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Photoacoustic Imaging Could Improve Melanoma Boundary Identification

In a pilot study on an excised tumor, the noninvasive technique identified tumor regions not visible to a surgeon.

By
Jill Sakai, Contributor
Tuesday, May 1, 2018

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U.S. Navy photo/Mass Communication Specialist 2nd Class Dominique M. Lasco

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Standard melanoma treatment requires surgical removal of the tumor as well as a margin around the edge of the visible lesion to increase the chance of complete removal. Selection of the margin must balance the importance of removing the entire tumor while minimizing surgical time, cost and patient discomfort. Currently, this process is guided by the practicing surgeon’s experience and can also be heavily influenced by the patient’s skin color.

Recent efforts are exploring photoacoustic imaging as a noninvasive, objective method to identify tumor boundaries, which are often irregularly shaped. Photoacoustic imaging applies laser pulses of nonionizing radiation to a tissue of interest to generate ultrasound waves that can be used to produce images. The approach is promising in melanoma since melanin provides high optical contrast from the surrounding tissue, which is needed to obtain clear photoacoustic images.

In a study published April 16 in the British Journal of Dermatology, a Korean research team reported results on an excised tumor, about 1.5 square inches in size, removed from the heel of a 57-year-old man. Immediately after surgery, they scanned the sample and assembled the images into a 3-D reconstruction of the lesion. Results of the imaging analysis matched well with pathological examination of the tissue removed from the heel and confirmed that the melanoma was completely removed but extended about 0.2 inches beyond the visible lesion boundary.

The pilot study supports the development of photoacoustic imaging as a preoperative screening tool to guide tumor resection, the authors say. Although widespread use to date has been impeded by technical limitations and a lack of equipment standardization, their system integrates a portable, tunable laser with an FDA-approved clinical ultrasound system to create a programmable device that they suggest can expand use of photoacoustic imaging in a wide variety of clinical and preclinical applications.