Search PubMed⌕ Search

Biomedical subjects

H Imhof

Publications and source records attributed to H Imhof.

At least 199 records · Page 11Linked to original sources
PubMed1991

An approach to a synopsis of EEG parameters, morphology of brain convolutions and mental activities.

A method for the projection of EEG data on the brain surface is proposed. The EEG data are obtained during the performance of mental tasks and represented as probability maps of power and coherence changes with respect to the averaged EEG at rest. The morphological data are obtained from 3D reconstructions of the brain by means of serial slices provided by an MRI scanner. Before scanning the positions of the EEG electrodes were marked by dummy electrodes of plexiglass filled with a contrast medium. Changes of power are color-coded and entered at the respective electrode positions, changes of coherence between the respective positions. The applicability of this procedure in the fields of psychology, psychiatry and neurology is discussed.

Adult↗
PubMed1991

[Sudeck's disease--MRT as a new diagnostic procedure].

In this prospective study, we determined the value of MR as an imaging technique in diagnosis and therapy with the option of simultaneous assessment of bone and soft tissue. 20 patients with clinical diagnosis of reflex sympathetic dystrophy syndrome (RSDS) and positive results in radiogram and three-phase radionuclide bone scanning were examined by MR, using T1- and T2-weighted images before and after Gadolinium-DTPA i.v. Soft tissue and bone signal intensity changes can be classified in our diagnostic-therapeutic scheme and proven by histopathological changes. The differentiation between clinical stages is possible and allows an evaluation of course and therapy. The higher costs are justified by shorter examination time without using radiation.

Adult↗
PubMed1991

Comparison of functional and structural brain disturbances in Wilson's disease.

We assessed the functional and structural brain disturbances in Wilson's disease (WD) by evoked potentials (EPs) and magnetic resonance imaging (MRI). All the 25 neurologically symptomatic and 44% of the 16 asymptomatic patients, assessed by both EPs (n = 48) and imaging (n = 41), had at least 1 abnormality of either prolonged EP conduction times, imaging-outlined presence of cerebral lesions, or brain atrophy. Our findings indicate that EPs and MRI are sensitive techniques for the evaluation of brain involvement in WD.

Adult↗
PubMed1991

[Diagnosis of cerebrovascular disorders using nuclear magnetic resonance tomography].

Regarding cerebrovascular diseases magnetic resonance imaging (MRI) provides informations which could not be obtained before by any other imaging method. MRI permits an early detection of ischemic infarctions, exact delineation of lesions near to skull base, and microangiopathy. Further diagnosis of arteriovenous malformations and venous thromboses can be done without using contrast media. Exclusion of acute hemorrhage or subarachnoidal hemorrhage is still a domain of computed tomography (CT). Other MR methods, like magnetic resonance angiography (MRA) and magnetic resonance spectroscopy (MRS) are expected to replace angiography and positron emission tomography (PET) in the near future, at least for some purposes.

Adult↗
PubMed1991

Evaluation of congenital diseases of the heart.

Three different new developments have taken place in the evaluation of congenital heart diseases. First, in the fetal period, intravaginal echocardiography allows earlier diagnosis of significant cardiac abnormalities that could lead to a wanted termination of pregnancy. Second, in adults and children, MR imaging has become a standard imaging modality in complex congenital heart diseases. Moreover MR imaging has become the best noninvasive imaging method in visualization of the great vessels. Finally, in surgery, the intraoperative epicardial echocardiography could improve operation results in the future (solving the regurgitation problem). Postoperatively, MR imaging has become an important diagnostic tool that helps to reduce repeated catheterization and angiography.

Diagnostic Imaging↗
PubMed1991

High-resolution real-time sonography and MR imaging in assessment of osteocartilaginous exostoses.

High-resolution real-time ultrasonography (US) and MR imaging, using both spin-echo (SE) and gradient-echo (GE) sequences, were performed prospectively in 14 patients with solitary osteocartilaginous exostoses to assess cartilage cap thickness and bursa formation. Results were compared to surgical and histopathologic findings in all cases. Both US and MR imaging were useful in evaluating exostotic cartilage cap thickness, which is supposed to be the most reliable sign of malignant transformation. Hyaline cartilage matrix had distinctive features in US and MR imaging caused by its specific histologic composition. The formation of bursae over the protruding exostoses, which results in pain and clinically could raise the suspicion of growth and malignant transformation, was demonstrated best using GE sequences. MR imaging was thus superior to US in the detection of bursa formation.

