Good urodynamic practice: Pressure signal quality immediately after catheter insertion for cystometry with a water-filled pressure transducer system and its relevance for the ICS zero procedure.

AIM: This study aims to evaluate the intracorporeal pressures immediately after the insertion of the catheters for urodynamic testing with a water-filled urodynamic pressure transducer system to determine the relevance of the International Continence Society (ICS) zeroing principles. METHODS: Here, a retrospective analysis of a random series of urodynamic recordings is performed. The initial pressures, immediately after the insertion of the catheters, have been compared with the pressures after some milliliters of filling and flushing away of the gel, used with insertion, and/or the mucus and debris from the inserted catheters. Differences of initially recorded intravesical and intrarectal pressures from those after flushing and filling are analyzed and associated with the ICS standard practice of zeroing. RESULTS: Statistically and clinically significant differences between the initial pressures and the pressures after filling and flushing are observed, with nonphysiological initial pressures in 62% of the studies. Some filling (20 ml or more in the bladder) and flushing of the pressure channels resulted in the registration of physiological pressures and synchronous response from both lines on abdominal pressure increases. CONCLUSIONS: The pressure signal quality of a water-filled urodynamic system immediately after catheter insertion is low with inaccurately displayed pressure values, but it changes to normal after flushing the pressure channels and some filling. Rezeroing of the intracorporeal pressures immediately after catheter insertion for cystometry is the inappropriate correction procedure that misleadingly modifies the false initial pressures, resulting in ongoing unrealistic urodynamic study pressures.

Accuracy of ultrasound for endotracheal intubation between different transducer types.

INTRODUCTION: Ultrasound has been increasingly utilized for the identification of endotracheal tube (ETT) location after an intubation attempt, particularly among patients in cardiac arrest. However, prior studies have varied with respect to the choice of transducer and no studies have directly compared the accuracy between transducer types. Our study is the first to directly compare the accuracy of ETT confirmation between the linear and curvilinear transducer. METHODS: This study was performed in a cadaver lab using three different cadavers chosen to represent varying neck circumferences. Cadavers were randomized to tracheal or esophageal intubation. Blinded sonographers assessed the location of the ETT using either a linear or curvilinear transducer in an alternating sequence. Accuracy of sonographer identification, time to identification, and operator confidence were assessed. RESULTS: Four hundred and five assessments were performed with 198 (48.9%) tracheal and 207 (51.1%) esophageal intubations. The linear transducer was 98% (95% CI 95.1% to 99.2%) accurate. The curvilinear transducer was 95% (95% CI 91.1% to 97.3%) accurate. The mean time to identification was significantly lower with the linear transducer [7.46 s (95% CI 6.23 to 8.7 s)] as compared with the curvilinear transducer [11.63 s (95% CI 9.05 to 14.2 s)]. The mean operator confidence was significantly higher with the linear transducer [4.84/5.0 (95% CI 4.76 to 4.91)] than with the curvilinear transducer [4.44/5.0 (95% CI 4.3 to 4.57)]. All operators preferred the linear transducer over the curvilinear transducer. CONCLUSION: The diagnostic accuracy of ultrasound for ETT confirmation did not significantly differ between ultrasound transducer types, but the curvilinear transducer was associated with a longer time to confirmation and lower operator confidence. Further studies are needed to determine if the accuracy would change with more novice providers or in specific patient populations.

Range-dependent impacts of ocean acoustic propagation on automated classification of transmitted bowhead and humpback whale vocalizations.

Significant effort has been made over the last few decades to develop automated passive acoustic monitoring (PAM) systems capable of classifying cetaceans at the species level. The utility of such systems depends on the systems' ability to operate across a wide range of ocean acoustic environments; however, anecdotal evidence suggests that site-specific propagation characteristics impact the performance of PAM systems. Variability in propagation characteristics leads to differences in how each cetacean vocalization is altered as it propagates along the source-receiver path. A propagation experiment was conducted in the Gulf of Mexico to investigate the range-dependent impacts of acoustic propagation on the performance of an automated classifier. Modified bowhead and humpback vocalizations were transmitted over ranges from 1 to 10 km. When the classifier was trained with signals collected near the sound source, it was found that the performance decreased with increasing transmission range-this appeared to be largely explained by decreasing signal-to-noise ratio (SNR). Generation of performance matrices showed that one method to develop a classifier that maintains high performance across many ranges is to include a varied assortment of ranges in the training data; however, if the training set is limited, it is best to train on relatively low SNR vocalizations.

