Biomedical subjects

M Mück

Publications and source records attributed to M Mück.

4 recordsLinked to original sources

PubMed1993

Magnetoencephalography using high temperature rf SQUIDs.

We have developed high-critical-temperature radio-frequency Super conducting QUantum Interference Devices (SQUIDs) with step-edge grain-boundary Josephson junctions and large flux focusers. These planar devices were fabricated from epitaxial YBa2Cu3O7 films and operated in the magnetometer and first-order gradiometer configurations while immersed in liquid nitrogen. At the temperature of 77K, we have attained a magnetic field resolution for the magnetometer better than 200 fT/Hz1/2 down to less than 1 Hz, i.e., over the low signal frequency range important for medical diagnostics. The results to date show a high promise for biomagnetic diagnostics. For the first time, we recorded the evoked responses from human brains using a high-temperature magnetometer and a first-order electronic gradiometer channel simultaneously. These results were obtained in a magnetically shielded room. An improvement in the magnetic field resolution by another order of magnitude is possible and probable.

Acoustic Stimulation↗

PubMed1993

High temperature RF SQUIDs for biomedical applications.

We have been investigating the feasibility of radio-frequency RF, low-noise superconducting quantum interference device (SQUID) magnetometers and gradiometers operating in liquid nitrogen at 77 K. Using flux-focusing structures fabricated from epitaxial YBa2Cu3O7-chi films, we have attained a magnetic field resolution for a magnetometer of better than 200 fT Hz-1/2 at less than 1 Hz, i.e. over the low signal-frequency range important for biomedical diagnostics. At 77 K, this magnetometer recorded diagnostically useful heart signals, voluntary eye-blink signals, and also the first evoked response of a human brain. These and similar results were obtained in a magnetically shielded room. We were also able to record heart signals in the absence of any shielding when using a first-order gradiometer. An improvement in the magnetic field resolution of our magnetometers and gradiometers by, at least, another order of magnitude is possible and probable.

Electric Conductivity↗

PubMed1993

Microcirculatory functions in systemic sclerosis: additional parameters for therapeutic concepts?

To study the functional reactivity of the cutaneous microcirculation in progressive systemic sclerosis (PSS), hyperemic responses after arterial occlusion (3 min) and during local heating (42 degrees C) were investigated with simultaneous measurements of red blood cell flux and cutaneous oxygen tension (pcuO2) of the skin in female patients (n = 19) with PSS and in healthy female controls (n = 15). Additionally, serum levels of 6-keto-prostaglandin 1 alpha (PGF1 alpha), a stable metabolite of prostacyclin, were compared to the microcirculatory data, and both were used to evaluate further a standardized therapy with 10-d intravenous calcitonin (100 IU/d) infusion in six PSS patients. In PSS, the initial mean pcuO2 value was significantly reduced and was inversely proportional to flux and to PGF1 alpha levels, whereas the flux and pcuO2 responses to the above hyperemic stimuli showed significant reductions, revealing a pattern of "hyperemic hypoxia" probably due to exhausted functional reserves of cutaneous perfusion. During calcitonin infusion significant rises in pcuO2 and temporarily in PGF1 alpha and flux were found. After 10 d of therapy, increased pcuO2 was associated significantly with decreased flux, indicating a shifting of blood from deeper regulatory vessels to the subepidermal capillaries. Both clinical improvement and the results of microcirculatory measurements demonstrate a beneficial effect of calcitonin on the cutaneous microcirculation in PSS patients, possibly due in part to a short-term increase in release of endogenous prostacyclin from the vascular endothelium during the infusion. The disturbed reactivity of the dermal vessels in PSS is important for the evaluation of therapeutic concepts and stresses, together with the elevated PGF1 alpha plasma levels, vascular factors in the pathogenesis of PSS.

Aged↗

PubMed1991

A serial read-out scheme for SQUID systems.

A serial read-out scheme for multichannel SQUID systems is discussed, which can decrease the expense of electronic components needed for conventional multichannel systems. In case of RF SQUID systems, this scheme allows the use of only one transmission line between all SQUIDs and the room temperature electronics, thus decreasing helium losses caused by heat transport through electrical wires. Additionally, part of the read-out electronics can be shared by all channels. The noise properties as well as the influence of multiplex frequency on the stability of the flux-locked loop and on slew rate are studied in some detail.

Equipment Design↗