The floating mass transducer at the round window: direct transmission or bone conduction?

The round window placement of a floating mass transducer (FMT) is a new approach for coupling an implantable hearing system to the cochlea. We evaluated the vibration transfer to the cochlear fluids of an FMT placed at the round window (rwFMT) with special attention to the role of bone conduction. A posterior tympanotomy was performed on eleven ears of seven human whole head specimens. Several rwFMT setups were examined using laser Doppler vibrometry measurements at the stapes and the promontory. In three ears, the vibrations of a bone anchored hearing aid (BAHA) and an FMT fixed to the promontory (pFMT) were compared to explore the role of bone conduction. Vibration transmission to the measuring point at the stapes was best when the rwFMT was perpendicularly placed in the round window and underlayed with connective tissue. Fixation of the rwFMT to the round window exhibited significantly lower vibration transmission. Although measurable, bone conduction from the pFMT was much lower than that of the BAHA. Our results suggest that the rwFMT does not act as a small bone anchored hearing aid, but instead, acts as a direct vibratory stimulator of the round window membrane.

Factors improving the vibration transfer of the floating mass transducer at the round window

With the placement of a floating mass transducer (FMT) at the round window, a new approach of coupling an implantable hearing system to the cochlea has been introduced. The aim of the present experimental study is to examine the influence of different ways of FMT placement at the round window on the vibration energy transfer to the cochlea.

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

An implantable transducer for monitoring the flow of Cerebrospinal fluid (CSF) for the treatment of hydrocephalus has been developed which is based on measuring the heat dissipation of a local thermal source. The transducer uses passive telemetry at 13.56 MHz for power supply and read out of the measured flow rate. The in vitro performance of the transducer has been characterized using artificial Cerebrospinal Fluid (CSF) with increased protein concentration and artificial CSF with 10\% fresh blood. After fresh blood was added to the artificial CSF a reduction of flow rate has been observed in case that the sensitive surface of the flow sensor is close to the sedimented erythrocytes. An increase of flow rate has been observed in case that the sensitive surface is in contact with the remaining plasma/artificial CSF mix above the sediment which can be explained by an asymmetric flow profile caused by the sedimentation of erythrocythes having increased viscosity compared to artificial CSF. After removal of blood from artificial CSF, no drift could be observed in the transducer measurement which could be associated to a deposition of proteins at the sensitive surface walls of the packaged flow transducer. The flow sensor specification requirement of +-10\% for a flow range between 2 ml/h and 40 ml/h. could be confirmed at test conditions of 37 degrees C.

A comparative study of water perfusion catheters and microtip transducer catheters for urethral pressure measurements

The aim of this study was to compare the maximum urethral closure pressure (MUCP) measures with two different techniques: water perfused catheter and microtip transducer catheters with respect to reproducibility and comparability for urethral pressure measurements. Eighteen women with stress urinary incontinence had repeat static urethral pressure profilometry on a different day using a dual microtip transducer and water perfused catheter (Brown and Wickham). The investigators were blinded to the results of the other. The microtip measurements were taken in the 45 degrees upright sitting position with the patient at rest at a bladder capacity of 250 ml using an 8 Fr Gaeltec(R) double microtip transducer withdrawn at 1 mm/s, and the transducer was orientated in the three o'clock position. Three different measures were taken for each patient. Three water perfusion measurements were performed with the patient at rest in the 45 degrees upright position at a bladder capacity of 250 ml using an 8 Fr BARD dual lumen catheter withdrawn at 1 mm/s. The mean water perfusion MUCP measure was 26.1 cm H(2)0, significantly lower than the mean microtip measure of 35.7 cm H(2)0. The correlation coefficient comparing each water perfusion measurement with the other water perfusion measures in the same patient was excellent, at 0.95 (p = 0.01). Correlation coefficient comparing each microtip measure with the other microtip measure in the same patient was also good, ranging from 0.70 to 0.80. This study confirms that both water perfusion catheters and microtip transducers have excellent or very good reproducibility with an acceptable intraindividual variation for both methods.

Comparison of Doppler-derived aortic velocities obtained from various transducer sites in healthy dogs and cats

In normal dogs and dogs with subaortic stenosis, it is known that the subcostal transducer site provides higher left ventricular ejection velocities than does the left apical site. We hypothesized that aortic flow velocities could also be obtained from the right parasternal long-axis view, optimized for the placement of the Doppler cursor as parallel as possible into the aortic root. In 15 healthy dogs and 13 healthy cats, high-pulsed repetition frequency Doppler flow velocity measurements in the proximal aorta were performed using two-dimensional echocardiographic guidance. The mean [ +/- standard error of the mean (SEM)] peak aortic flow velocities in healthy dogs were as follows: subcostal site 1.46 +/- 0.05 m/s; apical site 1.12 +/- 0.06 m/s; right parasternal long-axis site 1.09 +/- 0.05 m/s. In healthy cats, the following peak aortic flow velocities were observed: apical site 0.87 +/- 0.03m/s; right parasternal long-axis site 0.87 +/- 0.03 m/s. Aortic flow velocities obtained from the subcostal site were significantly higher in healthy dogs than those obtained from the left apical and right parasternal long-axis site (P< 0.001). There was no statistical difference between the peak aortic flow velocities obtained from right parasternal long-axis and left apical transducer position in all groups. We conclude therefore that right parasternal long-axis and left apical-derived aortic flow velocities are similar and may be used interchangeably in healthy dogs and cats.