Method for automatic detection of defective ultrasound linear array transducers based on uniformity assessment of clinical images - A case study.

The purpose of the present study was to test an idea of and describe a concept of a novel method of detecting defects related to horizontal nonuniformities in ultrasound equipment. The method is based on the analysis of ultrasound images collected directly from the clinical workflow. In total over 31000 images from three ultrasound scanners from two vendors were collected retrospectively from a database. An algorithm was developed and applied to the images, 150 at a time, for detection of systematic dark regions in the superficial part of the images. The result was compared with electrical measurements (FirstCall) of the transducers, performed at times when the transducers were known to be defective. The algorithm made similar detection of horizontal nonuniformities for images acquired at different time points over long periods of time. The results showed good subjective visual agreement with the available electrical measurements of the defective transducers, indicating a potential use of clinical images for early and automatic detection of defective transducers, as a complement to quality control.

Insertion of miniaturized cardiac monitors outside the catheter operating room: experience and practical advice.

Minor surgical procedures are increasingly being performed as outpatient procedures in settings outside hospital operating rooms (ORs). In electrophysiology, the recent miniaturization of insertable cardiac monitors (ICMs) has enabled the routine insertion of the device as a minimally invasive procedure without the need of a catheter OR. However, a shift to office-based environments for minor surgical procedures is associated with some concerns, particularly with respect to patient- and procedure-related safety in the new setting. In the present document, the authors provide practical advice on facilities, practices, and adaptations necessary when performing ICM insertions in office settings, based on available recommendations as well as their own experience with the use of the novel Reveal LINQ ICM. The main differences from in-hospital implant settings are simplified requirements of room, equipment, and insertion procedures, while ensuring and maintaining an adequate, sterile environment. Patient selection is important: certain groups of patients are recommended to be treated in the catheter OR (e.g. those at increased risk for bleeding or very frail elderly individuals). Insertion in alternative positions, as is sometimes performed for cosmetic reasons, should be referred to dedicated hospitals. Quality assurance and internal quality control are critical in the new procedural landscape, and it is important not to trivialize minor surgical procedures. Operators' sharing of experiences and lessons learned, e.g. in the form of registries, should be encouraged.

Transducer-based evaluation of tremor.

The International Parkinson and Movement Disorder Society established a task force on tremor that reviewed the use of transducer-based measures in the quantification and characterization of tremor. Studies of accelerometry, electromyography, activity monitoring, gyroscopy, digitizing tablet-based measures, vocal acoustic analysis, and several other transducer-based methods were identified by searching PubMed.gov. The availability, use, acceptability, reliability, validity, and responsiveness were reviewed for each measure using the following criteria: (1) used in the assessment of tremor; (2) used in published studies by people other than the developers; and (3) adequate clinimetric testing. Accelerometry, gyroscopy, electromyography, and digitizing tablet-based measures fulfilled all three criteria. Compared to rating scales, transducers are far more sensitive to changes in tremor amplitude and frequency, but they do not appear to be more capable of detecting a change that exceeds random variability in tremor amplitude (minimum detectable change). The use of transducer-based measures requires careful attention to their limitations and validity in a particular clinical or research setting. © 2016 International Parkinson and Movement Disorder Society.

Validation of PI-RADS v.2 for prostate cancer diagnosis with MRI at 3T using an external phased-array coil.

PURPOSE: To date, few studies have validated the Prostate Imaging Reporting and Data System Version 2 (PI-RADS v. 2) for the diagnosis of prostate cancer. Our aim was to validate PI-RADS v.2 using 3 Tesla (T) MRI. MATERIALS AND METHODS: This is a retrospective study of 54 consecutive patients who underwent 3T MRI with a body-array coil for diagnostic confirmation of prostate cancer or cancer staging between June 2013 and June 2015. Sensitivity, specificity, and agreement were calculated based on a criterion of PI-RADS score = 3. Inter-examiner agreement was determined by the weighted kappa statistic. RESULTS: Histological findings were positive for cancer in 33 patients and negative in 21 patients. Considering a PI-RADS score of 3 as positive for cancer, the accuracy of each reader was 85.20% and 70.40%, respectively, and agreement coefficients were κ = 0.69 and κ = 0.35. Considering PI-RADS 3 as absence of cancer, the accuracy of each reader was 77.80% and 77.80%, respectively, and agreement was κ = 0.55 and κ = 0.54. Inter-reader agreement was moderate/good (weighted κ = 0.53; 95% confidence interval: 0.39-0.66; P = 0.038). CONCLUSION: High accuracy was obtained for the diagnosis of prostate cancer using 3T MRI with a body coil and the PI-RADS v.2 score. J. Magn. Reson. Imaging 2016;44:1354-1359.

