Currently the only method for positively identifying malignant melanoma involves invasive and often undesirable biopsy
procedures. Available <i>ex-vivo</i> data indicates increased vascularization in the lower regions of excised melanoma, as
compared to dysplastic nevi. The ability to interrogate this region of tissue <i>in-vivo</i> could lead to useful diagnostic
information. Using a newly developed fiber based superficial probe in conjunction with a steady-state frequency-domain
photon migration (SSFDPM) system, we can probe the upper 1-2 mm of tissue, extracting functional information in the
near infrared (650-1000 nm) range. To test the resolution and detection range of the superficial probe in this context,
deformable silicone phantoms have been fabricated that simulate normal skin with melanocytic lesions. These phantoms
consist of a two-layered matrix with the optical properties of normal light skin, containing several cylindrical inclusions
that simulate highly absorbing pigmented lesions such as melanoma. These inclusions are varied in depth, diameter, and
optical properties in order to fully test the probe's detection capabilities. It was found that, depending on absorption, we
can typically probe to a depth of 1.0-1.5 mm in an inclusion, likely reaching the site of angiogenesis in an early-stage
melanoma. Additionally, we can successfully interrogate normal tissue below lesions 1.5mm deep when absorption is
about 0.4/mm or less. This data indicates that the superficial probe shows great promise for non-invasive diagnosis of
We present a fabrication process for Polydimethylsiloxane (PDMS) tissue simulating phantoms with tunable optical
properties to be used for optical system calibration and performance testing. Compared to liquid phantoms, cured
PDMS phantoms are easier to transport and use, and have a longer usable life than gelatin based phantoms.
Additionally, the deformability of cured PDMS makes it a better option over hard phantoms such as polyurethane
optical phantoms when using optical probes which require tissue contact. PDMS has a refractive index of about
1.43 in the near infrared domain which is in the range of the refractive index of tissue. Absorption properties are
determined through the addition of india ink, a broad band absorber in the visible and near infrared spectrum.
Scattering properties are set by adding titanium dioxide, an inexpensive and widely available scattering agent which
yields a wavelength dependent scattering coefficient similar to that observed in tissue in the near infrared. Phantom
properties were characterized and validated using a two-distance, broadband frequency-domain photon migration
system. Repeatability and predictability for the phantom fabrication process will be presented.
We develop a superficial diffusing probe with a 3 mm source-detector separation that can be used in combination with diffuse optical spectroscopic (DOS) methods to noninvasively determine full-spectrum optical properties of superficial in vivo skin in the wavelength range from 650 to 1000 nm. This new probe uses a highly scattering layer to diffuse photons emitted from a collimated light source and relies on a two-layer diffusion model to determine tissue absorption coefficient µa and reduced scattering coefficient µ. By employing the probe to measure two-layer phantoms that mimic the optical properties of skin, we demonstrate that the probe has an interrogation depth of 1 to 2 mm. We carry out SSFDPM (steady state frequency-domain photon migration) measurements using this new probe on the volar forearm and palm of 15 subjects, including five subjects of African descent, five Asians, and five Caucasians. The optical properties of in vivo skin determined using the superficial diffusing probe show considerable similarity to published optical properties of carefully prepared ex vivo epidermis+dermis.