Wearable digital camera
ADS1298 analog front end
Sub-retinal implant
Retinal implant
Artificial heart transplant
MSC825x multi-core processor
Lab-on-a-chip device
It’s an endless circle. People live longer, thanks to technology. But those longer lives often burden today’s healthcare budgets. As a result, designers are working harder to use even better technology to reduce costs, improve diagnostics and treatments, and move closer to the patent. And as lives get even longer thanks to these improvements, the cycle starts all over again.
“The U.S. spends an estimated $2.5 trillion on healthcare, which is nearly one-half of the $5.5 trillion spent worldwide,” said Yongmin Kim, professor of bioengineering at the University of Washington. Speaking at the annual 31st IEEE Engineering in Medicine and Biology Conference (EMBC’09), Kim pointed out that the top three healthcare expenses include medications, imaging, and advanced treatments ranging from gene therapy to implantable devices like stents.
“Comparative effectiveness research is the buzzword in healthcare,” said Richard Kuntz, chief science officer at Medtronic, also at EMBC’09. “So we have to show how added costs also add benefits, in a market where the value of an added year of patient life is pegged at about $45,000.”
Electronics technology is gearing up to meet future healthcare needs, spurred on by ubiquitous advances in portability and communications platforms. Milestones have been reached and continue to be reached in more accurate and reliable information. Powerful signal-processing ICs enable earlier and more precise diagnostics. A range of devices and platforms can connect patients and healthcare providers. And all of these developments are making healthcare more portable, allowing for quicker and simpler monitoring and treatment of a patient’s vital signs, often at the patient’s home or in a local clinic.
“In order to have practical home healthcare devices, designers must make use of analog and mixed-signal products that offer value to the consumer,” says Paul Errico, worldwide strategic marketing manager for Analog Devices. “This means making use of more integrated, lower power consumption and lower-cost design approaches.”
Jose Fernandez Villasenor, global applications medical specialist at Freescale Semiconductor, agrees. “Low-cost, low-power, and small size benefits can be achieved in home healthcare products by designing equipment that does not have to have very high sensitivity levels,” he says. “After all, these products can act as warning devices that alert healthcare providers early enough to make more detailed testing using clinical or hospital equipment that provides greater sensitivity and accuracy before medical conditions worsen.”
The promise of practical home healthcare products looks even rosier when we view the advances in portable consumer electronics products and wireless and Internet-based connectivity. Developed by researchers at Microsoft, the SenseCam wearable digital camera (Fig. 1) takes photographs passively, without the user’s intervention. A wide-angle fish-eye lens maximizes its field of view, an important feature since a regular wearable camera would likely produce many uninteresting images.
The SenseCam’s multiple sensors include light intensity and color detectors, a thermometer, a passive infrared detector for body heat, and a multi-axis accelerometer. The camera’s microprocessor, which can be programmed to take images once specific changes in the sensors’ output are detected, monitors the outputs of these sensors.
It is also possible to hook the camera to your belt, put it in your pocket, or attach it directly to your clothing. The most recent version, v2.3, typically stores 30,000 images. A log file records other sensor data along with timestamps. Additional user data, such as timestamped GPS traces, may be used in conjunction with the camera’s data via time correlation.
IT STARTS WITH SENSORS
A sensor forms a critical part of a patient’s diagnosis and treatment, and microelectromechanical-system (MEMS) sensor technology has been at the forefront of medical electronics. MEMS sensors are being used for patient fall detection, motion and mobility tracking, implantable drug delivery and neural-stimulus systems, respiratory monitoring, glucose and blood pressure monitoring, and wound-care systems. They provide researchers with the tools they need for advanced body organ and neural brain studies.
Medtronic has begun clinical trials in the U.S. for a device that uses a three-axis MEMS accelerometer to fine-tune how its RestoreSensor neurostimulator implant delivers electrical stimulation to nerves in the spinal cord to reduce pain. The implant records and stores the frequency of posture activity changes for analysis.
STMicroelectronics is developing a wireless MEMS sensor that acts as a transducer, antenna, and mechanical support for additional readout electronics in a breakthrough platform for glaucoma treatment. The Triggerfish platform from Swiss company Sensimed AG is designed to improve glaucoma treatments. It employs a tiny embedded strain gauge to monitor the eye’s curvature over a period of time, typically 24 hours. As a result, it can provide valuable disease management data not available using conventional opthalmatic equipment.
An ambitious low-cost sensing project is underway at the University of Florida to detect indications of diabetes and even cancer via a patient’s breath or saliva. Researchers there successfully tested a 100-µm aluminum-gallium-nitride/gallium-nitride (AlGaN/GaN) sensor that detects a patient’s pH or glucose concentration in less than 5 seconds. They estimate that such a chip can be mass produced at low cost (about 20 cents each) using conventional semiconductor IC manufacturing processes.
