Influence of bone conduction transducer type and placement on ocular and cervical vestibular evoked myogenic potentials.

Evaluating the effectiveness of different bone conduction (BC) transducers with controlled coupling force to elicit cervical and ocular vestibular evoked myogenic potentials (cVEMPs, oVEMPs) in healthy subjects by comparing response rates, amplitudes, latencies, thresholds and asymmetry ratios. Prospective experimental study including healthy participants. VEMPs were measured to different stimulation modes; the BC transducer coupling force was controlled to 5.4 (± 0.5) Newton. cVEMPs: to bone conducted vibration (BCV) with the B81 transducer on the mastoid; oVEMPs: to BCV with the B81 on the mastoid, BCV with the B81 on the forehead, and BCV with the Mini-Shaker 4810 on the forehead. Air conducted sound (ACS) with insert earphones was used as reference. Data of 24 normal subjects (mean age 25.3 (± 3.0) years) were analyzed. ACS and BCV with the B81on the mastoid evoked cVEMPs in 100% of ears. The highest oVEMP response rates were obtained with the B81 on the mastoid (83-92%), the lowest with the B81 on the forehead (17-22%). The Mini-Shaker elicited lower response rates (65%) compared to results from the literature without coupling force control and compared to ACS (78-87%). Amplitudes were higher for BCV than ACS. ACS and BCV on the mastoid caused higher asymmetry compared to BCV forehead stimulation. The B81 was feasible to elicit VEMPs with mastoid placement and can be used as an approved medical device to measure BCV VEMPs in a clinical set-up. Normative asymmetry values have to be established due to higher variability for mastoid stimulation.

U.S. Army Combat Medic eFAST Performance with a Novel Versus Conventional Transducers: A Randomized, Crossover Trial.

BACKGROUND: Point-of-injury extended focused assessment with sonography in trauma (eFAST) may identify life-threatening torso hemorrhage and expedite casualty evacuation. The purpose of this study was to compare combat medic eFAST performance between the novel and conventional ultrasound (US) transducers. METHODS: We conducted a randomized crossover trial. Medic participants, previously naïve to US, were randomized to the type of transducer first utilized. The primary outcome was eFAST completion time in seconds. Secondary outcomes included diagnostic accuracy, technical adequacy, and transducer ease-of-use rating. RESULTS: Forty medics performed 160 eFASTs. We found a statistically significant difference in eFAST completion times in favor of conventional transducers (304 vs. 358 s; P = 0.03). There was no statistically significant difference between the conventional and novel transducers in terms of diagnostic accuracy (97.7% vs. 96.0%; P = 0.25) and technical adequacy (65% vs. 72.5%; P = 0.11). Median transducer ease-of-use rating (Likert 1-5 scale) was statistically significant in favor of the conventional transducers (5 vs. 4; P = < 0.001). CONCLUSIONS: Extended focused assessment with sonography in trauma exam times was faster with the conventional transducers. Combat medics performed diagnostically accurate eFASTs with both transducer types in a simulated aid station setting after a brief training intervention. Conventional transducers were rated higher for ease-of-use.

Comparison of Acceptable Noise Level Generated Using Different Transducers and Response Modes.

The acceptable noise level (ANL) was defined by subtracting the background noise level (BNL) from the most comfortable listening level (MCL) (ANL = MCL - BNL). This study compared the ANL obtained through different methods in 20 Chinese subjects with normal hearing. ANL was tested with Mandarin speech materials using a loudspeaker or earphones, with each subject tested by himself or by the audiologist. The presentation and response modes were as follows: (1) loudspeaker with self-adjusted noise levels using audiometer controls (LS method); (2) loudspeaker with the subject signaling the audiologist to adjust speech and noise levels (LA method); (3) earphones with self-adjusted noise levels using audiometer controls (ES method); and (4) earphones with the subject signaling the audiologist to adjust speech and noise levels (EA method). ANL was calculated from three measurements with each method. There was no significant difference in the ANL obtained through different presentation modes or response modes sound. The correlations between ANL, MCL, and BNL obtained from each two methods were significant. In conclusion, the ANL in normal-hearing Mandarin listeners may not be affected by presentation modes such as a loudspeaker or earphones nor is it affected by self-adjusted or audiologist-adjusted response modes. Earphone audiometry is as reliable as sound field audiometry and provides an easy and convenient way to measure ANL.

