Low-cost diffuse optical spectroscopy for assisting sclerotherapy: A proof-of-concept study

Vascular malformations are localized anomalies in vascular morphogenesis. They are present at birth and never regress. Common clinical symptoms include pain, swelling, bleeding, functional impairment, airway obstruction, cosmetic deformities, and even death. Generally, the first-line treatment for low-flow vascular malformations is typically sclerotherapy, which involves injecting sclerosing agents to cause thrombosis, fibrosis, stenosis, and eventual regression of the treated vessels. Various imaging technologies, such as digital subtraction angiography, magnetic resonance angiography, ultrasound imaging, and photoacoustic microscopy, have assisted sclerotherapy. However, these methods often suffer from high costs, the need for skin contact, radiation exposure risks, and the use of contrast agents. In this study, we propose diffuse optical spectroscopy (DOS) as a new technique to assist sclerotherapy through vascular monitoring. We conducted Monte Carlo simulations and phantom experiments using low-cost continuous-wave DOS (CW-DOS) to demonstrate its remarkable sensitivity to the concentration of sclerotic blood. In addition, two in vivo rabbit experiments were performed to show its capability of monitoring thrombus formation and detecting sclerotic blood at different concentrations in real animals. The results show a monotonic decrease in diffuse reflectance signal intensity with increasing concentration of sclerotic blood or observation time post-injection of sclerosing agents. Therefore, CW-DOS shows potential as a valuable tool in assisting sclerotherapy through real-time vascular monitoring, offering advantages of low cost, non-contact operation, safety, and the absence of contrast agents.