Abstract
Photodynamic therapy (PDT) offers the potential for enhanced treatment of nonmelanoma skin cancer (NMSC) with minimal scarring. Yet, PDT has not achieved consistent long term effectiveness to gain widespread clinical acceptance for treatment of skin cancer. Therapeutic response varies between practitioners, patients and lesions. One important contributing factor is the absence of quantitative tools to perform in vivo dosimetry. To this end, we have developed a new quantitative imaging device that can be used to investigate parameters related to optimizing dosimetry. We present a spatial frequency domain imaging (SFDI) based device designed to: (1) determine the optical properties at the therapeutic wavelength, which can inform variations in light penetration depth and (2) measure the spatially resolved oxygen saturation of the skin cancer lesions and surrounding tissue. We have applied this system to a preliminary clinical study of nine skin cancer lesions. Optical properties vary greatly both spatially [101%, 48% for absorption and reduced scattering, respectively] and across patients [102%, 57%]. Blood volume maps determined using visible wavelengths (460, 525, and 630 nm) represent tissue volumes within ∼1 mm in tissue (1.17 ± 0.3 mm). Here the average total hemoglobin concentration is approximately three times greater in the lesion than that detected in normal tissue, reflecting increased vasculature typically associated with tumors. Data acquired at near infrared wavelengths (730 and 850 nm) reports tissue blood concentrations and oxygenations from the underlying dermal microvasculature (volumes reaching 4.36 ± 1.32 mm into tissue). SFDI can be used to quantitatively characterize in vivo tissue optical properties that could be useful for better informing PDT treatment parameters. Specifically, this information provides spatially resolved insight into light delivery into tissue and local tissue oxygenation, thereby providing more quantitative and controlled dosimetry specific to the lesion. Ultimately, by optimizing the execution of PDT, this instrument has the potential to positively improve treatment outcomes.
Highlights
Nonmelanoma skin cancer (NMSC), which includes basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), is the most common type of skin cancer in humans
While most nonmelanoma skin cancer (NMSC) are treated surgically, those who suffer from Neviod basal cell carcinoma syndrome or those who are immunocompromised, including those who are organ transplant recipients can develop many, relatively large lesions at high frequency [2,3,4]
Though this may not be a direct comparison between imaging modalities, little contrast is evident in the dermoscopic image of the lesion (Dermlite Foto, crossed-polarized three color digital image), whereas the quantitative absorption and reduced scattering maps reveal structural heterogeneities that may significantly impact the therapeutic light transport in tissue
Summary
Nonmelanoma skin cancer (NMSC), which includes basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), is the most common type of skin cancer in humans. While most NMSCs are treated surgically, those who suffer from Neviod basal cell carcinoma syndrome or those who are immunocompromised, including those who are organ transplant recipients can develop many, relatively large lesions at high frequency [2,3,4]. For these groups, standard treatments are not practical or advantageous, due to the sheer number, size, and frequency of occurrence of these lesions over a lifetime. Photodynamic therapy (PDT) offers the potential for enhanced treatment of nonmelanoma skin cancer (NMSC) with minimal scarring. We have developed a new quantitative imaging device that can be used to investigate parameters related to optimizing dosimetry
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