Infrared scanner discerns mole from melanoma

Marie Freebody, marie.freebody@photonics.com

Oncologists could benefit from a new noninvasive infrared scanning system that determines whether pigmented skin growths are benign moles or melanoma, a lethal form of cancer. According to its developers at Johns Hopkins University, a pilot clinical trial of 50 patients is currently under way with the hope that the infrared skin cancer detector could be used in clinical applications in the next five to 10 years.

The National Cancer Institute estimated that 68,720 new cases of melanoma were reported in the US in 2009, and it attributed 8650 deaths to the disease. The trouble with preventing death from melanoma is that doctors need to identify the melanoma-related mole or subsurface lesion at a very early stage, when the dimensions may be very small.

Today, doctors look for subjective clues such as the size, shape and coloring of a mole or precancerous lesion, but professor Cila Herman at the Johns Hopkins department of mechanical engineering and fellow researchers at Johns Hopkins Kimmel Cancer Center are hoping to take the guesswork out of the screening process.

“Nowadays, mainly subjective criteria, based on the appearance and history of the lesion, are used to diagnose skin cancer,” Herman said. “Our instrument would yield quantitative information regarding the malignant potential of the lesions, which will be useful to the physicians in their decisions regarding diagnosis and care.”

Since cancer cells divide more rapidly than normal healthy cells, they typically generate more metabolic activity and therefore emit a telltale higher heat signature. The innovative infrared scanner looks for these tiny temperature differences between healthy tissue and a growing tumor.

So tiny are the temperature differences between cancerous and healthy skin cells that the team had to find a way to intensify the distinction. The group found that blasting a patient’s skin with a harmless, one-minute stream of cold air immediately prior to recording infrared images revealed better results because cancer cells typically reheat faster than the surrounding healthy tissue, which enabled the IR camera to capture a greater temperature difference.

Before scanning, the targeted skin is cooled with a brief burst of compressed air. Courtesy of Will Kirk/Johns Hopkins University.

“We first record white-light and infrared images of the lesion and surrounding healthy skin at ambient conditions,” Herman said. “Next, we cool the skin and record infrared images during the reheating process. By processing these images and comparing the temperature of the lesion with the temperature of healthy tissue, and comparing the measured data with results obtained with a computational model, we can draw conclusions regarding the malignant potential of the lesion.”

Similar techniques have already been used to diagnose breast cancer, but it is thanks to a whole host of modern imaging equipment that new light is being shed on skin cancer diagnosis. According to Herman, tools such as computing, image processing and hardware (a precision camera that can record an infrared movie sequence) produce the high-accuracy measurements needed for the visualization and quantitative analysis of skin cancer.

While surgery will still be needed if the lesion is diagnosed as potentially malignant, the simple scanner could reduce the need for diagnostic biopsies. The researchers envision a handheld scanning system that dermatologists could use to evaluate suspicious moles. What’s more, the technology also might be incorporated into a full-body scanning system for patients with a large number of pigmented lesions.

The current pilot study is designed to determine how well the scanner can detect melanoma, but Herman and colleagues are so convinced of its potential that they are in the process of forming a company that will focus on the development and testing of a prototype scanner.

“Five to 10 years would be a realistic time frame to expect to see the infrared skin cancer detector used in clinical applications, depending on the resources available for prototype development and testing as well as the duration of the approval process,” Herman said. “The key effort will be to raise the necessary funding for the technical development of the commercial device as well as for large-scale clinical trials required for FDA approval.”