Achieving higher levels of integration in semiconductor technology is a major reason why medical electronics are advancing rapidly. Designed for electrocardiogram (ECG) and electroencephalogram (EEG) heart and brainwave monitoring, the ADS1298 analog front end (Fig. 2) from Texas Instruments (see “Tiny Analog Front End For ECG And EEG Apps Sips Power”) integrates eight low-noise programmable-gain amplifiers, eight high-resolution simultaneous-sampling analog-to-digital converters (ADCs), a clock oscillator, and a voltage reference.
“This chip answers portability, low-cost, small size, and high-performance challenges facing medical product designers,” says Steve Dean, TI’s medical marketing director. “Designers can save up to 95% in cost and power savings over discrete-component solutions. It is the only fully integrated analog front end of its kind on the market.”
SHARPER AND CHEAPER IMAGING
One area of medical electronics that’s making large gains is medical imaging, particularly ultrasound and magnetic-resonance imaging (MRI). Such systems are getting smaller, much more accurate, and very low in cost. They’re giving healthcare providers more detailed and clearer pictures of the body’s interior, leading to better diagnostics and therapy.
Modern ultrasound systems are portable and can be found using PCs, laptops, PDAs, and even mobile phones—a far cry from older and more expensive machines that took up a considerable amount of space. These improvements can be attributed to advances in the key electronic components that form the basis for such systems, namely amplifiers, filters, digital-to-analog converters (DACs), and more powerful digital signal processors (DSPs). “It is now possible to use ultrasound machines for things like early cancer detection from the patient’s home,” says Freescale’s Vallisensor.
TechniScan Inc. has secured a patent on 3D ultrasound imaging for breast cancer using proprietary methods in creating diagnostic images from complex wave fields. The technique, known as Warm Bath Ultrasound technology, delivers images within minutes. Not yet approved by the Food and Drug Administration (FDA), it is being used for investigative purposes.
Samplify Systems recently made available an autofocus beam-forming technology, Prism 3.0, for ultrasound imaging. Using a 32-channel ultrasound analog front-end receiver module, it’s based on the company’s SAM 1600 family of compressing ADCs. Its beam-forming technology’s integrated AutoFocus engine automatically refocuses the receiver to capture reflections at different scan depths, minimizing and simplifying real-time calculations needed in software using conventional methods.
“In ASIC form, we provide a 90% increase in performance over an FPGA approach for the same costs,” says Allan Evans, vice president of marketing for Samplify Systems.
Scientists at the University of Washington hope to introduce an ultrasound imaging system that primary care physicians can use to screen patients for coronary artery diseases in just 10 minutes, reducing the time needed to send patients to cardiac specialists for more expensive and invasive angiograms. The system checks vibrations to detect signs of blood artery blockage.
Collaborative research by scientists at the University of Texas M.D. Anderson Cancer Center and Sonovation Inc. holds promise for the development of a novel ultra-high-frequency ultrasound system designed for cancer treatment. The effort employs Sonovation’s advanced transducer technology, which also is used in the company’s SonicTouch biometric fingerprinting product. The ultrasound may be usable, alone or in combination with other treatments, to treat skin cancer and other dermalogical conditions.
BETTER MRIs
Highly integrated electronics products like the Analog Devices AD5791 20-bit DAC are enabling very accurate, high-resolution, and stable MRI scans (see “20-Bit DAC Sharpens MRI Images”). Exceptional image quality is achieved thanks to the DAC’s 1-ppm resolution, integral non-linearity, and output drift, as well as a low 9-nV/√Hz noise spectral density.
“The AD5791 offers 24 times the resolution of competitive units. It allows for better quality and clearer images for a radiologist to view. Lower noise means eliminating ghosting effects, and lower drift means lower costs, since the scanner needs fewer calibrations over a specific period of time,” says Brandon Cronin, Analog Devices’ product marketing manager for ADCs.
On the research front, many MRI efforts abound. One is a nuclear-magnetic resonance (NMR) device for use in doctors’ offices that could slash the cost and size of medical diagnostic systems, enabling the development of $15,000 portable systems than can replace much larger systems costing up to $200,000. The work is a joint project between Harvard University and T2 Biosystems.
At this year’s IEEE International Solid State Circuits Conference (ISSCC) in February, the first results were unveiled for the Palm NMR and Palm On-chip NMR, used in a 0.1-kg instrument the company says is 150 times more sensitive than conventional NMR systems that weigh 120 kg. The device can scan molecular-level structures in a sample of blood, urine, or saliva collected on a chip substrate.
Tiny ion-oxide particles are implanted in target anti-bodies on the chip. The cells are spun in one direction by a small magnet, then spun again in the opposite direction by an electric current. The system uses a CMOS transceiver called the T2 to determine the presence and magnitude of a target virus or antigen.
At Ohio State University, scientists are developing ways to enhance how brain tumors appear in MRI scans and during surgery, making them easier to identify and remove. They’ve made nano-composites of less than 20 nm that have both magnetic and fluorescent properties. The particles emphasize color contrasts within MRIs, allowing doctors to see potential or existing cancerous tumors before surgery as well as during surgery. The fluorescent nano-particles can change the color that the tumor appears in the brain when seen under a special light.