Routine Ultrasound Quality Assurance in a Multi-Unit Radiology Department: A Retrospective Evaluation of Transducer Failures.

The importance of quality assurance (QA) in medical ultrasound (US) has been widely recognized and recommendations concerning technical QA have been published over the years. However, the demonstrated impact of a properly working QA protocol on clinical routine has been scarce. We investigated the transducer write-off causes for a 5-y period in a multi-unit radiology department with an annual average of 230 transducers in demanding diagnostic use. The transducer faults and the initial observers of the faults leading to transducer write-offs were traced and categorized. The most common cause of transducer write-off was an image uniformity problem or element failure. Mechanical faults or excessive leakage current and defects in the lens constituted smaller yet substantial shares. Our results suggest that a properly working routine QA program can detect majority of the faults before they are reported by users.

The Effects of Fluidic Loading on Underwater Contact Sensing with Robotic Fins and Beams.

As robots become more involved in underwater operations, understanding underwater contact sensing with compliant systems is fundamental to engineering useful haptic interfaces and vehicles. Despite knowledge of contact sensation in air, little is known about contact sensing underwater and the impact of fluid on both the robotic probe and the target object. The objective of this work is to understand the effects of fluidic loading, fin webbing, and target object geometry on strain sensation within compliant robotic fins and beams during obstacle contact. General descriptions of obstacle contact were sought for strain measurements in fins and beams. Multiple phases of contact were characterized where the robot, fluid, and object interact to affect sensory signals. Unlike in air, the underwater structure-fluid-structure interaction (SFSI) caused changes to strain in each phase of contact. The addition of webbing to beams created a mechanical coupling between adjacent beams, which changed contact strains. Complex obstacle geometries tended to make contact less apparent and caused stretch in fins. This work demonstrates several effects of fluidic loading on strain sensing with compliant robotic beams and fins as they contact obstacles in air and underwater, and provides guidance for future work in underwater active sensing with compliant manipulators.

Bacterial contamination of ultrasound probes at a tertiary referral university medical center.

OBJECTIVE: The purpose of this study was to assess the adequacy of our institution's ultrasound probe-disinfecting protocols, determine compliance with the guidelines, and then implement changes if needed. MATERIALS AND METHODS: We first assessed the prevalence of bacterial contamination (and thus the potential for bacterial transmission) by swabbing all ultrasound probes (n = 31) in the radiology department and culturing the samples. Next, in conditions simulating the typical work environment, we determined the efficacy of our probe-disinfecting protocols by seeding probes with 10(4)-10(9) CFU/mL of methicillin-resistant Staphylococcus aureus (MRSA), disinfecting the seeded probes with 0.5% accelerated hydrogen peroxide, and then swabbing the disinfected probes to assess for bacterial growth. RESULTS: Seven of 31 (22.6%) probes were positive for bacterial growth--none of which were endocavity probes (0/4). Four of 14 visibly soiled probes (28.6%) showed bacterial growth, and four of seven probes positive for bacteria (57.1%) were visibly soiled. No MRSA grew after seeding probes with MRSA and then disinfecting with 0.5% accelerated hydrogen peroxide. Sonography guidelines and general disinfecting guidelines were reviewed. CONCLUSION: Our protocols for disinfecting nonendocavity and endocavity probes are compliant with sonography guidelines and general disinfecting guidelines. Although limited by a small sample size, our study showed that our protocol for disinfecting endocavity probes seems adequate. With a 25.9% bacterial contamination rate for nonendocavity probes, the adequacy of our protocol for disinfecting nonendocavity probes is more debatable; however, this bacterial contamination rate is at the lower end of the values reported in the literature. With the use of an effective disinfectant, education of sonographers, and implemented changes, we hope to decrease bacterial contamination rates and thus decrease the potential for bacterial transmission.

