Healthcare - Imaging Trends
Before Illness Strikes
Sophisticated imaging technologies are making it possible to detect ever more illnesses at an early stage. Virtual "flights" through the body are making some exploratory procedures unnecessary.
When it comes to early detection of many illnesses, imaging technologies such as magnetic resonance and computer tomography have become indispensable. The new SOMATOM Sensation 16 CT scanner generates a whole body 3D image of the arteries (left) in only 20 seconds. This patient's arteries are heavily calcified
The 21st century is set to usher in a new era in which medicine will be characterized by prevention and early recognition of a rapidly growing list of illnesses. Doctors and surgeons are already making use of imaging methods to gain a fascinating insight into the workings of the human bodywithout even having to touch the patient. With magnetic resonance and computer tomography, they can analyze the condition of internal organs, bones or even blood vessels, while ultrasonic waves provide three-dimensional images of fetuses in the womb. Furthermore, as these imaging systems become even faster and more precise, illnesses are being detected earlier and more reliably.
Dr. Bernd Ohnesorge and his team at Siemens' Medical Solutions Group in Forchheim, Germany, recently demonstrated the degree of quality that can be attained with today's imaging devices. The team has developed a new computer tomography program known as "Heart View CT" that produces incredibly sharp 3D images of a beating heart (see picture below). The program allows physicians to spot plaque and dangerous narrowings in the coronary vessels. Up to now, examinations of the heart have generally been conducted through insertion of a catheter. Although unpleasant for the patient, this procedure must be carried out in order to inject a contrast medium into the coronary arteries so that x-ray images can be taken at the same time. Thanks to the new method developed by Siemens, however, this process will no longer be necessary.
Probing the heartwithout a catheter. The Heart View CT computer tomography program developed by Richard Hausmann (left), Thomas Flohr and Bernd Ohnesorge freezes heart motion between beats (above) and generates images with a resolution of 0.5 mm. Using this method, doctors can spot plaque and dangerous narrowings in coronary arteriesboth of which can lead to heart attacks
A computer tomograph (CT) scanner usually consists of a ring-shaped system known as a gantry, which has a diameter of around 1.5 m. An x-ray tube and an x-ray detector are mounted on opposite sides of the gantry. The patient to be examined lies down on a table that slides into the scanner. Once inside, the gantry quickly revolves around the table, taking images of the body with focused x-rays. Within a few seconds, a series of cross-sectional views are produced, which the computer then reconstructs and combines to create a real-life three-dimensional view of the imaged area.
Until a few years ago, computer tomography scanners were equipped with only one detector, which meant that only one cross-section was generated per revolution of the gantry. But a new generation of equipment known as multilayer devices has since been introduced. These scanners generally have four detectors placed next to each other, allowing several cross-sectional images to be made per revolution. That means more of the body can be imaged in the same period of time.
In developing Heart View CT, Ohnesorge and his team made use of the latest CT generationthe Siemens Somatom Sensation 16, which, as the name suggests, features a total of 16 detectors. The ring in this model orbits the patient's body in only 400 milliseconds, making it possible to create a sharp image of the heart.
Since the heart is constantly in motion, the only way to capture it photographically is by having an extremely short exposure time. Ohnesorge's team managed to accomplish this by coupling the CT's image processing software with an electrocardiograph. The ECG monitors heart movements and essentially tells the scanner when to capture an image. Only image data captured in the 150 milliseconds between heartbeats is taken into account.
3D Images in Seconds. "Our technological developments have put us about a year ahead of the competition," says Ohnesorge. The Siemens system makes it possible to produce a completely three-dimensional volume study of the heart in only 20 seconds. What's more, the images have a resolution of half a millimeter. The final study contains around one gigabyte of data, which is about enough to fill two CD-ROMs.
Patient-friendly. A computer-animated journey through the intestine
A major advantage of Heart View CT is that it does not entail catheterizationan uncomfortable and time-consuming procedure. Instead, patients with heart problems serious enough to require a CT scan can be examined quickly, and need not necessarily stay in the hospital overnight. That translates into tremendous savings potential.
"But the new method can also play an important role when it comes to prevention," says Ohnesorge. Even though doctors can achieve a resolution of one-fourth of a millimeter with a cardiac catheter, "the catheter isn't very good at recognizing small deposits in blood vessels. That's where CT comes in."
