24-07-2012, 04:43 PM
. ELECTRONIC CAPSULES
electronic capsule.doc (Size: 2.58 MB / Downloads: 77)
INTRODUCTION
Evolution of technology in recent years opened the door for advanced microelectronic systems to be used in medical treatments and diagnostic analysis. Such systems known as smart pills, electronic digestible capsules and intelligent microsystems are rising quickly in this field, they enhance the treatment of several diseases (cancer, diabetes,… ) and carry out biomedical analysis in GI tract (temperature, pH, motility, …), GI diseases affect 60-70 million people annually while diagnosis and treatment exceed €10 Billion Euro per year.
Back to four decades, Mackay invented the first radio telemetry capsule with one transistor in 1957 and the first successful pH sensor capsule was achieved in 1972, since then research and developments were carried out enhancing and expanding in this field.
The invention of the transistor enabled the implementation of the first radiotelemetry ingestible capsules, which utilised simple circuits for in vivo telemetric studies of the gastro-intestinal (GI) tract [1]. These units could only transmit from a single sensor channel, and were difficult to assemble due to the use of discrete components [2]. The measurement parameters consisted of either temperature, pH or pressure. These first attempts of conducting real time non-invasive physiological measurements (understandably, given the extent of technology in 1957) suffered from poor reliability, low sensitivity and short lifetimes of the devices.
Capsules as Actuators
Drug delivery system is an issue of optimization for many interests, immediate release drug will be absorbed in the upper part of the small intestine after the stomach, extended release drug is desired to be absorbed in the lower level of the intestine.
Achievement of the second by normal coating tablets is difficult due to the complexity of the GI tract of human being, intubation is an alternative solution, but it is uncomfortable for patients.
Alternative solution will be of more interest, and the idea of developing swallowed capsules devices was demonstrated, over two decades engineers are trying to develop different capsules with the capability to control the time and the location of the drug release.
The earlier capsules in this domain were HF, InteliSite, and Telemetric Capsules. They are triggered by a radio frequency (RF) pulse from a generator outside the body, the heat generated in the circuit will melt a thread releasing a needle that pierces the container and spells out the drug. State-of-the-art in this domain are the Enterion™ capsule and ChipRx™.
Capsule basics
In general, a swallowable capsule is a selfcontained microsystem that performs a sensing or actuating function in the body. Usually the system consists of the core components in figure 2 encapsulated in a biocompatible material.
At one end of the chain are the sensors (or alternatively, actuators) that interface with the body. Sensors convert physical properties such as light, pressure, or temperature into electrical signals, while actuators perform the opposite function.
The signal-conditioning block provides analog processing such as amplification and filtering to “clean” the detected signal. The system’s brain, the CPU, digitizes the signal and might perform additional processing. The communication block can then transmit the signal to a receiver module outside the body. The communication medium can be RF, a magnetic field (inductive coupling), or ultrasound. Finally the power supply, based on either batteries or inductive coupling, provides energy for the system.
Capsules as Sensors
Monitoring the variation of temperature, pH, motility and other functions are getting easier and comfortable for patients. The need to collect biomedical information within a specific location is of high interest, most of the existing sensor capsules don’t provide location determination. Earlier products in this field are the Radio Pill, BRAVO, Heidelberg and Temperature capsules. Almost all of them use internal battery for power consumption. New capsules in this field are IDEAS, SmartPill and Tohoku capsules. IDEAS and SmartPill provide multi-sensors microsystem for real time analysis.
Retrieving video images from within the GI tract with wireless endoscopy was a breakthrough in year 2000, M2A from Given Imaging was the 1st to develop such a system, later RF System Lab from Japan produced the Norika capsule which is the-state-of-the-art in this domain. Another new system from IMS Stuttgart is the IVP (Intracorporeal Videoprobe). M2A/PillCam are powered by battery while Norika and IVP by external magnet field. A trade off must be taken between using battery inside the body with limited power supply and exposing the body with RF signal to power up the camera and LEDs
Experiment
The electronic pill comprise a biocompatible capsule, which consists of a chemicallyresistant polyether-terketone (PEEK) coating, the four microfabricated sensors, the ASIC control chip and a discrete component radio transmitter
The unit is powered by two SR44 Ag2O batteries (3.1 V), which provides an operating time of 35 hours at the rated power consumption of 15 mW.The sensors were fabricated on two separate 5x5 mm
Silicon chips located at thefront end of the capsule. The temperature sensor is embedded in the substrate, whereas the conductivity sensor is directly exposed to the surroundings. The pH and oxygensensors were enclosed in two separate 8 nL electrolyte chambers containing a 0.1MKOH solution retained in a 0.2 % calcium alginate gel. The electrolyte maintains astable potential of the integrated Ag/AgCl reference electrodes used by the two sensors.The oxygen and pH sensor are covered by a 12 µm thick film of teflon and nafionrespectively, and protected by a 15 µm thick dialysis membrane of polycarbonate.
