Dose parameter monitoring system and method for photodynamic therapy in cavity

Abstract

The invention relates to a dose parameter monitoring system and method for intracavitary photodynamic therapy, which can enable the diameter of an endoscopic ring scanning probe to be matched with an intracavitary biopsy channel of esophageal cancer, monitor the tumor morphology, tissue optical parameters, blood oxygen content and photosensitizer dose distribution of esophageal cancer lesions in real time, establish a tissue optical transmission model, and monitor the intracavitary biopsy channel of esophageal cancer. And a doctor is assisted in dose regulation and scheme formulation of photodynamic therapy. Comprising a three-mode endoscopic imaging module which is an imaging information acquisition module of the system and is used for performing endoscopic synchronous acquisition of three-mode information of an OCT mode, a diffuse reflection spectrum mode and a fluorescence signal mode in a photodynamic therapy process in a cavity; and the photodynamic therapy dose parameter monitoring module is a signal receiving and information processing module at the rear end of the system, receives the analog signal transmitted by the three-mode endoscopic imaging module, and calculates multi-dimensional photodynamic dose parameters such as blood oxygen content, tissue optical characteristics, a therapy light transmission model and photosensitizer concentration in the photodynamic therapy process.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detection, and in particular to a dose parameter monitoring system for intracavitary photodynamic therapy, and a method for the dose parameter monitoring system for intracavitary photodynamic therapy. Background Art

[0002] Esophageal cancer and colon cancer are common intracavitary tumors, with an incidence of about 6.3 cases per 100,000 people and a 5-year survival rate of only 10-30%. Photodynamic therapy (PDT) is a non-invasive therapy with advantages such as low trauma and low complications. Compared with other invasive therapies, it can maintain the patient's quality of life and has great potential to become a long-term progressive treatment method for patients with esophageal cancer and colon cancer, used for tumor ablation after surgical resection or when patients cannot undergo surgical treatment.

[0003] The dose regulation of PDT treatment will determine its final efficacy. Excessive light dose may damage the patient's normal tissue. Factors affecting the evaluation of photodynamic dose include: oxygen content distribution of the target lesion, photosensitizer concentration distribution, penetration depth of therapeutic light and other effects. The determination of tissue optical properties and the establishment of tissue light transmission model will determine the reliability of PDT dosimetric evaluation. Surgeons are in urgent need of an endoscopic ring scanning photodynamic therapy dose parameter monitoring method with the following characteristics: 1) The diameter of the endoscopic ring scanning probe can match the intracavitary biopsy channel of esophageal cancer; 2) The speed of endoscopic ring scanning imaging can achieve real-time imaging, and the single-frame image acquisition speed exceeds 5 frames / second; 3) It can realize in vivo PDT dose multi-parameter information detection, and real-time simulation and calculation of the penetration depth and therapeutic effect of PDT therapeutic light. Summary of the invention

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a dose parameter monitoring system for intracavitary photodynamic therapy, which can match the diameter of the endoscopic circular scanning probe with the intracavitary biopsy channel of esophageal cancer, monitor the tumor morphology, tissue optical parameters, blood oxygen content and photosensitizer dose distribution of esophageal cancer lesions in real time, establish a tissue light transmission model, and assist doctors in dose control and plan formulation for photodynamic therapy.

[0005] The technical solution of the present invention is: a dose parameter monitoring system for intracavitary photodynamic therapy, comprising:

[0006] A three-modality endoscopic imaging module is an imaging information acquisition module of the system, which performs endoscopic synchronous acquisition of three-modality information of OCT modality, diffuse reflectance spectroscopy modality, and fluorescence signal modality during intracavitary photodynamic therapy; the OCT modality adopts spectral domain OCT (1) based on an 800nm ​​wide-spectrum light source, the diffuse reflectance spectroscopy modality is composed of a 400-750nm white light LED light source (21) and a visible light spectrometer, the fluorescence signal modality adopts a 405nm laser (22) as an excitation light source, and a visible light spectrometer is used as a fluorescence signal collector;

[0007] The photodynamic therapy dose parameter monitoring module is a signal receiving and information processing module at the back end of the system. It receives the analog signal transmitted by the tri-modal endoscopic imaging module and calculates multi-dimensional photodynamic dose parameters such as blood oxygen content, tissue optical properties, treatment light transmission model, and photosensitizer concentration during photodynamic therapy.

