New hand-held device to diagnose skin cancer

Researchers have developed a hand-held device that uses lasers and sound waves and may change the way doctors treat and diagnose melanoma, the deadliest form of skin cancer.
The device is the first that can be used directly on a patient and accurately measure how deep a melanoma tumour extends into the skin, providing valuable information for treatment, diagnosis or prognosis.
The thicker the melanoma tumour, the more likely it will spread and the deadlier it becomes, said dermatologist Lynn Cornelius, one of the study's co-authors at Washington University in St Louis.
Being able to measure the depth of the tumour in vivo enables doctors to determine prognoses more accurately - potentially at the time of initial evaluation - and plan treatments and surgeries accordingly.

Current methods can't directly measure a patient's tumour very well. Because skin scatters light, high-resolution optical techniques don't reach deep enough.
"None are really sufficient to provide the two to four millimetre penetration that's at least required for melanoma diagnosis, prognosis or surgical planning," said engineer Lihong Wang, another coauthor of the study.

Recently, researchers including Wang have applied an approach called photoacoustic microscopy, which can accurately measure melanoma tumours directly on a patient's skin - thus allowing doctors to avoid uncertainty in some circumstances.
The technique relies on the photoacoustic effect, in which light is converted into vibrations. In the case of the new device, a laser beam shines into the skin at the site of a tumour.

Melanin, the skin pigment that's also in tumours, absorbs the light, whose energy is transferred into high-frequency acoustic waves. Unlike light, acoustic waves don't scatter as much when travelling through skin.
Tumour cells will produce more melanin than the surrounding healthy skin cells, and the acoustic waves can be used to map the entire tumour with high resolution.
The device has a detector that can then turn the acoustic signal into a three-dimensional image on a screen.
The researchers tested their device on both artificial tumours made of black gelatin and on real ones in live mice, showing that the instrument could accurately measure the depths of tumours - and do it in living tissue.

Cornelius said the tool can measure a tumour's entire volume - something that's never been possible with melanoma. If researchers can determine how the volume relates to cancer outcomes, then this tool could give doctors a new type of measurement for diagnosis and prognosis.
The study is published in The Optical Society's (OSA) journal Optics Letters.