The German company Siemens Medical Solutions has developed a completely new generation of ultrasound contrast media, also known as micro-bubbles, allowing them to track cancer and metastases. The new method is already being used 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. The bubbles are microscopically small gas bubbles, approximately ten times smaller in diameter than that of a human hair, and are injected into the patient's vein from where they circulate around the body. The bubbles then concentrate in characteristic patterns in particularly 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 (CPS), physicians can detect the concentration of bubbles safely and quickly, solving problems, and meeting the prerequisites for satisfactory diagnosis. The use of contrast media for ultrasound imaging is becoming more and more important for clinical examinations as it facilitates detection of smaller metastases, as well as benign and malignant tumours. This was not possible with previous ultrasound methods. Previous problems included the inability of methods to separate contrast medium signals from tissue signals. Different from the micro-bubbles used by 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 of micro-bubbles remains in the patient's circulation for approximately 15 minutes. They enable physicians to detect tumours, 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 colour. Dr Christoph Dietrich, chief physician of internal medicine at the Caritas hospital in Bad Mergentheim, Germany, has been working for a number of years with this method. 'This new ultrasound method using micro-bubbles is a safe and fast method to diagnose liver tumours,' comments Dr 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 tumours.'