Transc US images was performed adequately.

Cardiac evaluation in children with Prader–Willi syndrome

Aim:u2002 To assess cardiac anatomy and myocardial systolic function in children with Prader–Willi syndrome (PWS).

Quantitative Assessment of Oral Orbicular Muscle Deformation After Cleft Lip Reconstruction: An Ultrasound Elastography Study

Reconstruction of a cleft lip leads inevitably to scar tissue formation. Scar tissue within the restored oral orbicular muscle might be assessed by quantification of the local contractility of this muscle. Furthermore, information about the contraction capability of the oral orbicular muscle is crucial for planning the revision surgery of an individual patient. We used ultrasound elastography to determine the local deformation (strain) of the upper lip and to differentiate contracting muscle from passive scar tissue. Raw ultrasound data (radio-frequency format; rf-) were acquired, while the lips were brought from normal state into a pout condition and back in normal state, in three patients and three normal individuals. During this movement, the oral orbicular muscle contracts and, consequently, thickens in contrast to scar tissue that will not contract, or even expand. An iterative coarse-to-fine strain estimation method was used to calculate the local tissue strain. Analysis of the raw ultrasound data allows estimation of tissue strain with a high precision. The minimum strain that can be assessed reproducibly is 0.1%. In normal individuals, strain of the orbicular oral muscle was in the order of 20%. Also, a uniform strain distribution in the oral orbicular muscle was found. However, in patients deviating values were found in the region of the reconstruction and the muscle tissue surrounding that. In two patients with a successful reconstruction, strain was reduced by 6% in the reconstructed region with respect to the normal parts of the muscle (from 22% to 16% and from 25% to 19%). In a patient with severe esthetical and functional disability, strain decreased from 30% in the normal region to 5% in the reconstructed region. With ultrasound elastography, the strain of the oral orbicular muscle can be quantified. In healthy subjects, the strain profiles and maximum strain values in all parts of the muscle were similar. The maximum strain of the muscle during pout was 20% plusmn 1%. In surgically repaired cleft lips, decreased deformation was observed.

Elastography of healthy and reconstructed cleft lip

We have undertaken a study to assess the potentials of ultrasound elastography to evaluate cleft lip reconstruction. Rf-data is acquired with a linear array transducer (7-11 MHz) and a Philips Sonos 7500 equipment from patients and normal individuals during contraction of the lips. Cross-correlation analysis was performed to assess the deformation of the tissue along the ultrasound beams. In normal individuals, the muscle region is expanding due to the contraction of the muscle (contraction direction is perpendicular to the ultrasound beams). The surrounding tissue is compressed due to the muscle contraction. In patients with reconstructed cleft lip, the expanding muscle is interrupted in the region where scar tissue is supposed to be present. In conventional ultrasound the scar region is not always visible in the muscle tissue. Elastography of reconstructed cleft lip visualizes the effects of surgery but further research is needed to identify the clinical usefulness of this technique.

Computer-aided ultrasound diagnosis of hepatic steatosis

In this study, a Computer-Aided UltraSound (CAUS) diagnosis method for the detection and staging of hepatic steatosis (non-alcoholic fatty liver disease, NAFLD) is investigated using a bovine model (n=151). In humans as well as in cows, hepatic steatosis increases the risk of comorbidity [1,2,3,4]. Assessment of liver fat content is mostly done by taking liver biopsies [2,4,5]. The authors’ goal was to estimate the liver fat content using on non-invasive, echographic parameters. Since skin and subcutaneous fat layer influence the characteristics of echographic B-mode liver-images, both transcutaneous and intraoperative images were acquired to study this effect. During image acquisition a fixed preset of the ultrasound equipment controls was used. One liver biopsy was taken from each animal to assess the liver fat weight percentage (fat score). The software package CAUS was developed to perform objective and unambiguous analysis on echographic B-mode images by estimating several echographic parameters. Prior to the analysis of the images certain preprocessing steps were performed in order to achieve relative echo strength in decibel (dB), rather than image gray level, as a quantitative parameter. Furthermore, corrections were made for ultrasound propagation through skin/fat layer and through an average “healthy liver”. After these corrections, the biopsy results were correlated with the estimated echographic parameters and ROC curves and parameters were estimated to achieve the goal. High correlations with the liver fat score were found for several echographic parameters. ROC curve analysis show promising results for sensitivity (0.93), specificity (0.86) and area under the curve (0.93) in distinguishing fatty livers from healthy livers. This study showed the feasibility of generic computer-aided ultrasound for non-invasively diagnosing, maybe even screening, of liver steatosis.

Is 2D speckle tracking echocardiography useful for detecting and monitoring myocardial dysfunction in adult m.3243A>G carriers? - a retrospective pilot study.

