Surgical Management of Submucous Cleft Palate by Radical Muscle Dissection Veloplasty: Speech Outcomes in Patients with 22q11.2 Deletion Syndrome.

OBJECTIVE: To evaluate the benefit of anatomical muscle dissection repair for velopharyngeal insufficiency (VPI) in patients with submucous cleft palate (SMCP) with 22q11.2 deletion syndrome. DESIGN: Retrospective blinded randomised analysis of a surgeon's management over 10 years. SETTING: The study was performed at a specialised Paediatric hospital in the United Kingdom. PATIENTS: Children with SMCP and 22q11.2 deletion syndrome. INTERVENTIONS: All participants underwent radical muscle dissection veloplasty. OUTCOMES MEASURED: Pre- and post- operative measurements included severity of anatomical defect, speech samples and lateral images which were digitised, randomised then externally and blindly analysed using validated techniques. Stata software was used to perform statistical analysis. RESULTS: 57 children with 22q11.2 deletion syndrome were included in this analysis. Intra-operatively, the majority of cases were identified as SMCP Grade I anomalies. Post-operatively, a statistically significant improvement in hypernasality, resting palate length, palate length at maximum closure, palate excursion and gap size at maximum closure was observed. Secondary surgery was performed for 59% of patients by ten years. CONCLUSION: Muscle dissection repair improves hypernasality, palate closure function and the closure gap in patients with 22q11.2 deletion syndrome. Although over 50% of patients may require further surgery, muscle dissection repair should be a first step due to its utility at a younger age, when invasive investigations are impossible, its lower morbidity, speech and language benefits or altering the plans for less obstructive secondary surgery when it lead to reduced velo-pharyngeal gap and improved palate mobility even when adequate velo-pharyngeal closure was not achieved.

Gastrointestinal Transit Times in Health as Determined Using Ingestible Capsule Systems: A Systematic Review.

BACKGROUND: Ingestible capsule (IC) systems can assess gastrointestinal (GI) transit times as a surrogate for gut motility for extended periods of time within a minimally invasive, radiation-free and ambulatory setting. METHODS: A literature review of IC systems and a systematic review of studies utilizing IC systems to measure GI transit times in healthy volunteers was performed. Screening for eligible studies, data extraction and bias assessments was performed by two reviewers. A narrative synthesis of the results was performed. RESULTS: The literature review identified 23 different IC systems. The systematic review found 6892 records, of which 22 studies were eligible. GI transit time data were available from a total of 1885 healthy volunteers. Overall, seventeen included studies reported gastric emptying time (GET) and small intestinal transit time (SITT). Colonic transit time (CTT) was reported in nine studies and whole gut transit time (WGTT) was reported in eleven studies. GI transit times in the included studies ranged between 0.4 and 15.3 h for GET, 3.3-7 h for SITT, 15.9-28.9 h for CTT and 23.0-37.4 h for WGTT. GI transit times, notably GET, were influenced by the study protocol. CONCLUSIONS: This review provides an up-to-date overview of IC systems and reference ranges for GI transit times. It also highlights the need to standardise protocols to differentiate between normal and pathological function.

Velopharyngeal Incompetence in Children With 22q11.2 Deletion Syndrome: Velar and Pharyngeal Dimensions.

ABSTRACT: The surgical management of velopharyngeal incompetence (VPI) in children with 22q11.2 deletion syndrome (22q11.2 DS) is challenging. There are numerous approaches and children often undergo more than one operation. Our aim was to develop a method using images from routine lateral videofluoroscopy to study the dimensions of the velopharynx in this cohort.We analyzed 22 pre-operative lateral videofluoroscopy recordings of children with 22q11.2 DS and VPI. Fourteen had a submucous cleft palate (SMCP) and 8 had no obvious palatal abnormality but who were subsequently labelled as having an occult submucous cleft palate (OSMCP). The control data were 10 historic records of children with cleft lip and an intact palate. The authors identified key points on radiographs of the velum at rest and when elevated to measure the total velar length, functional velar length and pharyngeal depth and compared them ratiometrically.The intra-observer reliability was > 0.9 whereas the inter-observer reliability was > 0.74. The velopharyngeal depth/total velar length was significantly greater in 22q11.2 DS than the control group P < 0.001. There was no difference between SMCP and OSMCP patients, P = 0.556. There was no difference in the functional velar length/total velar length between 22q11.2 DS and controls (P = 0.763).In this study, the authors demonstrate a reliable method to gain useful ratiometric measurements of the velopharynx. This may help with treatment planning. Children with 22q11.2 DS and VPI have a larger velopharyngeal depth/total velar length ratio that may explain some of the difficulty in management.

