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Biomedical subjects

J Bunke

Publications and source records attributed to J Bunke.

17 recordsLinked to original sources
PubMed1994

[1H-MR spectroscopic imaging: an approach to evaluating alcohol breakdown in the brain].

The local alcohol concentration in the human brain was determined in 10 cases using MR spectroscopic imaging. Therefore 7 subjects with an average blood alcohol concentration of 0.8/000 were examined after oral intake of alcoholic beverages. Varying alcohol concentration was found intracranially which was recorded spectroscopically w.r.t. time. Relatively high ethanol concentrations were determined in the cerebellum as well as in the ventricular system. Contrary to this, lower concentrations were found in the regions of grey and white matter.

Adult↗
PubMed1993

[31P-magnetic resonance spectroscopy: impaired energy metabolism in latent hyperthyroidism].

31Phosphorus magnetic resonance spectroscopy allows an in vivo examination of energy metabolism. The present study was designed to evaluate whether in patients with latent hyperthyroidism alterations of muscle energy metabolism could be found similar to those observed in patients with overt hyperthyroidism. In 10 patients with overt hyperthyroidism before therapy and 20 with latent hyperthyroidism (also without therapy) and in 24 healthy volunteers magnetic resonance spectroscopy of the calf muscle was performed within a 1.5-Tesla magnet. Muscle concentrations of phosphocreatine, inorganic phosphate, and ATP were quantified compared to an external standard solution of K2HPO4. In the patients with overt hyperthyroidism and with latent hyperthyroidism a significant decrease of phosphocreatine was found. Further, the ATP concentration in patients with latent and manifest hyperthyroidism tended towards lower values. There were no significant differences in the decrease of phosphocreatine and ATP between both patient groups. Therefore, this study for the first time shows that alterations of energy metabolism in latent hyperthyroidism can be measured and that they are similar to those observed in overt hyperthyroidism.

Adult↗
PubMed1993

["Spectroscopic imaging." A new MR technique in the diagnosis of epilepsy?].

The technique of magnetic resonance spectroscopy fuses spectroscopic methods with the two-dimensional illustration of the metabolite concentrations by parallel acquisition of multiple single voxels from small tissue compartments. Therefore it is not necessary to define a voxel of interest before data acquisition. The interpretation of metabolite images is much easier than the analysis of single spectra, and metabolite concentrations on the right and left sides can be compared. The method has already proved reliable for brain tumors. The application of the procedure to patients suffering from epilepsy is described here in for the first time. Even in the temporal region, where most epileptogenic foci have their origin, one can obtain metabolite images of diagnostic quality without susceptibility artifacts. The epileptogenic focus is lateralized correctly, in accordance with electrophysiological and surgical evaluation, even in those cases where standard magnetic resonance imaging is normal. According to our preliminary findings the epileptogenic focus is characterized by a signal loss of N-acetyl-aspartate and creatine.

Adult↗
PubMed1992

[Experimental studies on magnetic resonance tomographic and magnetic resonance angiographic imaging of poststenotic flow patterns].

A phantom has been developed, which permits the perfusion of defined stenosis with variable flow rates. The post-stenotic flow patterns were imaged by means of conventional MRI sequences and special angiographic sequences using a 1.5 total body scanner (Gyroscan S15, Philips). For conventional MRI images, spin-echo-sequences (TR 500 ms, TE 27 ms with reconstruction of the magnitude and phase images) and gradient-echo-sequences (TR 60 ms, TE 27 ms, flip angle 15 degrees with reconstruction of the magnitude images) were used. For MR angiography 2D inflow (multiple-single-slice-technique, TR 40 ms, TE 14 ms, flip angle 60 degrees) and flow-adjusted-gradient-sequences (TR 24 ms, TE 10 ms, flip angle 60 degrees) were performed. In addition to an analysis of the appearances, the length of the changed signal intensity beyond the stenosis was evaluated. For constant flow rates it increases with the severity of the stenosis. For a constant stenosis the length of the post-stenotic signal change alters with flow rate. The changes also depend on the direction of flow and the gradients of the chosen sequences. The comparison of magnitude and phase images allows the discrimination between turbulent and non-turbulent flow. It therefore appears possible to estimate the severity of arteriosclerotic occlusive disease by means of MRI in the future.

Blood Flow Velocity↗
PubMed1992

Human brain tumors: spectral patterns detected with localized H-1 MR spectroscopy.

