Acoustic non-invasive diagnosis of urinary bladder obstruction

Elderly men are prone to developing Lower Urinary Tract Symptoms, such as a weak urinary stream, frequent (nocturnal) voiding and incomplete emptying of the bladder. The two most probable causes for these symptoms are a weakly contracting bladder muscle or Bladder Outlet Obstruction (BOO), frequently caused by Benign Prostatic Enlargement. The most frequently used urodynamic method to diagnose this condition is an invasive pressure-flow study: measurement of bladder pressure during voiding using a catheter inserted in the bladder via the urethra. In this thesis an alternative non-invasive diagnostic method is presented. This method is based on turbulence in the urinary stream, induced by an obstruction (enlarged prostate) in the urethra. This turbulence can be recorded using a simple microphone placed at the perineum (between scrotum and anus). In a realistic biophysical model of the urethra we have shown that the sound frequency spectrum (characterized by ! three parameters) was uniquely and monotonically related to the degree of the obstruction. In a population of healthy male volunteers the variability of perineal sound recording within volunteers was found to be smaller than between volunteers: volunteers can be distinguished on the basis of perineal sound recording. From these findings and the three parameters being uniquely and monotonically related to the degree of the obstruction it can be concluded that perineal sound recording is a promising method for a cheap, simple and quick non-invasive diagnosis of BOO and clinical validation is strongly indicated

A Biophysical Model of the Male Urethra: comparing viscoelastic properties of PolyVinyl Alcohol urethras to male pig urethras.

Aims: We aim at developing a non-invasive method for grading and diagnosing urinary bladder outlet obstruction, based on noise recording with a perineal contact microphone during voiding. We found that the noise production during voiding depends amongst others on the viscoelastic properties of the urethral wall. To further test our method, we need a realistic biophysical model of the male urethra. Methods: We made various model urethras with different viscoelastic properties from a 10% aqueous solution of PolyVinyl Alcohol cryogel. We measured the viscoelastic properties of each model and compared them to those of the male pig urethra. The male pig urethra was used, as it is physiologically comparable to the human male urethra. The viscoelastic properties of both model and pig urethras were measured by applying strain to the urethral wall in a stepwise manner and recording the pressure response. We fitted the step-response of a mechanical model to this pressure response and derived the viscoelastic properties from the coefficients of this response. Results: A uniform model urethra that was freeze-thawed three times, with a Y-shaped flow channel was found to best represent the male pig urethra. Conclusion: We consider the three times freeze-thawed model urethra with a Y-shaped flow channel the best model of the human male urethra. And we therefore use this model urethra for studying the relation between noise recording during urine flow and the degree of bladder outlet obstruction.RePub containts a preprint of the article. See http://www.interscience.Wiley.co

Analysing the effects of travel information on public transport traveller’s decision making and learning

This thesis examines the effect of travel information on a public transport traveller’s decision making over time. It investigates whether the effect of information is sustained over time and is affected by its type and reliability. It is postulated that the traveller will attain better decision outcomes over time, and this process is reinforced when given information. It is postulated that dynamic information would produce the best outcomes, followed by static information and no information. A series of computer-based experiments, in which the participants made hypothetical trips by public bus under various travel information and operating conditions, were conducted. At the aggregate level, the hypothesised relationships are not observed at a statistically significant level. At the disaggregate level, day-to-day decisions are shown to relate significantly to the outcome of the previous day, with the participant more likely to seek a more rewarding but riskier choice if the previous day sees no adverse outcome, and vice-versa. When the information is static, decision changes are few and incremental. When it is dynamic, these changes are more frequent and pronounced, with choices ‘anchored’ around values provided by the information. Nonetheless, a significant proportion of participants made no or few changes, regardless of information or operating conditions. The findings suggest a higher propensity for some travellers to use dynamic information over static information over time, regardless of reliability. On the other hand, those who acquire information do not necessarily maximise their utility, implying that they do so for other less quantifiable factors. The benefits of information provision could also be further circumscribed by the heterogeneity of responses. This set of findings suggests that assuming travellers respond to information in a utility-maximising and homogeneous manner may over-estimate the effect of information

Is the impaired flow after hypospadias correction due to increased urethral stiffness?

