Tracking cancer with micro-bubbles

Gas bubbles as a contrast agent and CPS technology can aid in detection and characterization of tumours and metastases

Using a completely new generation of ultrasound contrast media, also known as micro-bubbles, Siemens Medical Solutions is now tracking cancer and metastases with ultrasound diagnostics as well. The bubbles are microscopically small gas bubbles that are injected into the patient’s vein from where they circulate around the body – and start to concentrate in characteristic patterns in especially suspicious areas. The agent can even highlight areas not previously detected. Using a new ultrasound technology, developed especially for this purpose by Siemens, the so-called Cadence Contrast Pulse Sequencing Technology or CPS, the physician is able to detect the concentration of bubbles safely and quickly, solving problems, and meeting the prerequisites for satisfactory diagnosis. The new, patient-sparing method is used to date in several European hospitals with the focus on diagnosing liver cancer and other liver lesions. Additional medical fields of application are currently in the research phase.

Contrast media for ultrasound imaging are becoming more and more important for clinical examinations. Their use facilitates detection of smaller metastases (for example, in the liver), as well as benign and malignant tumors, that was not possible with previous ultrasound methods. For a safe and accurate diagnosis it is important to ensure that the injected contrast media is easily distinguishable from tissue. Today’s contrast media of the second generation lend themselves especially well to imaging with Cadence Contrast Pulse Sequencing Technology from Siemens which was especially developed and optimized for use with these ‘second generation’ of agents. By using CPS, certain sound sequences are transmitted that make the bubbles oscillate. The echoes of the contrast medium bubbles are separated from those of the tissue by using a special processing method. This makes it possible to watch the inflow of contrast medium on-screen.

“Using CPS technology from Siemens, we are able to accurately display the smallest tumor vessels even with low quantities of contrast medium,“ confirms assistant professor, Dr. Deike Strobel, head of the ultrasound department at the Medical Clinic I of the University Hospital in Erlangen, Germany. For a number of years now, she has been working and performing research with this effective and cost-efficient method. “Earlier, patients with inconclusive liver tumors were sent from Ultrasound to Computed Tomography, and if all else failed, to Magnetic Resonance Tomography or other examinations. However, using contrast medium sonography, provides for a safe and fast diagnosis of most liver tumors Contrast media with ultrasound is a truly revolutionary concept."

Siemens uses, among others, the Sonovue contrast medium by Bracco in Milan, Italy. Microscopic gas bubbles are approximately ten times smaller in diameter than that of a human hair. Different from contrast media of the first generation which burst after their initial contact with sound waves and supplied a one-time image only, the new generation micro-bubbles remain in the patient’s circulation for approximately 15 minutes, preserved by utilization of a lower sound output. As confirmed by a number of studies, they enable physicians to detect tumors, benign or malignant, in a highly reliable manner through certain blood circulation patterns. On-screen, liver tissue filled with contrast medium is shown as bright, for example, while metastases are displayed considerably darker in color.

Dr. Christoph Dietrich, chief physician of internal medicine at the Caritas hospital in Bad Mergentheim, Germany, for example, has been working for a number of years with this method. He successfully used the Siemens Technology together with Sonovue in manycases. “This new ultrasound method using micro-bubbles is a safe and fast method to diagnose liver tumors,“ comments Dietrich. “The so-called echo signal amplifiers consist of air and gas bubbles that are encased in different shells. The micro-bubbles are a strong reflector for ultrasound. The substances remain in the blood flow for a few minutes only and are exhaled through the lungs. Through improved ultrasound systems, it is possible to use this technology today, effectively reducing more complex, expensive or dispensable imaging methods. This applies in particular to differentiating benign and malignant liver tumors.”

For many years the use of contrast media has been a common method for other imaging modalities such as Computed Tomography, Magnetic Resonance Tomography and Nuclear Medicine. For some time now, the use of contrast medium in ultrasound has been growing in importance. Previous problems were on one hand the inability of existing methods to separate contrast medium signals from tissue signals – resulting in images with limited diagnostic usefulness. On the other hand, contrast medium of the first generation was not visible long enough and generated one single image only. The objective of the studies under way in different hospitals across Europe is to improve cancer diagnostics with contrast media for ultrasound. In addition, efforts are made to optimize the method for visualizing the bubbles. The German Society of Ultrasound in Medicine (DEGUM) is participating in this work in progress. Also, additional application areas, e.g. in cardiology, breast, are under investigation.

Siemens Medical Solutions is one of the world’s largest suppliers to the healthcare industry. The company is known for bringing together innovative medical technologies, healthcare information systems, management consulting, and support services, to help customers achieve tangible, sustainable, clinical and financial outcomes. From imaging systems for diagnosis, to therapy equipment for treatment, to patient monitors to hearing instruments and beyond, Siemens innovations contribute to the health and well-being of people across the globe, while improving operational efficiencies and optimizing workflow in hospitals, clinics, home health agencies, and doctors’ offices. Employing approximately 31,000 people worldwide and operating in more than 120 countries, Siemens Medical Solutions reported sales of 7.07 billion EUR, orders of 8.12 billion EUR and group profit of 1.05 billion EUR for fiscal 2004.