Spatiotemporal accuracy of real-time 3D echocardiography in the neonatal and pediatric setting--validation studies using small dynamic test objects.

UNLABELLED: The precision of real-time 3D-echocardiography (RT3DE) is not sufficiently validated for small, fast-moving structures such as the neonatal and pediatric heart. PURPOSE: To assess the spatiotemporal accuracy of RT3DE in small, moving test objects. MATERIALS AND METHODS: Small, calibrated test objects in the size of neonatal and pediatric heart chambers were made from polyurethane foam or metal wire mesh and moved in a water bath through a calibrated dynamic test system. Using matrix transducers (X7-2, ie33 and X4-1, Sonos 7500, Philips, Andover, USA), 2 D and live 3 D datasets under variation of the motion speed (0.033 - 0.133 m/s corresponding to 50 - 200 heart cycles/minute), the volume rate and transducer position were recorded and analyzed (QLab 7.0, Philips). RESULTS: 3 D datasets of the moving test objects showed relevant spatial distortion, which was obviously related to the sequential scanning technology of the matrix transducer. Different segments of a test object were not recorded simultaneously, but rather row-by-row, so that there was a time delay between the first and the last-recorded voxel of a single 3 D volume (mean±SD: 28.9 ±â€Š7.82 m/s or 80 ±â€Š7 % of the time duration of a 3 D volume). With increasing motion speed of the test object and reduced 3 D volume rate, the distortion artifacts increased significantly. CONCLUSION: 3 D acquisitions using matrix technology demonstrate relevant spatiotemporal inaccuracies. This may lead to misinterpretations during the evaluation of the synchronicity of valvular or ventricular motion and incorrect definition of volume estimations. In particular, at higher heart rates and higher rates of movement, these limitations have to be taken into account in clinical practice.

Volumetry of fetal hearts using 3D real-time matrix echocardiography - in vitro validation experiments and 3D echocardiographic studies in fetuses.

PURPOSE: The aim of this study was to assess the feasibility, accuracy and reliability of 3D real-time echocardiography for fetal heart volumetry. MATERIALS AND METHODS: Fifty unselected and consecutive fetuses, including 14 with cardiac malformations, were scanned prospectively using real-time 3D matrix technology and 2D echocardiography to determine ventricular volumes. Small phantoms as well as modified balloons (0.5 - 20 ml) were used to assess the validity of 2D and 3D distance, area and volume calculations and to study potential sources of error during data acquisition and analysis. The data was evaluated by two blinded observers. RESULTS: In vitro, real-time 3D and 2D underestimated the actual volumes by -5.49 % (3D) and -6.86 % (2D). The intraobserver and interobserver variability were excellent. In vivo, real-time 3D was superior to 2D with regard to intraobserver and interobserver variability (mean coefficient of variation 8.28 % (3D) versus 13.96 % (2D), and mean intraclass correlation coefficient 0.997 (3D) versus 0.885 (2D) for left ventricular volumes). Similar to in vitro, in vivo 2D volumes were calculated smaller than 3D volumes (mean difference -0.39 to -0.94 ml). The ventricular volumes and stroke volumes increased exponentially with gestation. Secondary to poor imaging windows in advanced gestation or inadequate delineation of endocardial borders in small hearts at less than 19 weeks, 3D data could not be analyzed sufficiently in 6 / 50 fetuses. CONCLUSION: Real-time 3D using a matrix transducer is a feasible, reliable and valid method for volume determination in the fetus beyond 19 weeks of gestation. If compared to 2D, real-time 3D echocardiography provides improved accuracy of cardiac volumetry, decreases intraobserver and interobserver variability and is a promising tool for the accurate assessment of cardiac size and function.

Rigid piston approximation for computing the transfer function and angular response of a fiber-optic hydrophone.

