BackgroundConventional photodynamic treatment (cPDT) of thin basal cell carcinomas (BCCs) has uncomfortably high rates of incomplete clearance. Incomplete clearance/recurrence rates for superficial BCCs are as high as 40% and even higher for tumours treated on the head and neck. Our experience has been that flushing is more pronounced on the head and neck during cPDT photoactivation. We postulated that haemoglobin, although delivering oxygen, may be acting as a competing chromophore.ObjectivesTo determine whether a 2-phased photoactivation protocol, in which blood is removed before the second phase intense pulsed light (IPL) activation, improves clearance rates.MethodsRetrospective observational study of 206 treatment-na & iuml;ve BCCs <= 1 mm thickness treated over a 7-year period with a 2-phased photoactivation protocol ('biphasic PDT'). The first phase consists of conventional red-light activation (20-37 Jcm-2). Second phase photoactivation uses IPL (30-45 Jcm-2) delivered with sufficient mechanical pressure in the handpiece to blanch the skin. Optical coherence tomography (OCT) has been used to aid in lesion diagnosis, to establish suitability of tumour for treatment and to improve verification of treatment outcomes.MethodsRetrospective observational study of 206 treatment-na & iuml;ve BCCs <= 1 mm thickness treated over a 7-year period with a 2-phased photoactivation protocol ('biphasic PDT'). The first phase consists of conventional red-light activation (20-37 Jcm-2). Second phase photoactivation uses IPL (30-45 Jcm-2) delivered with sufficient mechanical pressure in the handpiece to blanch the skin. Optical coherence tomography (OCT) has been used to aid in lesion diagnosis, to establish suitability of tumour for treatment and to improve verification of treatment outcomes.ResultsIn the final group of 175 tumours, of which most were located on the head and neck and over 40% were nodular, there were only four incomplete treatments over a 2-year median follow-up period (up to 7 years). The few incomplete clearances were easily managed.ConclusionsOne or two biphasic photodynamic treatments are highly effective (98% clearance) in thin, treatment-na & iuml;ve BCCs (<= 1 mm in thickness) selected on clinical and OCT assessment.

A non-invasive means to determine lesion depth (I.e. Breslow Thickness) and an indirect, lesion-specific assessment of cellular morphology could substantially improve the efficacy of melanoma screening. Such applications would be of great benefit in aiding diagnosis, reducing the number of unnecessary biopsies, and improving treatment options for patients. Using Spatial Frequency Domain Imaging (SFDI), we have developed a spectral method to isolate depth-specific scattering properties and hence, differentiate pigmented lesion volumes from underlying tissue by its structural morphology. This method was evaluated on solid phantoms that emulate the optical properties of suspect pigmented lesions over multiple thicknesses.

Detection of hemoglobin (tHb), water (tH2O), and microvascular perfusion dynamics is of great importance as these indicate early signs of tissue physiological changes related to diseases. We have developed a physiological model based on tissue absorption and scattering properties measured by a customized spatial frequency domain imaging (SFDI) system. We performed an in-vivo investigation to evaluate the imager’s ability to characterize dermal response under a noxious heating protocol. In this initial study, we found that noxious heating induced changes in extravascular water content, hemoglobin, and tissue morphology that can be interpreted as vascular perfusion and dilation, inflammation, and edema.

Clinical studies have demonstrated that epidermal pigmentation level can affect cerebral oximetry measurements. To evaluate the robustness of these devices, we have developed a phantom-based test method that includes an epidermis-simulating layer with several melanin concentrations and a 3D-printed cerebrovascular module. Measurements were performed with neonatal, pediatric and adult sensors from two commercial oximeters, where neonatal probes had shorter source-detector separation distances. Referenced blood oxygenation levels ranged from 30 to 90%. Cerebral oximeter outputs exhibited a consistent decrease in saturation level with simulated melanin content; this effect was greatest at low saturation levels, producing a change of up to 15%. Dependence on pigmentation was strongest in a neonatal sensor, possibly due to its high reflectivity. Overall, our findings indicate that a modular channel-array phantom approach can provide a practical tool for assessing the impact of skin pigmentation on cerebral oximeter performance and that modifications to algorithms and/or instrumentation may be needed to mitigate pigmentation bias.

Significance: For optical methods to accurately assess hemoglobin oxygen saturation in vivo, an independently verifiable tissue-like standard is required for validation. For this purpose, we propose three hemoglobin preparations and evaluate methods to characterize them.

