A novel fusion imaging system for endoscopic ultrasound

Abstract

Background and objective: Navigation of a flexible endoscopic ultrasound (EUS) probe inside the gastrointestinal (GI) tract is problematic due to the small window size and complex anatomy. The goal of the present study was to test the feasibility of a novel fusion imaging (FI) system which uses electromagnetic (EM) sensors to co-register the live EUS images with the pre-procedure computed tomography (CT) data with a novel navigation algorithm and catheter.

Methods: An experienced gastroenterologist and a novice EUS operator tested the FI system on a GI tract bench top model. Also, the experienced gastroenterologist performed a case series of 20 patients during routine EUS examinations.

Results: On the bench top model, the experienced and novice doctors reached the targets in 67 ± 18 s and 150 ± 24 s with a registration error of 6 ± 3 mm and 11 ± 4 mm, respectively. In the case series, the total procedure time was 24.6 ± 6.6 min, while the time to reach the clinical target was 8.7 ± 4.2 min.

Conclusions: The FI system is feasible for clinical use, and can reduce the learning curve for EUS procedures and improve navigation and targeting in difficult anatomic locations.

Figure 1

The FI system components. There are four coordinate systems (CS1-4) used during registration to provide the framework for moving between the pre-operative CT and the intraoperative EUS imagery: between the image coordinates and the navigation catheter, and between the navigation catheter and the 3-D display

Figure 2

The FI system interface during the phantom feasibility testing procedure: (a) active marker and target selection window, and (b) navigation window for hybrid imaging CT-EUS procedure

Figure 3

The 3-D reconstruction of the GI tract phantom model from CT scans. External white registration markers are visible on the box walls. Several tumor markers are positioned on the central (white) tubing which represents the GI tract

Figure 4

(a) Representative screen shot of the FI system interface during an EUS-CT procedure in a patient with A - co-registration at the level of the descending aorta (red arrows), imaged from the esophagus; and (b) co-registration at the level of a small submucosal tumor (lipoma, red arrows), imaged from the terminal esophagus. Beside the vascular structures and/or target structure (tumor), there is no correspondence in between anatomical structures visible on EUS and CT windows, as the lung tissue (containing air) and bony structures (spine) are visible only on CT, while EUS has a limited field of view