A system for visualizing a tissue region of interest includes an imaging element, a sheath, and a dilator. The imaging element is configured to visualize tissue. The sheath includes a channel configured to receive the imaging element. The imaging element is positionable along a central longitudinal axis of the sheath and positionable in an off-axis position relative to the central longitudinal axis. The sheath comprises a flexible section defining at least a portion of the channel. The dilator is configured to advance through the channel to force the imaging element into the off-axis position. The dilator is configured to cause the imaging element to bulge the flexible section as the dilator is advanced through the channel.