Image Guided High Intensity Focused Ultrasound
Ultrasound can be focused within a region with a diameter of about 1 mm using phased array transducers. The bio-effects of ultrasound can lead to local tissue heating, cavitation, and radiation force, which can be used for a variety of medical therapies such as tissue ablation, image guided drug delivery, and immune stimulation.
High Intensity Focused Ultrasound (HIFU) guided by ultrasound or MR imaging is a clinically approved technology for treatment of uterine fibroids, bone metastases essential tremor, and prostate cancer. Clinical research is ongoing in many other applications such as treatment for Parkinson related tremor, obsessive compulsive disorders, tumors in breast, liver, kidney and pancreas.
Image guided drug delivery (IGDD)
HIFU can be used in many different ways for IGDD: 1) local drug release from nanocarriers circulating in the blood, 2) increased extravasation of drugs and/or carriers, and 3) enhanced diffusivity of drugs. When using nanocarriers sensitive to mechanical forces or to temperature, their content can be released locally. Thermo-sensitive liposomes have been suggested for local drug release in combination with local hyperthermia more than 30 years ago. Microbubbles may be designed specifically to enhance cavitation effects. Preclinical work over the last 10 years has demonstrated that HIFU and microbubbles can lead to local and temporary opening of the blood-brain-barrier which is the most important impediment for pharmacological treatment of nearly all diseases of the central nervous system. Real-time imaging methods, such as magnetic resonance, optical and ultrasound imaging have led to novel insights and methods for IGDD Image guidance of ultrasound can be used for: 1) target identification and characterization; 2) spatio-temporal guidance of actions to release or activate the drugs and/or permeabilize membranes; 3) evaluation of biodistribution, pharmacokinetics and pharmacodynamics; 4) Physiological read-outs to evaluate the therapeutic efficacy.
Immune system stimulation
HIFU can be used for immune system stimulation in various ways. Its associated mechanical effects can release tumor antigens that can activate dendritic cells. With many drugs either already on the market, or under development for immune system stimulation (or inhibition of tumor associated immune suppression), there clearly is a bright future for combinatory approaches, together with HIFU. It has been shown that ultrasound can decrease Alzheimer related plaques in the brains of animal models. This effect has been tentatively attributed to immune system stimulation.
Chrit Moonen did his Masters in Molecular Sciences and his Ph.D. in biophysics (Wageningen University). He went for a postdoctoral period to the University of Oxford (Sir Georg Radda). He then worked at the University of California at Davis as a Visiting Research Scientist before becoming head of the NIH In Vivo NMR Research Center from 1987-1996. He moved back to Europe (Bordeaux, France) in 1996 where he has been director of the laboratory “Molecular and Functional Imaging: from Physiology to Therapy” until 2011. He is currently professor at the Division of Imaging at the University Medical Center in Utrecht, the Netherlands. He was President of the “International Society of Magnetic Resonance in Medicine” (2006), of the “Society for Molecular Imaging” (2009), and of European Society for Molecular Imaging (2016). He was chairman of the 2015 meeting of the International Society for Therapeutic Ultrasound. He received the European Magnetic Resonance Award 2000, is a Fellow of the International Society of Magnetic Resonance in Medicine, of the European Society of Magnetic Resonance in Medicine and Biology, and of the World Molecular Imaging Society. His recent work is mainly in MRI guided Focused Ultrasound, image guided drug delivery, and molecular and cellular imaging.