Adolescent↗
PubMed1991

[Evaluating the function of aortocoronary bypasses with magnetic resonance tomography].

Following an aortocoronary bypass operation the differential diagnosis of chest pain of recent onset may be difficult (ischaemia, thoracotomy induced pain). At this point noninvasive methods are preferable to angiography in order to reach exact diagnosis. Magnetic Resonance Imaging (MRI), a new noninvasive imaging method, makes it possible to get anatomical and blood flow information without the use of ionizing radiation or contrast agents. It was the aim of our study to examine the diagnostic impact of MRI for the assessment of aortocoronary bypass graft patency. We compared three different acquisition techniques (a spinecho sequence and two fast-gradient echo sequences). 26 patients were examined, 49 bypass grafts were eligible for comparative evaluation. As compared with the spinecho technique, fast echo gradient sequences had a higher sensitivity (FISP 93%, FLASH 88%) than the spinecho technique 79%, and a higher accuracy (FISP 88%, FLASH 82%) versus 73%, respectively. We conclude that MRI may have a high diagnostic potential in the evaluation of early postoperative aortocoronary bypass graft patency.

Adult↗
PubMed1990

[Changes in the thoracic roentgen image in patients with acquired immune deficiency syndrome].

Since the earliest reports of what was later termed the acquired immune deficiency syndrome (AIDS) appeared in 1980/81, with the recognition of opportunistic infections and Kaposi's sarcoma in homosexual men and i.v. drug abusers, more than 60% of AIDS patients develop pulmonary manifestations at some time in the course of their disease. Radiographic evaluation of the chest plays an important role in diagnosis. In fact, radiological changes are unspecific and either bacteriological proof or histological verification needs to be confirmed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[AIDS of the central nervous system].

The central nervous system of nearly every HIV-positive patient becomes affected by the AIDS virus itself or by one of the associated diseases during the course of the illness. Early diagnosis of lesions which demand therapeutic consequences is of the most importance concerning prolongation of life and improvement in its quality. In spite of the frequent underestimation of cerebral involvement by imaging methods and their unspecific findings they are often the only diagnostic means which permit-timely diagnosis and, at least in some diseases, therapeutic monitoring. Indications for cranial computed tomography (CCT) or magnetic resonance tomography (MRT) are already present with mild or transient neurological or psychiatric symptoms or the extracerebral manifestation of neurotropic organisms or tumours which metastasize to the brain, even in patients without subjective complaints.

AIDS Dementia Complex↗
PubMed1990

Cranial MRI in Wilson's disease.

Thirty-eight patients with biochemically proven Wilson's disease underwent magnetic resonance-imaging (MRI) of the brain as well as neurological examinations. The patients were scanned using spin-echo (SE) sequences; the neurologist was looking for typical symptoms: dysarthria, tremor, ataxia, rigidity/bradykinesia and chorea/dystonia. Pathological MR findings believed secondary to this uncommon inherited disorder of copper metabolism were found in twenty-two subjects. Focal abnormalities were seen in the lenticular, thalamic and caudate nuclei as well as in brain stem and white matter; these lesions were best demonstrated on T2-weighted sequences as hyperintense areas. In eight patients we found diffuse brain atrophy with consecutive widening of the ventricular system. Five subjects showed mild, nineteen severe neurologic deficits. Generally there was no correlation between MR findings and clinical neurological symptoms; the impairment of cell-metabolism causing functional alterations of the brain precedes morphological changes. During treatment with the copper chelator D-penicillamine there seemed to be a phased course of disease. Shortening of T1-relaxation due to paramagnetic influence of copper was not seen; a possible explanation could be intracellular deposition--a proton-electron-dipolar-dipolar-interaction would therefore be impossible.

Adult↗
PubMed1990

[Linear versus circular polarization of head coils: comparison on phantoms and in the clinic].

