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E Bücheler

Publications and source records attributed to E Bücheler.

At least 19 recordsLinked to original sources
PubMed1992

Magnetic resonance imaging and pulsed Doppler sonography of poststenotic jets: correlation between signal void and flow velocity distribution.

To correlate the appearance of poststenotic jets on gradient echo images with features of localized Doppler spectra of the jets, we studied an in vitro model of steady flow-through stenoses of 86, 96, and 99% area reduction. As fluids, water and a 40% glycerol solution in water were used. MRI was performed with a 1.5 T whole body imager and gradient echo images were obtained in planes parallel to the direction of flow. Doppler spectra were acquired separately from the MR measurements at 1 cm intervals for a distance of 10 cm downstream from the stenosis. Poststenotic signal void was observed for water and for the 40% glycerol solution only if the mean velocity within the stenosis exceeded a limit of 50-60 cm/sec. On the MR images, the jets could be divided into two segments: A proximal jet segment of uniform width equal to the diameter of the stenosis, followed by a distal jet segment which was characterized by broadening and then dissipating signal void. Except for the 99% stenosis, a high signal intensity core was present within the proximal jet segment. In the proximal jet segment, the Doppler measurements showed a low temporal fluctuation of the maximal flow velocity and only little flow opposite to the main flow direction. In the distal jet segment, the velocity fluctuation and the intensity of reverse flow increased sharply. The high signal intensity core of the jet was associated with a poststenotic zone of constant maximal flow velocity. The results demonstrate a close relationship between characteristic features of poststenotic jets in MRI and pulsed Doppler sonography.

Blood Circulation↗
PubMed1992

Noninvasive liver-iron quantification by computed tomography in iron-overloaded rats.

RATIONALE AND OBJECTIVES: The benefit of computed tomography (CT) for the noninvasive determination of liver-iron concentration in human iron-overload diseases is a controversy in the literature. To study the sensitivity of CT for liver-iron quantification under experimental conditions, the authors measured single- and dual-energy CT numbers in vivo in the livers of iron-overloaded rats. METHODS: Thirty-five rats were subjected to an iron-rich diet for various periods, from 1 to 20 weeks, then scanned by single- and dual-energy CT. CT absorption was correlated to liver-iron content, which was determined by wet ashing and spectrophotometry. RESULTS: Whereas a good correlation (r = 0.99 at 96 kV; r = 0.95 at 125 kV) between CT numbers and liver-iron concentration was found, CT was insensitive to low concentrations of iron. Dual-energy CT scanning results showed greater scattering in liver-iron quantification compared with single-energy CT. CONCLUSIONS: In rats, the sensitivity of single- and dual-energy CT is too low to quantify liver iron in the diagnostically most relevant region of mild liver siderosis (1-3 mg iron/g wet weight [w.wt]).

Animals↗
PubMed1992

[Superselective interventional angiography].

The authors report on the clinical application of superselective interventional angiography within the framework of revascularisation and occlusion. A coaxial catheter system is used for probing, consisting of an F 5 angiography catheter as guiding catheter and an F 3 catheter as internal catheter. The internal catheter is equipped with a shaft with segments of different flexibility and can take up a guide wire of 0.018" that is sufficiently stable to be rotated and guided. The interplay between the guide wire, which can be manipulated, and the flexible internal catheter enables superselective probing even of peripheral vascular areas. As may be required by the basic disease, the necessary interventional measures can be taken via the superselectively placed microcatheter. Superselective interventional angiography is indicated as an occlusive measure in preoperative vascular occlusion followed by palliative tumour resection, embolisation in haemangioma, chemoembolization in tumours of the liver. Superselective angiography is used for revascularisation in the local lysis of peripheral vessels. Due to the on-target superselective approach, side effects are markedly less than those observed with the interventions performed to date.

Angiography↗
PubMed1991

Appearance of poststenotic jets in MRI: dependence on flow velocity and on imaging parameters.

A flow model was used to study the appearance of poststenotic jets in MRI. Jets in CuSO4-doped water and bovine blood were imaged by spin-echo (SE) and fast-field-echo (FFE) pulse sequences at different degrees of stenosis and various flow rates. On flow-compensated FFE images, the jets were characterized by signal void if the mean flow velocity within the stenosis exceeded a limit, which was independent of the degree of the stenosis and the type of the fluid. On SE images and on FFE images without flow compensation, signal void occurred at significantly lower flow velocity. The extension of the poststenotic signal void on flow-compensated FFE images was increased by either reduction of the pixel diameter or by prolongation of the echo time. However, it was independent of the orientation of the imaging plane relative to the direction of flow. The results have an impact on attempts to use signal void for the assessment of turbulent jets with MRI.

Animals↗
PubMed1991

[Chemoembolization in primary hepatocellular carcinoma].

The only generally recognised form of treatment for primary liver cell carcinomas is partial liver resection; occasionally this may be curative. This form of treatment is only applicable in 5% to 30% of patients. All drug-based forms of treatment have proved of little value. The new interventional radiological method of chemo-embolisation has shown results in improving survival rates which are comparable with resection. By using a new coaxial catheter system, embolisation can be performed as a selective intrahepatic procedure; it has few side effects and the quality of life subsequently does not deteriorate.