Aim: To spectrally characterize three different hemoglobin preparations using multiple spectroscopic methods and to compare their absorption spectra to commonly used reference spectra.

Approach: Absorption spectra of three hemoglobin preparations in solution were characterized using spectroscopic collimated transmission: whole blood, lysed blood, and ferrous-stabilized hemoglobin. Tissue-mimicking phantoms composed of Intralipid, and the hemoglobin solutions were characterized using spatial frequency-domain spectroscopy (SFDS) and enhanced perfusion and oxygen saturation (EPOS) techniques while using yeast to deplete oxygen.

Results: All hemoglobin preparations exhibited similar absorption spectra when accounting for methemoglobin and scattering in their oxyhemoglobin and deoxyhemoglobin forms, respectively. However, systematic differences were observed in the fitting depending on the reference spectra used. For the tissue-mimicking phantoms, SFDS measurements at the surface of the phantom were affected by oxygen diffusion at the interface with air, associated with higher values than for the EPOS system.

Conclusions: We show the validity of different blood phantoms and what considerations need to be addressed in each case to utilize them equivalently.

Significance: Tissue simulating phantoms are an important part of validating biomedical optical techniques. Tissue pathology in inflammation and oedema involves changes in both water and hemoglobin fractions.

Aim: We present a method to create solid gelatin-based phantoms mimicking inflammation and oedema with adjustable water and hemoglobin fractions.

Approach: One store-bought gelatin and one research grade gelatin were evaluated. Different water fractions were obtained by varying the water-to-gelatin ratio. Ferrous stabilized human hemoglobin or whole human blood was added as absorbers, and the stability and characteristics of each were compared. Intralipid® was used as the scatterer. All phantoms were characterized using spatial frequency domain spectroscopy.

Results: The estimated water fraction varied linearly with expected values (R2  =  0.96 for the store-bought gelatin and R2  =  0.99 for the research grade gelatin). Phantoms including ferrous stabilized hemoglobin stayed stable up to one day but had methemoglobin present at day 0. The phantoms with whole blood remained stable up to 3 days using the store-bought gelatin.

Conclusions: A range of physiological relevant water fractions was obtained for both gelatin types, with the stability of the phantoms including hemoglobin differing between the gelatin type and hemoglobin preparation. These low-cost phantoms can incorporate other water-based chromophores and be fabricated as thin sheets to form multilayered structures.

Significance: Assessment of disease using optical coherence tomography is an actively investigated problem, owing to many unresolved challenges in early disease detection, diagnosis, and treatment response monitoring. The early manifestation of disease or precancer is typically associated with subtle alterations in the tissue dielectric and ultrastructural morphology. In addition, biological tissue is known to have ultrastructural multifractality.

Aim: Detection and characterization of nanosensitive structural morphology and multifractality in the tissue submicron structure. Quantification of nanosensitive multifractality and its alteration in progression of tumor.

Approach: We have developed a label free nanosensitive multifractal detrended fluctuation analysis(nsMFDFA) technique in combination with multifractal analysis and nanosensitive optical coherence tomography (nsOCT). The proposed method deployed for extraction and quantification of nanosensitive multifractal parameters in mammary fat pad (MFP).

Results: Initially, the nsOCT approach is numerically validated on synthetic submicron axial structures. The nsOCT technique was applied to pathologically characterized MFP of murine breast tissue to extract depth-resolved nanosensitive submicron structures. Subsequently, two-dimensional MFDFA were deployed on submicron structural en face images to extract nanosensitive tissue multifractality. We found that nanosensitive multifractality increases in transition from healthy to tumor.

Conclusions: This method for extraction of nanosensitive tissue multifractality promises to provide a noninvasive diagnostic tool for early disease detection and monitoring treatment response. The novel ability to delineate the dominant submicron scale nanosensitive multifractal properties may also prove useful for characterizing a wide variety of complex scattering media of non-biological origin.

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Autologous keratinocytes or stem cell based therapies are modern approaches for the treatment of skin loss in burn victims and chronic wound patients. The aim of this study is to identify depth-resolved structural changes in treated burn wounds using Spatial Frequency Domain Imaging (SFDI). When altering the investigated depth into tissue via the spatial frequency used in our calculations, we found changes in the scattering parameters for the treated samples. These scattering changes are correlated with histology, indicating a potential means to monitor re-epithelization and collagen formation during the treatment process across the entire wound area.