2009

Medical Design Advances Provide New Diagnostic and Treatment Options

Advances in medical design are paving the way for diagnostic and treatment options that previously were thought to be impossible. Today, surgeons, emergency medical personnel, and other healthcare professionals have a myriad of tools and techniques at their fingertips to help treat disease, create better orthopedic equipment and implants, and more accurately diagnose patients. Here is only a sampling of some of these new medical design breakthroughs.

Orthopedics and Implants

Researchers at Yale University have created artificial cells that are more powerful and efficient than the natural cells they mimic and could one day be used to power tiny medical implants. Scientists assessed whether an artificial version of the electrocyte – the energygenerating cells in electric eels – could be designed as a potential power source. The blueprint shows how the electrocyte’s different ion channels work together to produce the fish’s electricity.

Using the new blueprint as a guide, the scientists designed an artificial cell that could replicate the electrocyte’s energy production. The artificial cell is capable of producing 28% more electricity than the eel’s own electrocyte, with 31% more efficiency in converting the cell’s chemical energy – derived from the eel’s food – into electricity.

While eels use thousands of electrocytes to produce charges of up to 600 volts, the scientists show it would be possible to create a smaller “bio-battery” using several dozen artificial cells. The tiny bio-batteries would only need to be about 1⁄4 -inch thick to produce the small voltages needed to power tiny electrical devices such as retinal implants or other prostheses.

The cells still need a power source before they can start producing electricity. The cells could be powered in a way similar to their natural counterparts. It is possible that bacteria could be employed to recycle ATP – responsible for transferring energy within the cell – using glucose, a common source of chemical energy derived from food.

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A method of producing synthetic bone, using techniques normally used to make catalytic converters for cars, is being developed by researchers at the University of Warwick in the UK, who believe it could offer substantial clinical benefits to patients undergoing bone implant surgery. The technique involves extrusion of the implant material through a mold to produce a 3D honeycomb texture with uniform pores throughout. The material can then be sculpted by the surgeon to precisely match the defect. After implantation, bone cells are transported into the implant and begin to form new bone.

The researchers worked with a Ja - panese company that manufactures catalytic converters to produce samples. They used calcium phosphates — bioceramics that are routinely used in bone implant operations. By using the new technique, they were able to improve both the strength and porosity of the implant. The increased strength of the material means it could be used in spinal surgery, or in revision hip and knee operations, where non-degradable materials such as titanium or steel may be used. The advantage of increased and interconnected porosity is that the implant can quickly be filled with blood vessels, resulting in a more rapid healing process.

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Some 46 million people suffer from arthritis in the United States. The worst cases require painful surgeries to drill holes in and reinforce joints. Researchers working at the National Institute of Standards and Technology (NIST) are studying an unusually pliant yet strong synthetic cartilage replacement in hopes of providing arthritis victims with some relief.

NIST scientists and colleagues from Hokkaido University in Japan created a gel that, while having the pliancy of gelatin, won’t break apart even when deformed over 1,000 percent. Most conventionally prepared hydrogels — materials that are 80 to 90 percent water held in a polymer network — easily break apart like a gelatin. The addition of a second polymer to the gel made them so tough that they rivaled cartilage.

Establishing the details of the molecular structure will allow for more precise design of the next generation of hydrogels that are tough and rigid at the same time. Real cartilage goes through a process of constant daily destruction and regeneration under everyday stresses; the researchers hope a good synthetic cartilage could endure year after year under the rigors of the body before needing to be replaced.

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A new energy-capturing knee brace can generate enough electricity from walking to operate a portable GPS locator, a cell phone, a motorized prosthetic joint, or an implanted neurotransmitter. University of Michigan researchers have developed a wearable mechanism that works like regenerative braking charges a battery in some hybrid vehicles, collecting the kinetic energy that would otherwise be dissipated as heat when a car slows down. The knee brace harvests the energy lost when a human brakes the knee after swinging the leg forward to take a step.

The scientists tested the knee brace on six men walking on a treadmill at 2.2 miles per hour. They measured the subjects’ respiration to determine how hard they were working. A control group wore the brace with the generator disengaged to measure how the weight of the 3.5-pound brace affected the wearer. In the mode in which the brace is only activated while the knee is braking, the subjects required less than one watt of extra metabolic power for each watt of electricity they generated.

A lighter version would be helpful to hikers or soldiers who don’t have easy access to electricity. Similar mechanisms could be built into prosthetic knees for other implantable devices such as pacemakers or neurotransmitters that today require a battery and periodic surgery to replace that battery.