The transfer function of a fiber-optic hydrophone (FOH) is computed for various fiber core radii. The hydrophone is modeled as a rigid disk, with plane waves impinging at normal or oblique incidence. The total sound field is written as the sum of the incident field and the field diffracted from the hydrophone. The diffracted field is approximated by the field generated by a vibrating planar piston in an infinite rigid baffle. For normal incidence and a pointlike fiber core, an analytical solution is presented. For finite fiber core radii, and for oblique incidence, the transfer functions are computed numerically. The calculated transfer functions exhibit an oscillatory frequency dependency that is most pronounced for small fiber cores. The solution for a core radius of 2.5 microm can be very well approximated by the analytical solution for a pointlike core at frequencies of up to 30 MHz. The results for normal incidence can be directly employed to deconvolute ultrasonic pressure signals measured with an FOH. From the transfer functions for oblique incidence, the angular response of the hydrophone is calculated. The angular response obtained here differs significantly from the model commonly used for piezoelectric hydrophones. The effective hydrophone radius derived from the angular response shows a strong frequency dependency. For low frequencies, it is found to be larger than the outer fiber radius, whereas it generally lies between the outer radius and the fiber core radius for frequencies above 10 MHz.

[Functional properties of diagnostic ultrasound instruments. A concept of trial building blocks for implementing quality assurance]. / Funktionseigenschaften von Ultraschalldiagnostikgeräten. Ein Konzept von Prüfbausteinen zur Durchführung der Qualitätssicherung.

Today's medical diagnostic ultrasonic devices are complex technical systems and need adequate Quality Assurance (QA) with regard to ultrasonic safety and performance. As to ultrasonic safety the International Declaration Standard IEC 1157 issued in 1992 supports progress for design of future equipment. It will be increasing importance to connect and to balance out the requirements for acoustic safety and for the diagnostic potential of the equipment. In Germany the application of QA in ultrasonics has to consider limitations by structure. Against this background the author gives an overall view of QA for the performance of imaging and Doppler equipment. From recent technical and standardisation work expressing demands and solutions for QA derives a practical concept of a modular QA programme. As an example, the specific test steps and suitable instruments for the procedures are given for some QA programmes in B-mode and Doppler-mode (B, cwD, pwD). A proposal is made how to split up the QA programme into a level 1 left to the medical personnel and a level 2 put to practical use by technical services or equipment distributors.

[Ultrasonic diagnosis prior to vitrectomy. Critical evaluation of 51 cases]. / Ultraschalldiagnostik vor Vitrektomie. Kritische Auswertung von 51 Fällen.

In ophthalmology it is of increasing importance to assess intraocular pathology prior to vitroretinal surgery by means of B- and A-mode ultrasound. Even for the experienced examiner with advanced instrumentation, major problems can arise as to whether retinal detachment has developed or not. This task involves the ability for acoustical differentiation of thin tissue membranes. The authors compared preoperative ultrasonic results obtained in 51 cases with the surgical findings during vitrectomy. The presence or absence of retinal detachment was evaluated correctly in 33 cases (91.7%) using high resolution contact B-mode alone. In difficult cases maximal echo amplitudes reflected from the suspected membranes were evaluated using a hand-held A-mode transducer (level difference A-mode echography) in addition to contact B-mode. Even the combined technique, though helpful in most cases, could not detect the presence or absence of retinal detachment in all cases.

Super-reversed intraocular lens.

An intraocular lens (IOL) with an inverse (reversed) optic has the convex surface directed toward the retina, a design which has many advantages. We have developed a "super-reversed" IOL by increasing the angle of the haptic from 10 to 20 degrees and by increasing the convexity of the posterior surface (necessitating a concave anterior surface). The main advantage of this model is the distance of approximately 6.3 mm between the anterior corneal surface and the posterior IOL surface. This configuration mimics the natural situation. We report on the implantation of 473 lenses of this design.

[Computed tomographic volumetry of the orbit in endocrine orbitopathy]. / Computertomographische Volumetrie der Orbita bei endokriner Orbitopathie.

The volumes of the four recti muscles and the orbital fat was measured by CT in 40 normal persons and in 60 patients with clinically confirmed Graves' disease. Compared with normal persons, 42 patients (70%) showed an increase in muscle volume and 28 patients (46.7%) an increase in the amount of fat. In nine patients (15%) muscle volume was normal, but the fat was increased. By using volumetric measurements, the amount of fat in the orbits in patients with Graves' disease could be determined.