A realistic flow phantom model of the carotid artery in preterm infants for training and research.

INTRODUCTION: Cerebral blood flow is increasingly monitored in preterm infants. Doppler ultrasound of the carotid artery is a widely available method but is operator dependent. Our aim was to design and produce a realistic flow phantom model of the carotid artery of preterm infants. METHODS: Data from cerebral blood flow measurements using Doppler ultrasound of the right common carotid artery from 21 premature newborn infants were used to produce a Doppler flow phantom model with three different vessel diameters. Vessel diameter, continuous and pulsatile flow volume measurements were performed by two blinded observers (with more than eight and 20 years of experience). RESULTS: Vessel diameter measurements using the phantom were underestimated by 7%. Continuous flow volume measurements were overestimated by 7% by both observers (observer 1 mean difference 1.5 ± 1.96 SD -3.3 to 6.3 ml/min versus observer 2, 1.9 ± 1.96 SD -3.6 to 7.4 ml/min). Pulsatile flow measurements were overestimated by 12.6% by observer 1 (2.7 ± 1.96 SD -0.6 to 5.9 ml/min) and by 7.8% by observer 2 (1.7 ± 1.96 SD -1.6 to 4.9 ml/min). There was good interobserver and intraobserver reliability for the majority of measurements using continuous and pulsatile flow. CONCLUSION: It is feasible to produce a realistic flow phantom model of the neonatal carotid artery of preterm infants. Diameter measurements were underestimated and flow measurements were overestimated. These errors fell within acceptable limits for in vivo measurements. If these limitations were related to materials, this could be explored using a wall-less model. The flow phantom could be utilised for research and training clinicians in measuring cerebral blood flow using the carotid artery in this vulnerable group of infants.

Normative values for gastric motility assessed with the 3D-transit electromagnetic tracking system.

BACKGROUND: The Motilis 3D-Transit system allows ambulatory description of transit patterns throughout the gastrointestinal tract and offers an alternative method for studying gastric motility. We aimed to establish normative values for gastric motility assessed with the method. METHOD: A total of 132 healthy volunteers ingested the 3D-Transit capsule for assessment of gastrointestinal transit times. Recordings from 125 subjects were used for definition of normative values. Forty-six subjects were studied on two consecutive days. Recordings were reanalyzed using newly developed software providing information on gastric emptying (GE) as well as contraction frequency and movement during gastric contractions. RESULTS: The median GE time was 2.7 hours (range 0.1-21.2). In 89% of subjects, the capsule passed the pylorus within a postingestion period of 6 hours. The median frequency of gastric contractions was 3.1 per minute (range 2.6-3.8). The frequency was higher in women (3.2, range 2.7-3.8) than in men (3.0, range 2.6-3.5) and increased with age (0.004 per year) (P < .05). The median amplitudes were 35° (range 4-85) when based on rotation of the capsule and 11 mm (range 6-31) when based on capsule change in position. The rotation amplitude was higher in women and decreased with increasing BMI (P < .05). The position amplitude was also higher in women and increased with the amount of calories in the test meal, but decreased with increasing BMI and age (P < .05). Day-to-day variation (P > .05) was considerable while inter-rater variability was small. CONCLUSION AND INFERENCES: We have established normative values for gastric motility assessed with the 3D-Transit system.

Normative values for region-specific colonic and gastrointestinal transit times in 111 healthy volunteers using the 3D-Transit electromagnet tracking system: Influence of age, gender, and body mass index.

