A Scalable Model for Human Scala-Tympani Phantoms

2011 ◽  
Vol 5 (1) ◽  
Author(s):  
James R. Clark ◽  
Frank M. Warren ◽  
Jake J. Abbott
Keyword(s):  
Cochlear Implant ◽  
In Vivo Studies ◽  
Scala Tympani ◽  
Anatomical Data ◽  
Cadaver Studies

In cochlear-implant (CI) insertion experiments, scala-tympani (ST) phantoms are often used in place of in vivo studies or cadaver studies. During the development of novel CI technology, a scaled-up phantom is often desirable. In this paper, we create a scalable model of the human ST by synthesizing published anatomical data and images. We utilize the model to fabricate an accurate, inexpensive, and reproducible ST phantom at a 3:1 scale.

scholarly journals Computational models for contact current dosimetry at frequencies below 1 MHz

2020 ◽  
Author(s):  
Pia Schneeweiss ◽  
Dorin Panescu ◽  
Dominik Stunder ◽  
Mark W. Kroll ◽  
Christopher J. Andrews ◽  
...  
Keyword(s):  
Computational Models ◽  
Scientific Basis ◽  
The Body ◽  
In Vivo Studies ◽  
International Electrotechnical Commission ◽  
Safety Standards ◽  
Body Model ◽  
Current Path ◽  
Cadaver Studies

AbstractElectric contact currents (CC) can cause muscle contractions, burns, or ventricular fibrillation which may result in life-threatening situations. In vivo studies with CC are rare due to potentially hazardous effects for participants. Cadaver studies are limited to the range of tissue’s electrical properties and the utilized probes’ size, relative position, and sensitivity. Thus, the general safety standards for protection against CC depend on a limited scientific basis. The aim of this study was therefore to develop an extendable and adaptable validated numerical body model for computational CC dosimetry for frequencies between DC and 1 MHz. Applying the developed model for calculations of the IEC heart current factors (HCF) revealed that in the case of transversal CCs, HCFs are frequency dependent, while for longitudinal CCs, the HCFs seem to be unaffected by frequency. HCFs for current paths from chest or back to hand appear to be underestimated by the International Electrotechnical Commission (IEC 60479-1). Unlike the HCFs provided in IEC 60479-1 for longitudinal current paths, our work predicts the HCFs equal 1.0, possibly due to a previously unappreciated current flow through the blood vessels. However, our results must be investigated by further research in order to make a definitive statement. Contact currents of frequencies from DC up to 100 kHz were conducted through the numerical body model Duke by seven contact electrodes on longitudinal and transversal paths. The resulting induced electric field and current enable the evaluation of the body impedance and the heart current factors for each frequency and current path.

Kinematics of the Midtarsal Joint During Standing Leg Rotation

2002 ◽  
Vol 92 (2) ◽  
pp. 77-81 ◽  
Author(s):  
Christopher Nester ◽  
Peter Bowker ◽  
Peter Bowden
Keyword(s):  
Range Of Motion ◽  
Three Dimensional ◽  
In Vivo Studies ◽  
Kinematic Data ◽  
Joint Characteristics ◽  
Infrared Cameras ◽  
Cadaver Studies ◽  
Midtarsal Joint ◽  
Invasive Techniques

Building on previous work that was cadaver based or involved invasive techniques, this study quantifies the kinematics of an approximation of the midtarsal joint with a noninvasive method. Three-dimensional kinematic data describing the motion of the forefoot and heel during transverse plane rotation of the leg were collected from 25 subjects by means of reflective markers and four infrared cameras. The motion between these segments was assumed to be the best possible clinical approximation of the midtarsal joint. The kinematic characteristics of the midtarsal joint were described in terms of the range and direction of motion in each cardinal body plane, the ratio of the range of motion in each plane, and the orientation of the axis of rotation. The characteristics of the midtarsal joint changed during the range of motion; thus, multiple axes of rotation could be calculated and joint characteristics were varied among subjects. The results of this in vivo method were generally consistent with those of cadaver studies and invasive in vivo studies. (J Am Podiatr Med Assoc 92(2): 77-81, 2002)

scholarly journals Effects of in vivo repositioning of slim modiolar electrodes on electrical thresholds and speech perception

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sang-Yeon Lee ◽  
Young Seok Kim ◽  
Hyung Dong Jo ◽  
Yoonjoong Kim ◽  
Marge Carandang ◽  
...  
Keyword(s):  
Speech Perception ◽  
Cochlear Implant ◽  
Functional Outcomes ◽  
Cadaveric Study ◽  
Scala Tympani ◽  
Insertion Depth ◽  
Sentence Recognition ◽  
Open Set

