Noninvasive Optical Monitoring of Bladder

Filling to Capacity Using a Wireless Near

Infrared Spectroscopy Device

K.KEERTHI

11211A1108

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CONTENTS

• Abstract

• Introduction

• NIRS device-Methodology

• Sensor block diagram

• Invitro setup

• Invivo setup

• Limitations

• Conclusion

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ABSTRACT

• Lack of bladder fullness sensation is an issue that arises in

different neurogenic conditions and in addition to influencing

patients’ quality of life, can result in serious kidney damage.

• We describe a wireless wearable sensor for detecting bladder

fullness using near infrared spectroscopy (NIRS).

• Capable of detecting changes in bladder content noninvasively.

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INTRODUCTION

(a) Evolution:• NIRS is a technique increasingly used in NICUs to monitor

cerebral (or peripheral) tissue oxygenation and to tailor

haemodynamic and respiratory support.

• Recently NIRS device is used to study the haemodynamics

and oxygenation of bladder and used to evaluate bladder

function in health and disease.

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(b) Bladder Pathology

• Incontinence:It is the inability to hold urine in the bladder because voluntary

control over the urinary sphincter is either lost or weakened.

• Enuresis:

It refers to a repeated inability to control urination particularly

tourette's syndrome in children.

• Urinary retention:

It is also known as ischuria, is an inability to completely

empty the bladder.

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(c)Techniques:

• Ultrasonic Scanning:

This technique uses ultrasonic imaging to differentiate the

urinary bladder from surrounding tissues and organs, produce

volume information, and estimate urine level.

• Bioelectrical impedance analysis:This technique is principally used for determining extracellular

and total body water, for the changes in electrical impedance

used for detection of urine volume to be measured

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NIRS device-Methodology

• This method employs the absorption properties of human

tissue and water in the near infrared (NIR) light wavelength

range to measure changes in water content in the field beneath

a NIRS device.

• When the bladder rises into the NIR light field as it fills, the

water in the urine it contains results in high light absorption

that generates an abrupt decrease in the light intensity sensed

returning to the NIRS device.

• This event can be set to activate an alarm.

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Sensor Block Diagram

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Source led:• It is a 950 nm LED.

• Driven by a constant current driver, that in turn is controlled by a hardware timer.

Light detector:

• It is a 5.22 mmsq silicon photodiode.

• Integrated with a trans.-impedance amplifier.

Filter:

• Active twin-T notch filter is used.

• Center frequency at 60 Hz

Micro-controller:

• 16-bit low power microcontroller(MSP430F2274 Texas Instruments, TX,USA)

• Running at 16MHz.

• The filter’s output is sampled by a 10-bit analog to digital converter (ADC) integrated on the MCU.

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Battery:

• The sensor is powered by a 3.7 V, 850 mAh lithium-ion

polymer rechargeable battery.

• Provides up to 20 hours of continuous monitoring.

USB connection

Memory storage:• The sensor can log data on the 16 KB onboard flash memory

storage.• The data can be later downloaded into a PC for further

analysis.

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IN-VITRO SETUP

• The setup was made to simulate the bladder, urine and the abdominal tissue during bladder filling and voiding.

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IN-VIVO SETUP

• The sensor is capable of differentiating between full and empty bladder.

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LIMITATIONS

• Fat tissue layer under the optical opcode location for bladder.

• Output drifts due to slight temperature changes.

• Signal attenuation due to systemic interferences.

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CONCLUSION

• A compact wireless optical sensor prototype is designed for continuous noninvasive monitoring of the bladder in patients who are unable to sense when their bladder is full.

• The device is capable of differentiating between when the

bladder is empty or contains a small volume of urine and

when it becomes full, by using the absorption properties of

water at a wavelength of 950 nm.

• This would potentially enable patients at risk for urinary

retention to protect themselves from renal damage, elderly

subjects prone to incontinence to retain the ability to void

voluntarily, and children with problematic enuresis to become

conditioned to when they need to wake to void.

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REFERENCES• A. Macnab and B. Shadgan, “Biomedical applications of wireless continuous wave near

infrared spectroscopy,” Biomed. Spectrosc. Imag., vol. 1, no. 3, pp. 205–222, 2012.

• A. Macnab, B. Shadgan, K. Afshar, and L. Stothers, “Near-infrared spectroscopy of the bladder: New parameters for evaluating voiding dysfunction,” Int. J. Spectrosc., vol. 2011, pp. 1–8, 2011.

• A. Macnab, B. Friedman, B. Shadgan, and L. Stothers, “Bladder anatomy physiology and pathophysiology: Elements that suit near infrared spectroscopic evaluation of voiding dysfunction,” Biomed. Spectrosc. Imag., vol. 1, no. 3, pp. 223–235, 2012.

• C. H. vander Vaart, J. R. J. de Leeuw, J. P. W. R. Roovers, and A. P. M. Heintz, “The effect of urinary incontinence and overactive bladder symptoms on quality of life in young women,” BJU Int., vol. 90, no. 6, pp. 544–549, Oct. 2002.

• S. Vaidyanathan, G. Singh, B. M. Soni, P. L. Hughes, K. F. Parsons, and P. Sett, “Vesicoureteral reflux and bladder management in spinal cord injury patients.,” Spinal Cord, vol. 40, no. 3, pp. 150–152, Mar. 2002.

• P. Petrican and M. A. Sawan, “Design of a miniaturized ultrasonic bladder volume monitor and subsequent preliminary evaluation on 41 enuretic patients.,” IEEE Trans. Rehabil. Eng., vol. 6, no. 1, pp. 66–74, Mar. 1998.

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