Search PubMed⌕ Search

Biomedical subjects

W Ameling

Publications and source records attributed to W Ameling.

At least 19 recordsLinked to original sources
PubMed2000

Analysis of shape and motion of the mitral annulus in subjects with and without cardiomyopathy by echocardiographic 3-dimensional reconstruction.

The shape and dynamics of the mitral annulus of 10 patients without heart disease (controls), 3 patients with dilated cardiomyopathy, and 5 patients with hypertrophic obstructive cardiomyopathy and normal systolic function were analyzed by transesophageal echocardiography and 3-dimensional reconstruction. Mitral annular orifice area, apico-basal motion of the annulus, and nonplanarity were calculated over time. Annular area was largest in end diastole and smallest in end systole. Mean areas were 11.8 +/- 2.5 cm(2) (controls), 15.2 +/- 4.2 cm(2) (dilated cardiomyopathy), and 10.2 +/- 2.4 cm(2) (hypertrophic cardiomyopathy) (P = not significant). After correction for body surface, annuli from patients with normal left ventricular function were smaller than annuli from patients with dilated cardiomyopathy (5.9 +/- 1.2 cm(2)/m(2) vs 7.7 +/- 1.0 cm(2)/m(2); P <.02). The change in area during the cardiac cycle showed significant differences: 23.8% +/- 5.1% (controls), 13.2% +/- 2.3% (dilated cardiomyopathy), and 32.4% +/- 7.6% (hypertrophic cardiomyopathy) (P <.001). Apico-basal motion was highest in controls, followed by those with hypertrophic obstructive and dilated cardiomyopathy (1.0 +/- 0.3 cm, 0.8 +/- 0.2 cm, 0.3 +/- 0.2 cm, respectively; P <.01). Visual inspection and Fourier analysis showed a consistent pattern of anteroseptal and posterolateral elevations of the annulus toward the left atrium. In conclusion, although area changes and apico-basal motion of the mitral annulus strongly depend on left ventricular systolic function, nonplanarity is a structural feature preserved throughout the cardiac cycle in all three groups.

Adult↗
PubMed1996

Pattern recognition system for focal liver lesions using "crisp" and "fuzzy" classifiers.

RATIONALE AND OBJECTIVES: To determine the diagnostic performance of an artificial intelligence system for classification of focal liver lesions, in comparison to human observers. METHODS: One hundred forty-three focal hepatic lesions were evaluated with dynamic computed tomography. The study comprised 59 hemangiomas, 24 other benign lesions (focal nodular hyperplasia, adenoma), and 60 malignant liver lesions (18 primary, 42 secondary). All lesions but the hemangiomas were histologically examined by needle biopsy. For delineation of the lesion, a region of interest was defined interactively. The pattern recognition was performed in two steps with initial extraction of textural features: training of a classifier and classification of the lesions. The accuracy of classification of hepatic lesions into three groups (hemangioma, other benign processes, malignant lesions) was tested. The results were compared with those achieved by human observers using receiver operating characteristic statistical analysis. RESULTS: The accuracy (total rate of correct diagnoses) was 90.2%. False classifications were found owing to small size, weak contrast enhancement after bolus injection, respiratory movement, and atypical morphology of the lesion. The area under the receiver operating characteristic curve was not significantly different for computer and human observers. CONCLUSIONS: The system demonstrated a diagnostic accuracy comparable to human observers. Further improvement with increasing numbers of typical computed tomographic series for training of the classifier can be expected.

Adenoma↗
PubMed1996

Classification of lung tumors on chest radiographs by fractal texture analysis.

RATIONALE AND OBJECTIVES: The authors determine the usefulness of fractal texture analysis in classification of lung tumors on chest radiographs. METHODS: A method of fractal texture analysis was applied for classification of lung tumors on digitized chest radiographs. It was performed in 15 cases of benign lesions and in 26 cases of malignant tumors. All lesions were proved by histology. For classification, the fractal distances of the tumors were calculated and an energy measure related to the variances as a second characteristic was applied. The results were compared with those of a conventional classification method based on the co-occurrence matrix. RESULTS: Although the conventional method failed in classification of lung tumors, a clear separation between benign and malignant lesions was attained by fractal analysis. A differentiation between primary lung cancer and metastases was not possible. CONCLUSIONS: The results of our study demonstrate the usefulness of fractal texture analysis for classification of lung tumors on chest radiographs.