The effect of the transducers on paediatric thresholds estimated with auditory steady-state responses.

The objective of this study was to investigate the usefulness of auditory steady-state responses (ASSRs) for estimating hearing thresholds in young children, compared with behavioural thresholds. The second objective was to investigate ASSR thresholds obtained with insert earphones versus supra-aural headphones to determine which transducer produces ASSR thresholds most similar to behavioural thresholds measured with supra-aural headphones. This retrospective study included 29 participants (58 ears): 12 children (24 ears) in the insert group and 17 children (34 ears) in the supra-aural group. No general anaesthesia was used. For both groups, there was a strong correlation between behavioural and ASSR thresholds, with a stronger correlation for the insert group. When behavioural thresholds are difficult to obtain, ASSR may be a useful objective measure that can be combined with other audiometric procedures to estimate hearing thresholds and to determine appropriate auditory rehabilitation approaches.

Is Transducer Hygiene sufficient when Vaginal Probes are used in the Clinical Routine?

Vaginal ultrasound probes are semi-critical Group A medical products which must be disinfected following the manufacturer's instructions after every patient examination. According to the "Essential Requirements for Medical Devices (Directive 93/42/EEC, Annex I, paragraph 13)" the manufacturer's instructions for use for reusable products must contain suitable instructions for preparation processes. This presumes both an effective and material-compatible method. Evidence of effectiveness must be validated.In the Editorial in issue 1 Ultraschall in der Medizin/European Journal of Ultrasound 2005 we discussed the topic of transducer hygiene and stated that proper handling and cleaning as well as disinfection of probes in daily use are indispensable. This applies particularly to vaginal ultrasound probes routinely used in gynecological and obstetrical clinics, gynecological practices as well as IVF centers Normally the probe used in a transvaginal ultrasound examination is covered with a latex protective cover (with CE marking) which contains a certain amount of ultrasound gel. After the examination, the cover is removed and disposed of, and the gel is removed from the transducer. Since handling of the probe, ultrasound gel and cover can result in smear infections and cross-contamination with various pathogens (e. g. MRSA, HBV, HCV, HIV, herpes papilloma and cytomegalic viruses), after the protective cover is removed, the probe must be cleaned and subjected to disinfection with a bactericidal, fungicidal and virucidal effect. This is especially important in the event the cover ruptures during the vaginal examination, and the probe comes into direct contact with vaginal secretions or blood. The same likewise applies if the sterile protective cover is perforated during a follicular puncture. Usually special bactericidal, levurocidal and virucidal wipes or special submersion disinfection methods are available for disinfecting the vaginal ultrasound probes 11. Using special virucidal wipes on the probes is considered low-level disinfection. Primarily quaternary ammonia compounds are employed for this procedure. This method is easily applicable, has good cleaning characteristics, is effective against HPV and has high skin tolerance. However, it has the disadvantage of not removing all microorganisms during the disinfection process. Immersion procedures are high-level disinfection methods during which the transducer head is dipped in a special fluid for a certain amount of time. The disinfectants used for this include e. g. preparations based on glutaraldehyde or succinic aldehyde. However, in practice immersion disinfection has a number of disadvantages 13: 1. The procedure cannot be validated. 2. The probe permanently attached to the device must be placed in a separate holder and disinfected for at least 15 minutes. This is impracticable in routine operations in a clinic, outpatient facility or practice with a high number of examinations. 3. After this disinfection method, the probe has to be thoroughly rinsed with potable or higher-quality water in order to remove remnants of allergenic or locally toxic substances. 4. Frequently examinations take place in small interior areas with poor ventilation, thus under some circumstances posing an inhalant-related health hazard. 5. The required virucidal effect is frequently not achieved within 15 minutes 13. Furthermore, extended probe contact with liquid disinfecting agents in the long run results in increased wear of the transducer head membrane.Therefore it was interesting to note that in 2009 a fully-automatic disinfection system for ultrasound probes was introduced to the market (Trophon(EPR). This product, developed in Australia, promised relatively rapid high-level disinfection (HLD). During this software-controlled, mechanical disinfection procedure, the entire ultrasound probe (transducer head and handle) is placed in a sealed disinfection chamber, then hydrogen peroxide (H2O2) is discharged as an anti-microbial aerosol into the closed chamber.  The ultra-fine mist wets the entire surface of the probe with H2O2, thereby achieving high-level disinfection of the entire ultrasound probe. At the end of the process, a catalytic decomposition system breaks down the H2O2 into environmentally-friendly oxygen and water. When the chamber is opened, the probe is dry and ready for immediate use. The fully-automatic device was designed as a table unit to be placed directly next to the ultrasound equipment so that the probe does not need to be disconnected from the base unit. The entire disinfection process lasts 7 minutes: 2 minutes for the application and 5 minutes to remove the aerosol residue. In a validation study using carrier tests, Heeg and Gauer in 2014 showed that this procedure genuinely achieved HLD of ultrasound probes within 7 minutes, thus making it suitable for daily clinical routine. The procedure fulfills all requirements for HLD based on the medical device classification according to the legally-prescribed recommendation of the Commission for Hospital Hygiene and Prevention of Infection and the Federal Institute for Drugs and Medical Products (KRINKO/BfArM) in Germany. In the USA, this method was approved by the FDA as well as the leading probe manufacturers, and bears the testing certificate of the German Society for Hospital Hygiene (DGKH).All in all, it should be stated that the sole use of a latex protective cover when using a vaginal probe does not meet the necessary standard of care required for the provision of semi-critical medical products according to the joint recommendation of the German Federal Institute for Drugs and Medical Products (BfArM) and Commission for Hospital Hygiene and Prevention of Infection of the Robert Koch Institute, and constitutes a contravention of necessary patient and user protections. Use of the protective cover does not rule out smear infections and cross-contamination; therefore after each examination, the probe, after removal of the cover, must undergo disinfection measures providing bactericidal, fungicidal and virucidal effects. Since the transducer handle also poses a significant risk of transmission of germs, this component must likewise be sufficiently disinfected. In the event of perforation or rupture of the latex cover, thus resulting in the probe coming into contact with vaginal secretions or blood, the probe must be not only cleaned, but effectively disinfected with a virucide as well. It should also be noted that infection by bacteria and viruses can be caused not only by a contaminated probe, but by the ultrasound gel as well. According to studies by Heeg and Gauer 15, Buescher et al. as well as Ryndock et al., the fully automatic HLD system operated with hydrogen peroxide is currently the only validated system proven to provide HLD of ultrasound probes in a 7-minute cycle, thus suitable for application in the daily routine. Likewise it can also be presumed that this procedure also offers good material compatibility.