ObjectivesCardiomyopathy is a common complication of mitochondrial disorders, associated with increased mortality. Two dimensional speckle tracking echocardiography (2DSTE) can be used to quantify myocardial deformation. Here, we aimed to determine the usefulness of 2DSTE in detecting and monitoring subtle changes in myocardial dysfunction in carriers of the 3243A>G mutation in mitochondrial DNA.MethodsIn this retrospective pilot study, 30 symptomatic and asymptomatic carriers of the mitochondrial 3243A>G mutation of whom two subsequent echocardiograms were available were included. We measured longitudinal, circumferential and radial strain using 2DSTE. Results were compared to published reference values.ResultsSpeckle tracking was feasible in 90xa0% of the patients for longitudinal strain. Circumferential and radial strain showed low face validity (low number of images with sufficient quality; suboptimal tracking) and were therefore rejected for further analysis. Global longitudinal strain showed good face validity, and was abnormal in 56–70xa0% (depending on reference values used) of the carriers (nu2009=u200927). Reproducibility was good (mean difference of 0.83 for inter- and 0.40 for intra-rater reproducibility; ICC 0.78 and 0.89, respectively). The difference between the first and the second measurement exceeded the measurement variance in 39xa0% of the cases (nu2009=u200923; feasibility of follow-up 77xa0%).DiscussionEven in data collected as part of clinical care, two-dimensional strain echocardiography seems a feasible method to detect and monitor subtle changes in longitudinal myocardial deformation in adult carriers of the mitochondrial 3243A>G mutation. Based on our data and the reported accuracy of global longitudinal strain in other studies, we suggest the use of global longitudinal strain in a prospective follow-up or intervention study.

Computer-Aided UltraSound (CAUS) to determine liver fat content in animal model and in patients

The authors developed and tested a quantitative ultrasound technique (CAUS) for the staging of steatosis using Ultrasound Tissue Characteristics Parameters (UTCPs) from B-mode images [1]. CAUS method pre-processing steps in short: transformation of the gray level to logarithmic echo level by linearization of the post-pocessing Look Up Table (LUT); Back-Scan conversion of sector image format, i.e., transformation of carthesian DICOM into polar data, in order to linearize and rotate speckles horizontally; depth dependent gray level corrections, i.e., correction for the combined skin, fat and muscle layer (fat layer), automatic gain correction (AGC) by using gray level depth profile in phantom; attenuation correction, and finally automatic image segmentation for the removal of medium and large sized hepatic blood vessels and bile ducts. The following UTCPs were then estimated; Mean echo level (Mu), Standard Deviation of mean echo level (SD), Signal to Noise Ratio (SNR), Residual Attenuation coefficient (ResAtt), Axial (Ax) and Lateral (Lat) speckle size. This method was recently validated with an extensive animal study in 151 post-partem cows [2, 3]. Since also biopsies were taken, correlation with triacylglycerol (TAG) content could be investigated. High UTCP correlations were found for Mean echo level (Mu, r=0.7), Residual Attenuation coefficient (ResAtt, r=0.81), Signal to Noise Radio (SNR, r=0.74) with triacylglycerol (TAG) content. ROC analysis revealed high values for Sensitivity (87%) and Specificity (87%) for the classification into different risk groups. In the present study, data were obtained from 13 human patients (3 males) on Home Parenteral Nutrition (HPN, administrated at least 6 times per week) with a mean age of 42 yrs. Five independent intercostal US liver images per patient were acquired using a Sonos7500 (Philips Ultrasound, Andover, MA, USA) with a phased array transducer (S8, bandwidth 3-8 MHz). On all US patient data the CAUS method was performed and the results were validated using a quantification of liver fat concentration by proton Magnetic Resonance Spectroscopy (MRS, 3T Trio MR system, Siemens, Erlangen, Germany) at the same day. Again high correlation values with fat level were obtained for several UTCPs: Mu r=0.78, ResAtt r=0.88, SNR r=0.91, Lat r=-0.62. In conclusion, CAUS parameters may has potential in staging, and possibly even screening, of hepatic steatosis in human liver, thus preventing taking liver biopsies.

Quantitative analysis of coated needles for ultrasound guided intervention

For ultrasound guided interventions, the visibility of needles is of crucial importance for accurate positioning. Standard needles are only visible when the angle between transmitted ultrasound and needle is around 90 degrees. Therefore, needles were coated with a polyethersulfone coating containing specially developed polymeric microcapsules. Three different sizes of capsules were used, 10-25 m, 25-50 m and 50-75 m. Ultrasound data were acquired using a Philips iE33 echo apparatus equipped with an L11-3 linear array transducer. A fixed control setting with known flat depth-gain control and linear post-processing look-up table was used to allow transformation of the image gray levels into a dB scale of echo levels. The needles were positioned in a water tank filled with degassed water and mounted in a rotation arm. Data were acquired for angles from 90° down to 10° in steps of 10°. Data for each angle were rotated to 90° and averaged over all image lines to calculate an average reflection profile. The maximum of this profile was taken as the reflected, or backscattered echo level whereas the distance between the -6 dB fall-off points was taken as the thickness. The coated, as well as the normal needle, are clearly visible in the water tank. However, quantitative analysis demonstrates that the echogenicity of the coated needle is independent of the angle: the echo level is equal for all angles. This effect is observed for all used sizes of the microcapsules. The uncoated needle shows a decay of the echo level for angles smaller than 80° with a decrease of 8 dB for angles smaller than 60°. The thickness is overestimated at 90°, but decreases to the actual value for angles smaller than 60°. Additionally, a normal and coated needle were inserted in a chicken breast at an angle of 45° to demonstrate differences in performance under clinical circumstances. The normal needle was not visible at all, whereas the coated needle could be clearly depicted. In conclusion, coating needles with microcapsules improves the ultrasound visibility and makes the echo level angle independent.