[The effect of posterior chamber lenses or YAG laser capsulotomy on sensitivity to glare and twilight vision in comparison to phakic control groups (corrected)]. / Der Einfluss von Hinterkammerlinsen oder YAG-Laser-Kapsulotomie auf Blendempfindlichkeit und Dämmerungssehen im Vergleich zu phaken Kontroll gruppen [corrected]

Patients who had undergone extracapsular cataract extraction with implantation of a posterior chamber intraocular lens, and normal subjects of corresponding age and vision were examined with the mesoptometer and nyktometer to compare their twilight vision and glare sensitivity. All the results were poorer in patients with intraocular lenses. Statistically, some of the differences in the results of examinations performed in the two groups were highly significant. As the controls were strictly matched in age and visual acuity, these results confirm other studies with similar objectives. Additionally, some patients with posterior chamber lenses were examined who had also undergone YAG laser capsulotomy for secondary cataract. Although the number of cases was too small for statistical evaluation, it appeared that in this group twilight vision and glare sensitivity could not be improved in the same way as daylight visual acuity by means of this treatment. These findings indicate that since intraocular lenses are increasingly being implanted in younger patients, special attention should also be paid to scotopic vision and glare sensitivity during examinations for drivers' licenses, particularly in cases of good daylight vision. Special examinations, e.g., with the mesoptometer or nyktometer, should be carried out in all such cases. Increased glare sensitivity in eyes with lens implants should also be taken into consideration with regard to the increasing importance of computer and TV screens.

[Computed tomography of primary and secondary tumors of the eye and orbit]. / Computertomographie primärer und sekundärer Tumoren des Auges und der Orbita.

Only computed tomography (CT) is able to demonstrate ocular, orbital and peri-orbital soft tissues, calcification and bony structures directly and without superimposition of other tissues. 165 patients with tumours of the eye or orbit have been examined by CT and in 143 the diagnosis has been confirmed. The value of CT lies in its ability to demonstrate tumours and to define their orbital and extra-orbital extension and their relationship to neighbouring structures. In 51% of the lesions there was bone destruction and in 6% intracranial extension. Density measurements before and after intravenous contrast medium only rarely provided a specific diagnosis.

[An extremely malignant uveal melanoma]. / Extremes malignes Uveamelanom.

The authors present an extremely pronounced involvement of the orbita in malignant uveal melanoma with a ten-year course of disease. The results of imaging diagnostics (ultrasound, computed tomography, magnetic resonance tomography) are discussed.

[Magnetic resonance tomography (MRT) of the orbit]. / Magnetische Resonanztomographie (MRT) der Orbita.

By using high field strengths and surface coils, MRT achieves a resolution comparable with CT in the orbita. The advantages of MRT are good contrast resolution and imaging in several planes. Twenty-six patients have been examined by MRT, which has shown high sensitivity and good detail for the demonstration of pathological changes. In spite of this, MRT at present is not a realistic alternative to ultrasound and CT, because it is unable to demonstrate bone and calcification; its specificity is low, but the time and cost of the examination is high. It is indicated only for problems involving the optic nerve and chiasma.

[Quality assurance in ultrasound diagnostic equipment in West Germany. Experiences with current regulations]. / Zur Qualitätssicherung bei Ultraschalldiagnostikgeräten in der BRD. Erfahrungen mit den heutigen Regelungen.

Since 1980, the Health Service (KBV) of the FRG has introduced regulations for quality assurance of diagnostic ultrasound equipment. This step was taken to limit overshooting expansion of echography and Health Service costs. The author describes experiences and problems arising from application of the KBV regulations. Preventing diagnostic ultrasound from developing institutional structures and being included in existing health and safety acts, resulted in a lack of legitimate and qualified structures for quality assurance of the methods. This deficiency of structures also compromises the quality assurance by KV regulations and thus produces an administrative torso. Therefore, in West Germany, the first step to improve quality assurance ought to be to look for appropriate institutions for qualified equipment testing.

[Digital analysis of ultrasound M images for determining the dynamic behavior of the posterior ocular wall]. / Digitale Analyse von Ultraschall-M-Bildern zur Ermittlung des dynamischen Verhaltens der Augenrückwand.