Effect of mild pressure applied by the ultrasound transducer on fetal cephalic measurements at 20-24 weeks' gestation.

INTRODUCTION: The aim of this study was to assess the effect of mild pressure applied on the abdominal wall by the ultrasound transducer on fetal cephalic indices. MATERIAL AND METHODS: We examined by ultrasound 60 fetuses of healthy women, at 20-24 weeks of pregnancy, during routine prenatal evaluation. For every fetus biparietal diameter and head circumference were measured, with and without applying mild pressure by the ultrasound transducer. The weight and gestational age (GA) were calculated. RESULTS: The pressure applied by the transducer had a significant effect on the cephalic indices and on the weight and GA evaluations (p < 0.001). Fetal positioning significantly affected the impact that applied pressure had on head circumference and on the weight evaluation derived from it (p < 0.05). DISCUSSION: Applied pressure by an abdominal ultrasound probe affects cephalic indices and the derived weight and GA estimations. This may lead to incorrect diagnoses or hide pathological findings. The effect of applied pressure depends on fetal positioning. The examiner must be aware of this effect when evaluating the results of the measurements.

Analyzing comprehensive QoS with security constraints for services composition applications in wireless sensor networks.

Services composition is fundamental to software development in multi-service wireless sensor networks (WSNs). The quality of service (QoS) of services composition applications (SCAs) are confronted with severe challenges due to the open, dynamic, and complex natures of WSNs. Most previous research separated various QoS indices into different fields and studied them individually due to the computational complexity. This approach ignores the mutual influence between these QoS indices, and leads to a non-comprehensive and inaccurate analysis result. The universal generating function (UGF) shows the speediness and precision in QoS analysis. However, only one QoS index at a time can be analyzed by the classic UGF. In order to efficiently analyze the comprehensive QoS of SCAs, this paper proposes an improved UGF technique-vector universal generating function (VUGF)-which considers the relationship between multiple QoS indices, including security, and can simultaneously analyze multiple QoS indices. The numerical examples demonstrate that it can be used for the evaluation of the comprehensive QoS of SCAs subjected to the security constraint in WSNs. Therefore, it can be effectively applied to the optimal design of multi-service WSNs.