AbstractThe slim modiolar electrode has been reported to ensure better modiolar proximity than previous conventional perimodiolar electrodes and consistently high scala tympani localization. Nonetheless, variability in modiolar proximity exists even among slim modiolar electrodes, still leaving room for further improvement of modiolar proximity, which may positively affect functional outcomes. Given this, the pull-back maneuver was reported to increase the modiolar proximity of slim modiolar electrodes in a cadaveric study, but in vivo repositioning effects remain to be established. Here we identified that the pull-back maneuver led to better modiolar proximity than conventional insertion while maintaining a similar angular insertion depth. Notably, the reduced electrode-modiolus distance from the pull-back maneuver was associated with significantly lower impedances across electrodes postoperatively as well as reduced intraoperative electrophysiological thresholds than conventional insertion. Among adult cochlear implant recipients, this maneuver resulted in significantly better sentence recognition scores at three months postoperatively when compared to those with a conventional insertion; however, this benefit was not observed at later intervals. Collectively, slim modiolar electrodes with the pull-back maneuver further enhance the modiolar proximity, possibly leading to better open-set sentence recognition, at least in the early postoperative stage.

In vitro and in vivo studies of new cationic Zn(II)‐benzonaphthoporphyrazines as photosensitizers for PDT

2001 ◽  
Vol 5 (8) ◽  
pp. 645-651
Author(s):  
M. Peeva ◽  
M. Shopova ◽  
U. Michelsen ◽  
D. Wöhrle ◽  
G. Petrov ◽  
...  
Keyword(s):  
In Vivo Studies

Effect of caffeine on theophyliine on cerebral blood flow response to brain activation: In vitro and in vivo studies

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S198-S198
Author(s):  
Joseph R Meno ◽  
Thien-son K Nguyen ◽  
Elise M Jensen ◽  
G Alexander West ◽  
Leonid Groysman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Brain Activation ◽  
In Vivo Studies ◽  
Blood Flow Response ◽  
Flow Response

Effects of Unfractionated and Low Molecular Weight Heparins on Platelet Thromboxane Biosynthesis “In Vivo”

1994 ◽  
Vol 72 (06) ◽  
pp. 942-946 ◽  
Author(s):  
Raffaele Landolfi ◽  
Erica De Candia ◽  
Bianca Rocca ◽  
Giovanni Ciabattoni ◽  
Armando Antinori ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Unfractionated Heparin ◽  
Low Molecular Weight Heparin ◽  
Primary Source ◽  
In Vivo Studies ◽  
Low Molecular Weight ◽  
Heparin Administration ◽  
To Receive

SummarySeveral “in vitro” and “in vivo” studies indicate that heparin administration may affect platelet function. In this study we investigated the effects of prophylactic heparin on thromboxane (Tx)A2 biosynthesis “in vivo”, as assessed by the urinary excretion of major enzymatic metabolites 11-dehydro-TxB2 and 2,3-dinor-TxB2. Twenty-four patients who were candidates for cholecystectomy because of uncomplicated lithiasis were randomly assigned to receive placebo, unfractionated heparin, low molecular weight heparin or unfractionaed heparin plus 100 mg aspirin. Measurements of daily excretion of Tx metabolites were performed before and during the treatment. In the groups assigned to placebo and to low molecular weight heparin there was no statistically significant modification of Tx metabolite excretion while patients receiving unfractionated heparin had a significant increase of both metabolites (11-dehydro-TxB2: 3844 ± 1388 vs 2092 ±777, p <0.05; 2,3-dinor-TxB2: 2737 ± 808 vs 1535 ± 771 pg/mg creatinine, p <0.05). In patients randomized to receive low-dose aspirin plus unfractionated heparin the excretion of the two metabolites was largely suppressed thus suggesting that platelets are the primary source of enhanced thromboxane biosynthesis associated with heparin administration. These data indicate that unfractionated heparin causes platelet activation “in vivo” and suggest that the use of low molecular weight heparin may avoid this complication.

Ex Vivo Inhibition of Platelet Aggregation in Patients with Severe Limb Arteriopathy Treated with BAY U3405, a Specific IX A2 Receptor Antagonist

1994 ◽  
Vol 72 (05) ◽  
pp. 659-662 ◽  
Author(s):  
S Bellucci ◽  
W Kedra ◽  
H Groussin ◽  
N Jaillet ◽  
P Molho-Sabatier ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Randomized Study ◽  
In Vivo Studies ◽  
Walking Distance ◽  
Peripheral Blood Flow ◽  
Walking Ability ◽  
Double Blind ◽  
Platelet Factor

