The technique, published in The Journal of Nuclear Medicine, enables researchers to visualise tumour activity at the molecular level.
‘We hope this technique may be helpful for the early detection of disease,’ said Juergen K Willmann, MD, lead author of the study and assistant professor of radiology at Stanford University School of Medicine.
‘It may help save lives by finding cancer — such as breast, ovarian or pancreatic cancer — in the very early stages, when it is still curable.’
In the study, researchers intravenously injected microbubbles — gas-filled spheres small enough to travel through vessels — into mice with cancers.
The microbubbles, which were paired with a new peptide (a molecule that consists of a chain of amino acids) were designed to travel through the vascular system and attach to integrin — a well-characterised molecular marker that acts as a ’red flag’ for tumour vessel growth, or angiogenesis.
Tumour vessel growth occurs when active tumour cells create certain pathways to provide the tumour with a sufficient supply of oxygen, nutrients and other factors needed for growth.
Once the gas-filled microbubbles seek out the cancers and attach to their vessel walls, they send out signals that are picked up by standard clinical ultrasound scanners.
The imaging signals produced by the microbubbles are reflected back to the ultrasound transducer and illuminate the areas that outline the tumour, providing researchers with a sonogram of tumour vessel growth on a molecular level.
Contrast-enhanced ultrasound can be used to image blood perfusion in organs, to measure blood flow-rate in the heart and other organs and to perform other applications, such as characterisation of focal lesions in the liver.
Current interest is focused on modifying contrast agents to make them specifically useful for molecular imaging.
The microbubbles, paired with the new peptide that binds to tumour vessel cells as studied in the current research, may be more effective than antibody molecules, which are time-intensive to produce, are costly and may cause adverse reactions in patients.
Non-invasive imaging strategies may be particularly helpful for diagnosing cancer in its earliest stages as well as for developing therapeutic agents to treat cancer and monitoring whether treatment is working.