Deposits on arterial walls known as plaque can be especially dangerous if they detach, because they can lead to life-threatening obstructions. Heart View CT detects the plaque at an early stage, as it can look straight into the vascular wall. "Around half a million cardiac catheterization examinations are performed in Germany every year," says Ohnesorge. "About half are purely for diagnostic purposes, and the CT represents a sensible alternative in many of these cases." The members of the jury for the German Future Prize, which is awarded by the German President, were so impressed by the potential of the technology that they nominated the developers of Heart View CT for the final round of the competition in 2002.
An important potential area of application for the new technology is preventive screening of high-risk patients. "Of course, not everyone has to be examined by CTthat would be far too expensive," says Dr. Thomas Flohr, who co-developed the system with Ohnesorge and his colleague Dr. Richard Hausmann.
Ultrasound enters the fourth dimension
A 3D image of a fetus at 23 weeks
Siemens researchers have come up with 4D imaging, a technology that is taking medical ultrasound into a new dimension. Most ultrasound systems produce two-dimensional images. Some even produce static 3D images. But 4D ultrasound displays continuous motion as a rapid sequence of 3D images. This is expected to make the new technology ideal for obstetric, abdominal and vascular imaging. Patients will be able to see a baby moving in the womb and physicians will have an advanced tool for determining the age of a fetus, detecting spina bifida or even seeing a cleft palate.
To develop the capability to process the huge amount of information needed to display the real-time, moving, 3D ultrasound information from Siemens' newest ultrasound transducers, the researchers developed a patent-pending algorithm that reconstructs 3D volume images at a blinding 30 volumes per second. After demonstrating the feasibility of the algorithm, the team began product development. In record timea mere five monthsthey created a modular software component that is being integrated into Siemens' Sonoline AntaresTM ultrasound system. This will allow many customers to upgrade existing systems with a simple software/ hardware update and by attaching the latest 4D probe. Known as fourSightTM, the new technology was demonstrated at the annual meeting of the Radiological Society of North America in December 2002. It is expected to be available by 2004.
Arthur F. Pea
Flohr says it's better to start by establishing who is at the greatest risk of having a heart attack or stroke. This can be done by taking blood tests and finding out about the individuals' diet and alcohol and tobacco consumption, for example. "The highest-risk patients can then be examined relatively quickly with Heart View CT," says Flohr.
Mammography with Minimal Exposure. Cardiovascular disease is the most frequent cause of death among men in much of the Western world. Women aged 35 to 55, on the other hand, are more likely to die of breast cancer. That's why a program was launched several years ago in Germany to encourage women in their mid-thirties and upward to have regular, low x-ray-dose mammograms. To obtain a clear image of all the tissue in a breast, the breast is pressed gently between two metal plates (see box Mammography in the interview with Sue Barter). Approximately 3.5 million mammograms are taken in Germany each year, most of which still make use of the traditional x-ray method. Here, the machine exposes an x-ray film that has to be developed before a diagnosis can be made. A few years ago, however, digital technology was introduced that can replace this technique. Siemens, for example, offers "Digiscan M" a system that uses phosphor storage plates instead of x-ray films to capture the images taken. These plates can be reused up to 4,000 times.
After the scan is made, a reading device converts the plates' content into a digital image. This obviates the use of film and associated chemicals, and results in faster and more efficient processes in radiology departments. Furthermore, it solves the age-old probem of lost or unavailable files by producing a digital archive.
"The future of radiologyand of mammography in particularis digital," says Rüdiger Schulz-Wendtland, Professor of Gynecological Radiology at the Friedrich-Alexander University of Erlangen. In addition to the advantages already mentioned, he points out that digital technology makes it unnecessary to take additional x-ray scans: "If a suspicious structure is detected using the traditional method, it is often x-rayed a second time at a higher resolution. Not only does that subject the patient to even more x-rays; it also doubles the amount of work that has to be done," says Schulz-Wendtland. But these second mammograms can often be dispensed with if digital technology is used, as contrasts can be set and suspect areas enlarged accordingly on screen.
This fall, Siemens is set to take another major step toward a digital future when it launches the digital flatscreen "Mammomat NovationDR" detector. The device doesn't need storage film and is equipped with a receiver system of amorphous selenium. Conventional selenium-based detectors convert x-rays directly into electrical signals. In other words, into digital images. In order to do so, the phosphorous coatings of their storage films first have to be activated by laser light in a reading device. But this intermediate step causes data to be lost. The Mammomat NovationDR, on the other hand, works much more efficiently, which leads to higher-quality images.