Image-guided localized proton magnetic resonance (MR) spectroscopy of intracranial tumors was performed to correlate spectral patterns and histologic findings. Thirty-six patients were examined prior to any specific treatment. Evaluation based on signal intensity ratios showed that all tumor spectra differed from spectra of healthy brain tissue. Ratios of creatine to choline-containing compounds (Cr/Cho) and nitrogen acetyl-aspartate to Cho (NAA/Cho) were reduced significantly in all tumor spectra compared with spectra of normal tissue in contralateral brain hemispheres (P less than .005). Noncerebral tumors typically showed a vanishing or missing NAA signal, strongly reduced Cr signal, and additional signals, assigned to alanine in meningiomas and lipids in metastases. In contrast, 11 gliomas of grades 2 and 3 exhibited NAA/Cho ratios and Cr/Cho ratios that were less than normal but that were significantly larger (P less than .01) than corresponding values in eight meningiomas. Ten glioblastomas displayed spectra with various signal ratios, so no significant differences between them and other tumor types could be established. In nine gliomas a clearly detectable lactate signal was present. However, no direct correlation between lactate level and histologic tumor grading was found.

Adult↗
PubMed1990

[Localized 31P-NMR-spectroscopy using ISIS (image-selected in vivo spectroscopy) and surface coils: methodology and initial applications to studies of the liver, the transplanted kidney and the mediastinum].

A new method for image-guided localized phosphorus NMR spectroscopy of superficial tissues has been investigated using a 1.5 Tesla whole-body-MR-System. We used a surface coil combined with adiabatic excitation pulses and a modified ISIS sequence. This approach is related to imaging sequences and thus permits a flexible and accurate determination of the volume of interest from "conventional" proton images. The scope and advantages of the method are demonstrated by phantom studies. Clinical applications to the liver, renal transplants, and the mediastinum are described.

Humans↗
PubMed1990

Positron emission tomography of fluorine-18-deoxyglucose and image-guided phosphorus-31 magnetic resonance spectroscopy in brain tumors.

Positron emission tomography (PET) of 2(18F)-fluoro-2-deoxy-D-glucose (FDG) and volume-selective phosphorus-31 magnetic resonance spectroscopy (31P-MRS) are methods used to assess the energy metabolism of the brain. Both methods were studied with respect to their contribution to differential diagnosis in 23 patients with various brain tumors. The various neuroectodermal tumors differed with respect to their metabolic rate for glucose (MRGL). Benign and malignant tumors could be better differentiated by using tumor metabolism relative to contralateral brain and by evaluating heterogeneities in tumors. Low-grade gliomas usually showed normal 31P-MR spectra; high-grade gliomas were characterized by reduced and often split phosphodiester peaks and alkaline pH. Meningiomas, which had variable MRGL, typically showed extremely low phosphocreatine levels, reduced phosphodiesters, and alkaline pH. We concluded that FDG-PET and 31P-MRS examine different aspects of tumor metabolism. Therefore, both can contribute independently and complementarily to the differential diagnosis of brain tumors.

Astrocytoma↗
PubMed1990

[Automatic correction of the signal intensity of surface coils. Clinical application and relevance].

Homomorphic filtering permits correction of the decrease in signal intensity in magnetic resonance imaging with surface coils seen in tissues lying farther away from the coil. The study presented compares the originals with the images following automatic correction of signal intensity and demonstrates the superiority of the examinations with corrected signal intensity. In conclusion, it is recommended that automatic correction of signal intensity be used in magnetic resonance imaging with surface coils.

Humans↗
PubMed1987

[MR of the shoulder joint with surface coils at 1.5 tesla. Its anatomy and possible clinical use].

High spatial resolution magnetic resonance images of the shoulder were obtained in axial, sagittal and coronal orientations using a 1.5 T imaging system and anatomically shaped, wrap-around surface coils. Variations in scapular position induced by patient positioning change the relationship of the planes to the shoulder anatomy and make reproducibility of sagittal and coronal planes difficult. We, therefore, use--after axial orientation--image-oblique planes perpendicular and parallel to the glenoid fossa. In this manner MRI can visualise the anatomic structures of the shoulder including rotator cuff, long biceps tendon, articular capsule, articular cartilage, muscles and bones due to the high soft tissue contrast of MRI.

Humans↗
PubMed1987

[Definitions of pulse sequences and parameter weightings in the NMR tomogram].

Due to the different possibilities of image creation in MR tomography there is no clear terminology of pulse sequences and MR images. This paper tries to define the designation of pulse sequence parameters in a practical way and to specify the term "parameter weighting of MR images". Starting with general definitions, special definitions for CNS and liver are elaborated.

Central Nervous System↗
PubMed1987

[Experimental research and initial clinical experience with the fast field-echo sequence].

