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Biomedical subjects

J Hennig

Publications and source records attributed to J Hennig.

At least 163 records · Page 9Linked to original sources
PubMed1988

[Dual-photon absorptiometry: a new method of determining bone mineral content. I. Basic principles].

Today dual-photon absorptiometry (DPA) is recommended as the best procedure for diagnosing osteoporosis at an early stage considering its low cost, low radiation exposure and reasonable reliability. Cortical (neck of femur) and trabecular (L 2-4) bone mass has been determined repeatedly with DPA using 153Gd (NOVO Lab 22 a) in 545 females and 112 males with no evidence of bone diseases. Measured "normal" (age- and sex-related average) values for bone mineral content (BMC) differed significantly (p less than 0.01) from those of US inhabitants determined by the same equipment, i.e., they were on average about 30% lower, but matched well with corresponding results from Belgium. BMC-area was found the most suitable parameter both for cross-sectional and longitudinal studies, since it is independent of height and weight. But there is still need to reduce the overlap and improve accuracy and reproducibility for making decisions after shorter intervals. Assessment of the individual mineral loss and fracture risk by comparison with average values remains problematical due to the wide range of "normal" BMC values, and in women additionally due to the variable onset of menopause. For estimations of the individual fracture risk of elderly patients BMC should not be normalized on age, because at the age of 65 half of the women had "pathologic" values, i.e. were below the so-called "osteoporosis threshold". Comparison of the individually measured postmenopausal BMC with average values of premenopausal women and with BMC values normalized to their menopausal age may be helpful approaches to overcoming these difficulties.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Fast three-dimensional imaging of cerebrospinal fluid.

The RARE method is based on the principle of echo imaging to generate images with high T2 contrast. Since RARE is a fast imaging method, it can be used to acquire a high-resolution three-dimensional data set in less than 15 min. Thin slices from such a three-dimensional data set provide detailed information about the ventricular system.

Cerebrospinal Fluid↗
PubMed1987

[MR of the urinary tract in pregnancy].

A report on the application of standard 2D-FT MR combined with RARE-MR-Urography in a pregnant woman with right sided abdominal pain, dilated upper urinary tract and possible stone or inflammatory disease. This technique visualised the complete obstructed ureter in relation to the surrounding organs (uterus, vessels), allows precise diagnosis of the cause of the obstruction and avoids ionising radiation.

Adult↗
PubMed1987

[Initial clinical experiences with RARE-MR urography].

Potentials and limitations of a new, facultative non-tomographic Fast-Imaging sequence "RARE-MR-Urography" are presented. Its results in urological diseases are discussed on the basis of a pilot study of 35 patients. The images (4 s-32 s acquisition time) are extremely T2-weighted and display unbounded free water (urine). They reveal valuable information, not available with ultrasound or conventional radiology without application of contrast agents in the presence of urine retention. S/N problems reduce the accuracy of this method if the urinary tract contains only small amounts of urine.

Humans↗
PubMed1987

[RARE-MR urography: a fast nontomographic imaging procedure for demonstrating the efferent urinary pathways using nuclear magnetic resonance].

RARE-MR-Urography is a new fast data acquisition technique for magnetic resonance imaging. As a non-tomographic approach to the morphology of the urinary system, image information is similar to intravenous X-ray urography. As the sequence results in a heavily T2-weighted image displaying aqueous fluids, application of contrast agents is not necessary. Image quality is demonstrated by an exemplary case. Basic technical details and possible indications are discussed.

Adult↗
PubMed1987

[Nuclear magnetic resonance tomography of the sacroiliac joint. A new examination technic in the differential diagnosis of rheumatic diseases of the lumbosacral transition].

25 patients with the clinical diagnoses of possible sacroiliitis were investigated by Magnetic Resonance Tomography (MR). Using axial or coronal tomography in a T1-weighted sequence (7 slices, 1 echo, NEX: 2, slice thickness 8 mm, TR: 600 ms, TE: 33 ms) and in a T2-weighted sequence (7 slices, 4 echos, NEX: 2, slice thickness 8 mm, TR: 1800 ms, TE: 33, 66, 99, 132 ms) we found normal sacroiliac joints in 10 patients, in 12 patients we diagnosed a sacroiliitis, in 3 patients a sacroiliac sclerosis. Descriptive evaluation and T2-calculation we showed, that MR is specific in differentiation of inflammation from sclerosis. The mean T2-relaxation time is 126 ms in healthy subjects, 320 ms in sacroiliitis and 87 ms in sclerotic areas. The results are significant in the Student-T-test (5% level). In addition the method allows the distinction of sclerosis from inflammation with a resolution of 2 mm. In evaluating sacroiliac rheumatic diseases MR may be helpful as a new imaging technique to complete the information of conventional radiography, computer assisted tomography and scintigraphy.

