Brian Leaker

Dynamic multi-planar EPI of the urinary bladder during voiding with simultaneous detrusor pressure measurement

Magnetic resonance imaging gives high quality images of the urinary bladder with excellent contrast. We report here the first application of dynamic, multi-slice, echo planar imaging to a study of urinary bladder emptying. Changes in urinary bladder volumes and rates of urine expulsion from the bladder have been measured simultaneously with bladder pressure. The method shows promise for clinical applications involving compromised bladder function, for reappraising bladder contraction strength-volume relationships, and for investigating the rate of change of length, three-dimensional shape, and wall tension in different parts of the bladder during micturition.

Minimizing Stimulus Current in a Wearable Pudendal Nerve Stimulator Using Computational Models

After spinal cord injury, functions of the lower urinary tract may be disrupted. A wearable device with surface electrodes which can effectively control the bladder functions would be highly beneficial to the patients. A trans-rectal pudendal nerve stimulator may provide such a solution. However, the major limiting factor in such a stimulator is the high level of current it requires to recruit the nerve fibers. Also, the variability of the trajectory of the nerve in different individuals should be considered. Using computational models and an approximate trajectory of the nerve derived from an MRI study, it is demonstrated in this paper that it may be possible to considerably reduce the required current levels for trans-rectal stimulation of the pudendal nerve compared to the values previously reported in the literature. This was corroborated by considering an ensemble of possible and probable variations of the trajectory. The outcome of this study suggests that trans-rectal stimulation of the pudendal nerve is a plausible long term solution for treating lower urinary tract dysfunctions after spinal cord injury.

Design of sEMG assembly to detect external anal sphincter activity: a proof of concept

OBJECTIVE Conditional trans-rectal stimulation of the pudendal nerve could provide a viable solution to treat hyperreflexive bladder in spinal cord injury. A set threshold of the amplitude estimate of the external anal sphincter surface electromyography (sEMG) may be used as the trigger signal. The efficacy of such a device should be tested in a large scale clinical trial. As such, a probe should remain in situ for several hours while patients attend to their daily routine; the recording electrodes should be designed to be large enough to maintain good contact while observing design constraints. The objective of this study was to arrive at a design for intra-anal sEMG recording electrodes for the subsequent clinical trials while deriving the possible recording and processing parameters. APPROACH Having in mind existing solutions and based on theoretical and anatomical considerations, a set of four multi-electrode probes were designed and developed. These were tested in a healthy subject and the measured sEMG traces were recorded and appropriately processed. MAIN RESULTS It was shown that while comparatively large electrodes record sEMG traces that are not sufficiently correlated with the external anal sphincter contractions, smaller electrodes may not maintain a stable electrode tissue contact. It was shown that 3 mm wide and 1 cm long electrodes with 5 mm inter-electrode spacing, in agreement with Nyquist sampling, placed 1 cm from the orifice may intra-anally record a sEMG trace sufficiently correlated with external anal sphincter activity. SIGNIFICANCE The outcome of this study can be used in any biofeedback, treatment or diagnostic application where the activity of the external anal sphincter sEMG should be detected for an extended period of time.

Conditional neuromodulation of neurogenic detrusor overactivity using transrectal stimulation in patients with spinal cord injury: A proof of principle study

A proof of principle study of a novel wearable device to control neurogenic detrusor over‐activity in eight male spinal cord injured subjects using conditional neuromodulation.

Optimization of a wearable pudendal nerve stimulator using computational models.

After spinal cord injury, lower urinary tract functions may be disrupted. Trans-rectal stimulation of the pudendal nerve may enable patients to regain these functions via minimally invasive means. Using a finite element model of a wearable trans-rectal stimulator in the pelvic region, and a computational model of mammalian nerve fiber, various electrode configurations and the corresponding required current levels were studied. A configuration requiring considerably lower current level than previously reported was identified. For this configuration, the strength-duration curve was simulated and the effect of different stimulus waveforms on the required current was studied. In addition, the study examined whether a multi-electrode device could selectively activate different terminal branches of the pudendal nerve.