Real-time photoacoustic sensing for photo-mediated ultrasound therapy

High speed photo-mediated ultrasound therapy integrated with OCTA

Photo-mediated Ultrasound Therapy (PUT), as a new anti-vascular technique, can promote cavitation activity to selectively destruct blood vessels with a significantly lower amount of energy when compared to energy level required by other laser and ultrasound treatment therapies individually. Here, we report the development of a high speed PUT system based on a 50-kHz pulsed laser to achieve faster treatment, decreasing the treatment time by a factor of 20. Furthermore, we integrated it with optical coherence tomography angiography (OCTA) for real time monitoring. The feasibility of the proposed OCTA-guided PUT was validated through in vivo rabbit experiments. The addition of OCTA to PUT allows for quantitative prescreening and real time monitoring of treatment response, thereby enabling implementation of individualized treatment strategies.

Synchronous enhancement of upconversion and NIR-IIb photoluminescence of rare-earth nanoprobes for theranostics

This study develops a multifunctional molecular optical nanoprobe (SiO₂@Gd₂O₃: Yb³⁺/Er³⁺/Li⁺@Ce6/MC540) with a unique core-satellite form. The rare-earth doped nanodots with good crystallinity are uniformly embedded on the surface of a hydrophilic silica core, and the nanoprobe can emit near-infrared-IIb (NIR-IIb) luminescence for imaging as well as visible light that perfectly matches the absorption bands of two included photosensitizers under 980 nm irradiation. The optimal NIR-IIb emission and upconversion efficiency are attainable via regulating the doping ratios of Yb³⁺, Er³⁺ and Li⁺ ions. The relevant energy transfer mechanism was addressed theoretically that underpins rare-earth photoluminescence where energy back-transfer and cross relaxation processes play pivotal roles. The nanoprobe can achieve an excellent dual-drive photodynamic treatment performance, verified by singlet oxygen detections and live-dead cells imaging assays, with a synergistic effect. And a brightest NIR-IIb imaging was attained in tumoral site of mouse. The nanoprobe has a high potential to serve as a new type of optical theranostic agent for tumor.

Photo-mediated ultrasound therapy for the treatment of retinal neovascularization in rabbit eyes

Objectives

Retinal neovascularization (RNV) is the growth of abnormal microvessels on the retinal surface and into the vitreous, which can lead to severe vision loss. By combining relatively low‐intensity ultrasound and nanosecond‐pulse‐duration laser, we developed a novel treatment method, namely photo‐mediated ultrasound therapy (PUT), which holds a potential to remove RNV with minimal or no damage to the adjacent tissues.

Methods

RNV was created in both albino and pigmented rabbits (n = 10) through a single intravitreal injection with DL‐α‐aminoadipic acid. RNV was treated with PUT 8 weeks postinjection. After PUT treatment, animals were evaluated longitudinally for up to 6 weeks. Treatment outcomes were evaluated through fundus photography, red‐free fundus photography, fluorescein angiography (FA), and histopathology.

Results

In both albino and pigmented rabbits, there were no leakage in the treatment area immediately after PUT treatment as demonstrated by FA, indicating the cessation of blood perfusion of the RNV in the treated area. The fluorescence leakage did not recover in albino rabbits during the 6‐week posttreatment monitoring period, and only 9.9 ± 9.8% of the neovascularization remained at the end of 6 weeks. In the pigmented rabbits, the fluorescence leakage partially returned, but the level of leakage decreased over time during the 6‐week posttreatment monitoring period, and only 10.8 ± 9.8% of the neovascularization remained at the end of 6 weeks. Histology demonstrated removal of vasculature without damage to the surrounding neurosensory retina.

Conclusions

These results demonstrate that PUT could precisely remove RNV without damage to the surrounding neurosensory retina in both rabbit strains.

Photo-Mediated Ultrasound Therapy for the Treatment of Corneal Neovascularization in Rabbit Eyes

Purpose

Corneal neovascularization (CNV) is the invasion of new blood vessels into the avascular cornea, leading to reduced corneal transparency and visual acuity, impaired vision, and even blindness. Current treatment options for CNV are limited. We developed a novel treatment method, termed photo-mediated ultrasound therapy (PUT), that combines laser and ultrasound, and we tested its feasibility for treating CNV in a rabbit model.