BACKGROUND: The 3D-Transit electromagnet tracking system (Motilis Medica, SA, Lausanne, Switzerland) is an emerging tool for the ambulatory assessment of gastrointestinal (GI) transit and motility. Using this tool, we aimed to derive normative values for region-specific colonic and GI transit times and to assess the influence of age, gender, and body mass index (BMI). METHODS: Regional and total colonic transit times (CTT), gastric emptying (GET), small intestinal (SITT), and whole gut (WGTT) transit times were extracted from 111 healthy volunteers from the United Kingdom and Denmark (58 female; median age: 40 years [range: 21-88]). The effects of age, gender, and BMI were assessed using standard statistical methods. KEY RESULTS: The ascending, transverse, descending, and rectosigmoid colon transit times accounted for 32%, 34%, 17%, and 17% of total CTT in females, and 33%, 25%, 14%, and 28% of total CTT in males. CTT and WGTT were seen to cluster at intervals separated by approximately 24 hours, providing further evidence of the non-continuous nature of these measurements. Increasing age was associated with longer CTT (P = .021), WGTT (P < .001) ascending (P = .004), transverse (P < .001), and total right (P < .001) colon transit times, but shorter rectosigmoid (P = .004) transit time. Female gender was significantly associated with longer transverse (P = .049) and descending (P < .001) colon transit times, but shorter rectosigmoid (P < .001) transit time. Increasing BMI was significantly associated with shorter WGTT (P = .012). CONCLUSIONS AND INFERENCES: For the first time, normative reference values for region-specific colonic transit have been presented. Age, gender, and BMI were seen to have an effect on transit times.

Comparison of Cartesian and Non-Cartesian Real-Time MRI Sequences at 1.5T to Assess Velar Motion and Velopharyngeal Closure during Speech.

Dynamic imaging of the vocal tract using real-time MRI has been an active and growing area of research, having demonstrated great potential to become routinely performed in the clinical evaluation of speech and swallowing disorders. Although many technical advances have been made in regards to acquisition and reconstruction methodologies, there is still no consensus in best practice protocols. This study aims to compare Cartesian and non-Cartesian real-time MRI sequences, regarding image quality and temporal resolution trade-off, for dynamic speech imaging. Five subjects were imaged at 1.5T, while performing normal phonation, in order to assess velar motion and velopharyngeal closure. Data was acquired using both Cartesian and non-Cartesian (spiral and radial) real-time sequences at five different spatial-temporal resolution sets, between 10 fps (1.7×1.7×10 mm3) and 25 fps (1.5×1.5×10 mm3). Only standard scanning resources provided by the MRI scanner manufacturer were used to ensure easy applicability to clinical evaluation and reproducibility. Data sets were evaluated by comparing measurements of the velar structure, dynamic contrast-to-noise ratio and image quality visual scoring. Results showed that for all proposed sequences, FLASH spiral acquisitions provided higher contrast-to-noise ratio, up to a 170.34% increase at 20 fps, than equivalent bSSFP Cartesian acquisitions for the same spatial-temporal resolution. At higher frame rates (22 and 25 fps), spiral protocols were optimal and provided higher CNR and visual scoring than equivalent radial protocols. Comparison of dynamic imaging at 10 and 22 fps for radial and spiral acquisitions revealed no significant difference in CNR performance, thus indicating that temporal resolution can be doubled without compromising spatial resolution (1.9×1.9 mm2) or CNR. In summary, this study suggests that the use of FLASH spiral protocols should be preferred over bSSFP Cartesian for the dynamic imaging of velopharyngeal closure, as it allows for an improvement in CNR and overall image quality without compromising spatial-temporal resolution.

Impact of orthodontic appliances on the quality of craniofacial anatomical magnetic resonance imaging and real-time speech imaging.

AIMS: The aim of this work was to investigate the effects of commonly used orthodontic appliances on the magnetic resonance (MR) image quality of the craniofacial region, with special interest in the soft palate and velopharyngeal wall using real-time speech imaging sequences and anatomical imaging of the temporomandibular joints (TMJ) and pituitaries. METHODS: Common orthodontic appliances were studied on 1.5 T scanner using standard spin and gradient echo sequences (based on the American Society for Testing and Materials standard test method) and sequences previously applied for high-resolution anatomical and dynamic real-time imaging during speech. Images were evaluated for the presence and size of artefacts. RESULTS: Metallic orthodontic appliances had different effects on image quality. The most extensive individual effects were associated with the presence of stainless steel archwire, particularly if combined with stainless steel brackets and stainless steel molar bands. With those appliances, diagnostic quality of magnetic resonance imaging speech and palate images will be most likely severely degraded, or speech imaging and imaging of pituitaries and TMJ will be not possible. All non-metallic, non-metallic with Ni/Cr reinforcement or Ni/Ti alloys appliances were of little concern. LIMITATIONS: The results in the study are only valid at 1.5 T and for the sequences and devices used and cannot necessarily be extrapolated to all sequences and devices. Furthermore, both geometry and size of some appliances are subject dependent, and consequently, the effects on the image quality can vary between subjects. Therefore, the results presented in this article should be treated as a guide when assessing the risks of image quality degradation rather than an absolute evaluation of possible artefacts. CONCLUSIONS: Appliances manufactured from stainless steel cause extensive artefacts, which may render image non-diagnostic. The presence and type of orthodontic appliances should be always included in the patient's screening, so the risks of artefacts can be assessed prior to imaging. Although the risks to patients with fixed orthodontic appliances at 1.5 T MR scanners are low, their secure attachment should be confirmed prior to the examination.