Researchers at the Massachusetts Institute of Technology (MIT) have developed an MRI sensor that provides a molecular view of the brain, potentially significantly improving the specificity and resolution of brain-imaging procedures. The sensor responds to the brain’s neurotransmitter dopamine. It connects molecular phenomena in the nervous system with whole-brain imaging techniques.
IMPLANTS PROGRESSING
Body organ implants are making steady progress for replacing human eyes, pancreases, ears, hearts, and other organs. Retinal implants are a hot topic at many research centers. At Stanford University, researchers have come up with a unique retinal implant (Fig. 3) that solves a constantly challenging problem: getting data (light) and power into a retinal implant easily. Their photovoltaic 3-mm wide retinal chip gets both data and power from near-infrared light.
The implant consists of any array of solar cells. The device—technically a subretinal implant because it is placed behind the retina—is part of a system that includes a video camera that captures images, a pocket PC that processes the video feed, and a bright near-infrared LCD built into video goggles. The pulsed 900-nm wavelength image that shines into the eyes is more than enough to produce an electrical signal.
The choice of a near-infrared display was dictated by the fact that it is invisible. The researchers recognized that some patients might still have some working photoreceptors that could be stimulated by visible light. If it’s bright enough, such light could muddy the image generated in the brain.
Much work has been occurring at MIT to develop a retinal implant that could restore a useful level of vision to those with retinitis pigmentosa or age-related macular degeneration, two of the leading causes of blindness. A retinal prosthesis under development would take over the function of lost retinal cells by electrically stimulating the nerve cells that normally carry visual input from the retina to the brain.
This prosthesis would not restore normal vision, but it could help the blind to more easily navigate a room or walk down a sidewalk. Patients with this implant would wear a pair of glasses with a camera that sends images to a microchip attached to the eyeball (Fig. 4). The glasses also contain a coil that wirelessly transmits power to receiving coils surrounding the eyeball.
When the chip receives visual information, it activates electrodes that stimulate nerve cells in the areas of the retina corresponding to the features of the visual scene. The electrodes directly activate optical nerves that carry signals to the brain, bypassing the damaged layers of the retina. The MIT work is a joint effort involving the Massachusetts Eye and Ear Infirmary, the Boston Veterans Administration (VA) Medical Center, and Cornell University.
A total artificial heart transplant (Fig. 5) is on the drawing board at MicroMed Cardiovascular Inc., working with the Texas Heart Institute under funding from the National Institutes of Health (NIH). This design employs a pair of continuous flow pumps, essentially repurposed DeBakey ventricular assist devices (VADs), to completely replace the heart’s natural ventricles.
POWERFUL COMPUTING
The emergence of high-end microcontroller units (MCUs) and multi-core DSPs has greatly improved our ability to detect, diagnose, and treat a multitude of medical diseases, illnesses, and disorders. One the of the more recent multi-core processors is the MSC825x family from Freescale (Fig. 6). Freescale also recently unveiled its 8- and 32-bit Flexis MM, JE, and LH family of low-power MCUs, which consume less than 450 nA. They’re aimed at embedded portable medical designs such as glucose meters and heart-rate monitors.
The use of DSP techniques for early cancer detection is the goal of professor K.J. Ray Liu at the University of Maryland. He employs DSP techniques to extract information from DNA to identify changes that occur as cancer develops, which he hopes will ultimately lead to the ability to predict whether cells will become cancerous.
“Nowadays a doctor can tell you, for example, what your cholesterol level is and express it by a number,” he says. “Hopefully through our work, one day a doctor will be able to give you a number related to cancer—whether the number is within normal range, whether it shows cells are transitioning to the cancerous stage and preventive treatment is needed, or whether the number is high and you need to watch for cancer developing in, say, your liver or breast.”
Peering into the short-term future, we can see lab-on-a-chip devices, spurred on by advances in microfluidic MEMS technology, enabling low-cost testing and diagnostics of a wide variety of body fluids and ailments. Several such products are already on the market such as the Becton Dickenson HandyLab Jaguar platform, Micronics PanNAT platform, and Rheniox CARD (chemistry and reagent device).
A notable development in lab-on-a-chip devices comes from Brigham Young University, which has achieved an important breakthrough in the development of a nanometer-size lab on a chip (Fig. 7) that can identify viruses quickly and inexpensively.
About 1 cm2, the chip contains 200 two-segmented millimeter-long channels of an infinitely small diameter that range from 145 nm down to 25 nm. Proteins, cholesterol, and viruses can be placed on the chip and pulled through by capillary action. The conduits are engineered to sizes just smaller than the particles they intend to isolate.
“Within a channel, there would be openings of different sizes. Imagine two pipes joined together, one a lot smaller than the other,” explains professor Aaron Hawkins, leader of the research team for this effort. Particles of a particular size get trapped, while smaller ones pass through. The researchers used dye-tagged capsids, or the protein shell, of the hepatitis B and the herpes simplex virus, which are 30 and 120 nm in diameter, respectively, for test purposes. The NIH is supporting this research effort.