Pictures of the Future      Fall 2005

Software-Guided Intervention

The usefulness of computer technology is not limited to managing patient data or to diagnostic procedures. Software-based systems can also aid physicians performing treatment.

In the industrialized nations, the quality of medical care has reached a very high level. Even so, not every patient receives the right treatment. In a 2003 report, for example, the Professional Health Council estimated that there are 40,000 instances of malpractice in Germany every year. But experts believe that’s only the tip of the iceberg. According to a 1999 study by the Bonn University Medical Center, the incidence of medical errors in Germany may be as high as 400,000 cases, many of which remain undetected—and things are no better in other countries. Also in 1999, the Institute of Medicine (IOM) in Washington, D.C., published a report titled "To Err is Human," according to which more people in the U.S. die from medical errors every year than from traffic accidents. These estimates are based on two studies and range from 50,000 to 100,000 fatalities. The IOM report prompted President Clinton to call for massive investments in information technology for the healthcare system, especially in software for improving safety in medications, diagnosis and therapy.

The potential for improvement is immense. For example, better communications could substantially reduce the incidence of wrong medications prescribed in hospitals—an area in which Siemens’ Soarian software (see Pictures of the Future, Spring 2005,  "Lakeside Hospital" and ? "Telemedicine: Reading from Home"), in conjunction with electronic patient files, can help. Software furthermore helps improve the quality of diagnoses, for instance in the early detection of cancer (see  "Experts Inside the Algorithms"). On the therapeutic side, intelligent systems are especially useful in treating cardiovascular diseases, the leading cause of death in industrialized nations. In the U.S. for instance, one person dies of cardiovascular disease every 33 seconds. According to the Center for Disease Control in Atlanta, such diseases cost the American healthcare system $351 billion in 2003. Many of these disorders are caused by pathological narrowing of blood vessels near the heart. To treat these, cardiologists use a flexible catheter, which they introduce into a blood vessel and maneuver toward the heart with the aid of a thin guide wire. Then the physician expands the narrowed section by inflating a balloon and stabilizes the vessel by implanting a stent—a tubular prop. To help the cardiologist see where to guide the catheter, a contrast agent is injected into the patient that makes blood vessels visible in the X-ray image displayed on a monitor by an angiography system.

In more difficult procedures, the wire must be introduced into very small branches of the coronary arteries, or positioned with millimeter precision at a particular location. "Manual control of guide wires can be extremely complicated in vessels with intricate branches," says Arne Westphal, marketing manager for Cardiology at Siemens Medical Solutions (Med). For this tricky task, Siemens has worked with Stereotaxis, Inc., its cooperative partner in the U.S., to develop an angiography system based on the use of magnetic navigation. In the Axiom Artis dFC MN, for instance, two refrigerator-sized rotatable magnets create controllable magnetic fields within the patient that navigate a magnetictipped guide wire or catheter to its destination. Using a joystick, the cardiologist can control the magnets and thus move the magnetic field with millimeter precision. This guides the wire, which can also be advanced or withdrawn by means of a small motor. The magnetic control system guides the wire around even the sharpest curves.

Cardiologists at St. Georg General Hospital in Hamburg, Germany, have been testing the magnetic navigation system for two years. Their clinical research is focused on using catheter ablation (vaporization) in treating disturbances in the normal rhythm of the heartbeat. This approach uses a special catheter with a metallic tip that can be heated to about 60 °C to obliterate cells in the heart muscle. The motorized navigation system assures positioning with millimeter precision. During the ablation procedure, additional X-ray control is often unnecessary. "This substantially reduces radiation exposure to both the doctor and the patient—for the latter by some 50 to 80 %—in comparison with procedures without magnetic control," explains Dr. Sabine Ernst, a St. Georg cardiologist. She performs the operation from an adjacent control room and no longer has to stand beside the patient in the cath lab throughout the procedure.

Autopilot to the Heart. Automatic navigation is an alternative to the joystick. In this approach, angiography is preceded by tomography. A three-dimensional image of the heart is then generated from the tomograms using syngo Inspace 3D software, developed by Siemens with its partner HipGraphics, of Baltimore. All the physician now needs to do is mouse-click on the destination location, and the catheter automatically advances to the selected spot.

There are also other potential applications. "Some of our customers are even looking at the possibility of using the system to keep patients from having to undergo bypass surgery," explains Westphal.

Normally the guide wire stops at an almost totally blocked site in a vessel. The cardiac surgeon then proceeds to install a bypass around the blockage. "But even in a vessel that seems totally occluded there is still a small open passage," Westphal explains. Even a highly skilled physician would have difficulty in locating this tiny passage, but the software-controlled wire systematically searches it out.

In certain patients, cardiologists may wish to avoid using X-rays altogether. For instance such an option would be beneficial to children with congenital heart defects who have already undergone multiple catheterizations

According to a study by the National Radiological Protection Board in the UK, one in every 1,000 children will develop a tumor within five years after a catheterization. Researchers are therefore experimenting with magnetic resonance (MR) tomography as an alternative imaging method for cardiac catheterization that doesn’t use radiation.

Magnetic resonance imaging is especially well suited to displaying soft tissues. Unlike Xray angiography, which creates a projection image, MR creates a series of sectional images. To enable the cardiologist to observe the catheter in real time, the section level and position must be tracked continuously. Methods for accomplishing this are being developed by Dr. Wolfgang Nitz and Dr. Peter Speier in the Applications Development department at Siemens Med. One of their developments is a prototype MR-compatible catheter that carries a micro-coil at its tip. That makes it possible to determine the location of the catheter tip in MR scanners. A software program developed by Speier and coworker Dr. Sven Zühlsdorff uses this information to track the position of the sectional image, so that a clear view of the catheter tip can always be obtained. "This puts us two or three years ahead of the competition," asserts Nitz.

3D Images During Surgery. Siemens is also taking a new approach in 3D imaging during emergency operations. For instance, previously, a patient suspected of having suffered a cerebral hemorrhage had to be transported from a sterile angiographic room to a different room for a verification CT scan, and then returned to the angio room. In a life-threatening situation, this meant having to waste precious time before the hemorrhage could be stopped. "With the new generation of angiographic C-arm systems, like the AXIOM Artis dBA DynaCT, the verification CT scan is obtained while performing treatment—and without relocating the patient," reports DynaCT Product Manager Michael Martens.

In DynaCT, the X-ray source of the angiographic system revolves around the patient and generates sectional images, as in computed tomography. The imaging process is carried out by an advanced version of syngo Inspace 3D that’s capable of depicting even low-contrast regions such as soft tissues and liquids, so that cerebral hemorrhages and tumors can be discerned.

"Although the resolution of low-contrast tissues isn’t quite as good as in conventional CT, it’s sufficient for intervention in the angio lab," says Dr. Hideyuki Takano of Chiba Cancer Center in Chiba, Japan, who has already used DynaCT in examining brain tumors and liver carcinomas.

With a 60 % market share, Siemens is the market leader in angiographic systems for neuroradiology. Martens is confident that this new technology will become widely accepted as the standard method during the coming year.
                                                                                                                  Michael Lang