Carcinoma, Hepatocellular↗
PubMed1991

[Initial experiences with the use of gadolinium DTPA in infants and children under 2 years of age].

The use of Gadolinium-DTPA as a paramagnetic contrast agent in MRI with adults and juveniles concerning brain and spinal cord pathology is well proven since years. Tolerance and safety were excellent. In the FRG it is only introduced for children over two years of age. Therefore this report deals with the experience in four infants and small children under the age of two, who received gadolinium-DTPA for diagnostic purposes in pre- or post-operative circumstances. They all were suffering from neurological tumors and got additional diagnostic information in three cases. Clinical side-effects like urticaria, vomiting or convulsions had not been observed nor had pathologic changes of the biochemical parameters been noticed.

Central Nervous System Neoplasms↗
PubMed1990

[Computed tomographic differential diagnosis of primary pelvic osteo-, chondro- and Ewing's sarcomas].

The value of CT for the differential diagnosis of primary malignant tumours in the pelvis was investigated in the case of three types of tumour: osteosarcomas, chondrosarcomas and Ewing's sarcomas. A total of 78 CT examinations in 29 patients was used. The results show that CT, using suitable techniques (high resolution etc.) constitutes a valuable diagnostic method for differentiating these bone tumours. This applies not only for the localisation of the tumour and for defining its extent, but also for showing the morphology of intra- and extra-osseous soft tissue components and their patterns of calcification. It is possible to recognise patterns of growth and of tissue destruction that are typical of individual tumours.

Bone Neoplasms↗
PubMed1990

[The diagnostic value of MR tomography following gadolinium-DTPA compared to computed tomography in bladder tumors].

In a prospective study, 58 patients with carcinomas of the bladder were examined by CT and MRI; in 48, gadolinium-DTPA was administered intravenously. MRI provided exact staging in 89%, compared with 80% with CT. There was 13% over-staging with CT and 11% with MRI. MRI, unlike CT did not result in any under-staging. In 36 patients a quotient could be calculated from the signal intensity of the tumour and surrounding soft tissues both before and after the intravenous contrast medium and the increased quotient after contrast administration could be estimated. There was a significant increase in the tumour/muscle quotient with a mean of 72 +/- 22% (minimum 43%, maximum 153%), corresponding to a marked increase of the signal from the tumour when compared with the pre-contrast images. This had the following advantages compared with CT: accurate differentiation between superficial and intramural spread. MRI was better than CT at demonstrating tumours in the roof of the bladder and at the trigone.

Adult↗
PubMed1990

[MRT of acute soft tissue hematomas at 1.5 T: animal experimental results].

In 16 Göttingen minipigs 31 soft-tissue haematomas of different location were produced by reinjection of freshly drawn arterial and venous blood. Immediately after the injection, MRI of the haematomas was performed and continued for 2-3 h. The MRI appearance of the haematomas depended on the site of the injection. Intramuscular haematomas demonstrated on T2-weighted gradient-echo images a decrease in signal intensity within a few minutes after injection. With the same scan parameters, subcutaneous haematomas had a high signal intensity still at 3 h after injection. When section of the cadaver was performed, the subcutaneous haematomas consisted of compact clot, whereas with intramuscular injection diffuse infiltration of the muscle was present.

Acute Disease↗
PubMed1990

[Magnetic resonance tomographic diagnosis of retrobulbar neuritis using inversion recovery sequences].

Inversion recovery sequences with short inversion periods (STIR sequences) are particularly suitable for the examination of the intra-orbital and intracanalicular portion of the optic nerve, since they selectively suppress interference from neighbouring fat. This technique makes possible direct demonstration of retrobulbar neuritis that had to be diagnosed exclusively by clinical criteria up to now. As evidence of inflammatory changes in 15 out of 18 patients with acute retrobulbar neuritis, there were areas of increased signal intensity in the affected nerve; in six cases the nerve was also swollen. In eight normals and five patients with healed retrobulbar neuritis, the signal and calibre of the optic nerves were normal.

Adult↗
PubMed1990

[The importance of thoracic CT in the diagnosis of pulmonary sarcoidosis].

The CT findings in the lungs of 52 patients with histologically confirmed sarcoidosis are described. In addition to a nodular pattern, reticulo-nodular, reticular, diffuse infiltrative and streaky shadowing due to fibrosis could be recognised. Pleural lesions, bronchial ectasis and mediastinal and hilar lymph node changes could be diagnosed. The high sensitivity of CT contrasted with its relatively low specificity. At present CT is useful for analysing the pulmonary pattern when planning lung biopsy or lavage. In some cases, the diagnosis of pulmonary sarcoidosis can be made by CT, but the exact criteria for diagnosis and differential diagnosis must be borne in mind.

Adult↗
PubMed1990

[Clinical and technical experiences with digital luminescent radiography in phlebography of the leg].