Submucous cleft palate: a systematic review of surgical management based on perceptual and instrumental analysis.

Objective : Submucous cleft palate (SMCP) is a congenital condition associated with abnormal development of the soft palate musculature. In a proportion of cases, this results in velopharyngeal insufficiency (VPI), the treatment for which includes pharyngeal flap surgery, pharyngoplasty, and palate reconstruction. The aim of this paper is to determine whether there is superiority of one or more types of surgical procedure over the others in improving speech in patients with VPI secondary to SMCP. Methodology : Nine databases, including MEDLINE and EMBASE, were searched between inception and January 2013 to identify articles published relating to the surgical management of SMCP. Only studies that reported outcome measures for postoperative speech were included in the systematic review. Results : Twenty-six studies analyzing the outcomes of surgery for VPI in patients with SMCP met the inclusion criteria. In these studies, speech outcomes were measured either in a binary fashion (i.e., normal speech or evidence of VPI) or using scales of VPI severity. Of the 26 studies, only two utilized blinded speech assessment, and 12 included both preoperative and postoperative speech assessment. Conclusions : The review found little evidence to support any specific surgical intervention. This is in large part due to the inclusion of mixed etiologies within study populations and the lack of unbiased validated preoperative and postoperative speech assessment. Further methodologically rigorous studies need to be conducted to provide a secure evidence base for the surgical management of SMCP.

Speech MRI: morphology and function.

Magnetic Resonance Imaging (MRI) plays an increasing role in the study of speech. This article reviews the MRI literature of anatomical imaging, imaging for acoustic modelling and dynamic imaging. It describes existing imaging techniques attempting to meet the challenges of imaging the upper airway during speech and examines the remaining hurdles and future research directions.

Model validation for a noninvasive arterial stenosis detection problem.

A current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use one-dimensional shear wave experimental data from novel acoustic phantoms to validate a corresponding viscoelastic mathematical model. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.

High-order space-time finite element schemes for acoustic and viscodynamic wave equations with temporal decoupling.

We revisit a method originally introduced by Werder et al. (in Comput. Methods Appl. Mech. Engrg., 190:6685-6708, 2001) for temporally discontinuous Galerkin FEMs applied to a parabolic partial differential equation. In that approach, block systems arise because of the coupling of the spatial systems through inner products of the temporal basis functions. If the spatial finite element space is of dimension D and polynomials of degree r are used in time, the block system has dimension (r + 1)D and is usually regarded as being too large when r > 1. Werder et al. found that the space-time coupling matrices are diagonalizable over [Formula: see text] for r ⩽100, and this means that the time-coupled computations within a time step can actually be decoupled. By using either continuous Galerkin or spectral element methods in space, we apply this DG-in-time methodology, for the first time, to second-order wave equations including elastodynamics with and without Kelvin-Voigt and Maxwell-Zener viscoelasticity. An example set of numerical results is given to demonstrate the favourable effect on error and computational work of the moderately high-order (up to degree 7) temporal and spatio-temporal approximations, and we also touch on an application of this method to an ambitious problem related to the diagnosis of coronary artery disease. Copyright © 2014 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.

Submucous Cleft Palate: A Systematic Review of Surgical Management Based on Perceptual and Instrumental Analysis.

Objective: Submucous cleft palate (SMCP) is a congenital condition associated with abnormal development of the soft palate musculature. In a proportion of cases, this results in velopharyngeal insufficiency (VPI), the treatment for which includes pharyngeal flap surgery, pharyngoplasty, and palate reconstruction. The aim of this paper is to determine whether there is superiority of one or more types of surgical procedure over the others in improving speech in patients with VPI secondary to SMCP. Methodology: Nine databases, including MEDLINE and EMBASE, were searched between inception and January 2013 to identify articles published relating to the surgical management of SMCP. Only studies that reported outcome measures for postoperative speech were included in the systematic review. Results: Twenty-six studies analyzing the outcomes of surgery for VPI in patients with SMCP met the inclusion criteria. In these studies, speech outcomes were measured either in a binary fashion (i.e., normal speech or evidence of VPI) or using scales of VPI severity. Of the 26 studies, only two utilized blinded speech assessment, and 12 included both preoperative and postoperative speech assessment. Conclusions: The review found little evidence to support any specific surgical intervention. This is in large part due to the inclusion of mixed etiologies within study populations and the lack of unbiased validated preoperative and postoperative speech assessment. Further methodologically rigorous studies need to be conducted to provide a secure evidence base for the surgical management of SMCP.