Non-Contact Colonoscopy. But however effective the available technology is, preventive and early-recognition medicine can only be put to good use if patients are prepared to take the initiative. That's not always the case, however, as demonstrated by a recent campaign to highlight the benefits of colon cancer prevention procedures to the German public.
Celebrities were called upon to encourage people to undergo colonoscopyan unpopular and sometimes painful procedure, but one that can save lives. Colon cancer- if it reaches an advanced stageis almost impossible to cure. A patient may have it for years before serious symptoms start to appear. And yet many people don't visit a doctor until it's too late. After lung cancer, colon cancer is the second most frequent kind of tumor found among German patients, with 50,000 new cases annually. And although 90 % of patients could be cured if treatment were to begin early enough, 30,000 die of colon cancer each year.
To make the idea of having an examination less unpleasant, researchers at Siemens Corporate Research in Princeton, New Jersey, developed "virtual colonoscopy"a non-contact procedure that generates images of the entire intestine in only a matter of seconds. With its help, doctors can embark on a computer-animated journey along the intestine, without having to insert an endoscopic camera. Instead, the images are captured by either a magnetic resonance tomograph or a computer tomograph. Unlike computer tomography, magnetic resonance does not involve use of any ionizing radiation.
It takes ten seconds to record the necessary data, after which an image-processing computer highlights the contrasting areas, revealing any polyps. Polyps in the intestinal mucus membrane are often the first signs of cancer, as they can turn into malignant carcinomas. "Compared to the method used thus far, virtual colonoscopies are much more popular," explains Dr. Christoph Zindel, a physician and marketing manager at Siemens Medical Solutions in Erlangen. And that's crucial when it comes to encouraging patients to have a colo-rectal examination.
There is, however, still disagreement as to which procedure is better for the early detection of cancerous growths. Zindel believes that magnetic resonance tomography is preferable because no x-rays are involved, but computer tomographs generate images more rapidlyand that's a significant advantage in view of the fact that the intestines are constantly moving.
Rheumatism Recognition. While experts in some areas are busy debating which method is best, doctors in other areas would be glad to have just one procedure for quickly collecting reliable data about their patient's condition. For example, it is hoped that a process will soon be available to help medical professionals detect chronic polyarthritis as early as possible.
A new method of diagnosing rheumatism with infrared light. Fluid in the cavities of arthritic joints (above left) is cloudy, which diffuses laser light (bright area). A healthy joint (below left) causes little or no diffusion because the fluid is clear
70 % of patients suffer irreversible changes to the joints in their hands and feet within the first two years after polyarthritis strikesbut it's virtually impossible to diagnose the condition at that stage of the illness with conventional methods. It would therefore be a tremendous boost to have a procedure that could monitor the spread of polyarthritis in its earliest stages.
That's why Siemens, in cooperation with the Free University of Berlin, the Charité Hospital and the University of Göttingen, Germany, has developed a prototype infrared scanner that can detect rheumatic problems early on and in a simple way. With this new system, the patient's finger joints are penetrated by infrared light, which is captured by a detector on the other side of the finger to create an image of the fluid in the joint cavity. In healthy people, this fluid is clear, but as polyarthritis develops, deposits of protein and tissue form in the cavity. The fluid therefore becomes cloudy, which means that the laser light diffuses, allowing the detector to register the change as quantitative data.
Bioinformatics expert Dr. Volker Tresp and his team at Siemens Corporate Technology in Munich took on the challenge of linking the various measurement parameters. Neural networks compare parameters such as clarity and the degree of light scattering, making it possible to determine whether the patient's condition has improved or deteriorated.
The resulting values are automatically entered into the data processing program, which simplifies the overall diagnostic process. In this way, the program can automatically provide a weekly overview or a graphic depiction of the progress of the illness. This makes it easier to determine whether a particular medication or course of treatment is working. The German Rheumatism League estimates that around 500,000 people of all ages are currently affected by chronic polyarthritis in Germany.
Rheumatism scanners, computer and magnetic resonance tomography, mammography, colonoscopythere's no doubt that thanks to preventive medicine, many disease-related changes within the body can now be detected and treated at a very early stage. Millions of people are therefore being spared from some of the most serious consequences of many illnesses.
What's more, the latest developments show that with the help of digital technology, doctors will be able to conquer a variety of other ailments and illnesses over the coming years. Perhaps we really will be able to relieve the sick and elderly of much suffering in the future.
Tim Schröder