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H G Trier

Publications and source records attributed to H G Trier.

At least 19 recordsLinked to original sources
PubMed1994

[Functional properties of diagnostic ultrasound instruments. A concept of trial building blocks for implementing quality assurance].

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.

Equipment Design↗
PubMed1990

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.

Equipment Design↗
PubMed1990

[Ultrasonic diagnosis prior to vitrectomy. Critical evaluation of 51 cases].

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.

Diabetic Retinopathy↗
PubMed1989

[Computed tomographic volumetry of the orbit in endocrine orbitopathy].

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.

Adipose Tissue↗
PubMed1988

[The effect of posterior chamber lenses or YAG laser capsulotomy on sensitivity to glare and twilight vision in comparison to phakic control groups (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.

Adaptation, Ocular↗
PubMed1987

[Magnetic resonance tomography (MRT) of the orbit].

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.

Adolescent↗
PubMed1987

[Computed tomography of primary and secondary tumors of the eye and orbit].

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.

Adolescent↗
PubMed1987

[An extremely malignant uveal melanoma].

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.

Female↗
PubMed1985

[Quality assurance in ultrasound diagnostic equipment in West Germany. Experiences with current regulations].

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.

Equipment Safety↗
PubMed1984

[Digital analysis of ultrasound M images for determining the dynamic behavior of the posterior ocular wall].

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.

Choroid↗
PubMed1984

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.

Anthropometry↗
PubMed1983

[The Doppler Simulator DS 81. A new calibration method for ultrasound-cw-Doppler blood flow measurement devices].

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.

Blood Flow Velocity↗
PubMed1982

[An ocular toxicity study with flupirtine as an example of evaluation of possible ocular drug side effects in human volunteers (author's transl)].

Animal experiments do not provide complete information on all the possible ocular side effects and the toxicity of a new drug. Several functional or dynamic parameters of vision can only be tested in humans as they are either do not exist in laboratory animals or their assessment requires a subjective contribution by the test person. A study was carried out on a new analgesic substance (Flupirtine) in which a large number of such parameters were tested in young healthy volunteers. The results were subjected to statistical analysis with a two-factor partlyhierarchical anova and no toxic effects were detected. The study shows how such parameters of visual function can be tested in humans.

Adult↗
PubMed1982

[Quality assurance for diagnostic ultrasonic equipment in A- and B-mode in ophthalmology (author's transl)].

Quality assurance for diagnostic ultrasound in ophthalmology is of growing importance and will be the subject of new standards and regulations. Methods for equipment performance testing by means of electric test signals in A- and B-mode equipment are described, both for comparative evaluation of equipment and for routine quality assurance tests. Newly developed test signal generator for checking the time scale in ultrasonic biometry of the eye are presented.

Eye Diseases↗