Near-infrared Navigation System for Real-time Visualization of Blood Flow in Vascular Grafts

Summary

We describe the procedure for real-time monitoring of blood flow in vascular grafts using indocyanine green (ICG), a near-infrared (NIR) dye, and a portable near-infrared navigation (NAVI) detectible camera system. The flow of dye in vascular grafts and the camera efficiency have been compared with Doppler and cine-angiography procedures.

Abstract

Vascular grafting failures are often attributed to inadequate anastomotic perfusion assessments. If successful, vascular anastomosis can be rapidly confirmed through the visualization of continuous blood flow upon completion of the grafting process. Surgeons can then minimize graft failures, thus decreasing morbidity in a cost-effective manner. Fluorescence image-guided surgery using near-infrared (NIR) dye is one of the methods that can be performed to monitor grafting success. To address the current logistical challenges and costs of these systems, a compact camera system was used for intraoperative fluorescence real-time NIR imaging. Combined with benchtop experiments, a swine model was used to demonstrate the procedure of using a near-infrared navigation system (NAVI) to visualize grafted vessels in vivo. This was done by performing bilateral arteriovenous grafts and imaging intravenously injected ICG as it circulated through the grafted vessels. The fluorescent images obtained by NAVI were corroborated with Doppler flow measurements and cine-angiography, the current gold standard for the evaluation of vascular grafts.

Introduction

Intraoperative assessments of blood flow following arterial or venous grafting, as well as direct visualization methods evaluating anastomosis, allow surgeons to make immediate decisions on the likelihood of success or failure, allowing for repair, if needed^1,2. Techniques frequently employed are fluoroscopic angiography³, direct visualization, palpation of pulsatile flow, pulse oximetry², Doppler ultrasound⁴, transit time flowmetry^5,6,7, computed....

Protocol

Animal studies were performed following approval from the University of Missouri Animal Care and Use Committee. The University of Missouri is USDA-licensed and AAALAC-International accredited.

1. Pre-operation procedure

1. Obtain a domestic Yorkshire/large white pig (4 months old; 57 kg) one day prior to the study and provide water ad libitum.
2. Sedate the pig with 5 mg/kg Telazol and 2.2 mg/kg xylazine. Provide 3-4% isoflurane by nose cone until the pig can be intuba.......

Discussion

Development of NAVI for ICG Imaging Applications

NIR-based fluorescence imaging is emerging as a simple alternative procedure for intraoperative imaging, demonstrating significant benefits by: (1) eliminating the radiation exposure required by fluoroscopy and computed tomography and (2) reducing the surgical time, thus decreasing per-patient costs while maintaining efficacy and increasing safety. In this paper, we demonstrated the procedure for using NAVI to perform fluorescence imaging (using IC.......

Materials

Name	Company	Catalog Number	Comments
Telazol	Zoetis		Reconstitute with sterile water prior to use
Xylazine (AnaSed)	AKORN Animal Health
0.9% NaCl	Abbott
Indocyanine green	AKRON
Heparin	Baxter
Visipaque (iodixanol)	GE Healthcare	564v
Guide catheter	Boston Scientific
LED 770-03AU, 18 mW	Roithner Laser Technik GmbH, Wiedner Hauptstrasse, Austria
Short pass filter	Edmund optics, Barrington, NJ, USA
NIR imaging  camera (Igen NV20/20-IC)	B&H optics, New york, NY, USA
Micropac USB-AVCPT interface	Sabrent, USA
CT instrument	Varian Medical System manufactured by Omega Medical Imaging
TS420 Perivascular Flow Module	Transonic Systems Inc., Ithaca, NY	TS420 & T402
PR Series Flow Probes	Transonic Systems Inc., Ithaca, NY	3PSB
Digital Board to Flow module	ADInstruments Inc., Colorado Springs, CO
Lab Chart	ADInstruments Inc., Colorado Springs, CO