Imagine a world in which the diagnosis of cancer did not involve a surgical biopsy. With photoacoustics and molecular imaging, that world may soon become a reality. Both technologies have great implications for the diagnosis and evaluation of cancer.

Over one hundred years ago, photoacoustics were discovered by Alexander Graham Bell. He found that a rotating disk made sounds when bombarded with photons. The sound could be detected with a stethoscope. When the disk absorbed the heat energy from the photons, it released sound waves that matched the frequency of its rotation.

In a modern photoacoustic system, pulsed light is sent through a biological medium. The light is absorbed and deflected within the space. The spatial distribution creates sound sources that are transformed into images. Images are produced by acoustic sensors. The system can image molecular properties at high resolution in vivo, or within the body.

The amount of light absorbed depends on the type of tissue. When blood is scanned, oxygenated and deoxygenated blood have different appearances. This allows the device to pick out detailed features, like arteries and veins, without injecting dyes into a patient’s bloodstream. It produces detail comparable to a CT scan or an MRI. However, molecular imaging is much cheaper. It can be done with a handheld device instead of a machine that costs millions of dollars.

Images can also be gathered by binding gold nanoparticles to specific biomarkers. For instance, nanoparticles can be combined with a specific kinase and then introduced through the imaging system. Other occurrences of the kinase in the cells would show dramatically in the photoacoustic image. The presence of certain kinases and proteases help scientists identify certain biological processes. These processes determine tumor behavior. They also determine how well tumors respond to treatment.

Molecular imaging can determine several factors in cancer metastasis. First, it can determine prognosis. Certain biomarkers indicate the aggressiveness of angiogenesis and metastasis. The level of aggressiveness determines how intense the treatment needs to be. Second, it can make predictions. It can do this by detecting the presence or absence of therapeutic targets. These targets then determine the type of chemotherapy oncologists will prescribe.

Third, imagine allows doctors to measure therapeutic response. They can know instantly how well a cancer therapy is working. Finally, it helps scientists to increase their understanding of the biology of cancer. They can learn why some patients respond to treatments while others do not.

Photoacoustic molecular imaging can guide biopsy needles deep into tissue. It can also measure oxygen levels in both vascular and lymph nodes, which indicates whether or not a tumor is malignant. It could be a precursor to photothermal cancer therapy. Radiant energy would be converted to a thermal energy that could destroy cancer cells. Detailed images would make the treatment highly localized and decrease harm to normal tissues.

Photoacoustics and molecular imaging can help us understand cancer like never before. It can also help to improve quality of life and patient outcomes. In time, it may replace expensive CT scans and MRIs. It may even replace invasive surgical biopsies.