This diagnostic instrument would be preferred by patients and physicians alike because it is noninvasive and provides immediate results

Dermapathologists will be interested to learn about a new handheld, point-of-care (POC) device that images melanoma tumors and enables the in vivo diagnosis of melanoma.

Because this diagnostic technology is noninvasive and provides immediate results, it is likely to be preferred by patients and doctors alike and could thus substantially reduce the volume of skin biopsies referred to dermapathologists and pathology laboratories.

For the First Time, a Tool to Accurately Measure Depth of Tumors

This new diagnostic technology was developed by researchers at Washington University St. Louis (WUSTL) in St. Louis, Missouri. Their instrument accurately measures how deep the tumor extends into the skin, providing physicians with information valuable for patient treatment and prognosis, noted an a press release link distributed by The Optical Society.

This device is described in a scientific paper published by OSA’s journal Optics Letters, on August 6, 2014.

Developed by researchers at Washington University St. Louis in St. Louis, Missouri, the handheld instrument (pictured above) diagnoses and images melanoma tumors, accurately measuring their thickness. The motor, translation stage, ultrasonic transducer and optical fibers are all incorporated into the probe for easy operation. (Photo credit Yong Zhou, copyright The Optical Society.)

Thickness of Tumor Critical in Treatment and Prognosis

Melanoma is the fifth most common cancer type in the United States. The incidence of melanoma is rising faster than any of the seven most common forms of cancer, according to the Skin Cancer Foundation. It also is the deadliest form of skin cancer, causing 75% of skin cancer deaths.

The thicker the melanoma tumor, the more likely it will spread and the deadlier it becomes, noted Lynn Cornelius, M.D., Chief of the Division of Dermatology at the WUSTL School of Medicine and one of the study’s authors. The ability to measure the depth of a tumor in vivo enables doctors to determine prognoses more accurately—potentially at the time of diagnosis—and plan treatments and surgeries accordingly, she said.

Pictured above is Lynn Cornelius, M.D., Chief of the Division of Dermatology at Washington University in St. Louis, Missouri. Cornelius was co-author of the recent study of a handheld, point-of-care (POC) device developed at WU that images melanoma tumors and enables the in vivo diagnosis of melanoma. Should this technology be cleared for clinical applications, it could lead to a reduction in the number of skin biopsies referred by dermatologists to anatomic pathology laboratories.

Current imaging methods fail to accurately measure the depth of a patient’s tumor because skin scatters light. This prevents high-resolution optical techniques from reaching deep enough. No existing optical techniques “are really sufficient to provide the two to four millimeter penetration that’s at least required for melanoma diagnosis, prognosis, or surgical planning,” declared Lihong Wang, Ph.D., the WUSTL Gene K. Beare Distinguished Professor of Biomedical Engineering and study coauthor.

He noted that researchers have tried high-frequency ultrasound, but it doesn’t have enough image contrast. They’ve also tried magnetic resonance imaging (MRI) and positron emission tomography (PET), neither of which have sufficient resolution.

Cornelius noted that tissue biopsies currently used in diagnosing melanoma involve removing part of a tumor. When located in a cosmetically sensitive area, for instance, provisional measurements of the tumor depth are not always reliable. When excising the tumor, the surgeon may find that it goes deeper into the skin than initially thought, requiring the patient to undergo an additional surgery, she added.

Photoacoustic Microscopy Maps Tumors in 3-D

The noninvasive diagnostic approach applied by Wang’s research team is called photoacoustic microscopy (PAM). It accurately measures melanoma tumors directly on a patient’s skin. The PAM technique converts light into vibrations.

In the case of this new device, a laser beam shines into the skin at the site of the tumor, noted the OSA press release. Melanin—the skin’s pigment—present in tumors absorbs the laser light and transfers the energy into high-frequency acoustic waves. Acoustic waves don’t scatter as much as light when traveling through skin.

Because tumor cells produce more melanin than surrounding healthy skin cells, the acoustic waves can map the entire tumor with high resolution, noted the study authors. The instrument’s detector turns the acoustic signal into a three-dimensional image on the instrument’s screen. The handheld instrument delivers light all around and below the tumor, generating a bright image of the tumor’s bottom to provide an accurate measurement of the tumor’s depth, they explained.

The image above illustrates how photoacoustic imaging maps a melanoma tumor. (Copyright Nature Biotechnology)

Diagnostic Device Ready for Commercialization Following Clinical Trials

The device has been tested on tumors in live mice, which demonstrated its accuracy in measuring tumor thickness in live tissue. “We show that melanomas with 4.1 and 3.7 mm thicknesses can be successfully detected in phantom and in in vivo experiments, respectively,” wrote the study authors.

The researchers are currently conducting tests on human patients. Wang said, however, the device must prove its effectiveness in clinical trials before it can be made available commercially.

Noting that for the first time, physicians have a tool that can measure a melanoma tumor’s entire volume, Cornelius stated in the OSA press release that the device initially would be used to help plan and prepare for surgery. If researchers can determine how melanoma tumor volume relates to cancer outcomes, then this tool could provide a more accurate method for diagnosing melanoma and determining a patient’s prognosis than is possible today, she added.

Another Approach to Diagnosing Melanomas

This new diagnostic tool developed by researchers at Washington University St. Louis demonstrates how the rapid development of new technologies can create ways to diagnose cancers and disease that are noninvasive for patients and capable of delivering a faster, more accurate answer to physicians.

Dermatopathologists will want to follow the performance of this handheld through its clinical trials and clearance by the Food and Drug Administration because of the potential for this device to eventually reduce the number of skin biopsies collected by dermatologists and referred to anatomic pathology laboratories.

—Patricia Kirk

Related Information:

New Hand-Held Device Uses Lasers, Sound Waves for Deeper Melanoma Imaging

Handheld photoacoustic microscopy to detect melanoma depth in vivo