Smartphone Fluorescence Imaging for PpIX Skin Dosimetry
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Solution Overview
Problem
Current clinical dosimetry methods for protoporphyrin IX (PpIX) in photodynamic therapy (PDT) lack practical devices and predictive methods for personalizing treatment parameters, leading to variable treatment outcomes due to heterogeneity in drug absorption and accumulation between patients and lesions.
Innovation Solution
A fluorescence imaging apparatus and system using a smartphone-based platform with a 3D printed base, custom light sources, and optical filters to provide quantitative wide-field dosimetry by measuring PpIX levels in the skin, overcoming measurement reproducibility issues and environmental variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wide-field fluorescence imaging is used to guide PDT, then treatment personalization and outcome prediction improve, but measurement reproducibility and control over environmental variability worsen
Solution Approach 1:
The imaging system is divided into modular components: a housing unit containing excitation light sources and optical filters, a computing device with optical sensor, and a cushion for stable coupling. This segmentation allows each component to be optimized independently while maintaining overall system reproducibility through standardized interfaces and procedures.
Solution Approach 2:
The system performs preliminary fluorescence imaging measurements before PDT treatment to assess PpIX accumulation levels. This preliminary dosimetry guides treatment parameter personalization (incubation time, light dose) and enables predictive assessment of treatment outcomes before actual therapy begins.
2Adaptability or versatility
If quantitative dosimetry devices are implemented, then treatment personalization improves, but device complexity and cost increase
Solution Approach 1:
The imaging system uses a computing device (smartphone or similar) that serves multiple functions: capturing fluorescence images, processing dosimetry data, and potentially guiding treatment decisions. This multi-functionality reduces the need for separate specialized devices while maintaining quantitative dosimetry capabilities.
Solution Approach 2:
The system creates a visual copy (fluorescence image) of the PpIX distribution in tissue, which can be analyzed quantitatively. This optical copy allows treatment planning without requiring direct physical measurement or intervention during the incubation phase, simplifying the overall process.
3Loss of time
If fluorescence imaging is performed at point-of-care, then treatment guidance timeliness improves, but environmental light interference increases
Solution Approach 1:
The system extracts and isolates the weak fluorescence signal from PpIX by using specific excitation wavelengths and optical filters that block exterior light interference. The optical filter in the housing selectively transmits only the fluorescence emission wavelengths while blocking the excitation light and ambient light, enabling point-of-care measurement despite environmental conditions.
Solution Approach 2:
The cushion serves as an intermediary element that couples the imaging system to the skin surface while providing optical isolation. It creates a controlled measurement environment that blocks exterior light from entering the measurement field while allowing fluorescence photons to reach the sensor.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and reproducible quantification of PpIX levels and PDT-induced photobleaching, facilitating individualized treatment planning and improving treatment outcomes by correlating fluorescence measurements with patient responses.
Implementation Method 1
an optical filter disposed between the optical sensor and the exit aperture; wherein the optical filter is configured to prevent transmission of electromagnetic radiation having a wavelength in the predetermined excitation wavelength range
Implementation Method 2
a cushion removeably attached to the first end of the housing and surrounding the exit aperture, the cushion configured to couple the first end of the housing to a surface of an object to prevent light from an exterior of the cushion from entering an interior of the cushion
Implementation Method 3
a fluorescence imaging apparatus... the plurality of excitation light sources configured to emit light in a predetermined excitation wavelength range
Data Source
AI summary
While clinical treatment of actinic keratosis by photodynamic therapy (PDT) is widely practiced, there is well-known variability in response, primarily caused by heterogeneous accumulation and PDT-induced photobleaching of the photosensitizer protoporphyrin IX (PpIX) between patients and between lesions. One of the key factors in regularizing this treatment would be to have an easily accessible indicator of PpIX present in the lesions at the time of light delivery. Described herein, a smartphone-based fluorescence imager was developed to allow simple quantitative photography of the lesions and their PpIX levels.