SummaryA double-blind, placebo-controlled randomized study with BAY U3405, a specific thromboxane A2 (TX A2) receptor blocker, was performed in patients suffering from severe stade II limb arteriopathy. BAY U3405 or placebo was administered in 16 patients at 20 mg four times a day (from day 1 to day 3). Hemostatic studies were done before therapy, and on day 2 and day 3 under therapy. On day 3, BAY U3405 was shown to induce a highly statistically significant decrease of the velocity and the intensity of the aggregations mediated by arachidonic acid (56 ± 37% for the velocity, 58 ± 26% for the intensity) or by U46619 endoperoxide analogue (36 ± 35% for the velocity, 37 ± 27% for the intensity). Similar results were already observed on day 2. By contrast, such a decrease was not noticed with ADP mediated platelet aggregation. Furthermore, plasma levels of betathrombo-globulin and platelet factor 4 remained unchanged. Peripheral hemodynamic parameters were also studied. The peripheral blood flow was measured using a Doppler ultrasound; the pain free walking distance and the total walking ability distance were determined under standardized conditions on a treadmill. These last two parameters show a trend to improvement which nevertheless was not statistically significant. All together these results encourage further in vivo studies using BAY U3405 or related compounds on a long-term administration.

Inactivation of Factor XIa in Vivo: Studies in Chimpanzees and in Humans

1996 ◽  
Vol 76 (04) ◽  
pp. 549-555 ◽  
Author(s):  
Walter A Wuillemin ◽  
C Erik Hack ◽  
Wim K Bleeker ◽  
Bart J Biemond ◽  
Marcel Levi ◽  
...  
Keyword(s):  
Antithrombin Iii ◽  
Life Time ◽  
In Vivo Studies ◽  
Clinical Samples ◽  
Plasma Samples ◽  
C1 Inhibitor ◽  
Elimination Kinetics ◽  
Factor Xia ◽  
Best Parameter

SummaryC1-inhibitor (C1Inh), antithrombin III (ATIII), α1-antitrypsin (a1AT), and α2-antiplasmin (a2AP) are known inhibitors of factor XIa (FXIa). However, their precise contribution to FXIa inactivation in vivo is not known. We investigated FXIa inactivation in chimpanzees and assessed the contribution of these inhibitors to FXIa inactivation in patients with presumed FXI activation.Chimpanzees were infused with FXIa and the various FXIa-FXIa inhibitor complexes formed were measured. Most of FXIa was complexed to C1Inh (68%), followed by a2AP (13%), a1AT (10%), and ATIII (9%). Analysis of the plasma elimination kinetics revealed a half-life time of clearance (t1/2) for the FXIa-FXIa inhibitor complexes of 95 to 104 min, except for FXIa-a1AT, which had a t1/2 of 349 min. Due to this long t1/2, FXIa-a1AT complexes were predicted to show the highest levels in plasma samples from patients with activation of FXI. This was indeed shown in patients with disseminated intravascular coagulation, recent myocardial infarction or unstable angina pectoris. We conclude from this study that in vivo C1Inh is the predominant inhibitor of FXIa, but that FXIa-a1 AT complexes due to their relatively long t1/2 may be the best parameter to assess FXI activation in clinical samples.

Effects of Ellagic Acid upon the Rabbit Fibrinolytic System

1972 ◽  
Vol 27 (01) ◽  
pp. 063-071
Author(s):  
S. G Iatridis ◽  
P. G Iatridis
Keyword(s):  
Continuous Infusion ◽  
Ellagic Acid ◽  
Animal Experimentation ◽  
Inhibitory Effect ◽  
In Vivo Studies ◽  
Clot Lysis ◽  
Hageman Factor ◽  
Lysis Activity ◽  
Site Of Action

SummaryThe present investigation deals with in vivo studies of possible relations of active Hageman factor (HFa) to the problems of thrombolysis. The study is based upon animal experimentation in which 40 normal, 5 dicumarolized and 5 heparinized rabbits each received ellagic acid (Elac 10-2 M) by intravenous continuous infusion at a rate of 1 ml/min for a period of 25 min. The data suggest that the Elac infusion induced in vivo activation of HF. Streptokinase (SK) injection 25 min from the start of Elac i. v. infusion failed to induce clot lysis in blood drawn one min after its injection. The phenomenon was more prominent with low (SK 250 U or 500 U) concentrations of SK. With higher concentrations, SK-induced clot lysis activity was not affected by Elac infusion.In dicumarolized and heparinized rabbits Elac infusion still counteracted the fibrinolysis activating effect of low concentration of SK. The possibility that the above described phenomenon was due to either hypercoagulability or to a non-specific inhibitory effect of Elac upon SK was explored and excluded.It is concluded that HFa and SK have the same site of action. Thus it seems that HFa may block the precursor upon which SK acts by forming a complex with it. It is stressed that activation of this precursor by HFa requires a suitable surface.

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