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Biomedical subjects

J Hennig

Publications and source records attributed to J Hennig.

At least 181 records · Page 10Linked to original sources
PubMed1975

Vitrectomy-instrumentation-system MS 7.

An instrumentation-system (MS 7) for open-sky- as well as for pars-plana-vitrectomy is described. The intraocular canula is equipped with a special rotating cutting device. Suction is generated by a suction-pump in the power supply unit. Intraocular illumination is obtained by a detachable light pipe on the vitrectomy-canula or-for the bimanual technique-by a special hand-piece with infusion and fiber optic illumination. The infusion-canula in the hand-piece can be replaced by a micro-scissor with infusion-channel. Despite the motor the whole system can be easy cleaned and sterilized.

Humans↗
PubMed1975

[An instrument for vitrectomy (author's transl)].

The development of a new vitrectomy instrument has contributed to advancement in vitreous surgery to a large extent. The principle of this instrument is the suction of the vitreous into a needle and its simultaneous resection. In the meantime several constructions have been described. The resection apparatus, observation possibilities and illumination are discussed.

Humans↗
PubMedDate not supplied

Time-resolved measurements of brain activation after a short visual stimulus: new results on the physiological mechanisms of the cortical response.

This paper presents examinations of the time course of the signal from the visual cortex following a brief (2 s) light stimulus. Signal was generated from a 2 x 2 x 2 ml voxel using a modified point-resolved spectroscopy experiment. In accordance with previous studies a triphasic time course was observed. The results indicate that the observable signal contains contributions from non blood oxygen level dependent signal changes occurring immediately after the onset of stimulation. The response to multiple stimuli could be fitted with a response model which is linear with respect to the BOLD-phase of the response. This suggests that the experiments using a very weak stimulus were performed below the limit of the arterial reserve. This is in marked contrast to other studies performed by functional magnetic resonance imaging as well as optical imaging. First results using echo planar imaging confirm the common origin of the signals in the activated cortical areas.

Adult↗
PubMedDate not supplied

MR imaging of the pericardial cyst.

Findings obtained with magnetic resonance (MR) imaging in four patients with pericardial cyst are reported. MR imaging allowed not only localization and diagnosis in all four cases but characterization of cystic content. MR imaging, including RARE (rapid acquisition with relaxation enhancement) MR hydrography, which shows only liquids with T2s greater than 500 msec, proved to be useful in characterizing the fluid content of a mediastinal lesion and monitoring follow-up. In one case, MR imaging allowed differentiation of a pericardial cyst from a suspected necrotic lymph node in a patient with colic carcinoma, with subsequent correction of staging and therapy. The authors conclude that MR imaging is the method of choice for diagnosis (especially in unusual locations) and monitoring of pericardial cysts and for differential diagnosis of malignant mediastinal cystic tumors that show a solid part.

Diagnosis, Differential↗
PubMedDate not supplied

Overlapping section coverage in multisection imaging.

A method is proposed in which the section position for two-dimensional Fourier transform multisection imaging is advanced from one phase-encoding step to the next, so that information is sampled continuously over the total volume under observation. This "ramp scan" technique allows reconstruction of images from any arbitrary position within the sampled volume. The imaging properties depend strongly on the order of distribution of phase-encoding steps to the different section positions. In practice, images are reconstructed at each nominal position of a multisection experiment, plus at each position halfway between sections. The volume under study is thus represented by overlapping sections. The gaps between sections that arise in conventional multisection imaging--even with optimized pulse shapes--are thus avoided. This approach is applicable not only to conventional spin-echo imaging but to other techniques such as RARE (rapid acquisition with relaxation enhancement) and gradient-echo and echo-planar imaging.

Fourier Analysis↗
PubMedDate not supplied

Analysis of myocardial motion based on velocity measurements with a black blood prepared segmented gradient-echo sequence: methodology and applications to normal volunteers and patients.

The paper describes a strategy for measuring and characterizing myocardial motion in terms of velocity parameters derived from measurements with a segmented black blood prepared phase contrast gradient echo sequence. The characteristic parameters are calculated by transforming the velocities measured on a pixel-by-pixel basis across the left ventricle from the laboratory frame of reference into a cylindrical coordinate system, in which the motion velocities within the short axis plane are represented in polar coordinates and which is located at the center of the myocardium and moving with it over the ECG cycle. First results in a study with 12 healthy volunteers gave highly consistent values for the radial (expansion/compression) as well as the rotational velocities. Except for one volunteer, motion at the R wave of the ECG starts with clockwise rotation, followed by contraction and expansion accompanied by counterclockwise rotation. First examinations of patients with global and focal disease demonstrate the potential to detect disturbances in the local as well as the overall motion patterns.

Adult↗