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Photothermal therapy (PTT) has garnered considerable attention as an attractive treatment tool for cancer due to precisely selective treatment and minimal side effects. The primary challenge of PTT, which hinders its widespread application, is the limited therapeutic depth. This limitation arises from optical scattering in biological tissues, causing inadequate heat distribution within the deep tissue. To overcome this challenge, ultrasound‐assisted PTT (ULTRA‐PTT) is proposed that leverages the temporary formation of gas bubbles induced by ultrasound within the light propagation path. These bubbles act as optical clearing agents, effectively reducing optical scattering in biological tissues. To facilitate ULTRA‐PTT, a dedicated handpiece consisting of a ring‐shaped ultrasound transducer and a laser delivery module is developed. In‐vivo experiments show that ULTRA‐PTT statistically outperforms conventional PTT in melanoma treatment, mostly due to its ability to deliver sufficient laser energy to deep‐seated cancer cells. These findings underscore the potential of ULTRA‐PTT to expand the clinical applications of PTT beyond local tumors occurring in superficial tissue. [ABSTRACT FROM AUTHOR]

Ultrasound-induced optical clearing microscopy (US-OCM) addresses limited imaging depth in optical microscopy, caused by light scattering in biological tissues. It uses ultrasound-induced gas bubbles to better image biological samples. However, controlling the bubble location using only ultrasound is challenging. This study introduces a novel method, "optrasound," combining optical and ultrasound energies for precise bubble control. It presents the ultrasound field and uses a focused laser to trigger bubble formation. Optrasound-induced deep microscopy improves light beam width by 3.39 times at a depth of 350 µm because the gas bubbles reduce light scattering. This technique can precisely localize a bubble cloud while matching the US-OCM performance. [ABSTRACT FROM AUTHOR]

Dermatological lesions are typically located just a few millimeters below the surface of the skin, which constrains the efficacy of optical-based therapeutic methods such as photothermal and photodynamic therapy due to limited therapeutic depth caused by optical scattering. As an alternative, high-intensity focused ultrasound (HIFU) has been explored for its potential to treat a variety of dermatological conditions because it offers greater flexibility in terms of treatment depth. Since dermatological lesions have a small thickness ranging from 1.5 to 2.0 mm, high-frequency ultrasound (3-10 MHz or higher) is preferred as the focal area is proportional to the operating frequency. However, due to the difficulty in fabricating HIFU array transducers at this frequency range, the majority of HIFU treatments for dermatology rely on single element transducers. Despite the advantages of HIFU, single-element-based HIFU systems are limited in prevalent use for dermatology treatment due to their fixed focal length and mechanical movement for treatment, which can be time-consuming and unsuitable for treating multiple lesions. To address this, we present a newly developed HIFU linear array and 128-channel driving electronics specifically designed for dermatology treatment. This array consists of 128 elements, has a center frequency of 3.7 MHz, an elevation focal length of 28 mm, and an F-number of 1.27 in the elevation direction. The array has a footprint of 71.6 mm by 22 mm. Experiments using a tissue-mimicking phantom have demonstrated that the HIFU linear array and system are capable of transmitting sufficient ultrasound energy to create coagulation inside the phantom., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)