Compact Smartphone-Based Laser Speckle Contrast Imaging Endoscope Device for Point-of-Care Blood Flow Monitoring: Instrument Validation Study (Preprint)

Abstract

Laser speckle contrast imaging (LSCI) is widely accepted as a powerful visualization tool for quantifying blood flow in tissues. The benefits of this technology include simplicity of configuration, ease of use, and intuitive results. With significant advancements in smartphone and camera technologies, recent attempts have been made to develop a smartphone-based LSCI application that can be used as a Point-Of-Care (POC) device to examine vascular disorders in situ.

A novel smartphone-based portable LSCI endoscope device was developed and validated to perform endoscopic POC testing for the diagnosis of vascular disorders in vivo.

Device implementation: The flexible endoscope consisted of compact light sources (white LED and green laser), imaging optics, and a flexible fiberscope assembled in a 3D printed hand-held cartridge for access and illumination of the cavity organs in the body. The rear camera of the smartphone was mounted on an endoscope for endoscopy and LSCI image acquisition and processing. Tissue-mimicking phantom flow experiment: A 2.5% microparticle mixture was injected into a light-transparent silicon tube with inner-diameter 1.0 mm, submerged in a tissue-mimicking gel to mimic blood flow in tissue. It was then pumped at a constant flow rate (0.023–0.094 ml/min) using a syringe pump. The perfused phantom was imaged using the prototype endoscopic device. In vivo small animal experiment: Healthy Sprague–Dawley rats (n=2) and 0.05% BBN-induced bladder cancer rat models (n=3) were intravenously anesthetized. Their bladders were emptied by rinsing the inner sidewalls with a PBS solution. The probe tip of the endoscope device was used to gain access to the bladder sidewall via the urinary tract for examination.

Blood flow phantom experiment: Tissue phantom blood flow was visualized using raw laser speckle images of the developed endoscope device. The flow was quantified as a speckle flow index (SFI), which showed linearity with the preset pump flow rate. In vivo small animal experiment: The bladders of healthy and cancerous rats were distinguishable in structure and vasculature.

The low-cost portable mobile endoscope device for monitoring blood flow and perfusion changes using a smartphone can be beneficial as a primary diagnostic tool for patients at home and as a cost-effective POC testing assay.