Background Suppression in Photoacoustic Imaging of Magnetic Contrast Agents

Principal Investigator: Xiaohu Gao

Photoacoustic (PA) imaging is based on the detection of acoustic signals induced by the distribution of optical heterogeneities in targeted objects when the objects are irradiated by short laser pulses. Contrast agents are usually employed to help enhance the contrast of structures such as vasculature or fluids, when imaging in the body. When molecular contrast agents are coupled to biological objects such as cancer cells, the cells can be differentiated from background. However, in vasculature, the strong background signal from blood can mask contrast agents making quantitative measurements extremely difficult. Furthermore, the problem can not be solved by simply increasing the contrast agent concentration as this leads to toxicity.

The investigator has developed a method and system for magneto-motive PA imaging that utilizes nanoparticles to help differentiate a contrast agent from background signal. The invention involves introducing magnetic nanoparticles with PA properties into a moving biofluid. The nanoparticles are labeled with moieties, which may include antibodies, ligands, antigens, or cell marker proteins. The nanoparticles then bind to target objects of interest, which may include biomarkers, therapeutic drugs, toxins, microparticles, viruses, or cells. A magnetic field applied to the area of interest accumulates the nanoparticles and allows an initial PA signal to be collected. The magnetic field is then used to manipulate the objects and subsequent PA signals are collected during and after the manipulation. Subtraction of the PA signals collected provides a background-suppressed image of the target objects.

• The invention provides a method for detecting magnetically labeled biomarkers, drugs, toxins, viruses, or cells. 

• It can be used in the manipulation and movement of labeled biomarkers, drugs, toxins, viruses, or cells in the body. 

• Manipulation and accumulation of targets such as cancerous cells and viruses to a focal region facilitates further procedures, such as removal for genetic and biochemical analyses and non-invasive eradication, to be more easily performed. 

• In areas where background signal inhibits imaging, such as in vasculature, the invention provides background-suppressed imaging capabilities. 

• Contrast agent concentrations are sometimes increased to help in the detection of cancerous cells. This is toxic to the body and through this invention, lower levels of contrast agent can be used to achieve similar or even better levels of contrast.

For more info, contact: Roï Eisenkot