The optimization and application of photodynamic diagnosis and autofluorescence imaging in tumor diagnosis and guided surgery: current status and future prospects

Abstract

Photodynamic diagnosis (PDD) and autofluorescence imaging (AFI) are emerging cancer diagnostic technologies that offer significant advantages over traditional white-light endoscopy in detecting precancerous lesions and early-stage cancers; moreover, they hold promising potential in fluorescence-guided surgery (FGS) for tumors. However, their shortcomings have somewhat hindered the clinical application of PDD and AFI. Therefore, it is imperative to enhance the efficacy of PDD and AFI, thereby maximizing their potential for practical clinical use. This article reviews the principles, characteristics, current research status, and advancements of PDD and AFI, focusing on analyzing and discussing the optimization strategies of PDD and AFI in tumor diagnosis and FGS scenarios. Considering the practical and technical feasibility, optimizing PDD and AFI may result in an effective real-time diagnostic tool to guide clinicians in tumor diagnosis and surgical guidance to achieve the best results.

Keywords: autofluorescence imaging; diagnosis; fluorescence-guided surgery; optimization strategy; photodynamic diagnosis; photosensitizer; tumor.

Figure 1

Photodynamic diagnosis (PDD) is based on the different concentrations of photosensitizer (PS) in normal and tumor tissues. (A) After injection of PS, under PDD laser light (330-440nm) irradiation, normal tissue emits green fluorescence while tumor tissue displays red fluorescence. (B) Under excitation light irradiation, the PS molecule absorbs energy from the ground state to the single excited state. Subsequently, the PS returns to the ground state while emitting light of a higher wavelength (lower energy) than that used for excitation.

Figure 2

Schematic diagram of the photodynamic diagnosis PDD mediated by a bioactive nanoconjugate (BNC) composed of nanoparticles (NPs), antibody, and photosensitizer.

Figure 3

Jablonski diagram illustrates the molecular mechanism of autofluorescence phenomenon produced by fluorophores under laser light irradiation.

Figure 4

Schematic diagram of the tumor fluorescence-guided surgery system mediated by AFI and PDD, including an excitation light source, appropriate fluorescence detector, and fluorescence signal acquisition and processing system.