SignificanceThe quantification of protoporphyrin IX (PpIX) in skin can be used to study photodynamic therapy (PDT) treatments, understand porphyrin mechanisms, and enhance preoperative mapping of non-melanoma skin cancers.AimWe aim to develop a smartphone-based imager for performing simultaneous radiometric fluorescence (FL) and white light (WL) imaging to study the baseline levels, accumulation, and photobleaching of PpIX in skin.ApproachA smartphone-based dual FL and WL imager (sDUO) is introduced alongside new radiometric calibration methods for providing SI-units of measurements in both pre-clinical and clinical settings. These radiometric measurements and corresponding PpIX concentration estimations are applied to clinical measurements to understand mechanistic differences between PDT treatments, accumulation differences between normal tissue and actinic keratosis lesions, and the correlation of photosensitizer concentrations to treatment outcomes.ResultsThe sDUO alongside the developed methods provided radiometric FL measurements (nW / cm2) with a demonstrated sub nanomolar PpIX sensitivity in 1% intralipid phantoms. Patients undergoing PDT treatment of actinic keratosis (AK) lesions were imaged, capturing the increase and subsequent decrease in FL associated with the incubation and irradiation timepoints of lamp-based PDT. Furthermore, the clinical measurements showed mechanistic differences in new daylight-based treatment modalities alongside the selective accumulation of PpIX within AK lesions. The use of the radiometric calibration enabled the reporting of detected PpIX FL in units of nW / cm2 with the use of liquid phantom measurements allowing for the estimation of in-vivo molar concentrations of skin PpIX.ConclusionsThe phantom, pre-clinical, and clinical measurements demonstrated the capability of the sDUO to provide quantitative measurements of PpIX FL. The results demonstrate the use of the sDUO for the quantification of PpIX accumulation and photobleaching in a clinical setting, with implications for improving the diagnosis and treatment of various skin conditions.
Lighting gel filters are widely used in commercial industries, but their adoption in scientific applications is limited, despite their low cost and form factor advantages. Here, we compare the optical performance of lighting gel filters to commonly used dielectric and colored glass filters in terms of absorbance spectra, passband transmission, angle of incidence dependence, autofluorescence, and photostability. Further comparison is performed in both preclinical and clinical imaging applications. The results show that gel filters might be a superior filter choice in several optical systems, including compact designs and fluorescence imaging applications. Compact designs using gel filters could have a significant advantage for applications such as point-of-care diagnostics, smartphone device add-ons, and single-use fluorescent assays.
Fluorescence imaging for surgical guidance is a proven modality that allows for visualization of fluorescent markers in numerous biological imaging applications. As the field continues to develop there is an urgent need for fluorescence-imaging standards and targets that enable system characterization, performance monitoring, and the development of analytical algorithms. 3D-printing technology has shown promise in providing biomimicking phantoms that allow simulation of realistic clinical conditions. Here, we present a comprehensive method for 3D printing fluorescent and tissue-equivalent material using photo-curable resins. We show the ability to print Indocyanine-green (ICG) equivalent material in complex shapes that would enable the evaluation of ICG-specific clinical systems. The method presented allows tuning of both the reduced scattering and absorption coefficients at multiple wavelengths, allowing for application-specific manufacturing of 3D-printed phantoms.
Lighting gel filters have been used for over 100 years to modify the color of traditional light sources. Very few applications of gel filters have been recorded in scientific literature despite their potential in low-cost optical design . We propose that key factors that prevent wider adoption of gel filters in scientific applications are a lack of extensive optical characterization and comparison to commonly used dielectric and color glass filters. Here, we perform optical characterization of lighting gel filters and compare their transmission, auto-fluorescence, and photobleaching performance to dielectric and color glass filters. The results indicate that gel filters are a viable low-cost alternative with unique advantages that make them suitable for scientific applications including low-cost smartphone imaging systems and disposable lab-on-chip fluorescence tests.
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