Digital luminescence radiography is being increasingly integrated into clinical routine work and is fundamentally suited to replace x-ray film/screen takes. After the necessary optimization of the specific image processing procedure we examined the diagnostic efficacy of this method in respect of phlebography of the leg. If the radiation dose was reduced by 47% in relation to the reference system, the usefulness of the findings in arriving at the diagnosis was by no means reduced under the conditions of high contrast that apply in phlebography, but there was also no additional advantage in respect of diagnostic accuracy. The technical advantages concern mainly the absence of wrong exposures, the possibility of subsequent processing of the image to improve the image quality, and digital storage.

Evaluation Studies as Topic↗
PubMed1990

[Supercilium acetabuli. A stress indicator of the hip joint cartilage].

A thousand radiographs of the hip joints in adults were evaluated quantitatively and the following statistical conclusions were drawn: the normal forms of the supercilium acetabuli are either parallel or convex. Wedge-shaped supercilia indicate increased stress on the cartilage only in cases with hip dysplasia. A supercilium of more than 4mm raises the suspicion of increased stress on the cartilage. Normally, the joint space as shown on a radiograph does not fall short of 3mm. Eight formulas have been defined which can be used after planimetry of the supercilium and the articular surface in order to indicate increased stress on the cartilage and a risk of developing an arthrosis of the hip. These formulae are of practical value if the radiographs appear normal to visual inspection.

Acetabulum↗
PubMed1989

[MRT of extracranial hematomas at 1.5 T using spin echo and gradient echo sequences].

Magnetic resonance imaging (MRI) at 1.5 T was performed in 25 extracranial haematomas using spin-echo (SE) and fast-field-echo (FFE) sequences. The age of the haematomas was in 11 cases less than 2 days and in 9 cases more than 14 days. Fresh haematomas were isointense to skeletal muscle on T1-weighted SE images. With T2-weighted SE sequences, fresh haematomas had high signal intensity on the first day, but became inhomogeneous with predominantly low signal intensity on the following days. Areas of low signal intensity could be demonstrated by T2-weighted FFE sequences already on the first day after bleeding. Subacute haematomas were recognised by their high signal intensity on the T1-weighted SE images. Also with T2-weighted SE and FFE sequences, subacute haematomas showed increasingly high signal intensity. The characteristic appearance of haematomas facilitates their identification with MRI.

Hemarthrosis↗
PubMed1989

[Digital luminescence radiography. A new method of study in thoracic diagnosis at the intensive care unit].

The digital luminescence-radiography (DLR) technique relies on a complete digitalization of the X-ray image. Luminescence crystals on the imaging plate serve as an energy reservoir following their exposure to ionized radiation from any conventional X-ray source. A Helium-Neon laser stimulates the electrons in their high energy bands and therefore will be dropped back emitting luminescence. This luminescence is digitized by the DLR-System thus delivering a complete digital image to the image processor for subsequent processing and evaluation. The processed digital image is then recorded on a conventional film or a monitor screen. More than 3000 chest examinations using DLR have been performed on intensive care unit (ICU) patients at the University Hospital Eppendorf following the first eleven months since the clinical introduction of this new technique. The positive aspects of DLR such as high-contrast resolution and optimal reproducibility were clinically evaluated under ICU conditions. It was shown that DLR greatly improves the quality of the chest X-rays of all ICU patients and offers the following advantages: reproducibility, lateral chest projection, no insufficient exposure, reduction of exposure dose, electronical post-processing and storage, quality preserving digital storage and copying.

Humans↗
PubMed1989

[Poststenotic flow in MRT: phantom measurements using spin-echo and gradient-echo sequences].

A flow model was used to study the appearance of poststenotic flow on spin-echo (SE) and fast-field-echo (FFE) images. On SE-images, extensive signal void distal to the stenosis was observed even with low flow velocities. FFE-sequences with short echo time and flow-compensated gradients demonstrated poststenotic loss of signal intensity only with high flow velocities. On FFE-images, the poststenotic signal loss increased with the severity of the stenosis, if total flow across the stenosis was maintained. The lower limit of the mean flow velocity within the stenosis, for which signal void was observed, appeared essentially independent of the degree of the stenosis. The results demonstrate the capability of flow-compensated FFE-sequences to assess poststenotic turbulent flow.

Arterial Occlusive Diseases↗
PubMed1988

[High-resolution MRT with increased magnetic field gradients and a 512(2)-data matrix: initial clinical experiences].

By increasing the strength of the magnetic field gradients of a whole-body imager to 9.4mT/m, it was possible to obtain spin-echo images with short echo delays and high spatial resolution. The reduction of the pixel size was effected either by decreasing the field of view or by increasing the scan matrix (512(2) pixel). To prevent loss of signal-to-noise ratio, the scan parameters had to be carefully selected. With the 512(2) matrix, the resolution could be increased without decreasing the field of view, so that backfolding artifacts were avoided. In comparison with the 256(2) matrix, the 256 x 512 matrix provided improved resolution in the frequency encoded direction without an increase in acquisition time.

Humans↗