Technical challenges
In addition to the standard constraints in electronic design, a number of main challenges arise for systems that operate inside the human body. The foremost challenge is miniaturization to obtain an ingestible device. The availability of small-scale devices can place severe constraints on a design, and the interconnection between them must be optimized. Also the alternative, full integration on silicon, can be a long and expensive process. The size constraints lead to another challenge, noise. The coexistence of digital integrated circuits, switching converters for the power supply, and communication circuits in close vicinity of the analog signal conditioning could result in a high level of noise affecting the input signal. Therefore, capsule designers must take great care when selecting and placing components, to optimize the isolation of the front end.
electronic capsule.doc (Size: 2.58 MB / Downloads: 77)
INTRODUCTION
Evolution of technology in recent years opened the door for advanced microelectronic systems to be used in medical treatments and diagnostic analysis. Such systems known as smart pills, electronic digestible capsules and intelligent microsystems are rising quickly in this field, they enhance the treatment of several diseases (cancer, diabetes,… ) and carry out biomedical analysis in GI tract (temperature, pH, motility, …), GI diseases affect 60-70 million people annually while diagnosis and treatment exceed €10 Billion Euro per year.
Back to four decades, Mackay invented the first radio telemetry capsule with one transistor in 1957 and the first successful pH sensor capsule was achieved in 1972, since then research and developments were carried out enhancing and expanding in this field.
The invention of the transistor enabled the implementation of the first radiotelemetry ingestible capsules, which utilised simple circuits for in vivo telemetric studies of the gastro-intestinal (GI) tract [1]. These units could only transmit from a single sensor channel, and were difficult to assemble due to the use of discrete components [2]. The measurement parameters consisted of either temperature, pH or pressure. These first attempts of conducting real time non-invasive physiological measurements (understandably, given the extent of technology in 1957) suffered from poor reliability, low sensitivity and short lifetimes of the devices.
Capsules as Actuators
Drug delivery system is an issue of optimization for many interests, immediate release drug will be absorbed in the upper part of the small intestine after the stomach, extended release drug is desired to be absorbed in the lower level of the intestine.
Achievement of the second by normal coating tablets is difficult due to the complexity of the GI tract of human being, intubation is an alternative solution, but it is uncomfortable for patients.
Alternative solution will be of more interest, and the idea of developing swallowed capsules devices was demonstrated, over two decades engineers are trying to develop different capsules with the capability to control the time and the location of the drug release.
The earlier capsules in this domain were HF, InteliSite, and Telemetric Capsules. They are triggered by a radio frequency (RF) pulse from a generator outside the body, the heat generated in the circuit will melt a thread releasing a needle that pierces the container and spells out the drug. State-of-the-art in this domain are the Enterion™ capsule and ChipRx™.
Capsule basics
In general, a swallowable capsule is a selfcontained microsystem that performs a sensing or actuating function in the body. Usually the system consists of the core components in figure 2 encapsulated in a biocompatible material.
At one end of the chain are the sensors (or alternatively, actuators) that interface with the body. Sensors convert physical properties such as light, pressure, or temperature into electrical signals, while actuators perform the opposite function.
The signal-conditioning block provides analog processing such as amplification and filtering to “clean” the detected signal. The system’s brain, the CPU, digitizes the signal and might perform additional processing. The communication block can then transmit the signal to a receiver module outside the body. The communication medium can be RF, a magnetic field (inductive coupling), or ultrasound. Finally the power supply, based on either batteries or inductive coupling, provides energy for the system.
Capsules as Sensors
Monitoring the variation of temperature, pH, motility and other functions are getting easier and comfortable for patients. The need to collect biomedical information within a specific location is of high interest, most of the existing sensor capsules don’t provide location determination. Earlier products in this field are the Radio Pill, BRAVO, Heidelberg and Temperature capsules. Almost all of them use internal battery for power consumption. New capsules in this field are IDEAS, SmartPill and Tohoku capsules. IDEAS and SmartPill provide multi-sensors microsystem for real time analysis.
Retrieving video images from within the GI tract with wireless endoscopy was a breakthrough in year 2000, M2A from Given Imaging was the 1st to develop such a system, later RF System Lab from Japan produced the Norika capsule which is the-state-of-the-art in this domain. Another new system from IMS Stuttgart is the IVP (Intracorporeal Videoprobe). M2A/PillCam are powered by battery while Norika and IVP by external magnet field. A trade off must be taken between using battery inside the body with limited power supply and exposing the body with RF signal to power up the camera and LEDs
Experiment
The electronic pill comprise a biocompatible capsule, which consists of a chemicallyresistant polyether-terketone (PEEK) coating, the four microfabricated sensors, the ASIC control chip and a discrete component radio transmitter
The unit is powered by two SR44 Ag2O batteries (3.1 V), which provides an operating time of 35 hours at the rated power consumption of 15 mW.The sensors were fabricated on two separate 5x5 mm
Silicon chips located at thefront end of the capsule. The temperature sensor is embedded in the substrate, whereas the conductivity sensor is directly exposed to the surroundings. The pH and oxygensensors were enclosed in two separate 8 nL electrolyte chambers containing a 0.1MKOH solution retained in a 0.2 % calcium alginate gel. The electrolyte maintains astable potential of the integrated Ag/AgCl reference electrodes used by the two sensors.The oxygen and pH sensor are covered by a 12 µm thick film of teflon and nafionrespectively, and protected by a 15 µm thick dialysis membrane of polycarbonate.
Technical challenges
In addition to the standard constraints in electronic design, a number of main challenges arise for systems that operate inside the human body. The foremost challenge is miniaturization to obtain an ingestible device. The availability of small-scale devices can place severe constraints on a design, and the interconnection between them must be optimized. Also the alternative, full integration on silicon, can be a long and expensive process. The size constraints lead to another challenge, noise. The coexistence of digital integrated circuits, switching converters for the power supply, and communication circuits in close vicinity of the analog signal conditioning could result in a high level of noise affecting the input signal. Therefore, capsule designers must take great care when selecting and placing components, to optimize the isolation of the front end.