Nasendoscopy: an analysis of measurement uncertainties.

Objective : The purpose of this study was to analyze the optical characteristics of two different nasendoscopes used to assess velopharyngeal insufficiency and to quantify the measurement uncertainties that will occur in a typical set of clinical data. Design : The magnification and barrel distortion associated with nasendoscopy was estimated by using computer software to analyze the apparent dimensions of a spatially calibrated test object at varying object-lens distances. In addition, a method of semiquantitative analysis of velopharyngeal closure using nasendoscopy and computer software is described. To calculate the reliability of this method, 10 nasendoscopy examinations were analyzed two times by three separate operators. The measure of intraoperator and interoperator agreement was evaluated using Pearson's r correlation coefficient. Results : Over an object lens distance of 9 mm, magnification caused the visualized dimensions of the test object to increase by 80%. In addition, dimensions of objects visualized in the far-peripheral field of the nasendoscopic examinations appeared approximately 40% smaller than those visualized in the central field. Using computer software to analyze velopharyngeal closure, the mean correlation coefficient for intrarater reliability was .94 and for interrater reliability was .90. Conclusion : Using a custom-designed apparatus, the effect object-lens distance has on the magnification of nasendoscopic images has been quantified. Barrel distortion has also been quantified and was found to be independent of object-lens distance. Using computer software to analyze clinical images, the intraoperator and interoperator correlation appears to show that ratio-metric measurements are reliable.

Adaptive averaging applied to dynamic imaging of the soft palate.

Achieving sufficient temporal and spatial resolution with adequate signal-to-noise ratio (SNR) in dynamic soft palate imaging is challenging. Triggered acquisitions require repeated reproducible speech samples, and while real-time imaging is more reliable, it may lack SNR. Adaptive averaging was implemented to improve SNR in nongated imaging during repetition of a speech task. Similar images were identified using localized cross-correlation before averaging. Adaptive averaging was applied to the soft palate region of images from six volunteers and one patient acquired with various sequences. In volunteers, soft palate SNR increased by 53 ± 17% with four averages. The additional SNR was used to enable reduced slice thickness in two example subjects. Adaptive averaging was also compared to pseudotriggered images in one example and, in another, it was applied to an unrepeated speech task. In a patient with a repaired cleft palate, the technique was used to demonstrate residual velopharyngeal insufficiency. This initial work demonstrates that increased temporal or spatial resolution may be traded for reduced SNR, which can be recovered using adaptive averaging. This will be a valuable tool in assessing velopharyngeal function, particularly in pediatric patients where cooperation may make gated studies difficult or when their head sizes require increased spatial resolution while maintaining temporal resolution.

Ureteric guidewire damage by Holmium:YAG laser: preliminary results.

Typically, guidewires are regularly used to provide access or act as a guide during laser lithotripsy. This may result in the tip of the fibre being in close proximity to the guidewire during the firing period and consequently, this could result in accidental damage to the guidewires during the procedure. To replicate this scenario, an experimental model was designed enabling accurate and reproducible positioning of the laser fibre relative to the guidewire. The guidewire was exposed to the laser energy for a range of typical settings used in the clinic. The results demonstrate that the guidewire is susceptible to laser energy damage, especially in close proximity to the fibre.

In vitro simulation of stent fracture mechanisms in ureteric nitinol wire stents.

The ZebraStent is a new-concept lumen-less teflon-coated nitinol double-J wire-stent, designed to facilitate the passage of residual fragments after extracorporeal shock wave lithotripsy. In clinical practice we observed a small number of stent fractures. Hence, an experimental model was designed to simulate the physical forces that may lead to material fatigue of the stent. Flexion force was simulated by "half circular kidney mimicking structures" (HCKMS) into which the upper part of the stent was placed. All experiments were done for a minimum of 5 million cycles representing a stent indwelling time of 9 months, or until stent fracture, and simulating respiratory kidney movement. It was demonstrated that as the diameter of the HCKMS decreases, thus leading to an increased bending of the stent, the likelihood of stent fracture increased proportionally and occurred earlier. From our results it appears that stent fractures can be avoided by observing a maximum indwelling time of 6-8 weeks (which should suffice for the duration of a average SWL treatment), by choosing the correct (and shortest possible) stent length, and perhaps by manufacturer's modifications decreasing the stent's resistance to flexion. The ZebraStent concept remains appealing if it is considered as a short-term stent for post-SWL residual fragments.

