Scanning single fiber endoscopy: a new platform technology for integrated laser imaging, diagnosis, and future therapies

Abstract

Remote optical imaging of human tissue in vivo has been the foundation for the growth of minimally invasive medicine. This article describes a new type of endoscopic imaging that has been developed and applied to the human esophagus, pig bile duct, and mouse colon. The technology is based on a single optical fiber that is scanned at the distal tip of an ultrathin and flexible shaft that projects red, green, and blue laser light onto tissue in a spiral pattern. The resulting images are high-quality color video that is expected to produce future endoscopes that are thinner, longer, more flexible, and able to directly integrate the many recent advances of laser diagnostics and therapies.

Figure 1

Timeline of technological innovations in endoscopy and minimally invasive surgery

Figure 2

Distal tip of a SFE probe in cross-section view (vertical expanded 2X more than horizontal for viewing): 1. tube piezoelectric drive signal wiring, 2. piezoelectric mount collar, 3. ring of light collection multimode optical fibers, 4. illumination lens package, 5. piezoelectric tube actuator, 6. scanning single mode optical fiber as a base-excited cantilever, 7. stainless steel tube enclosure. Current size of the rigid distal tip is 1.2 mm in outer diameter and 8 to 10 mm in length for fiber scanning at 30 frames per second at 500-lines per color image. Side-viewing is possible by adding 90-degree reflection at the tip.

Figure 3

Scan method of the SFE. A piezoelectric tube is driven with a sinusoid where the X and Y axes are 90 degrees out of phase while the signal amplitude is modulated. This results in a space-filling spiral scan. Backscattered light measured by the detector at each pixel location is assembled to form an image displayed on a screen. Between frames (*) the fiber scanner is brought to rest and a spectroscopic measurement can be made to diagnose tissue or high-power laser light can be turned on for laser therapy in a frame-sequential manner.

Figure 4

Images of a US Air Force standard resolution target acquired with a monochrome SFE. Figures 4A–C shows an image was acquired with a 30Volt, 15V and 5V scan, respectively. The scanning fiber system acquired these images at 30 Hz, at 250 spirals per scan or 500 lines per image. The SFE used to acquire these images is 1.2 mm in diameter, with a single ring of 50 μm glass multimode fibers used to collect the backscattered light to photomultiplier detectors, and a PENTAX lens assembly was used to focus laser light projected from the scanning fiber. The bar-space patterns on the image are separated by 88.3 μm at location 2–4, 27.9 μm at location 4–2, and by 13.9 μm at location 5–2, top right in 4C. Note there is an ovular indentation marked on the test target that is visible in the magnified images.

Figure 5

5A. TCE probe 5B TCE probe color image of the author’s gastroesophageal junction.

Figure 6

6A. TCE probe being withdrawn from the first human subject with live video image being displayed above the TCE base station in background. 6B Illustration of a duodenoscope launching a SFE probe into the human bile duct, artwork by Duff Hendrickson.

Figure 7

7A. Image from fluoroscope showing (1) SFE probe, (2) bile duct, and (3) duodenoscope, 7B SFE image of the duodenoscope working channel and (4) guide wire, 7C SFE image of the pig bile duct.

Figure 8

8A. Illustration of dissected mouse abdominal cavity, showing distal, medial, and proximal colon as well as caecum 8B. Sample sites along mouse colon 8C. Average IBD and control tissue spectra. Note that every 5^th variable is plotted in this figure, and the dashed lines represent one standard deviation of acquired spectral data.