Where do pulse oximeter probes break?

Pulse oximetry, a non-invasive method for accurate assessment of blood oxygen saturation (SPO2), is an important monitoring tool in health care facilities. However, it is often not available in many low-resource settings, due to expense, overly sophisticated design, a lack of organised procurement systems and inadequate medical device management and maintenance structures. Furthermore medical devices are often fragile and not designed to withstand the conditions of low-resource settings. In order to design a probe, better suited to the needs of health care facilities in low-resource settings this study aimed to document the site and nature of pulse oximeter probe breakages in a range of different probe designs in a low to middle income country. A retrospective review of job cards relating to the assessment and repair of damaged or faulty pulse oximeter probes was conducted at a medical device repair company based in Cape Town, South Africa, specializing in pulse oximeter probe repairs. 1,840 job cards relating to the assessment and repair of pulse oximeter probes were reviewed. 60.2 % of probes sent for assessment were finger-clip probes. For all probes, excluding the neonatal wrap probes, the most common point of failure was the probe wiring (>50 %). The neonatal wrap most commonly failed at the strap (51.5 %). The total cost for quoting on the broken pulse oximeter probes and for the subsequent repair of devices, excluding replacement components, amounted to an estimated ZAR 738,810 (USD $98,508). Improving the probe wiring would increase the life span of pulse oximeter probes. Increasing the life span of probes will make pulse oximetry more affordable and accessible. This is of high priority in low-resource settings where frequent repair or replacement of probes is unaffordable or impossible.

Analyzing the impact of ambient temperature indicators on transformer life in different regions of Chinese mainland.

Regression analysis is applied to quantitatively analyze the impact of different ambient temperature characteristics on the transformer life at different locations of Chinese mainland. 200 typical locations in Chinese mainland are selected for the study. They are specially divided into six regions so that the subsequent analysis can be done in a regional context. For each region, the local historical ambient temperature and load data are provided as inputs variables of the life consumption model in IEEE Std. C57.91-1995 to estimate the transformer life at every location. Five ambient temperature indicators related to the transformer life are involved into the partial least squares regression to describe their impact on the transformer life. According to a contribution measurement criterion of partial least squares regression, three indicators are conclusively found to be the most important factors influencing the transformer life, and an explicit expression is provided to describe the relationship between the indicators and the transformer life for every region. The analysis result is applicable to the area where the temperature characteristics are similar to Chinese mainland, and the expressions obtained can be applied to the other locations that are not included in this paper if these three indicators are known.

Investigation of a significant increase in referrals during neonatal hearing screening: a comparison of Natus ALGO Portable and ALGO 3i.

OBJECTIVE: Neonatal hearing screening programs in Flanders and the Netherlands use Natus ALGO screening devices. Since 2006 in Flanders and 2009 in the Netherlands, both programs have replaced the older ALGO Portable devices with the newer ALGO 3i devices. However, in both countries, ALGO 3i devices have a significantly higher rate of referrals than ALGO Portable devices. In Flanders, the refer rate has more than doubled with the switch to ALGO 3i devices. In the Netherlands, screening centers which used ALGO 3i devices also showed a significant increase in referrals. In both countries, the percentage of children diagnosed with permanent hearing loss remained approximately the same. DESIGN: A technical comparison of both device types was carried out to identify possible causes for the increase in referrals. The stimulus output of two ALGO Portable and three ALGO 3i devices was recorded and analysed for stimulus level, spectral properties, and stimulus irregularities. RESULTS: ALGO 3i devices stimulate at a peak level 4.6 dB lower than ALGO Portable devices, have a different stimulus spectrum and show unexplained stimulus irregularities during 4% of the stimulation time. CONCLUSIONS: A number of technical differences were found between both device types which could explain the increase in referrals.

Measurement of in vivo tendon function.

