Techniques for fluorescence detection of protoporphyrin IX in skin cancers associated with photodynamic therapy

Abstract

Photodynamic therapy (PDT) is a treatment modality that uses a specific photosensitizing agent, molecular oxygen, and light of a particular wavelength to kill cells targeted by the therapy. Topically administered aminolevulinic acid (ALA) is widely used to effectively treat cancerous and precancerous skin lesions, resulting in targeted tissue damage and little to no scarring. The targeting aspect of the treatment arises from the fact that ALA is preferentially converted into protoporphyrin IX (PpIX) in neoplastic cells. To monitor the amount of PpIX in tissues, techniques have been developed to measure PpIX-specific fluorescence, which provides information useful for monitoring the abundance and location of the photosensitizer before and during the illumination phase of PDT. This review summarizes the current state of these fluorescence detection techniques. Non-invasive devices are available for point measurements, or for wide-field optical imaging, to enable monitoring of PpIX in superficial tissues. To gain access to information at greater tissue depths, multi-modal techniques are being developed which combine fluorescent measurements with ultrasound or optical coherence tomography, or with microscopic techniques such as confocal or multiphoton approaches. The tools available at present, and newer devices under development, offer the promise of better enabling clinicians to inform and guide PDT treatment planning, thereby optimizing therapeutic outcomes for patients.

Расчет Передаточных Функций Многослойных Биотканей В Задачах Коррекции Их Спектров Флуоресценции

“…ПП IX является эффективным эндогенным флуорофором для визуализации опухолей и фотосенси-билизатором для фотодинамической терапии. Он имеет максимум поглощения на λ ex = 405 nm и флуоресцирует в красной области спектра с максимумами на λ em = 635 и 705 nm [35]. Для стандартизации методов флуорес-центной диагностики и фотодинамической терапии с использованием 5-АЛК-индуцированного ПП IX, оче-видно, необходимо иметь возможность количественного определения его концентрации в ткани пациента.…”

“…В качестве флуоресцирующей субстан-ции рассматривается 5-АЛК-индуцированный протопор-фирин IX (ПП IX), широко используемый для флуо-ресцентной диагностики и фотодинамической терапии рака [35]. Оптические параметры кожи, необходимые для расчета ее передаточных функций, определяются на основе решения обратной задачи спектроскопии диффуз-ного отражения с использованием аппроксимационного аналога метода МК [36].…”

Light-Emitting Woven Fabric for Treatment with Photodynamic Therapy and Monitoring of Actinic Keratosis

“…These PpIX are characterized by a red fluorescent color when viewed with a Wood lamp which uses ultraviolet (UV) light to examine the skin ( [13,[44][45][46][47]; Figure 11). It is therefore possible to monitor the amount of PpIX in tissues by measuring the fluorescence before or during treatment.…”

“…It is therefore possible to monitor the amount of PpIX in tissues by measuring the fluorescence before or during treatment. This procedure is called fluorescence diagnosis (FD) [13,45,48]. The use of LEF already developed in our research as a tool for FD is also investigated in this work.…”

Progress in dermatology

“…Rollakanti et al [19] review the use of fluorescence measurements as a tool to optimize aminolevulinic acid (ALA)-based PDT of non-melanoma skin cancer. The exogenous exposure of skin cancer precursors and skin cancers to a physiological heme precursor (ALA) results in selective accumulation of porphyrins, predominantly protoporphyrin IX, in the neoplastic cells.…”