Dr. Victor X. D. Yang Profile

Dr. Victor X. D. Yang

at Univ of Toronto

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Publications (2)

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Proceedings Article | 4 March 2022 Presentation + Paper

Dynamic laser-based photomodulation of endovascular hydrogel embolization for the treatment of various cerebrovascular disorders

Jerry Ku, Yuta Dobashi, Christopher Pasarikovski, Joel Ramjist, John D. Madden, Konrad Walus, Victor X. Yang

Proceedings Volume 11945, 1194503 (2022) https://doi.org/10.1117/12.2605294

KEYWORDS: Aneurysms, Animal model studies, Angiography, Tumors, Polymers, Blood vessels

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Introduction: Endovascular embolization is becoming an increasingly utilized method of treating a variety of neurovascular disorders, including aneurysms, arteriovenous malformations (AVMs), and tumors. Many of the existing limitations of this treatment are related to the embolization agents currently available, including material compaction or migration, disease recurrence, or off-target embolization. Hydrogels are a promising class of materials that may be utilized to address some of these concerns. Methods: We compounded hydrogel formulations that were low-viscosity, shear thinning, photo-sensitive, and radioopaque. We developed a method of intravascular micro-catheter hydrogel delivery with dynamic modulation of hydrogel physical characteristics at the tip of the catheter, via photo-crosslinking with an integrated UV emitting optical fibre. This allowed for rapid transition from liquid to solid state to block blood flow at the vascular target, as well as dynamic modulation to suit the needs of a variety of neurovascular disorders. We performed preliminary testing of this novel methodology in animal models of neurovascular disease. Results: With dynamic modulation of photo-crosslinking, we were able to deliver hydrogels with a viscosity range of up to 10^4 Pa*s. The technique allowed for successful deposition of the hydrogel precursor in animal models for aneurysms, AVMS, and tumors. Post-procedural angiography demonstrated satisfactory occlusion of target vessels without evidence of complications. Conclusions: This novel embolization method holds promise in improving the safety and efficacy of the endovascular treatment of a variety of different pathologies and should be investigated further with direct comparative studies.

Proceedings Article | 4 March 2022 Poster + Paper

Optimizing conditions for light delivery for intracranial photodynamic therapy for high grade gliomas: a 3D model study of light dosimetry

Jerry Ku, Yuta Dobashi, Joel Ramjist, Christopher Pasarikovski, Victor X. Yang

Proceedings Volume 11940, 119400I (2022) https://doi.org/10.1117/12.2605333

KEYWORDS: 3D modeling, Photodynamic therapy, Optical fibers, Tumors, Tissue optics, Light scattering, Light emitting diodes, Blood

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Introduction: Photodynamic therapy (PDT) is a promising adjunctive treatment for high grade brain tumors. However, early clinical trials have utilized significant variations in the conditions of light delivery, including the type of fibre and diffusing fluid. Our goal of this study was to sweep these conditions to determine optimal parameters for light delivery to the tumor resection cavity using a 3D model. Method: A 3D model to mimic an intracranial cavity was created and a PDT device was assembled using multiple 2W output lasers connected to cylindrical diffusing fibres. A variety of light delivery conditions were tested, including the use of bare fibres versus fibres placed inside balloon catheters, with deionized water or intralipid solutions. India ink was utilized to mimic blood products in the resection cavity. Light intensity at the edge of the model, signifying incident intensity at the tissue surface, was measured in multiple axes to assess for strength and uniformity. Light intensity and uniformity were compared between groups using Kruskal-Wallis analysis of variance. Results: Light delivery was significantly higher with the bare fibre compared to the balloon catheter across all types of circulating fluid (34.2 ± 3.54 vs. 30.8 ± 1.31 mV/cm2, p<0.05), but less uniform. The light uniformity increased as the concentration of intralipid increased. In conditions with the addition of india ink, the bare fibre performed better than the balloon catheter. Conclusion: In this phantom model assessment, bare fibres with 0.1% or 0.5% intralipid solution led to improved light delivery compared to other parameters. Photodynamic therapy of the cavity following surgical resection of HGG should be performed with optimal light delivery parameters to ensure treatment efficacy.

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