Dermatology at Photonics West, from skin-cancer detection to tattoo tomography

San Francisco, CA--Of the many topics at the BiOS technical conference at SPIE's Photonics West 2012, I chose to sit in on a few sessions in Conference 8207A, "Photonics in Dermatology and Plastic Surgery." The reason is that my family has a history of skin cancer, which was covered in this conference (and for the record, my family has no history of plastic surgery). Many, although not all, topics in the conference relate to optical-coherence tomography (OCT), because OCT can produce microscopically accurate 3-D images of skin -- valuable for diagnosis of subtle skin changes.

Some OCT-related topics included "Simultaneous dual-wave OCT for dermatological applications," done at Medizinische Univ. Wien (Austria) (8207A-04), "Reduction of OCT image artifacts for improved imaging of skin," from the University of Western Australia (8207A-07), and "Deep-skin structural and microcirculation imaging with extended-focus OCT," presented by researchers from Medizinische Univ. Wien and Ludwig-Maximilians-Univ. (Munich, Germany).

Examples of non-OCT photonic dermatological iamging approaches included "Characterization of skin lesions using two-photon excited multispectral flourescence-lifetime imaging," done by a large group of UK resarchers (8207A-03), "Multispectral imaging of port-wine stain treatment outcomes," done at Oregon Health & Science University (8207A-11), and "Pulsed photothermal depth profiling of tattoos undergoing laser-removal treatment," pursued by a group at the Jozef Stefan Institute (Slovenia) (8207A-15).

Skin-cancer detection
However, it was "Ex-vivo and in-vivo full-field optical coherence tomography on skin," achieved by a group of French and Swiss researchers (8207-A-26), that particularly interested me, as it showed the use of full-field OCT (FFOCT) to obtain micron-scale isotropic 3D resolution of ex-vivo (excised) skin samples for pathological detection of basal-cell carcinoma (BCC). The clinical need is to be able to image at various scales with zoom, finding BCC at a structural level (disordered stroma, high cell density). The researchers are able to see BCC at different depths, and even have preliminary in-vivo (meaning that the skin is still on the patient) results. They want to develop an in-vivo probe with dual interferometers.

In addition, researchers at the University of British Columbia and the BC Cancer Agency Research Centre (both in Canada) have achieved "Real-time Raman spectroscopy for in-vivo evaluation of skin cancers" (8207A-27). Their data show results on the three types of skin cancer (BCC, squamous-cell carcinoma, and of course melanoma) that are quite impressive: when compared to the analysis of potential skin cancers by trained dermatologists, the use of in-vivo Raman spectroscopy produced more-accurate results with far fewer false positives. And note that each false positive avoided means one less unnecessary excision.

Tattoo tomography
Researchers at JenLab GmbH (Germany) used their laser multiphoton tomographic equipment to image tattoo inks under the skin (8207A-28). The ink particles ranged from 4 to 510 nm in size and clustered in large but sparse groups. The mechanism of laser tattoo removal is under study, as its mechanism is not well-understood. And, to all tattooees: note that certain tattoo pigments, such as azopigment Red 22, have carcinogenic amines.