Conventional photothermal therapy (PTT) for cancer typically employs an end-firing flat fiber (Flat) to deliver laser energy, leading to the incomplete treatment of target cells due to a Gaussian-shaped non-uniform beam profile. The purpose of the current study is to evaluate the feasibility of multi-lens arrays (MLA) for enhanced PTT by delivering laser light in a fractional micro-beam pattern. Computational and experimental evaluations compare the photothermal responses of gelatin phantoms and aqueous dye solutions to irradiations with Flat and MLA. In vivo colon cancer models have been developed to validate the therapeutic capacity of MLA-assisted irradiation. MLA yields 1.6-fold wider and 1.9-fold deeper temperature development in the gelatin phantom than Flat, and temperature monitoring identified the optimal treatment condition at an irradiance of 2 W/cm2 for 180 s. In vivo tests showed that the MLA group was accompanied by complete tumor eradication, whereas the Flat group yielded incomplete removal and significant tumor regrowth 14 days after PTT. The proposed MLA-assisted PTT spatially augments photothermal effects with the fractional micro-beams on the tumor and helps achieve complete tumor removal without recurrence. Further investigations are expected to optimize treatment conditions with various wavelengths and photosensitizers to warrant treatment efficacy and safety for clinical translation.

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Thermal responses of adipose tissue to high intensity focused ultrasound (HIFU) were quantitatively evaluated for effective clinical lipolysis. A single-element HIFU transducer (4 MHz and 4.5 mm focal depth) was used in a linear motion to thermally treat the tissue at various acoustic energy densities and treatment gaps. Both interstitial temperature rise and denatured lesions increased with the energy density (up to 21.1 ± 1.9 K and 0.40 ± 0.15 mm2). No thermal overlapping was observed due to selective application of the ultrasonic beams. The optimization of noninvasive HIFU treatment parameters may ensure clinical outcomes of HIFU-assisted lipolysis in terms of efficacy and safety.

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