Flexible miniature compound lens design for high-resolution optical coherence tomography balloon imaging catheter

Abstract

We report on a new optics design for an optical coherence tomography (OCT) balloon imaging catheter. The design involves a miniature compound gradient-index (GRIN) rod lens, which consists of a fiber optic mode-field reducer and relay rod lenses to achieve predictable high lateral resolution at a desired large working distance. The compound lens design significantly simplifies the engineering process for an OCT catheter and enables 3-D full circumferential cross sectional imaging of large luminal organs such as human esophagus. An as-designed OCT catheter is developed and demonstrated for real-time in vivo swine esophagus imaging in a 3-D spiral fashion. Keywordsoptical coherence tomography; endomicroscopy; balloon catheter; internal organ imaging Optical coherence tomography (OCT) is a rapidly evolving noninvasive imaging technology that provides high-resolution cross sectional images of tissue microanatomy. 1 While initially applied to eye imaging, the development of miniature fiber optic catheters/endoscopes has enabled high-resolution OCT imaging of internal luminal organs in vivo. Most of the OCT catheters developed so far have a small diameter (e.g., ∼1 to 2 mm), a high lateral resolution (e.g., 15 to 40 µm), and a short working distance (e.g., 1 to 4 mm). 2-6 These catheters are well suited for imaging small lumens or for imaging only a small sector of large lumens when the probes are in direct contact with the tissue surface. The short working distance unfortunately precludes full circumferential imaging of large luminal organs such as human esophagus (which has a diameter of ∼ 18 to 25 mm when the natural esophageal folds are flattened e.g., by balloon inflation). There is an increasing clinical need for systematic imaging assessment of the entire esophagus for Barrett's esophagus surveillance and early cancer detection, 7,8 inspiring strong interest in developing a new type of OCT catheter-a balloon imaging catheter, which basically integrates a miniature OCT imaging probe within the inner lumen of a doublelumen balloon catheter with the balloon (when inflated) to flatten the natural folds of the esophagus. The concept of such an OCT balloon imaging catheter was introduced in 2000 and was recently demonstrated for imaging the entire esophagus. 9,10 A major challenge with the OCT imaging probe is achieving a small focused spot size (i.e., high transverse resolution) at a large working distance (e.g., 9 to 12 mm) while keeping the optical components small (e.g., NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript of a diameter 1 to 2 mm), so that the imaging probe would be able to pass through a small inner balloon tubing and shaft, while the entire balloon catheter can be delivered into the esophagus through a 2.8-to 3.4-mm accessory port of a standard gastrointestinal (GI) endoscope. The systematic OCT imaging of the entire esophagus can then be integrated with a routine endoscopy procedure.We present a new optics design for the OCT balloon imaging catheter. Different fr...

High‐Resolution Optical Coherence Tomography Imaging in Gastroenterology

“…One solution to this dilemma was to use a balloon-based centering device ( Figure 6.1A). Balloonbased helical scanning catheters act to dilate the esophagus and to center and stabilize the imaging optics within the lumen [15][16][17]. This is advantageous when the lumen size is large and exceeds the ranging depth of the OCT imaging system.…”

Photoacoustic imaging and characterization of the microvasculature

“…10͒. In the future, a spiral-scanning mechanism can be adopted from OCT endoscopy 80 for volumetric imaging.…”

Circumferential optical coherence tomography angiography imaging of the swine esophagus using a micromotor balloon catheter

“…Circumferential beam scanning was originally implemented with proximal rotary actuation transmitted by a torque cable housing the optical fiber. Later studies demonstrated an optical design using miniature compound gradient-index rod lenses to achieve a small focused spot size (~39 µm, full width at half maximum (FWHM)) at a ~9 mm working distance [7]. In addition, high resolution balloon OCT imaging was achieved by correcting the astigmatism from the plastic sheath with a cylindrical aluminum reflector [8].…”