Standardizing accelerometer-based activity monitor calibration and output reporting.

Wearable accelerometer-based activity monitors (AMs) are used to estimate energy expenditure and ground reaction forces in free-living environments, but a lack of standardized calibration and data reporting methods limits their utility. The objectives of this study were to (1) design an inexpensive and easily reproducible AM testing system, (2) develop a standardized calibration method for accelerometer-based AMs, and (3) evaluate the utility of the system and accuracy of the calibration method. A centrifuge-type device was constructed to apply known accelerations (0-8g) to each sensitive axis of 30 custom and two commercial AMs. Accelerometer data were recorded and matrix algebra and a least squares solution were then used to determine a calibration matrix for the custom AMs to convert raw accelerometer output to units of g's. Accuracy was tested by comparing applied and calculated accelerations for custom and commercial AMs. AMs were accurate to within 4% of applied accelerations. The relatively inexpensive AM testing system (< $100) and calibration method has the potential to improve the sharing of AM data, the ability to compare data from different studies, and the accuracy of AM-based models to estimate various physiological and biomechanical quantities of interest in field-based assessments of physical activity.

In vivo O-Space imaging with a dedicated 12 cm Z2 insert coil on a human 3T scanner using phase map calibration.

Recently, spatial encoding with nonlinear magnetic fields has drawn attention for its potential to achieve faster gradient switching within safety limits, tailored resolution in regions of interest, and improved parallel imaging using encoding fields that complement the sensitivity profiles of radio frequency receive arrays. Proposed methods can broadly be divided into those that use phase encoding (Cartesian-trajectory PatLoc and COGNAC) and those that acquire nonlinear projections (O-Space, Null space imaging, radial PatLoc, and 4D-RIO). Nonlinear projection data are most often reconstructed with iterative algorithms that backproject data using the full encoding matrix. Just like conventional radial sequences that use linear spatial encoding magnetic fields, nonlinear projection methods are more sensitive than phase encoding methods to imperfect calibration of the encoding fields. In this work, voxel-wise phase evolution is mapped at each acquired point in an O-Space trajectory using a variant of chemical shift imaging, capturing all spin dynamics caused by encoding fields, eddy currents, and pulse timing. Phase map calibration is then applied to data acquired from a high-power, 12 cm, Z2 insert coil with an eight-channel radio frequency transmit-receive array on a 3T human scanner. We show the first experimental proof-of-concept O-Space images on in vivo and phantom samples, paving the way for more in-depth exploration of O-Space and similar imaging methods.

A comparison of two methods for phase response calibration of hydrophones in the frequency range 10-400 kHz.

A comparison is made of two methods for determining the phase response of hydrophones in the kilohertz frequency range: The three-transducer spherical-wave reciprocity method and the method of optical interferometry. The implementation of the methods and the corresponding experimental systems are described. To facilitate a comparison, the methods are used to determine the phase response of three commercially available measuring hydrophones over the frequency range from 10 to 400 kHz. The results are compared, showing agreement within the estimated uncertainties of the methods. An investigation is conducted into the sources of uncertainties in the methods which increase with frequency. The major sources of uncertainty are residual positioning errors giving rise to phase uncertainties; a significant problem for the reciprocity method is that it requires one hydrophone to be rotated during the measurement procedure. An additional source of uncertainty at higher frequencies may be present if the position of the sensing element is not central within the outer hydrophone boot.

How perfect are you with defective probes? Information on the results of the mini-trial on technical quality assurance during the "Ultraschall 2012" conference in Davos.

This article deals with the technical quality assurance of ultrasound B-systems. As part of a mini-trial during the Dreiländertreffen in Davos "Ultrasound 2012", we addressed the question as to whether physicians can detect faulty probes spontaneously during live scanning B-mode. For this purpose a special diagnostic device had been prepared so that groups of piezoelectric elements in the array were without function. Then the images had to be characterized by test persons without knowledge of the faulty elements. The results show that a deterioration of the image could be detected starting at five disabled elements. Due to the small number of test persons, our statements are only preliminary.

Development of a standard fall data format for signals from body-worn sensors : the FARSEEING consensus.