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Students at Johns Hopkins University have designed and built a device to enable critically ill intensive care unit (ICU) patients to leave their beds and walk while remaining tethered to lifesupport equipment. The invention allows doctors to better understand whether carefully supervised rehabilitation, as opposed to continuous sedation and bed rest, can improve the recovery of intensive care patients. The device, called the ICU MOVER Aid, has two components: a mobility aid that combines the rehabilitative features of a walker and the safety features of a wheelchair, and a separate wheeled tower to which life-support equipment can be attached.

The ICU MOVER also can serve as a wheelchair and “catch” a walking patient who needs to sit down immediately because of fatigue or a sudden change in his or her medical condition. The unit features a walker-type framework. Immediately behind the patient, however, a fabric seat is attached to the frame so that a tired patient can sit down.

As a separate component, the prototype features a tower that accommodates two oxygen tanks, a cardiac monitor, intravenous infusion pumps to provide medications, and a ventilator to support breathing. The MOVER requires only two hospital staff members to accompany the walking patient.

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Advanced Medical Devices

Scientists at NASA’s Jet Propulsion Laboratory have developed the Multi- Angle and Rear Viewing Endoscopic tooL (MARVEL), an auxiliary endoscope that a surgeon would use in conjunction with a conventional endoscope to get additional perspective.

A conventional endoscope provides mostly a frontal view. The MARVEL could be inserted through the same opening as a conventional endoscope, but could be adjusted to provide a view from almost any angle. The MARVEL camera image would be displayed on the same monitor as the conventional endoscopic image, as an inset within the image. For example, while viewing a tumor from the front in the conventional endoscopic image, the surgeon could simultaneously view the tumor from the side or the rear in the MARVEL image, and could thereby gain additional visual cues that would aid in precise threedimensional positioning of surgical tools to remove the tumor.

The MARVEL includes a miniature electronic camera and radio transmitter mounted on the tip of a surgical tool. The radio transmitter would eliminate the need for wires. The handgrip of the tool would be connected to a linkage similar to that of an endo-scissor, but the linkage would be configured to enable adjustment of the camera angle instead of actuation of a scissor blade. The thicknesses of the tool shaft and the camera would be less than 4 mm, so the cameratipped tool could be inserted and withdrawn through a dime-sized opening.

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A researcher at the University of Texas at Austin has developed a laser “microscalpel” that destroys a single cell while leaving nearby cells intact, which could improve the precision of surgeries for cancer, epilepsy, and other diseases. Femtosecond lasers produce extremely brief, high-energy light pulses that sear a targeted cell so quickly and accurately the lasers’ heat has no time to escape and damage nearby healthy cells. As a result, the medical community envisions the lasers’ use for more accurate destruction of many types of unhealthy material. These include small tumors of the vocal cords, cancer cells left behind after the removal of solid tumors, individual cancer cells scattered throughout brain, or other tissue and plaque in arteries.

The new microscope system can deliver femtosecond laser pulses up to 250 microns deep inside tissue. The system includes a tiny, flexible probe that focuses light pulses to a spot size smaller than human cells. The system was used to destroy a single cell within layers of breast cancer cells grown in the laboratory. Within a few years, the probe’s 15- millimeter diameter could be reduced three-fold, so it would match endoscopes used today for laparoscopic surgery. The probe tip also could be made disposable for operating on people who have infectious diseases or destroying deadly viruses and other biomaterials.

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A team led by researchers at Stanford University has developed a prototype blood scanner that can find cancer markers in the bloodstream in early stages of the disease, potentially allowing for earlier treatment and dramatically improved chances of survival. The system is based on MagArray biodetection chips and can find cancer-associated proteins in a blood serum sample in less than an hour. The device uses magnetic nanotechnology to spot the cancer proteins while there are relatively few of them in the bloodstream.

The device is able to detect many different kinds of proteins at the same time, which is important for two reasons. First, researchers are still uncertain which cancer biomarkers are the best diagnostic indicators. Second, detecting multiple biomarkers simultaneously will allow a doctor to diagnose more specifically the kind of cancer a patient may have.

