Devices and Methods for Dosimetry of Personalized Photodynamic Therapy of Tumors: A Review on Recent Trends

Abstract

Significance: Despite the widespread use of photodynamic therapy in clinical practice, there is a lack of personalized methods for assessing the sufficiency of photodynamic exposure on tumors, depending on tissue parameters that change during light irradiation. This can lead to different treatment results. Aim: The objective of this article was to conduct a comprehensive review of devices and methods employed for the implicit dosimetric monitoring of personalized photodynamic therapy for tumors. Methods: The review included 88 peer-reviewed research articles published between January 2010 and April 2024 that employed implicit monitoring methods, such as fluorescence imaging and diffuse reflectance spectroscopy. Additionally, it encompassed computer modeling methods that are most often and successfully used in preclinical and clinical practice to predict treatment outcomes. The Internet search engine Google Scholar and the Scopus database were used to search the literature for relevant articles. Results: The review analyzed and compared the results of 88 peer-reviewed research articles presenting various methods of implicit dosimetry during photodynamic therapy. The most prominent wavelengths for PDT are in the visible and near-infrared spectral range such as 405, 630, 660, and 690 nm. Conclusions: The problem of developing an accurate, reliable, and easily implemented dosimetry method for photodynamic therapy remains a current problem, since determining the effective light dose for a specific tumor is a decisive factor in achieving a positive treatment outcome.

Keywords: computer modeling; diffuse reflectance spectroscopy; fluorescence imaging; fluorescent diagnostics; optical spectroscopy; photodynamic dosimetry; photodynamic therapy.

Figure 1

A distribution of patients treated with PDT by localization from 1990 to 2024 across the globe.

Figure 2

A schematic diagram of a cervical neoplasm boundary examination by means of spectral and video fluorescence diagnostic methods [52]. Reproduced with permission from IOP Publishing.

Figure 3

Schematic diagram of the dosimetry system [56]. Reproduced with permission from SPIE.

Figure 4

Tumor phototheranostics scheme: (a) “soft contact” and “during PDT” modes; (b) video- and spectral-fluorescence diagnostics, phototheranostics with 635 or 660 nm lasers [16]. Reproduced with permission from Elsevier.

Figure 5

Assessment of gingival tissue oxygenation level before and after PDT (p < 0.001, power > 0.99) [68]. Reproduced with permission from Frontiers.

Figure 6

Scheme of the study. (a) Spectroscopy system; (b) optical fiber with distal end indicated by red arrow; (c) cross-section of the distal end of the fiber [70]. Reproduced with permission from SPIE.

Figure 7

Combined monitoring of photodynamic irradiation: (a,b) spectral-fluorescence diagnostics before PDT; (c,d) distributions of integral intensities of diffusely scattered laser radiation, Ce6 fluorescence, and hemoglobin oxygenation during PDT [78]. Reproduced with permission from Elsevier.

Figure 8

Scheme of the system for diffuse reflectance/fluorescence spectroscopy. The probe profile is shown in the lower right. The reflectance source (R), fluorescence source (F) and the first four detection fibers (A through D) are labeled [82]. Reproduced with permission from Wiley.

Figure 9

Distribution of fluorescence indices in tissues before and after low-dose PDT [83]. Reproduced with permission from Elsevier.

Figure 10

Modeled dependence of the relative fluence rate of laser radiation on the penetration depth at different spot diameters (indicated by the number near the curve; mm) in the cervical tissue. (a) Logarithmic scale; (b) linear scale [88]. Reproduced with permission from IOP Publishing.

Figure 11

Diagram of the step-by-step treatment planning procedure for i-PDT [107]. Reproduced with permission from MDPI.

Figure 12

The iPDT treatment of brain tumors is a procedure that has been developed to improve the effectiveness of surgical removal of these tumors. (a) The light applicator comprises a fiber guide inserted into the balloon to guide the 70 mm cylindrical diffuser. This is a clinical application. (b) A model of the device filled with 150 mL of a diffusing solution was constructed. The 70 mm long cylindrical diffuser was positioned at the center of the borosilicate glass tube [109]. Reproduced with permission from Elsevier.