Multi-Lens Array (MLA)-Assisted Power- Modulated Photothermal Therapy for Enhanced Cancer Treatment

Photothermal therapy (PTT) has been used as a non-invasive and effective anti-tumor treatment by localizing optical energy in the tissue. The aim of the current study was to investigate the efficacy and safety of PTT against tumor by applying multi-lens arrays (MLA) for having uniform micro-beam distributions and power modulation (MD) for sustaining constant treatment temperature in the tissue. A 1064 nm laser system delivered the equivalent energy (270 J) through two different manners (flat optical fiber; Flat and MLA) to a target under three different irradiation conditions: 1.5 W/cm 2 for 180 s, 3 W/cm 2 for 90 s and 3 W/cm 2 for 60 s followed by 1.5 W/cm 2 for 60 s (MD). In vivo tests demonstrated that MLA was able to expand a distribution of constant temperature (up to 40%) and the extent of thermal coagulation (up to two-fold) in the tumor than Flat. Irrespective of delivery method, MD maintained a constant temperature (around 60 °C) for 60 s, compared to fixed power, resulting in insignificant tumor recurrence ten days after treatment. MLA-assisted PTT with MD could enhance a therapeutic capacity against the tumor tissue by covering a wide treatment area with larger coagulative necrosis and less thermal injury.