[0008] The present invention can make the diameter of the endoscopic circular scanning probe match the intracavitary biopsy channel of esophageal cancer, monitor the tumor morphology, tissue optical parameters, blood oxygen content and photosensitizer dose distribution of esophageal cancer lesions in real time, establish a tissue light transmission model, and assist doctors in dose control and plan formulation of photodynamic therapy.

[0009] A working method for a dose parameter monitoring system for intracavitary photodynamic therapy is also provided. The tissue light scattering coefficient is calculated by using the least square method based on the OCT imaging depth z, the light source intensity I 0 and the depth-resolved image light signal I(z) of OCT to fit the light scattering coefficient μ at 800 nm t , the target theoretical formula for fitting is as follows:

[0010]

[0011] Calculation of tissue light absorption coefficient: Hemoglobin is the main absorbing substance in the visible light spectrum involved in PDT treatment. The blood oxygen content StO is determined based on the difference in absorption intensity between oxygenated hemoglobin and deoxygenated hemoglobin in the 400-750nm spectrum. 2 and blood volume percentage BVF, based on the standard absorption coefficients of oxygenated and deoxygenated hemoglobin Combine the following formula to calculate the light absorption coefficient μ of the tissue a，z :

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic structural diagram of a dose parameter monitoring system for intracavitary photodynamic therapy according to the present invention is shown.

[0014] Figure 2 A schematic structural diagram of an endoscopic ring-scanning probe of a three-modality endoscopic imaging module according to the present invention is shown.

[0015] Figure 3 A schematic diagram of the timing of alternating excitation pulses of the diffuse reflectance spectrum and the fluorescence spectrum of the tri-modality endoscopic imaging module according to the present invention is shown.

[0016] Figure 4 A data processing flow chart of a photodynamic therapy dose parameter monitoring module according to the present invention is shown. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0018] It should be noted that the term "comprises" and any variations in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, application, apparatus, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, applications, products or equipment.

[0019] like Figure 1 As shown, the dose parameter monitoring system for intracavitary photodynamic therapy comprises:

[0020] The tri-modality endoscopic imaging module is the imaging information acquisition module of the system, which performs endoscopic synchronous acquisition of tri-modality information of OCT modality, diffuse reflectance spectroscopy modality, and fluorescence signal modality during intracavitary photodynamic therapy; the OCT modality adopts spectral domain OCT 1 based on an 800nm ​​wide-spectrum light source, the diffuse reflectance spectroscopy modality is composed of a 400-750nm white light LED light source 21 and a visible light spectrometer, and the fluorescence signal modality adopts a 405nm laser 22 as an excitation light source, and a visible light spectrometer is used as a fluorescence signal collector;

[0021] The photodynamic therapy dose parameter monitoring module is a signal receiving and information processing module at the back end of the system. It receives the analog signal transmitted by the tri-modal endoscopic imaging module and calculates multi-dimensional photodynamic dose parameters such as blood oxygen content, tissue optical properties, treatment light transmission model, and photosensitizer concentration during photodynamic therapy.

[0022] The present invention can make the diameter of the endoscopic circular scanning probe match the intracavitary biopsy channel of esophageal cancer, monitor the tumor morphology, tissue optical parameters, blood oxygen content and photosensitizer dose distribution of esophageal cancer lesions in real time, establish a tissue light transmission model, and assist doctors in dose control and plan formulation of photodynamic therapy.

[0023] Preferably, the white light LED light source of the diffuse reflection spectrum and the 405nm laser light source of the fluorescence spectrum are coupled to one channel using a Y-type multimode optical fiber 23; a spectroscope 24 is used to couple the diffuse reflection light signal and the fluorescence signal to an adjustable reflector 25 of a spectrometer channel and coupled into the spectrometer; the spectrometer is composed of a spectroscopic prism 26 and a linear array CMOS 27, and the spectroscopic prism divides the frequency of the signal light and incidents it onto the linear array CMOS to collect the spectral signal.