A computer-assisted interactive method for M-scan analysis is presented. The digital M-scan, which is taken from the posterior wall of the human eye - in vivo - , is a sequence of digitised, broadband r.f.-time amplitude echograms (center frequency: 15 MHz). The effect of pulsation in the normal posterior wall of the eye and the dynamic changes and tissue movements after stress conditions can be pointed out and estimated quantitatively. A detected set of dynamic features can be used for an exact determination of the layers of the posterior ocular wall. For the indication of the dependence between changes of the thickness of the layers and the heart rate, the finger pulse is digitised and stored synchronously to the echograms. Good correlation will be expected for the movements in the choroid of the eye and the heart rate. The registration of the dynamics is performed in the color-coded M-scan by an adapted image processing software. Results of the M-scan analysis are presented as examples of the normal posterior wall.

Computer-aided ultrasonic measurements of the corneal thickness.

This report regards the measurements of the central corneal thickness by means of a computerized ultrasonic biometry system that had been developed by the authors. The characteristics of this system are: (a) a data rate of 10 measurements/s (reduced from the technical maximum of 800/s); (b) a resolution of 0.02 mm, and (e) statistical evaluation of data by automatic measurement histogram. The preliminary results on models and living human eyes suggest an equivalence of the improved ultrasonic measurement in cases where an immersion technique is feasible, with optical methods usually applied in clinical routine.

[The Doppler Simulator DS 81. A new calibration method for ultrasound-cw-Doppler blood flow measurement devices]. / Der Doppler-Simulator DS 81. Eine neue Kalibriermethode für Ultraschall-cw-Doppler-Blutfluss-Messgeräte.

Quality assurance in commercial cw-Doppler devices demands the use of special techniques in providing reproducible, optimized patient examination conditions for the individual instrument, and to permit a comparison with results obtained by other equipment. Equipment can be tested on two different technical levels: by checking the total performance by means of a Doppler phantom, or by testing the relevant components by means of electrical test signals. The use of Doppler phantoms involves certain drawbacks with respect to some equipment parameters and the routine equipment check. In the German Federal Republic, new official regulations (KBV), including the minimum requirements for Doppler equipment have been issued. To fulfil the legal requirements, a special test device, The Doppler Simulator DS 81 (1981), has proved suitable. The device provides a graduated scale of discrete, synthetic Doppler frequencies; these are fed into the Doppler equipment under test, and the response is recorded on the instrument's strip chart recorder or viewing screen. They are used as reference frequencies and for calibration. This method represents a further step towards reproducible or quantitative Doppler sonography.

Ocular tissue characterization by RF-signal analysis: results and experience of a 4 year in vivo-study.

A technique for Radio-Frequency (RF)-tissue characterization with hand-held transducer in the 5-25 MHz frequency range was clinically tested during 4 years on ocular tissues, especially on membranes, and tumours of the inner eye.

[Use of ultrasound in ophthalmology]. / Zur Ultraschallanwendung in der Ophthalmologie.

In ophthalmology, ultrasound is applied in diagnostics as well as in surgery and therapy. This paper gives a short survey on both applications. Ultrasonic phacoemulsification is of considerable practical importance for modern cataract micro-surgery with intraocular lens implantation. Applications of that kind require consideration of ultrasonic bioeffects and equipment safety. Diagnostic use of ultrasound includes biometry (echometry), tissue examination and characterization, and vascular investigations in eye and orbit. The application of diagnostic ultrasound on in-patients, its individual indications, and the appropriate methods (A, B, automatic biometric devices for axial length measuring, M, Doppler) are described. Examples of commercially available instruments for the different applications are given. In comparison with other disciplines ophthalmic A-mode and B-mode echography is characterized by: refined depth resolution and lateral resolution; the important part of quantitative methods for clinical evaluation of echograms; and the advanced level of quality assurance for equipment performance. Refined tissue evaluation requires optimized and reproducible equipment parameters. To ensure these conditions the clinical echographer must be educated and willing to test performance and quality of his equipment. Finally, a perspective of actual research in diagnostic ultrasound of the eye is given.