KEYWORDS: Photodynamic therapy, Breast cancer, Tumor growth modeling, Tumors, Surgery, Luminescence, In vivo imaging, Near infrared, Microscopy, Cancer
This conference presentation was prepared for the Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXXI conference at SPIE BiOS 2023.
We are investigating use of methylene blue photodynamic therapy (MB-PDT) to treat deep tissue abscesses. Monte Carlo simulations incorporating patient-specific CT images (60 subjects) were utilized to examine the effect of optical properties on the generation of patient-specific treatment plans. We investigated the influence of varying abscess wall absorption and Intralipid-induced scattering within the cavity on threshold optical power and eligibility for MB-PDT. When Intralipid concentration and delivered optical power were optimized simultaneously for each patient, eligibility for MB-PDT increased greatly from 42% to 92%, though this was diminished by the presence of absorption within the cavity.
Significance: Antimicrobial photodynamic therapy (PDT) effectively kills bacterial strains found in deep tissue abscess cavities. PDT response hinges on multiple factors, including light dose, which depends on patient optical properties.
Aim: Computed tomography images for 60 abscess drainage subjects were segmented and used for Monte Carlo (MC) simulation. We evaluated effects of optical properties and abscess morphology on PDT eligibility and generated treatment plans.
Approach: A range of abscess wall absorptions (μa , wall) and intra-cavity Intralipid concentrations were simulated. At each combination, the threshold optical power and optimal Intralipid concentration were found for a fluence rate target, with subjects being eligible for PDT if the target was attainable with <2000 mW of source light. Further simulations were performed with absorption within the cavity (μa , cavity).
Results: Patient-specific treatment planning substantially increased the number of subjects expected to achieve an efficacious light dose for antimicrobial PDT, especially with Intralipid modification. The threshold optical power and optimal Intralipid concentration increased with increasing μa , wall (p < 0.001). PDT eligibility improved with patient-specific treatment planning (p < 0.0001). With μa , wall = 0.2 cm − 1, eligibility increased from 42% to 92%. Increasing μa , cavity reduced PDT eligibility (p < 0.0001); modifying the delivered optical power had the greatest impact in this case.
Conclusions: MC-based treatment planning greatly increases eligibility for PDT of abscess cavities.
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