Fractals↗
PubMed1993

[The diagnosis of focal liver lesions by the texture analysis of dynamic computed tomograms].

Characterisation of focal liver lesions on computed tomography (CT) depends on correct interpretation of morphology and dynamic changes during bolus injection of contrast medium. The aim of this study was to develop a texture analysis concept for computer based interpretation of dynamic CT images. 148 focal liver lesions were investigated by serial CT. The study comprised 61 haemangiomas, 25 other benign lesions (FNH/adenomas) and 62 malignant lesions (primary or secondary). FNH, adenomas and malignant lesions were histologically proven. Diameter was 8-145 mm (mean 31 mm). Regions of interest were interactively defined. After extraction of characteristic textural features, a pattern classifier was trained. All CT series were evaluated using the "leaving-one-out" method. 134 of the 148 lesions were correctly classified (positive predictive value 0.9). Sensitivity for the presence of malignancy was 0.93 (80/86), specificity was 0.9 (56/62). False classification of a lesion was found to depend strongly on the quality of the examination (bolus intensity, positional change of the lesion due to respiratory movements).

Diagnosis, Differential↗
PubMed1992

Initial experience with a multiplane transoesophageal echo-transducer: assessment of diagnostic potential.

BACKGROUND: the prototype of a transoesophageal echocardiographic transducer with a rotatable cross-sectional scanning plane underwent initial evaluation. METHODS: the 5 MHz, phased array, 64 element transducer is incorporated into a 16 by 11 by 40 mm echoscope tip. The instrument also has pulsed wave and colour flow Doppler capabilities. Exterior controls allow continuous mechanical rotation of the scanning plane from 0 degree, corresponding to the conventional transverse plane, through 180 degrees, thereby encompassing all possible planes. RESULTS: 103 patients underwent examination without complications; two additional patients were excluded because of difficulty in swallowing the probe. Advantages include precise alignment of aortic valve long- and short-axis views, long-axis views of the ascending aorta (mean visualized length: 6 cm), and full scanning of the entire circumference of the mitral valve and the left ventricle. Separation of paravalvular and transvalvular leakage in prosthetic valves is distinctly improved. CONCLUSION: multiplanar transoesophageal imaging is feasible and increases the diagnostic yield, especially in mitral and aortic pathology and in the assessment of left ventricular wall motion. Three-dimensional reconstruction is an attractive potential application.

Adult↗
PubMed1992

[Initial clinical trial of a multi-planar transesophageal echoscope].

The prototype of a multiplanar transesophageal echocardiographic transducer was evaluated clinically. This 5 MHz, phased array, 64-element transducer allows to continuously rotate the imaging plane from the transverse (0 degree) position to a maximal 180 degrees position, thus encompassing transverse, longitudinal, and every intermediate position. The transducer is incorporated in the echoscope tip measuring 16 by 11 by 40 mm. The shaft of the instrument is 110-cm long and has a 9-mm diameter. The instrument has pulsed wave, continuous wave, and color Doppler capabilities. 176 clinical patients were examined with the multiplane transducer. No complications occurred. Advantages of this transducer included: 1) comprehensive scanning of the whole mitral circumference and mitral valve; 2) quick and precise alignment of aortic valve long and short axis views, including long axis views of the ascending aorta, with a mean visualized length of 6 cm; 3) improved imaging and evaluation of transvalvular and paravalvular regurgitant jets in mitral and aortic valve prostheses; 4) complete evaluation of all left ventricular segments using multiple planes from transgastric and transesophageal transducer positions. An important potential application is three-dimensional reconstruction of cardiac structures and color Doppler jets.

Adult↗
PubMed1989

[3-dimensional organ representation with ultrasound. Experimental studies--computer simulation].

