Imaging directed photothermolysis through two-photon absorption demonstrated on mouse skin - a potential novel tool for highly targeted skin treatment

Precise closure of single blood vessels via multiphoton absorption-based photothermolysis

We report a novel approach to selectively close single blood vessels within tissue using multiphoton absorption-based photothermolysis (multiphoton photothermolysis) without the need of exogenous agents. The treatment process is monitored by in vivo reflectance confocal microscopy in real time. Closure of single targeted vessels of varying sizes ranging from capillaries to venules was demonstrated. We also demonstrated that deeply situated blood vessels could be closed precisely while preserving adjacent overlying superficial blood vessels. In vivo confocal Raman spectroscopy of the treatment sites confirmed vessel closure as being mediated by local coagulative damage. Partial vessel occlusion could be achieved, and it is accompanied by increased intravascular blood cell speed. Multiphoton photothermolysis under real-time reflectance confocal imaging guidance provides a novel precision medicine approach for noninvasive, precise microsurgery treatment of vascular diseases on a per-vessel/per-lesion basis. The method could also be used for building ischemic stroke models for basic biology study.

Precise Spatially Selective Photothermolysis Using Modulated Femtosecond Lasers and Real-time Multimodal Microscopy Monitoring

The successful application of lasers in the treatment of skin diseases and cosmetic surgery is largely based on the principle of conventional selective photothermolysis which relies strongly on the difference in the absorption between the therapeutic target and its surroundings. However, when the differentiation in absorption is not sufficient, collateral damage would occur due to indiscriminate and nonspecific tissue heating. To deal with such cases, we introduce a novel spatially selective photothermolysis method based on multiphoton absorption in which the radiant energy of a tightly focused near-infrared femtosecond laser beam can be directed spatially by aiming the laser focal point to the target of interest. We construct a multimodal optical microscope to perform and monitor the spatially selective photothermolysis. We demonstrate that precise alteration of the targeted tissue is achieved while leaving surrounding tissue intact by choosing appropriate femtosecond laser exposure with multimodal optical microscopy monitoring in real time.

Modern trends in biophotonics for clinical diagnosis and therapy to solve unmet clinical needs

This contribution covers recent original research papers in the biophotonics field. The content is organized into main techniques such as multiphoton microscopy, Raman spectroscopy, infrared spectroscopy, optical coherence tomography and photoacoustic tomography, and their applications in the context of fluid, cell, tissue and skin diagnostics. Special attention is paid to vascular and blood flow diagnostics, photothermal and photodynamic therapy, tissue therapy, cell characterization, and biosensors for biomarker detection.

Simultaneous spatial frequency modulation imaging and micromachining with a femtosecond laser

A Ti:Al2O3 chirped-pulse amplification system is used to simultaneously image and machine. By combining simultaneous spatial and temporal focusing (SSTF) with spatial frequency modulation for imaging (SPIFI), we are able to decouple the imaging and cutting beams to attain a resolution and a field-of-view that is independent of the cutting beam, while maintaining single-element detection. This setup allows for real-time feedback with the potential for simultaneous nonlinear imaging and imaging through scattering media. The novel SSTF machining platform uses refractive optics that, in general, are prohibitive for energetic, amplified pulses that might otherwise compromise the integrity of the focus as a result of nonlinear effects.

Confocal microscopy to guide erbium:yttrium aluminum garnet laser ablation of basal cell carcinoma: an ex vivo feasibility study

For the removal of superficial and nodular basal cell carcinomas (BCCs), laser ablation provides certain advantages relative to other treatment modalities. However, efficacy and reliability tend to be variable because tissue is vaporized such that none is available for subsequent histopathological examination for residual BCC (and to confirm complete removal of tumor). Intra-operative reflectance confocal microscopy (RCM) may provide a means to detect residual tumor directly on the patient and guide ablation. However, optimization of ablation parameters will be necessary to control collateral thermal damage and preserve sufficient viability in the underlying layer of tissue, so as to subsequently allow labeling of nuclear morphology with a contrast agent and imaging of residual BCC. We report the results of a preliminary study of two key parameters (fluence, number of passes) vis-à-vis the feasibility of labeling and RCM imaging in human skin ex vivo, following ablation with an erbium:yttrium aluminum garnet laser.