By tagging cancer proteins with tiny magnetic particles, rather than electrically charged or glowing particles as in other detectors, the new system can obtain a clearer signal from a smaller number of cancer proteins. At the heart of the detector is a silicon chip that has 64 embedded sensors that monitor for changes in nearby magnetic fields. Attached to these sensors are “capture antibodies” that grab specific cancerrelated proteins as they float by and hold onto them. Then a second batch of antibodies is added to the mix. They latch onto magnetic nanoparticles as well as the cancer biomarkers that are being held captive by the sensors. When the MagArray sensors detect the magnetic field of nanoparticles, they’ve found cancer markers as well.

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A student at Cornell University has developed a prototype of a therapeutic ultrasound device that fits in the palm of a hand, is battery-powered, and can stabilize a gunshot wound or deliver drugs to brain cancer patients. It is wired to a ceramic probe, called a transducer, and it creates sound waves so strong they instantly cause water to bubble, spray, and turn into steam.

Ultrasound is commonly used as a nondestructive imaging technique in medical settings. Sound waves, inaudible to humans, can generate images through soft tissue. But higher-energy ultrasound can treat such conditions as prostate tumors or kidney stones by breaking them up. The device also can relieve arthritis pressure and even help treat brain cancer by pushing drugs quickly through the brain following surgery.

The technology could lead to such innovations as cell-phone-size devices that military medics could carry to cauterize bleeding wounds, or dental machines to enable the body to instantly absorb locally injected anesthetic.

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Imaging Techniques

Magnetic resonance imaging (MRI) is affected by movement artifacts, distorting elements in the image that show the movement of the body. Even if the patient does not move during the imaging, movement artifacts cannot be ruled out. Some parts of the body are always moving; the heart muscle, for example, changes shape during the pumping cycle.

With the aid of an ultra-broadband radar device, these movements can be taken into consideration and the MRI measurements can be corrected. The joint use of both technologies is being tested with the aid of a prototype developed at the Physikalisch Technische Bundesanstalt (PTB, Germany’s national metrology institute). The prototype uses ultra-wideband (UWB) radar techniques for the detection of tumors, as well as for navigation technology in MRIs. Ultra-wideband electromagnetic pulses generated by a UWB radar and transmitted by an antenna probe the human body with low integral power. The receiving antenna detects the reflected signals coming from different depths of the body.

With an MR-compatible UWB radar, the landmarks of the heart muscle during breathing could be followed without disturbing the actual MR measurement. Both a real-time adjustment of the MR frequency according to the current position of the heart, and a retrospective position correction of the MR data could be carried out.

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University of Washington researchers have developed a pill with a camera that can detect the earliest signs of esophageal cancer. The tiny camera is designed to take high-quality, color pictures in confined spaces. This new design has created a smaller endoscope that is more comfortable for the patient than current technology. Because internal scans are expensive, most people don’t find out they have the condition until it’s progressed.

The scanning endoscope developed at the UW consists of a single optical fiber for illumination and six fibers for collecting light, all encased in a pill. Once swallowed, an electric current flowing through the endoscope causes the fiber to bounce back and forth so that its lone electronic eye sees the whole scene, one pixel at a time. At the same time, the fiber spins and its tip projects red, green, and blue laser light. The image processing then combines all this information to create a two-dimensional color picture.

The fiber swings 5,000 times per second, creating 15 color pictures per second. The resolution is better than 100 microns, or more than 500 lines per inch. Although conventional endoscopes produce images at higher resolution, the tethered-capsule endoscope is designed specifically for low-cost screening, because it doesn’t require anesthesia and sedation.

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Researchers from Beth Israel Deaconess Medical Center (BIDMC) in Boston have developed a new imaging system that will essentially light up and color cancerous tumors, enabling surgeons to evaluate whether they’ve resected an entire diseased area. The fluorescence- assisted resection and exploration (FLARE) system consists of a near infrared (NIR) imaging system, a video monitor, and a computer.

The additional information comes from the use of chemical dyes called near-infrared (NIR) fluorophores designed to target specific structures when injected into patients. When exposed to NIR light, which is invisible to the human eye, the contrast agents light up targeted cells and are viewed on a video monitor during surgery. If, for instance, cancer cells are targeted, the image of the lit-up cancer cells can be superimposed over the surgical field, allowing surgeons to cut away the fluorescent “glowing” cells and sparing nerves and other healthy structures in the area.

The system has two independent channels of near-infrared fluorescence, so two different things can be highlighted on the surgical field, and those things are only limited by one’s imagination and the chemistry. For example, a surgeon might want to see a tumor with one channel and nerves with another. When using the FLARE system, the surgeon sees a screen with four windows — one for color video, one for each of the two independent channels of NIR fluorescence, and a fourth called the “merge” window.

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