This is the first report on the 3-dimensional representation of organs with US. The prerequisite for this was a coordinated transducer movement, in such a manner that the organ under examination was represented by US sections differing in only one of the space coordinates. Such transducer movement was made possible by 2 devices. In the first instance, longitudinal movement of the transducer resulted in the production of parallel sections of the organ while, in the other instance, rotation of the transducer head permitted sections arranged around a fixed center-point. Using a special computer program, the sections were contoured in such a manner that only the surface of the organ was represented. These sections were then arranged in space. The 3-dimensional representation can be effected both by binary image representation and by representation with closed (intact) body surface. The advantage of the binary image representation is the fact that the organ surfaces "extracted" from the original US sections are directly incorporated within the 3-dimensional image build-up, with no further computer manipulations. It can be seen that the rotation of the transducer head represents the practicable possibility for the use in the clinical setting.

Computer Simulation↗
PubMed1989

[Clinical application of 3-dimensional ultrasound display. Initial results].

Using a newly developed ultrasound transducer and a corresponding computer program, it proved possible to construct a three-dimensional (3-D) display--at 7, 9, 11 and 13 weeks of pregnancy, respectively--of three structures lying one inside the other: embryo, amniotic sac and uterus. By means of a special computer technique the three structures could be displayed both in relation to one another and singly. Spatial rotations of the reconstructed body can be displayed on the video screen as can the individual bodies in different cross-sections. With narrow angles between individual sections this method may become important in the intra-uterine diagnosis of malformations and also of neoplasms.

Amnion↗
PubMed1989

[Prerequisites for the clinical application of 3-dimensional ultrasonic imaging].

After satisfactory experimental results with three-dimensional data acquisition and presentation of the kidney in vitro, we wanted to show how our technique could be used for medical application in vivo, such as ultrasonic 3D reconstruction of organs. The sector scans were taken by rotating the scan head 10 degrees in any direction around the length of the axis. The organ was scanned with 18 images and reconstructed. The digital images, using the organ contours, allowed 3D reconstruction of the original organ, relying on the computer memory. The first results in reconstructing uteri show how this scan head can be used in combination with the computer programs for medical application. For the first time, it has become possible to present computer-generated views of an organ cross-section that has been impossible to obtain by means of traditional ultrasound techniques. Recent experiments using this method show new ways of diagnosing tumors.

Adult↗
PubMed1988

[Three-dimensional imaging in ultrasonic diagnosis. Initial results].

A new method of three-dimensional (3-D) reconstruction of 2-D ultrasound images of the kidney is described. It is based on a coordinated spatial reconstruction of sequential cross-sectional images. The ultrasound head is moved longitudinally between two rails (parallel sections) and rotated. With a suitable computer program and contouring of each cross-section (so that the organ limits are defined for the computer) these cross-sectional pictures can be reconstructed into 3-D organ images. The kidney can then be presented spatially either as a binary picture or with closed surface. Ultrasound investigators are still unaccustomed to colour reproduction of 3-D reconstructed organs. It remains to be seen whether the method is valuable in routine clinical use.

Color↗
PubMed1978

[Computer system for the automatic analysis of cath-lab data. Reliability of pattern-recognition and measurements (author's transl)].

The computer-system for the on-line-analysis of hemodynamic data developed in Aachen enables the clinical user to perform the immediate on-line analysis of ECG, pressure-curves and thermo- or dye-dilution-curves in a dialog mode. The procedure of pressure analysis as well as the calculations by the computer for the individual haemodynamic parameters are described. The comparison of the medical-manual evaluation of the pressure curves on paper-registration and the computer results of the same measurement shows a very good correlation for wave-recognitions and wave-measurements for this system, integrated in the daily routine since 24 months. As well in the application of various fluid-filled catheters used in praxis as in tip-manometers it could be proved for the pressure-analysis in the different positions of the heart, that the computer-system produced reliable evaluations for all catheter materials used. The flexible conception of the computer program with its fast adaption to new problems allows its use not only in the clinical routine, but also and especially in the handling of scientific questions in the frame-work of haemodynamic analysis.

Cardiac Catheterization↗