[0024] Preferably, the scanning acquisition frequency of the OCT modality is 20kHz; the acquisition frequencies of the diffuse reflectance spectrum modality and the fluorescence signal modality are both 40kHz, and the white light LED light source and the 405nm laser are pulse-triggered to control the alternating switching of the light source to avoid signal overlap between the two modalities. The pulse triggering frequency is 20kHz and the duty cycle is 40%; the three modalities of OCT, diffuse reflectance spectrum, and fluorescence signal are synchronized with the reference clock by a waveform generator 42 to achieve synchronous acquisition of tri-modal information.

[0025] Preferably, the system integration of the three modes is completed by a double-clad optical fiber 31, the core of the double-clad optical fiber uses an 800nm ​​single-mode optical fiber, and the inner cladding uses a multi-mode optical fiber; the sample arm of the OCT mode is connected to the double-clad port of the double-clad optical fiber; the diffuse reflectance spectrum / fluorescence signal mode port is connected to the multi-mode port of the double-clad optical fiber.

[0026] Preferably, the scanning endoscopic circular scanning probe 33 adopts a micro-motor circular scanning solution, the double-clad optical fiber is fixed by a metal ring 331, the optical signal is focused by a gain lens 332 and incident on the diseased tissue in the cavity through a concave reflector 333, and the micro-motor 334 at the rear end of the concave reflector rotates and the optical fiber dragging motor 32 pulls back to realize the endoscopic circular scanning three-modal information collection in the cavity.

[0027] Preferably, the signal acquisition card 41 of the photodynamic therapy dose parameter monitoring module receives the image information sent by the three-modality endoscopic imaging module and transmits it to the professional workstation 43, calculates the tissue stratification information and light scattering characteristics according to the OCT modality image information, and calculates the light absorption characteristics of the tissue according to the information of the diffuse reflectance spectrum modality, thereby forming the tomographic tissue optical parameters of the tissue.

[0028] Preferably, the photodynamic therapy dose parameter includes the penetration depth of the therapeutic light; the photodynamic therapy dose parameter monitoring module simulates the propagation path of the therapeutic photons in the tissue based on the calculated tomographic tissue optical properties and the Monte Carlo light transmission model to calculate the penetration depth of the therapeutic light.

[0029] Preferably, the photodynamic therapy dose parameter includes blood oxygen content; the photodynamic therapy dose parameter monitoring module calculates the proportion of oxygenated hemoglobin in hemoglobin and determines the blood oxygen content based on the difference in absorption spectra between oxygenated hemoglobin and deoxygenated hemoglobin and according to the calculated tomographic tissue optical parameters.

[0030] Preferably, the photodynamic therapy dose parameter includes the photosensitizer concentration; the photodynamic therapy dose parameter monitoring module corrects the influence of tissue light absorption and light scattering on the fluorescence signal based on the fluorescence distribution of the photosensitizer and the calculated tomographic tissue optical parameters, and inversely calculates the photosensitizer concentration distribution in the tissue.

[0031] A working method for a dose parameter monitoring system for intracavitary photodynamic therapy is also provided. The tissue light scattering coefficient is calculated by using the least square method based on the OCT imaging depth z, the light source intensity I 0 and the depth-resolved image light signal I(z) of OCT to fit the light scattering coefficient μ at 800 nm t , the target theoretical formula for fitting is as follows:

[0032]

[0033] Calculation of tissue light absorption coefficient: Hemoglobin is the main absorbing substance in the visible light spectrum involved in PDT treatment. The blood oxygen content StO is determined based on the difference in absorption intensity between oxygenated hemoglobin and deoxygenated hemoglobin in the 400-750nm spectrum. 2 and blood volume percentage BVF, based on the standard absorption coefficients of oxygenated and deoxygenated hemoglobin Combine the following formula to calculate the light absorption coefficient μ of the tissue a，z :

[0034]

[0035] More specifically, if Figure 1-3 As shown, the dose parameter monitoring system for intracavitary photodynamic therapy comprises: a trimodal endoscopic imaging module and a photodynamic therapy dose parameter monitoring module;

[0036] The tri-modality endoscopic imaging module, as the imaging information acquisition module of the system, can realize the endoscopic synchronous acquisition of tri-modality information of OCT, diffuse reflectance spectrum and fluorescence signal during intracavitary photodynamic therapy.