Chronic tendon pathologies (eg, rotator cuff tears, Achilles tendon ruptures) are common, painful, debilitating, and a significant source of medical expense. Treatment strategies for managing tendon pathologies vary widely in invasiveness and cost, with little scientific basis on which to base treatment selection. Conventional techniques for assessing the outcomes of physical therapy or surgical repair typically rely on patient-based assessments of pain and function, physical measures (eg, strength, range of motion, or stability), and qualitative assessments using magnetic resonance imaging or ultrasound. Unfortunately, these conventional techniques provide only an indirect assessment of tendon function. The inability to make a direct quantitative assessment of the tendon's mechanical capabilities may help to explain the relatively high rate of failed tendon repairs and has led to an interest in the development of tools for directly assessing in vivo tendon function. The purpose of this article is to review methods for assessing tendon function (ie, mechanical properties and capabilities) during in vivo activities. This review will describe the general principles behind the experimental techniques and provide examples of previous applications of these techniques. In addition, this review will characterize the advantages and limitations of each technique, along with its potential clinical utility. Future efforts should focus on developing broadly translatable technologies for quantitatively assessing in vivo tendon function. The ability to accurately characterize the in vivo mechanical properties of tendons would improve patient care by allowing for the systematic development and assessment of new techniques for treating tendon pathologies.

A method for calibration of bone driver transducers to measure the mastoid impedance.

When using bone vibrator transducers for clinical measurements, the transfer of energy from the bone driver depends on the impedance match between the driver and the load (human mastoid or otherwise) to which the driver will be applied. Current clinical calibration methods are incapable of quantifying this impedance mismatch, hence they fail to account for inter-subject variations of the energy transferred from the driver to the load. This study proposes a straightforward method for determining an absolute field calibration of a Radio Ear B71 bone driver, found by measuring the electrical input impedance of the transducer loaded by known masses. This absolute calibration is based upon a circuit model of the driver, describing it with three frequency-dependent parameters. Once these three parameters are known, measurements of the driver input voltage and current may be used to determine arbitrary mechanical load impedances (such as the in situ mastoid impedance), and thus the frequency dependence of the transmitted energy. The results of the proposed calibration method are validated by comparison with direct mechanical measurements using specialized equipment not available in the clinic, and a refined bone driver circuit model is proposed to better capture the observed behaviors.

Prediction of VO2max with daily step counts for Japanese adult women.

The purpose of the study was to develop a new non-exercise VO(2max) prediction model using a physical activity (PA) variable determined by pedometer-determined step counts (SC, steps day(-1)) in Japanese women aged 20-69 years old. Eighty-seven and 102 subjects were used to develop the prediction model, and to validate the new model, respectively. VO(2max) was measured using a maximal incremental test on a bicycle ergometer. SC was significantly related to VO(2max) (partial correlation coefficient r = 0.40, P < 0.001) after adjusting for BMI (kg m(-2)) and age (years). When the new prediction equation developed by multiple regression to estimate VO(2max) from age, BMI, and SC (R = 0.71, SEE = 5.3 ml kg(-1) min(-1), P < 0.001) was applied to the Validation group, predicted VO(2max) correlated well with measured VO(2max) (r = 0.81, P < 0.001), suggesting that SC is a useful PA variable for non-exercise prediction of VO(2max) in Japanese women.

A blended sensor restores chronotropic response more favorably than an accelerometer alone in pacemaker patients: the LIFE study results.

BACKGROUND: Adaptive rate sensors used in permanent pacemakers incorporate an accelerometer (XL) to increase heart rate with activity. Limited data exists regarding the relative benefit of a blended sensor (BS) (XL and minute ventilation) versus XL alone in restoring chronotropic response (CR) in chronotropically incompetent (CI) patients. METHODS: One thousand five hundred thirty-eight patients from the limiting chronotropic incompetence for pacemaker recipients (LIFE) study were implanted with a pacemaker and 1,256 patients had data collected at 1 month. Patients performed a treadmill test 1-month postimplant while programmed in nonrate responsive mode (DDD-60) to determine CI. Only patients who completed at least three exercise stages and achieved a peak perceived exertion >or=16 were included in the analyses. The metabolic chronotropic relationship (MCR) slope was used to evaluate CR in 547 patients. Patients were randomized to XL or BS with a conservative fixed rate response factor (XL = 8, MV = 4). CI patients performed a follow-up 6-month treadmill test. RESULTS: CI prevalence in this patient population (n = 547) was 34%. No differences in baseline characteristics existed between groups. Although both groups showed significant within-group improvements in MCR slope from 1 to 6 months (both P < 0.001), the BS group had a significantly higher MCR slope at 6 months compared to the XL group (P = 0.011). Improvement in quality of life (QOL) did not differ between groups. CONCLUSIONS: In this general pacemaker population with CI, a BS programmed empirically restores CR more favorably than an XL sensor programmed nominally. Further studies are needed to determine if individual sensor optimization would lead to improvement in functional capacity, higher MCR slopes, and QOL.