Purpose: A low flow rate without clinical symptoms is commonly found in boys after hypospadias correction. Urethral calibration usually shows no abnormalities. We investigated whether this flow rate impairment might be caused by increased neo-urethral wall-stiffness. Methods: From Polyvinyl Alcohol cryogel two models of the urethra were made, a hypospadias model and a control model. Both models had a constant and equal inner diameter and equal compliance. The hypospadias model had a less compliant distal segment mimicking the distal neo-urethra after hypospadias correction. In both models flow rate was recorded as a function of bladder pressure. To test whether the length of the less compliant segment had an effect on the flow rate, both models were shortened by cutting off 1 cm segments. Results: In a physiological range of bladder pressures (10 - 130 cmH2O) the mean flow rate(± 1sem) in the hypospadias model was 2.8± 0.3 ml/s, significantly lower (p < .05) than in the control model (5.4 ± 0.6 ml/s). Shortening of the hypospadias model showed some increase in flow rate, however not statistically significant. In the control model there was also no significant variation in flow rate. Conclusion: We showed that a low compliant segment of a urethral model reduces the flow rate. Extrapolating these results to asymptomatic boys with a low urinary flow rate after hypospadias repair might justify a watchful waiting policy.RePub contains a preprint of the article. See: http://www.intl.elsevierhealth.com/journals/jpu

Meta-analysis of genome-wide scans for total body BMD in children and adults reveals allelic heterogeneity and age-specific effects at the WNT16 locus

To identify genetic loci influencing bone accrual, we performed a genome-wide association scan for total-body bone mineral density (TB-BMD) variation in 2,660 children of different ethnicities. We discovered variants in 7q31.31 associated with BMD measurements, with the lowest P = 4.1×10-11 observed for rs917727 with minor allele frequency of 0.37. We sought replication for all SNPs located ±500 kb from rs917727 in 11,052 additional individuals from five independent studies including children and adults, together with de novo genotyping of rs3801387 (in perfect linkage disequilibrium (LD) with rs917727) in 1,014 mothers of children from the discovery cohort. The top signal mapping in the surroundings of WNT16 was replicated across studies with a meta-analysis P = 2.6×10-31 and an effect size explaining between 0.6%-1.8% of TB-BMD variance. Conditional analyses on this signal revealed a secondary signal for total body BMD (P = 1.42×10-10) for rs4609139 and mapping to C7orf58. We a

Variability and Repeatability of Perineal Sound Recording in a Population of Healthy Male Volunteers

Objectives: In a population of 16 healthy male volunteers we studied the variability and repeatability of perineal Sound recording as a non-invasive method for diagnosing bladder outlet obstruction. Materials and Methods: The volunteers had a flat age-distribution (22-62 years), a median IPSS-score of 1 (range: 0-18) and voided at least 10 times. From each perineal Sound recording the frequency spectrum was calculated and characterized by its weighted average frequency, standard deviation and skewness. We assessed the variability of these parameters using the Kruskal-Wallis test, differences between volunteers Using Dunn&apos;s test and the repeatability by the normalized standard deviation of the differences between pairs of recordings in each volunteer. Results: For each parameter the variability within Volunteers was significantly smaller than the variability between volunteers (Kruskal-Wallis, P &lt; 0.05). For each parameter more than one volunteer was significantly different from three or more volunteers (Dunn&apos;s test, P &lt; 0.05). The repeatability of each parameter was comparable to that of the maximum flow rate. Conclusion: Perineal Sound recording gives repeatable results, which are significantly different between volunteers. In combination with the earlier published results from model-experiments the present results increase the probability that perineal sound recording can be used as a very simple and cheap method to non-invasively diagnose BOO. Clinical testing of this method is therefore strongly indicated. Neurourol. Urodynam. 27:802-806, 2008. (c) 2008 Wiley-Liss, Inc

Noninvasive Vascular Strain Imaging: from Methods to Application

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