Preclinical-grade microendoscope for optical coherence tomography and angiography inside the bladder

Abstract

We present a preclinical-grade, forward-viewing endomicroscope for in-contact optical coherence tomography (OCT) and optical coherence angiography (OCA) imaging through the working channel of a conventional cystoscope. Beam scanning is achieved with a fiber scanner driven by a tubular piezoelectric actuator. A focusing lens at the fiber tip helps engineering of the operation frequency within a compact probe length to avoid lateral undersampling. Microstructuring of fused silica through selective laser-induced etching was used for manufacturing a self-aligning housing for the probe head. The entire micro-optical system is assembled and encapsulated within a custom-developed sterilizable packaging with 4.5 mm outer diameter. The presented design and fabrication strategy can be used for any forward-viewing probe, independent of its imaging modalities. We demonstrate OCT imaging within a 2.1-mm diameter field of view at a transverse resolution of 19 μm and microvasculature visualization through OCA. The presented probe's mechanical characteristics and optical performance make it particularly attractive for outpatient care use in the detection of tissue pathology inside the bladder. The presented fabrication methodology provides a reliable strategy for enabling preclinical trials with endoscopic imaging probes.

Magnetic position sensing for self-calibration and image registration of scanning fiber endoscopes

“…With a custom-developed encapsulation, this probe was proved to survive multiple standard sterilization process for multiple use. 16 After sterilization, the dynamic behavior of the scanner changed noticeably, which imposed the need of open-loop calibration before every measurement session. 16 Figure 4 shows a rendering and a schematic of the modified endomicroscope with the position sensor.…”

“…16 After sterilization, the dynamic behavior of the scanner changed noticeably, which imposed the need of open-loop calibration before every measurement session. 16 Figure 4 shows a rendering and a schematic of the modified endomicroscope with the position sensor. The excitation/collection light is delivered to/from the probe head to the proximal end through a single mode fiber (SM980G80, Thorlabs Inc.), which also acts as the scanning cantilever.…”

“…For actuation, the probe features a tubular piezoelectric actuator 0.8 mm in outer diameter and 3.7 mm in length (custom manufactured by PI Ceramic GmbH, Germany). The main difference of this new probe design compared to the probe discussed in our work 16 is the functional fiber tip, which serves both as the focusing element with an aspheric surface at its distal end, and as the mount for the micro-magnet (R0100D-10, SuperMagnetMan LLP, properties listed above). We used a commercial 3D nano-printer (Photonic Professional GT+, Nanoscribe GmbH, Germany) to manufacture this element.…”

“…In addition, a glass structure with precision passive alignment features produced using the same process enclosed both the optical and mechanical components. With a custom-developed encapsulation, this probe was proved to survive multiple standard sterilization process for multiple use 16 . After sterilization, the dynamic behavior of the scanner changed noticeably, which imposed the need of open-loop calibration before every measurement session 16 …”

“…Since it is not model-based, it can also accommodate nonlinear scanner behavior. We incorporated this sensor in an OCT endomicroscope that we have recently published 15 , 16 by modifying the on-tip optics of a fiber scanner. We discuss the details of the field-to-position mapping, and the sensor data post-processing methods necessary to attain accurate position information.…”