A microswitch cluster to enhance arm-lifting responses without dystonic head tilting by a child with multiple disabilities.

This study assessed whether a microswitch duster with favorite stimulation could help a 9.1-yr.-old child with multiple disabilities increase arm-lifting responses without dystonic, sideways head tilting. The microswitch cluster involved two microswitches, one at the child's arm to monitor the lifting response, and the other at the child's head to monitor whether it was tilted during arm lifting. Analysis showed that the percentage of arm-lifting responses occurring without head tilting increased most visibly when favorite stimulation focused on those (appropriate) responses.

Comparison of ultrasound quality assurance phantom measurements from matched and mixed scanner-transducer combinations.

Our goal in this work was to compare the results of common phantom tests made using matched and mixed ultrasound (US) scanner-transducer combinations. Sets of common US quality assurance (QA) measurements were made using matched US scanner-transducer combinations (i.e., transducers purchased for use with a particular scanner), as well as unmatched (mixed) combinations. Measurements of vertical and horizontal distance accuracy, and depth of penetration were performed using three common transducer types. Means, standard deviations, and differences between the mean mix and match measurements divided by the standard deviation (match-mix difference, or MMD), and two-sided, paired t-tests were computed for the groups of mixed and matched measurements. MMDs for vertical and horizontal distance accuracy test results were less than 0.87 in all cases, well below our threshold value of 2.0, which indicates that a significant difference exists. MMDs for the depth of penetration measurements were less than 1.50, again below the threshold value. These results suggest that all of the mixed and matched data sets were very similar. The more sensitive t-tests indicate statistically significant differences in only 2 of the 18 pairs of data sets. In conclusion, this study suggests that QA measurements generated by mixed or matched scanner-transducer combinations are very comparable. The ability to obtain QA phantom test data from mixed scanner-transducer combinations reduces the time required for US QA testing.

Some extensions of the Gaussian beam expansion: radiation fields of the rectangular and the elliptical transducer.

A straightforward extension of Gaussian beam expansion is presented for calculation of the Fresnel field integral [J. J. Wen and M. A. Breazeale, J. Acoust. Soc. Am. 83, 1752-1756 (1988)]. The source distribution function is expanded into the superposition of a series of two-dimensional Gaussian functions. The corresponding radiation field is expressed as the superposition of these two-dimensional Gaussian beams and is then reduced to the computation of these simple functions. This treatment overcomes the limit that the shape of source is of circular axial-symmetry. The numerical examples are presented for the field of the (uniform) elliptical and the rectangular piston transducers and agree well with the results given by complicated computation.

High-frequency backscatter and attenuation measurements of porcine erythrocyte suspensions between 30-90 MHz.

There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology and vascular surgery. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biologic tissues, such as blood, in the high-frequency range is crucial. VHF attenuation and backscatter experiments were made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range. Attenuation and backscatter at hematocrits of 6%, 10%, 15%, 20%, 25% and 30% from 30 to 90 MHz were measured using a modified substitution method that allows the utilization of focused transducers. The results show that the attenuation coefficient from all suspensions increased linearly with frequency and the backscatter coefficient for low hematocrit suspensions was found to have a maximum between 10% and 15%. At higher hematocrits, a decrease in the frequency-dependence was observed, possibly indicating that Rayleigh scattering is no longer valid because the wavelength in the VHF range is comparable to the size of a porcine RBC.