[0037] The tri-modality endoscopic imaging module includes acquisition information of three modalities: OCT, diffuse reflectance spectroscopy, and fluorescence signals; the OCT modality adopts a spectral domain OCT 1 structure based on an 800nm ​​wide-spectrum light source;

[0038] The diffuse reflectance spectroscopy mode is composed of a white light LED light source 21 (400–750 nm) and a visible light spectrometer; the fluorescence signal mode uses a 405 nm laser 22 as an excitation light source and a visible light spectrometer as a fluorescence signal collector;

[0039] The white light LED light source 21 of the diffuse reflection spectrum and the 405nm laser light source 22 of the fluorescence spectrum are coupled to one channel using a Y-type multimode optical fiber 23; a spectroscope 24 is used to couple the diffuse reflection light signal and the fluorescence signal to the adjustment reflector 25 of the spectrometer channel and couple them into the spectrometer; the spectrometer is composed of a spectroscopic prism 26 and a linear array CMOS 27, and the spectroscope divides the frequency of the signal light and incidents it on the linear array CMOS to collect the spectrum signal;

[0040] The A-Scan acquisition frequency of the OCT modality is 20kHz; Figure 3 As shown, the acquisition frequency of diffuse reflectance spectrum and fluorescence mode is 40kHz. The white light LED light source and 405nm laser use pulse triggering to control the alternating switch of the light source to avoid signal overlap of the two modes. The pulse triggering frequency is 20kHz and the duty cycle is 40%; the three modes of OCT, diffuse reflectance spectrum and fluorescence signal are synchronized by a waveform generator 42 to achieve synchronous acquisition of three-mode information. The system integration of the three modes is completed by double-clad optical fiber 31. The core of the double-clad optical fiber uses 800nm ​​single-mode optical fiber and the inner cladding uses multi-mode optical fiber; the sample arm of the OCT mode is connected to the double-clad port of the double-clad optical fiber; the diffuse reflectance spectrum / fluorescence signal mode port is connected to the multi-mode port of the double-clad optical fiber;

[0041] The endoscopic ring scanning probe 33 adopts a micro-motor ring scanning solution. The double-clad optical fiber is fixed by a metal ring 331. The optical signal is focused by a gain lens 332 and incident on the lesion tissue of the cavity through a concave reflector 333. The micro-motor 334 at the rear end of the concave reflector rotates and the optical fiber dragging motor 32 pulls back to realize the endoscopic ring scanning three-mode information collection in the cavity.

[0042] The photodynamic therapy dose parameter monitoring module is a signal receiving and information processing module at the back end of the system. It receives the analog signal transmitted by the tri-modal endoscopic imaging module and calculates the multi-dimensional photodynamic dose parameters such as blood oxygen content, tissue optical properties, treatment light transmission model, photosensitizer concentration, etc. during the photodynamic therapy process.

[0043] The signal acquisition card of the photodynamic therapy dose parameter monitoring module is responsible for receiving the image information sent by the three-modality endoscopic imaging module, calculating the tissue layering information and light scattering characteristics according to the OCT modality image information, and calculating the light absorption characteristics of the tissue according to the diffuse reflectance spectrum modality information, and forming the tomographic tissue optical parameters of the tissue. The photodynamic therapy dose parameters detected by the photodynamic therapy dose parameter monitoring module include the penetration depth of the therapeutic light; the monitoring module will simulate the propagation path of the therapeutic photons in the tissue based on the calculated tomographic tissue optical characteristics and the Monte Carlo light transmission model, and calculate the penetration depth of the therapeutic light;

[0044] The photodynamic therapy dose parameter detected by the photodynamic therapy dose parameter monitoring module includes the blood oxygen content; the monitoring module will calculate the proportion of oxygenated hemoglobin in hemoglobin and determine the blood oxygen content based on the difference in absorption spectra between oxygenated hemoglobin and deoxygenated hemoglobin and the calculated tomographic tissue optical parameters;