Piezoelectric alveolar ridge-splitting technique with simultaneous implant placement: a cohort study with 2-year radiographic results

PURPOSE Extended grafting procedures in atrophic ridges are invasive and time-consuming and increase cost and patient morbidity. Therefore, ridge-splitting techniques have been suggested to enlarge alveolar crests. The aim of this cohort study was to report techniques and radiographic outcomes of implants placed simultaneously with a piezoelectric alveolar ridge-splitting technique (RST). Peri-implant bone-level changes (ΔIBL) of implants placed with (study group, SG) or without RST (control group, CG) were compared. MATERIALS AND METHODS Two cohorts (seven patients in each) were matched regarding implant type, position, and number; superstructure type; age; and gender and received 17 implants each. Crestal implant bone level (IBL) was measured at surgery (T0), loading (T1), and 1 year (T2) and 2 years after loading (T3). For all implants, ΔIBL values were determined from radiographs. Differences in ΔIBL between SG and CG were analyzed statistically (Mann-Whitney U test). Bone width was assessed intraoperatively, and vertical bone mapping was performed at T0, T1, and T3. RESULTS After a mean observation period of 27.4 months after surgery, the implant survival rate was 100%. Mean ΔIBL was -1.68 ± 0.90 mm for SG and -1.04 ± 0.78 mm for CG (P = .022). Increased ΔIBL in SG versus CG occurred mainly until T2. Between T2 and T3, ΔIBL was limited (-0.11 ± 1.20 mm for SG and -0.05 ± 0.16 mm for CG; P = .546). Median bone width increased intraoperatively by 4.7 mm. CONCLUSIONS Within the limitations of this study, it can be suggested that RST is a well-functioning one-stage alternative to extended grafting procedures if the ridge shows adequate height. ΔIBL values indicated that implants with RST may fulfill accepted implant success criteria. However, during healing and the first year of loading, increased IBL alterations must be anticipated.

Pyroelectric and piezoelectric scanning microscopy applied to reveal the bipolar state of 4-iodo-4′-nitrobiphenyl (INBP)

Two recent scanning probe techniques were applied to investigate the bipolar twin state of 4-iodo-4′-nitrobiphenyl (INBP) crystals. Solution grown crystals of INBP show typically a morphology which does not express that of a mono-domain polar structure (Fdd2, mm2). From previous X-ray diffraction a twinning volume ratio of [similar]70 : 30 is now explained by two unipolar domains (Flack parameter: 0.075(29)) of opposite orientation of the molecular dipoles, joined by a transition zone showing a width of [similar]140 μm. Scanning pyroelectric microscopy (SPEM) demonstrates a continuous transition of the polarization P from +P into −P across the zone. Application of piezoelectric force microscopy (PFM) confirms unipolar alignment of INBP molecules down to a resolution of [similar]20 nm. A previously proposed real structure for INBP crystals built from lamellae with antiparallel alignment is thus rejected. Anomalous X-ray scattering was used to determine the absolute molecular orientation in the two domains. End faces of the polar axis 2 are thus made up by NO2 groups. Using a previously determined negative pyroelectric coefficient pc leads to a confirmation also by a SPEM analysis. Calculated values for functional group interactions (DA), (AA), (DD) and the stochastic theory of polarity formation allow us to predict that NO2 groups should terminate corresponding faces. Following the present analysis, INBP may represent a first example undergoing dipole reversal upon growth to end up in a bipolar state.

Vessel orientation-dependent sensitivity of optoacoustic imaging using a linear array transducer

For clinical optoacoustic imaging, linear probes are preferably used because they allow versatile imaging of the human body with real-time display and free-hand probe guidance. The two-dimensional (2-D) optoacoustic image obtained with this type of probe is generally interpreted as a 2-D cross-section of the tissue just as is common in echo ultrasound. We demonstrate in three-dimensional simulations, phantom experiments, and in vivo mouse experiments that for vascular imaging this interpretation is often inaccurate. The cylindrical blood vessels emit anisotropic acoustic transients, which can be sensitively detected only if the direction of acoustic radiation coincides with the probe aperture. Our results reveal for this reason that the signal amplitude of different blood vessels may differ even if the vessels have the same diameter and initial pressure distribution but different orientation relative to the imaging plane. This has important implications for the image interpretation, for the probe guidance technique, and especially in cases when a quantitative reconstruction of the optical tissue properties is required.

Helicobacter pylori Inhibits Dendritic Cell Maturation via Interleukin-10-Mediated Activation of the Signal Transducer and Activator of Transcription 3 Pathway.

Helicobacter pylori infects the human gastric mucosa causing a chronic infection that is the primary risk factor for gastric cancer development. Recent studies demonstrate that H. pylori promotes tolerogenic dendritic cell (DC) development indicating that this bacterium evades the host immune response. However, the signaling pathways involved in modulating DC activation during infection remain unclear. Here, we report that H. pylori infection activated the signal transducer and activator of transcription 3 (STAT3) pathway in murine bone marrow-derived DCs (BMDCs) and splenic DCs isolated ex vivo. Isogenic cagA-, cagE-, vacA- and urease-mutants exhibited levels of phosphoSTAT3 that were comparable to in the wild-type (WT) parent strain. H. pylori-infected BMDCs produced increased immunosuppressive IL-10, which activated STAT3 in an autocrine/paracrine fashion. Neutralization of IL-10 prevented H. pylori-mediated STAT3 activation in both BMDCs and splenic DCs. In addition, anti-IL-10 treatment of infected H. pylori-BMDCs was associated with increased CD86 and MHC II expression and enhanced proinflammatory IL-1β cytokine secretion. Finally, increased CD86 and MHC II expression was detected in H. pylori-infected STAT3 knockout DCs when compared to WT controls. Together, these results demonstrate that H. pylori infection induces IL-10 secretion in DCs, which activates STAT3, thereby modulating DC maturation and reducing IL-1β secretion. These findings identify a host molecular mechanism by which H. pylori can manipulate the innate immune response to potentially favor chronic infection and promote carcinogenesis. © 2014 S. Karger AG, Basel.