Objective measurement of real-world fall events by using body-worn sensor devices can improve the understanding of falls in older people and enable new technology to prevent, predict, and automatically recognize falls. However, these events are rare and hence challenging to capture. The FARSEEING (FAll Repository for the design of Smart and sElf-adapaive Environments prolonging INdependent livinG) consortium and associated partners strongly argue that a sufficient dataset of real-world falls can only be acquired through a collaboration of many research groups. Therefore, the major aim of the FARSEEING project is to build a meta-database of real-world falls. To establish this meta-database, standardization of data is necessary to make it possible to combine different sources for analysis and to guarantee data quality. A consensus process was started in January 2012 to propose a standard fall data format, involving 40 experts from different countries and different disciplines working in the field of fall recording and fall prevention. During a web-based Delphi process, possible variables to describe participants, falls, and fall signals were collected and rated by the experts. The summarized results were presented and finally discussed during a workshop at the 20th Conference of the International Society of Posture and Gait Research 2012, in Trondheim, Norway. The consensus includes recommendations for a fall definition, fall reporting (including fall reporting frequency, and fall reporting variables), a minimum clinical dataset, a sensor configuration, and variables to describe the signal characteristics.

Methods to eliminate stimulus transduction artifact from insert earphones during electroencephalography.

OBJECTIVE: To reduce stimulus transduction artifacts in EEG while using insert earphones. DESIGN: Reference Equivalent Threshold SPLs were assessed for Etymotic ER-4B earphones in 15 volunteers. Auditory brainstem responses (ABRs) and middle latency responses (MLRs)-as well as long-duration complex ABRs-to click and /dα/ speech stimuli were recorded in a single-case design. RESULTS: Transduction artifacts occurred in raw EEG responses, but they were eliminated by shielding, counter-phasing (averaging across stimuli 180° out of phase), or rereferencing. CONCLUSIONS: Clinical grade ABRs, MLRs, and cABRs can be recorded with a standard digital EEG system and high-fidelity insert earphones, provided one or more techniques are used to remove the stimulus transduction artifact.

Investigation of the suitability of tissue phantoms for testing the constancy of ultrasonic transducer arrays in quality assurance.

PURPOSE: To ensure high quality ultrasound diagnostics, proper functioning of the devices used is a necessary prerequisite. Ultrasound transducers have proven to be the most failure-prone part of the signal chain. Their technical monitoring is possible in principle with the help of tissue phantoms. The background of the present study is to determine which type of phantoms and which measurement parameters are best suited to a consistency test as part of routine quality assurance of ultrasound imaging systems. MATERIALS AND METHODS: A classic wire-type phantom (ATS Mod. 539, ATS Labs Bridgeport, USA) and a 3 D cyst phantom (TCC, Timelkam, Austria) were used for the studies and comparative tests were conducted between intact transducers and those in which faults had been simulated. The collected measurement data show a relatively large scatter. Therefore, statistical analysis methods were used, and the discrimination analysis proved to be a useful tool. RESULTS: Local failures which arise, e. g. due to the breakdown of individual piezoelectric elements or element groups in the transducer array, can be detected with the help of the gray value targets of the ATS phantom, but only in those cases in which the error-affected sound field part actually overlaps with the target under consideration. The TCC phantom is not suitable for the detection of such errors. Global transducer failures, i. e. those that affect the entire array, can even be detected with both types of phantoms. CONCLUSION: When the emphasis of quality assessment is on the detection of local defects in the array that make up the largest part of the transducer faults, studies with conventional phantoms are only of limited value.

Ultrasound transducer function: annual testing is not sufficient.

AIMS: The objective was to follow-up the study 'High incidence of defective ultrasound transducers in use in routine clinical practice' and evaluate if annual testing is good enough to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level. METHODS AND RESULTS: A total of 299 transducers were tested in 13 clinics at five hospitals in the Stockholm area. Approximately 7000-15,000 ultrasound examinations are carried out at these clinics every year. The transducers tested in the study had been tested and classified as fully operational 1 year before and since then been in normal use in the routine clinical practice. The transducers were tested with the Sonora FirstCall Test System. There were 81 (27.1%) defective transducers found; giving a 95% confidence interval ranging from 22.1 to 32.1%. The most common transducer errors were 'delamination' of the ultrasound lens and 'break in the cable' which together constituted 82.7% of all transducer errors found. The highest error rate was found at the radiological clinics with a mean error rate of 36.0%. There was a significant difference in error rate between two observed ways the clinics handled the transducers. There was no significant difference in the error rates of the transducer brands or the transducers models. CONCLUSION: Annual testing is not sufficient to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level and it is strongly advisable to create a user routine that minimizes the handling of the transducers.