[0045] The photodynamic therapy dose parameter detected by the photodynamic therapy dose parameter monitoring module includes the photosensitizer concentration; the monitoring module will correct the influence of tissue light absorption and light scattering on the fluorescence signal based on the fluorescence distribution of the photosensitizer and the calculated tomographic tissue optical parameters, and inversely calculate the photosensitizer concentration distribution in the tissue;

[0046] In the dose parameter monitoring system for intracavitary photodynamic therapy proposed in the present invention, the tri-modal endoscopic imaging module will be suitable for the dose parameter collection of intracavitary photodynamic therapy for esophageal cancer, colon cancer, etc.; the various dose parameters calculated by the photodynamic therapy dose parameter monitoring module will provide doctors with quantifiable reference indicators to adjust the photosensitizer injection amount and treatment light intensity during the photodynamic therapy process to achieve the best therapeutic effect.

[0047] The specific embodiments of the present invention are described in detail below.

[0048] Example 1: Dose parameter detection for photodynamic therapy of esophageal cancer

[0049] like Figure 4 As shown, the workflow of the present invention is:

[0050] (1) Intravenous injection of photosensitizers in patients with esophageal cancer;

[0051] (2) starting the signal acquisition board, the waveform generator 42 and the tri-modal endoscopic imaging system, inserting the endoscopic circular scanning probe into the esophageal cancer biopsy channel, and completing the tri-modal endoscopic circular scanning detection of the esophageal lesion site by means of motor lateral scanning and optical fiber back pulling;

[0052] (3) Determine the optimal treatment plan, treatment duration, and treatment light power through the feedback of the photodynamic dose parameters (blood oxygen concentration, treatment light penetration depth, and photosensitizer concentration) from the photodynamic therapy dose parameter monitoring module;

[0053] (4) Perform photodynamic therapy on the patient according to the set treatment plan, treatment duration, and treatment light power.

[0054] Example 2: Dose parameter detection for photodynamic therapy of colon cancer

[0055] The workflow of the present invention is:

[0056] (1) Intravenous injection of photosensitizers in patients with colon cancer;

[0057] (2) Start the signal acquisition board, waveform generator, and tri-modal endoscopic imaging system, insert the endoscopic circular scanning probe into the colon cancer biopsy channel, and complete the tri-modal endoscopic circular scanning detection of the esophageal lesion site by means of motor lateral scanning and optical fiber pull-back;

[0058] (3) Through the feedback of the photodynamic dose parameters (blood oxygen concentration, therapeutic light penetration depth and photosensitizer concentration) of the photodynamic therapy dose parameter monitoring module, it is found that the photosensitizer concentration is higher than the expected value, so the preset therapeutic light power is reduced;

[0059] (4) Perform photodynamic therapy on the patient according to the set treatment plan, treatment duration, and treatment light power.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A dose parameter monitoring system for intracavitary photodynamic therapy, characterized in that: It includes: A three-modality endoscopic imaging module is an imaging information acquisition module of the system, which performs endoscopic synchronous acquisition of three-modality information of OCT modality, diffuse reflectance spectroscopy modality, and fluorescence signal modality during intracavitary photodynamic therapy; the OCT modality adopts spectral domain OCT (1) based on an 800nm ​​wide-spectrum light source, the diffuse reflectance spectroscopy modality is composed of a 400-750nm white light LED light source (21) and a visible light spectrometer, the fluorescence signal modality adopts a 405nm laser (22) as an excitation light source, and a visible light spectrometer is used as a fluorescence signal collector; The photodynamic therapy dose parameter monitoring module is a signal receiving and information processing module at the back end of the system. It receives the analog signal transmitted by the tri-modal endoscopic imaging module and calculates multi-dimensional photodynamic dose parameters such as blood oxygen content, tissue optical properties, treatment light transmission model, and photosensitizer concentration during photodynamic therapy.

2. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 1, characterized in that: The white light LED light source of the diffuse reflection spectrum and the 405nm laser light source of the fluorescence spectrum are coupled to a channel using a Y-type multimode optical fiber (23); a diffuse reflection light signal and a fluorescence signal are coupled to an adjustment reflector (25) of a spectrometer channel using a beam splitter (24) and coupled into the spectrometer; the spectrometer is composed of a beam splitter prism (26) and a linear array CMOS (27); the beam splitter prism divides the frequency of the signal light and incidents it on the linear array CMOS to collect the spectrum signal.

3. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 2, characterized in that: The scanning acquisition frequency of the OCT mode is 20kHz; the acquisition frequencies of the diffuse reflectance spectrum mode and the fluorescence signal mode are both 40kHz; the white light LED light source and the 405nm laser are controlled to switch the light source alternately by pulse triggering to avoid signal overlap of the two modes; the pulse triggering frequency is 20kHz and the duty cycle is 40%; the three modes of OCT, diffuse reflectance spectrum and fluorescence signal are synchronized with the reference clock by a waveform generator (42) to achieve synchronous acquisition of trimodal information.

4. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 3, characterized in that: The system integration of the three modes is completed by a double-clad optical fiber (31), the core of the double-clad optical fiber uses an 800nm ​​single-mode optical fiber, and the inner cladding uses a multi-mode optical fiber; the sample arm of the OCT mode is connected to the double-clad port of the double-clad optical fiber; the diffuse reflection spectrum / fluorescence signal mode port is connected to the multi-mode port of the double-clad optical fiber.

5. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 4, characterized in that: The scanning endoscopic circular scanning probe (33) adopts a micro-motor circular scanning solution. The double-clad optical fiber is fixed by a metal ring (331). The optical signal is focused by a gain lens (332) and incident on the lesion tissue of the cavity through a concave reflector (333). The micro-motor (334) at the rear end of the concave reflector rotates and the optical fiber dragging motor (32) pulls back to realize the endoscopic circular scanning three-modal information collection in the cavity.

6. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 1, characterized in that: The signal acquisition card (41) of the photodynamic therapy dose parameter monitoring module receives the image information sent by the three-modality endoscopic imaging module and transmits it to the professional workstation (43), calculates the tissue layering information and light scattering characteristics based on the OCT modality image information, and calculates the light absorption characteristics of the tissue based on the information of the diffuse reflectance spectrum modality, thereby forming the tomographic tissue optical parameters of the tissue.

7. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 6, characterized in that: The dose parameters of photodynamic therapy include the penetration depth of the therapeutic light. The dose parameter monitoring module of photodynamic therapy is based on the calculated optical properties of the tomographic tissue and combined with the Monte Carlo light transmission model to simulate the propagation path of the therapeutic photons in the tissue and calculate the penetration depth of the therapeutic light.

8. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 6, characterized in that: The photodynamic therapy dose parameters include blood oxygen content; the photodynamic therapy dose parameter monitoring module calculates the proportion of oxygenated hemoglobin in hemoglobin and determines the blood oxygen content based on the difference in absorption spectra between oxygenated hemoglobin and deoxygenated hemoglobin and the calculated tomographic tissue optical parameters.

9. The dose parameter monitoring system for intracavitary photodynamic therapy according to claim 6, characterized in that: The photodynamic therapy dose parameters include the photosensitizer concentration; the photodynamic therapy dose parameter monitoring module is based on the fluorescence distribution of the photosensitizer, combined with the calculated tomographic tissue optical parameters, to correct the influence of tissue light absorption and light scattering on the fluorescence signal, and inversely calculate the photosensitizer concentration distribution in the tissue.

10. The working method of the dose parameter monitoring system for intracavitary photodynamic therapy according to claim 6, characterized in that: Calculation of tissue light scattering coefficient: The light scattering coefficient μ at 800 nm is fitted by the least squares method based on the OCT imaging depth z, the light source intensity I0 and the OCT depth-resolved image light signal I(z). t , the target theoretical formula for fitting is as follows: Calculation of tissue light absorption coefficient: Hemoglobin is the main absorbing substance in the visible light spectrum involved in PDT treatment. The blood oxygen content StO2 and blood volume percentage BVF are determined based on the difference in absorption intensity between oxygenated hemoglobin and deoxygenated hemoglobin in the 400-750nm spectrum. According to the standard absorption coefficients of oxygenated and deoxygenated hemoglobin Combine the following formula to calculate the light absorption coefficient μ of the tissue a，z :

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