Two different head coils--one with linear polarization and the other with circular polarization--were compared under the same measurement conditions. Comparison was done on a phantom with water-filled and gadolinium-filled pin-holes, as well as on anatomical MR images of 23 volunteers. In three volunteers the whole brain was examined while, in the remaining 20 volunteers the sella region or cerebellopontine angle region was examined. Criteria for comparison were signal-to-noise ratio, background noise, and detail resolution (phantom), as well as subjective criteria--image sharpness, anatomical, contrast, and recognition of anatomical details--, evaluated on anatomical MR images by four radiologists independently of each other. The results show a significant improvement of signal-to-noise ratio, lower background noise and therefore marked improvement of images sharpness, and moderate improvement in the recognition of anatomical details using the circular polarized head coil; as for as detail resolution and anatomical contrast were concerned, however, no significant difference was seen between the two coils. Major advantages of the circular, polarized head coil in clinical application are shorter measurement times (reduced number of acquisitions), as well as thinner slices without loss of signal-to-noise ratio.

Brain↗
PubMed1990

[Spondylitis: the clinical picture and follow-up assessment by magnetic resonance tomography].

MRI of proven spondylitis was performed in 39 patients. Acute spondylitis appeared hypointense on T1-weighted and hyperintense on T2-weighted images. Following intravenous application of Gd-DTPA, enhancement of the marrow and disk was seen. With progressive healing increasing signal was seen on T1-weighted images. This was caused by the presence of focal fat marrow representing the first sign of therapy response. Corresponding to the clinical healing process T1-signal increased due to fatty marrow, while the T2-signal decreased as well as the enhancement following Gd-DTPA application. Therefore, MR imaging can be recommended as the method of choice for early diagnosis of spondylitis and assessment of therapy response.

Adult↗
PubMed1990

[MRT in the follow-up of the healing process of spongy bone transplants--initial experiences].

We present our first experience with MR in bone grafts in 23 patients. Graft implantation followed curettage of benign bone lesions. The locations were, rather exclusively, the long tubular bones. T1-and T2-weighted spin echo-sequences including intravenous application of Gadolinium-DTPA were performed (Magnetom 63, 1,5 T). A total of 29 examinations (1 follow-up control in 6 pat.) was divided into 5 groups, with regard to different stages after surgery, which varied from 1 week to more than 3 years postoperatively. The MR results were related to the respective groups. The results show typical stages of bone graft incorporation, but also greater individual variations in the duration of incorporation. Our first results, however, represent only "snapshots" of different patients at different stages after bone graft surgery. Therefore some important questions are still unanswered but may perhaps be explained with the help of subsequent prospective studies.

Adult↗
PubMed1990

[MRT using Gd-DTPA in the diagnosis of tumor and pseudotumor intracardiac masses].

Magnetic resonance examinations were performed in 15 patients suffering from echocardiographically detected intracardiac masses. All patients were examined with a 1.5 T superconducting machine, using spin echo technique, including Gd-DTPA, and gradient echo sequences. The MR findings were confirmed partially by histology and angiography, otherwise by good correlation to clinical findings. MR results were divided into three groups: 1. tumour, 2. thrombosis, 3. pseudotumorous mass, and corresponded well with the final diagnosis: in 8 patients tumour, in 5 patients thrombosis, and in two patients pseudotumorous masses, including one hydatid cyst and one case of lipomatosis. Tumours showed in contrast to thrombosis marked enhancement after gadolinium injection, whereas the hydatid cyst and the lipomatosis demonstrated characteristic signal behaviour. Problems existed in differentiation mass vs slow flow, in the detection of very small masses, and in the assessment of wall-fixation and motion of a mass during cardiac cycle. The results demonstrate that MRI with Gd-DTPA can give important additional information in the differential diagnosis of echocardiographically detected intracardiac masses.

Adolescent↗
PubMed1990

[Magnetic resonance tomography of the failed back surgery syndrome: a comparison with computed tomography].

The term "failed back surgery syndrome" includes a variety of clinical-neurological symptoms following disc surgery. In a prospective study 18 patients suffering from monoradicular symptoms after disc surgery were examined by MRI and CT (both prior to and following intravenous application of contrast material). Findings were then compared to microsurgery. MRI produced correct diagnoses in 17 cases, CT in 13 cases. Recurrent disc herniation caused symptoms four times, and epidural scar formation twice. In twelve cases there was herniated disc material as well as an epidural scar present; disc material preponderated nine times, scar formation in three instances.

Adult↗