Adult↗
PubMed1986

RARE imaging: a fast imaging method for clinical MR.

Based on the principles of echo imaging, we present a method to acquire sufficient data for a 256 X 256 image in from 2 to 40 s. The image contrast is dominated by the transverse relaxation time T2. Sampling all projections for 2D FT image reconstruction in one (or a few) echo trains leads to image artifacts due to the different T2 weighting of the echo. These artifacts cannot be described by a simple smearing out of the image in the phase direction. Proper distribution of the phase-encoding steps on the echoes can be used to minimize artifacts and even lead to resolution enhancement. In spite of the short data acquisition times, the signal amplitudes of structures with long T2 are nearly the same as those in a conventional 2D FT experiment. Our method, therefore, is an ideal screening technique for lesions with long T2.

Humans↗
PubMed1986

Fat and water separation at 0.23 T using simultaneous shift selective imaging.

Based on the principle of selective inversion of the fat or water signal, we have developed a method which allows the simultaneous acquisition of separated fat and water images. In combination with multiecho techniques, this allows the determination of shift selective relaxation times. A detailed analysis of the relaxation behavior of a human leg at 0.23 T shows, that T2 of fat and water can differ by a factor of two or more. We think, that the potential of MRI for differential diagnosis can be greatly enhanced using our method.

Adipose Tissue↗
PubMed1986

[Pathology of the craniocervical junction as shown by magnetic resonance tomography. 68 cases].

In cases of a suspected lesion at the level of the cranio-cervical junction, MR should be considered as the imaging technique of choice. Tumours, inflammation and degenerative processes can be reliably demonstrated and diagnosed. Administration of contrast media, for example, gadolinium-DTPA, is necessary in selected cases only. Comparing "examination time" of x-ray myelography and high resolution x-ray CT with MR, one can well tolerate the long "acquisition" of MR images.

Arnold-Chiari Malformation↗
PubMed1986

[Diagnostic imaging potentialities of nuclear resonance tomography. Changes in vertebrae, ligaments and intervertebral disks in comparison with computed tomography].

This is a study of 49 patients with lesions of the spine excluding primary tumors of the spinal cord. All patients were examined by computed tomography and magnetic resonance imaging. Comparing both methods we observed slight diagnostic advantages for magnetic resonance imaging in inflammatory and neoplastic disease. Especially for evaluation of the spinal cord and subarachnoid space MR-imaging is far superior to computed tomography.

Adult↗
PubMed1985

Identification of the dadX gene coding for the predominant isozyme of alanine racemase in Escherichia coli K12.

Evidence is presented that alanine racemase activity in E. coli K12 is due to two distinct gene products. The predominant isozyme is inducible by either alanine stereoisomer and repressible by glucose. The gene dadX coding for its structure is located by the dadA gene determining the structure of D-amino acid dehydrogenase. The regulatory site for the expression of both genes, dadR, is located on the other side of dadA. The orientation of the dad operon established by multiple-point crosses and deletion mapping is as follows: fadR ...dadRAX ...hemA. The dadX alanine racemase activity is unusually refractory to changes of incubation temperature. It differs strikingly from that of the other isozyme, probably the product of the alr gene. The latter isozyme shows a typical dependence upon incubation temperature. The synthesis of alr alanine racemase is constitutive in respect of both alanine and glucose. In dadX mutants, in which alanine racemase activity equals only 15% of that in wild-type cells grown in the absence of an inducer or catabolite repressor, the dad operon cannot be induced by D-alanine. We presume, therefore, that L-alanine is involved more directly than D-alanine in dad operon regulation.

Alanine Racemase↗
PubMed1985

[Low-field magnetic resonance tomography with an iron-shielded resistive magnet].

As an alternative to costly MRI systems with superconductive magnets, first experiences with an iron-shielded resistive system (Tomikon BMT 1100, Bruker Medizintechnik--Rheinstetten) are reported. The magnetic field strength is 0.235 T, corresponding to a proton resonance frequency of 10 MHz. Our system is used mainly for research, the image quality being comparable with that of superconducting systems. Especially favourable is the low magnetic stray field of the self-shielding system. It allows unproblematic handling of patients in a clinical environment. Economic aspects are not discussed.

Brain Diseases↗