Methods

A suture-induced CNV model was established in New Zealand White rabbits, which were randomly divided into two groups: PUT and control. For the PUT group, the applied light fluence at the corneal surface was estimated to be 27 mJ/cm² at 1064-nm wavelength with a pulse duration of 5 ns, and the ultrasound pressure applied on the cornea was 0.43 MPa at 0.5 MHz. The control group received no treatment. Red-free photography and fluorescein angiography were utilized to evaluate the efficiency of PUT. Safety was evaluated by histology and immunohistochemistry. For comparison with the PUT safety results, conventional laser photocoagulation (LP) treatment was performed with standard clinical parameters: 532-nm continuous-wave (CW) laser with 0.1-second pulse duration, 450-mW power, and 75-µm spot size.

Results

In the PUT group, only 1.8% ± 0.8% of the CNV remained 30 days after treatment. In contrast, 71.4% ± 7.2% of the CNV remained in the control group after 30 days. Safety evaluations showed that PUT did not cause any damage to the surrounding tissue.

Conclusions

These results demonstrate that PUT is capable of removing CNV safely and effectively in this rabbit model.

Translational Relevance

PUT can remove CNV safely and effectively.

The Effect of Laser and Ultrasound Synchronization in Photo-Mediated Ultrasound Therapy

OBJECTIVE

Photo-mediated ultrasound therapy (PUT) is a novel, non-invasive, agent-free, highly selective, and precise anti-vascular technique. PUT removes microvessels through promoting cavitation activity precisely in targeted microvessels by applying synchronized nanosecond laser pulses and ultrasound bursts. The synchronization between laser and ultrasound is critical to the outcome of PUT.

METHODS

Through theoretical simulation and experimental study, the effect of synchronization between laser pulses and ultrasound bursts on cavitation activity during PUT is evaluated.

RESULTS

By using a theoretical model, we found that cavitation activity was enhanced when laser pulses and ultrasound bursts were synchronized such that the produced photoacoustic wave overlaid the rarefactional phase of the ultrasound wave. This finding was then verified through in vitro studies where cavitation was monitored by using a passive cavitation detector. Furthermore, we demonstrated that the in vivo treatment outcome of PUT in rabbits was directly related to the synchronization between laser and ultrasound. The anti-vascular effect could only be observed when laser and ultrasound were properly synchronized in vivo.

CONCLUSION

PUT is more efficient when the laser-induced photoacoustic wave overlays the rarefactional phase of the ultrasonic wave.

SIGNIFICANCE

This is a systematic study to investigate the synchronization effect of PUT, which would be significant for further understanding the mechanism and further improving the treatment efficiency of PUT.

Photo-mediated Ultrasound Therapy to Treat Retinal Neovascularization

This report describes a novel therapeutic technique called photo-mediated ultrasound therapy (PUT). PUT applies synchronized short pulse duration (nanosecond) laser and ultrasound burst on targeted tissue, offering high-precision localized treatment. PUT is based on controlled induction and promotion of micro-cavitation activity in the target tissue. PUT is able to safely and effectively treat retinal neovascularization in rabbits with persistent nonperfusion up to 4 weeks after PUT in the choroidal vasculature.Clinical Relevance- PUT can selectively remove retinal angiogenesis in clinically-relevant disease models in humansized eyes (rabbit) without damaging surrounding tissue.

3-D X-Ray-Induced Acoustic Computed Tomography With a Spherical Array: A Simulation Study on Bone Imaging

X-ray-induced acoustic computed tomography (XACT) is a promising imaging modality combining high X-ray absorption contrast with the 3-D propagation advantages provided by high-resolution ultrasound waves. The purpose of this study was to optimize the configuration of a 3-D XACT imaging system for bone imaging. A 280 ultrasonic sensors with peak frequency of 10 MHz was designed to distribute on a spherical surface to optimize the 3-D volumetric imaging capability. We performed both theoretical calculations and simulations of this optimized XACT imaging configuration on a mouse-sized digital phantom containing various X-ray absorption coefficients. Iteration algorithm based on total variation has been used for 3-D XACT image reconstruction. The spatial resolution of imaging was estimated to about [Formula: see text] along both axial and lateral directions. We simulate XACT imaging of bone microstructures using digital phantoms generated from micro-CT images of real biological samples, showing that XACT imaging can provide high-resolution imaging of the mouse paw. Results of this study will greatly enhance the potential of XACT imaging in the evaluation of bone diseases for future clinical use.