New imaging technique a real time look inside a body

New imaging technique a real time look inside a body

A new laser imaging technique now allows for a real time look inside the body of a small animal. 

The technique, which uses light and ultrasound, provides enough resolution to see active organs, flowing blood, circulating melanoma cells and firing neural networks. 

The new technology allows researchers to watch as drugs are distributed throughout an animal, tracking how different organs respond. The researchers, based at the Duke University and The California Institute of Technology (Caltech), used a technique called 'single-impulse photoacoustic computed tomography (SIP-PACT)' to produce the images. 

It uses both light and ultrasound imaging to look inside living animals, and the researchers claim that it breaks the longstanding image resolution and speed barriers in the whole-body imaging of small animals. 

It provides a full cross-sectional view of a small animal's internal body in real time, and the researchers used it to image the full cross-section of an adult rat 50 times per second.

Photoacoustic imaging has been highly expected to get real-time whole-body imaging of a small animal with rich functional information,' said Dr Junjie Yao, co-author of the study and assistant professor of biomedical engineering at Duke University.

'With this advance, researchers can easily watch as drugs are distributed throughout an animal and track how different organs respond.'

Photoacoustic imaging combines a variety of imaging techniques into one platform. 

Traditional light-based microscopy provides fast, high-resolution images that retain important information about the inner workings of the body based on the wavelengths (colors) of light that the tissue absorbs, reflect or emits. 

For example, melanin absorbs near-infrared light, while blood's reaction to light differs depending on how much oxygen it's carrying.

However, the significant amount of light that scatters as it travels through tissue limits the depth of imaging to just a few millimeters. 

By contrast, ultrasound waves easily travel through tissue, providing a much more in-depth view - but they don't have the ability to read tissue's chemical components, missing important, potentially diagnostic information that light reveals. 

 Magnetic Resonance Imaging (MRI) can also see deep into tissue, but the method requires a strong magnetic field and takes second to minutes to form an image. 

Meanwhile, X-rays and positron emission tomography (PET) deliver too much radiation to be practical over long time periods. 

But photoacoustic imaging uses powerful, very short laser bursts that safely cause cells to emit ultrasound waves, which travel unimpeded back through the tissue. 

In the new research, Dr Yao and colleagues led by Dr. Lihong Wang at the California Institute of Technology added the highly desired speed and panoramic views to the repertoire of photoacoustic imaging technology. 

They built a circular ultrasonic detector and a fast data-acquisition system that can triangulate the origin of an ultrasonic wave from anywhere within the body of a small animal. 

The result is an imaging technique that reveals up to five centimeters into the biological tissue with sub-millimeter-level resolution, while retaining the information provided by light-based microscopy. 

'It's basically compressing one second's worth of summer-noon sunlight over a finger nail area into a single nanosecond,' said Dr Yao, who has been working with the technology for nearly a decade. 

'When the laser hits a cell, the energy causes it to heat up a tiny bit and expand instantaneously, creating an ultrasonic wave. 

'It's like the difference between pushing on something to slowly move it and striking it to cause a vibration.

'The panoramic effect provides information from all directions and all angles, so you do not lose any information from each laser shot.

'You can see the dynamics of the body in action - the pumping of the heart, the dilation of arteries, the functioning of various tissues.

In their study, the researcher described how they used the technique to track cancerous melanoma cells traveling through the blood vessels of a mouse, and they also shot a video of entire brain neural networks firing in real time. 

'This approach is especially powerful because it does not rely on the injection of any type of contrast agent,' said Dr Yao. 

This technology holds great potential for both pre-clinical imaging and clinical translation.'