Pulsed light imaging for wide-field dosimetry of photodynamic therapy in the skin

Scott C. Davis; Kristian Sexton; Michael Shane Chapman M.D.; Edward Maytin M.D.; Tayyaba Hasan; Brian W. Pogue

doi:10.1117/12.2040174

14 March 2014 Pulsed light imaging for wide-field dosimetry of photodynamic therapy in the skin

Scott C. Davis, Kristian Sexton, Michael Shane Chapman M.D., Edward Maytin M.D., Tayyaba Hasan, Brian W. Pogue

Proceedings Volume 8931, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXIII; 89310W (2014) https://doi.org/10.1117/12.2040174
Event: SPIE BiOS, 2014, San Francisco, California, United States

Abstract

Photodynamic therapy using aminoluvelinic acid (ALA) is an FDA-approved treatment for actinic keratoses, pre-cancerous skin lesions which pose a significant risk for immunocompromised individuals, such as organ transplant recipients. While PDT is generally effective, response rates vary, largely due to variations in the accumulation of the photosensitizer protoporphyrin IX (PpIX) after ALA application. The ability to quantify PpIX production before treatment could facilitate the use of additional interventions to improve outcomes. While many groups have demonstrated the ability to image PpIX in the clinic, these systems generally require darkening the room lights during imaging, which is unpopular with clinicians. We have developed a novel wide-field imaging system based on pulsed excitation and gated acquisition to image photosensitizer activity in the skin. The tissue is illuminated using four pulsed LED’s to excite PpIX, and the remitted light acquired with a synchronized ICCD. This approach facilitates real-time background subtraction of ambient light, precluding the need to darken the exam room. Delivering light in short bursts also allows the use of elevated excitation intensity while remaining under the maximum permissible exposure limits, making the modality more sensitive to photosensitizer fluorescence than standard approaches. Images of tissue phantoms indicate system sensitivity down to 250nM PpIX and images of animals demonstrate detection of PpIX fluorescence in vivo under normal room light conditions.

Citation Download Citation

Scott C. Davis, Kristian Sexton, Michael Shane Chapman M.D., Edward Maytin M.D., Tayyaba Hasan, and Brian W. Pogue "Pulsed light imaging for wide-field dosimetry of photodynamic therapy in the skin", Proc. SPIE 8931, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXIII, 89310W (14 March 2014); https://doi.org/10.1117/12.2040174

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KEYWORDS

Luminescence

Imaging systems

Photodynamic therapy

Skin

Light emitting diodes

Cameras

Tissue optics

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