Development of an MR-Compatible High-Definition Flexible Endoscope for Real-Time MR Image-Guided Microwave Ablation

This study aims to develop a magnetic resonance (MR)-compatible flexible endoscope for minimally invasive real-time MR image-guided microwave ablation as proposed by the author with a widely available 3-Tesla close-bore MR scanner and to assess the feasibility of including a position tracking sensor. A unique MR-compatible high-definition (HD) endoscope was developed to access a target organ from outside the scanner bore by obtaining endoscope optical camera and scan images simultaneously. The camera unit consists of a CMOS image sensor with 400 x 400 pixels. The camera head and the lens barrel are made of phosphor bronze and a Pebax elastomer sheath with a 2.1 mm diameter shielded by tin-plated copper wires. The image resolution was up-converted to 700 x 700 pixels using a high-resolution image processing technique. The endoscope had two working channels (2.0 mm in each outer diameter) and two sensor ports (2.5 mm in each outer diameter). One port had a gradient-magnetic-based tracking sensor to identify the tip position and orientation; the outer diameter and length of the endoscope were 11 and 1200 mm. A pig was scanned as a pre-procedural MR image and the result was used as navigation images to assess the endoscope's feasibility. The camera image quality was sufficient to identify organs without critical noise during scanning, and its resolution was 295 times that of the conventional MR-compatible fiber endoscope we developed. The refresh rates of the sensor position and orientation were <0.5 s, which includes data transmission from the scanner to the navigation software. The verification study showed that the proposed MR-compatible endoscope has the potential to enable a surgeon to access target organs from the outside bore while simultaneously obtaining optical and scanned images.