In the FFE-sequence the new parameter "flip angle" introduces, besides the possibility of fast MR-imaging, an increased variability of external MR parameters. Experimental studies in healthy volunteers and patient examinations were carried out to establish the most useful parameter combinations giving reasonable contrasts. Variation of external parameters allows a manipulation of image contrasts: using small flip angles in combination with longer TE good T2-weighted images can be achieved; large flip angles with short TR and TE produce a sufficient T1-weighting. In this way the FFE sequence proves to be a valuable method for rapid assessment of pathologic lesions.

Evaluation Studies as Topic↗
PubMed1987

[Image-guided localized 31P NMR spectroscopy of the human brain at 1.5T].

Using a 1.5 Tesla whole body system, image-guided localized 31P NMR spectra of normal brain tissue and of various intracranial tumours have been obtained. The spectra of normal brain tissue were reproducible, although further studies are necessary to determine physiological variability. Compared with the normal spectrum, the spectra of tumours usually showed reduced intensity of the phosphocreatine peaks and increased intensity of the peaks of inorganic phosphate, of phosphodiesters and particularly phosphomonoesters. To our limited experience there has been no correlation between the spectra and tumour histology. In follow-up studies of brain tumours undergoing treatment by chemotherapy or radiotherapy 31P MR spectroscopy demonstrated metabolic changes at a time when 1H MR imaging did not show any changes in tumour size or structure. Further investigations have to be done in order to evaluate the usefulness of 31P MRS for detecting therapeutic response in follow-up studies.

Brain↗
PubMed1987

Postoperative magnetic resonance imaging artifacts. Report of three cases.

Artifacts are occasionally encountered on magnetic resonance imaging after operation. These may be due to minute metallic particles from neurosurgical instruments. Particles not detectable on plain x-ray films or computerized tomography scans may cause local change of magnetic resonance activity, resulting in a deceptive magnetic resonance appearance. Three illustrative case reports are presented.

Adult↗
PubMedDate not supplied

MR imaging of poststenotic flow phenomena: experimental studies.

Poststenotic flow patterns were analyzed in a flow phantom with a 1.5-T magnetic resonance (MR) imager, with use of different MR imaging and MR angiographic pulse sequences. Spin-echo, fast field-echo, two-dimensional inflow (multiple single-section technique), and flow-adjusted-gradient sequences were applied. For the spin-echo sequences, modulus and phase images were reconstructed from each data set. The length of the region of poststenotic changes in signal amplitude and phase measured at a constant flow rate increased with stenosis grade. Likewise, the length of the region of poststenotic changes measured at a constant stenosis grade increased with flow rate. Moreover, the results depended on the alignment of the flow direction with the readout gradient. Comparison of modulus and phase images allowed discrimination of turbulent and nonturbulent flow, which yields additional information on stenosis grade in clinical MR angiography.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Artifacts in MR imaging after surgical intervention.

Artifacts are encountered repeatedly in magnetic resonance (MR) imaging after neurological orthopedic surgery, although there is no evidence of metallic foreign bodies on radiography and CT. Experiments demonstrated that surgical filling materials, such as bone cement and bone transplants are not the cause of the artifacts. On the other hand, we have been able to show that short-term contact between a diamond drill and untempered operating instruments can cause abrasions and set free minute metallic fragments. Those particles are missed by X-ray procedures including CT but cause MR artifacts by local disturbance of the homogeneity of the magnetic field. Therefore, MR represents a highly sensitive method to trace extremely small amounts of magnetic substances. Postsurgical MR, however, may be of limited value because of the disturbing artifacts.

Animals↗
PubMedDate not supplied

Combined 1H-MR imaging and localized 31P-spectroscopy of intracranial tumors in 43 patients.

Combined imaging and volume-selective spectroscopy of normal human brain tissue and tumors located anywhere in the brain could be obtained routinely in a clinical setting. Image-guided localized phosphorus MR spectra of healthy brain tissue have been reproducible, but further examinations seem necessary to determine individual physiologic variations. Compared with healthy brain tissue, spectra from meningiomas demonstrated the most obvious differences: the phosphocreatine peak decreased below the level of adenosine triphosphate, and the phosphodiester signal was reduced, whereas the phosphomonoester peak increased in some cases. Malignant gliomas showed less distinct changes: in particular, the phosphodiester peak was reduced and, in several cases, seemed to split. Often the phosphocreatine signal was diminished. In tumors with cystic components a poor signal-to-noise ratio was found. Four nonmalignant astrocytomas could not be differentiated from normal brain tissue spectroscopically. It has to be proved by an increased number of cases and quantification whether the observed spectral patterns can be correlated to histology. In three patients, follow-up studies during and after radiotherapy were performed. Metabolic changes were observed in one patient in a time frame in which imaging methods did not detect any change. Phosphorous spectroscopy has the potential to emerge as a useful tool in this field.

Adult↗