Assessment of tissue Doppler imaging measurements of arterial wall motion using a tissue mimicking test rig.

The aim of this in vitro study is to assess the accuracy of the tissue Doppler imaging arterial wall motion (TDI AWM) technique in measuring dilation over a range of distances and velocities. A test rig, consisting of two parallel blocks of tissue mimicking material (TMM), has been developed to generate known wall motion. One block remains stationary while the other moves in a cyclical motion. A calibrated laser range finder was used to measure the TMM motion. The TDI AWM measurements were found to underestimate the dilation by 21% +/- 4.7% when using the recommended scanner parameters. The size of the error was found to increase with a decrease in ultrasound output power. Results suggested that errors in the TDI AWM dilation measurements relate to underestimates in the velocity measured by the TDI technique. The error demonstrated in this study indicates a limitation in the value of TDI AWM result obtained in vivo. (E-mail: abigail.thrush@bartsandthelondon.nhs.uk).

Measurement of physiological recovery from exacerbation of chronic obstructive pulmonary disease using within-breath forced oscillometry.

BACKGROUND: Within-breath reactance from forced oscillometry estimates resistance via its inspiratory component (X(rs,insp)) and flow limitation via its expiratory component (X(rs,exp)). AIM: To assess whether reactance can detect recovery from an exacerbation of chronic obstructive pulmonary disease (COPD). METHOD: 39 subjects with a COPD exacerbation were assessed on three occasions over 6 weeks using post-bronchodilator forced oscillometry, arterial blood gases, spirometry including inspiratory capacity, symptoms and health-related quality of life (HRQOL). RESULTS: Significant improvements were seen in all spirometric variables except the ratio of forced expiratory volume in 1 s (FEV(1)) to vital capacity, ranging in mean (SEM) size from 11.0 (2.2)% predicted for peak expiratory flow to 12.1 (2.3)% predicted for vital capacity at 6 weeks. There was an associated increase in arterial partial pressure of oxygen (PaO(2)). There were significant mean (SEM) increases in both X(rs,insp) and X(rs,exp) (27.4 (6.7)% and 37.1 (10.0)%, respectively) but no change in oscillometry resistance (R(rs)) values. Symptom scales and HRQOL scores improved. For most variables, the largest improvement occurred within the first week with spirometry having the best signal-to-noise ratio. Changes in symptoms and HRQOL correlated best with changes in FEV(1), PaO(2) and X(rs,insp). CONCLUSIONS: The physiological changes seen following an exacerbation of COPD comprised both an improvement in operating lung volumes and a reduction in airway resistance. Given the ease with which forced oscillometry can be performed in these subjects, measurements of X(rs,insp) and X(rs,exp) could be useful for tracking recovery.

A new SWL titanium stent (Zebra Stent): resistance to shockwave exposure.

BACKGROUND AND PURPOSE: Recently, a new-concept lumen-less Teflon-coated double-J wire stent (Zebra stent) has been introduced to facilitate residual stone clearance, in particular after SWL. Its metal core expresses highly mismatched acoustic impedance. It was the aim of this study to exclude damage to the stent through shockwaves. Also, its Teflon coating should to some degree prevent encrustation, and stents removed from stone formers were examined for encrustation. MATERIALS AND METHODS: Series of 2000 shockwaves of an average and a maximum energy were applied to defined areas of Zebra stents in a waterbath on a Siemens Multiline Lithotriptor. Stents were then examined for core and sheath damage by digital photography, scanning electron microscopy, and microradiography. In addition, two Zebra stents and one conventional double-J stent from two stone formers were assessed in the same way for damage and encrustation. RESULTS: There was no damage whatsoever to either of the stents. Whereas there was considerable encrustation on the conventional double-J stent, there was none on the Zebra stents after 4 and 5 weeks in situ. CONCLUSIONS: Zebra stents resist shockwaves to a maximum number and energy sufficiently to be applied safely under SWL. Whether they resist encrustation to a higher degree in the short term than conventional stents remains to be established.