A 1.2 mm proximal scanning endoscopic OCT probe was developed for 3-D imaging as shown in Fig. 1(b). Rotational scanning is accomplished by using a fiber optic rotary joint (Princetel Inc., Pennington, New Jersey) coupled with a rotational motor (Animatics, Santa Clara, California). Torque from the motor is translated from the proximal to the distal end of the probe by a triple wound commercial torque coil with an outer diameter (OD) of 0.965 mm (Asahi Intecc, Santa Ana, California). In order to achieve long-range imaging, the probe was designed to have an extended working distance of 20 mm. Focusing of the light is accomplished via a gradient index (GRIN) lens (0.23 pitch, 1 mm OD, GoFoton, Somerset, New Jersey) together with a precisely measured spacer made from no-core fiber. The no-core fiber was first spliced and then cleaved to leave a 280 µm portion at the end of standard single-mode fiber. The fiber and GRIN lens were attached with ultraviolet (UV) glue before placement within a custom-designed metal housing for protection. During imaging, the probe was proximally rotated within a protective fluorinatedethylenepropylne (FEP) sheath (1.8 mm OD, Zeus Inc., Orangeburg, South Carolina) at a rate of 25 frames per second. A dual motor linear stage (Zaber Technologies Inc., Vancouver, British Columbia) was used for linear translation, allowing for helical scanning over 20 cm in the span of 40 s. The axial resolution of the system was 10 µm in tissue and the lateral resolution at the focal point of the probe was 112 µm, which is mainly a tradeoff with extending the working distance of the probe.