Bending Section Endoscope
The bending section of an endoscope must be sufficiently controllable and flexible that the physician can position the tip in any necessary location within the body cavity being examined.
The bending section is steered by at least one cable extending through the tube and connecting to a control mechanism in the housing of the endoscope. However, these systems are prone to nonlinearity, with backlash and cable slackening, which results in insufficient control and inaccurate tip response.
Vertebrae
Endoscopes are used for performing diagnostic or therapeutic procedures within many body regions, such as esophagus, stomach, small and large bowel, intestinal, bile duct, respiratory airways, nasal cavities, urethra, fallopian tubes, and other organs and passageways. During these procedures, the endoscope is maneuvered through the lumen, channel, orifice, or passageway of the desired body region, and images are transmitted to a video camera, or transferred to an eyepiece for display or capture (e.g., with a fiberoptic bundle).
An endoscope is constructed such that the outer perimeter cross-section of the insertion tube conforms to the geometry of a body region into which it will be inserted. This allows the insertion tube to more precisely fit within the desired body region.
One variation of the non-circular outer perimeter of an endoscope insertion tube is to have a D-shaped cross-section, as shown in FIGS. 5A-5F. The bending portion of the endoscope consists of vertebrae that are D-shaped in cross-section, with a first pair of protrusions projecting from a first surface of the vertebra and defining a vertical bending axis and a second pair of protrusions projecting from the second surface of the vertebra and defining he horizontal bending axis.
These protrusions are spaced from the longitudinal bending axis of the bending section to provide symmetrical bending characteristics across the bending section. This is accomplished by selecting the size and shape of the protrusions so that the distance from the longitudinal axis for each control wire when retracting or extending the respective control wire matches the displacement of the respective control wire for a desired degree of bend in any direction.
In addition, the bending section of the endoscope is articulated by retracting and extending selected control wires 67-70 through four cylindrical apertures on an inside surface adjacent the protrusions. Selectively retraction and extending the control wires through these apertures causes the vertebrae to rock on the protrusions to turn the bending section a desired degree of bend.
Vertebrae are made from beryllium-copper or another material suitable for investment casting, because of their strength and fine grain structure. To ensure torsional stability, the bending section is covered with a heavy braid that is balanced with the clearance for the control wires through the apertures on the vertebrae.
Protrusions
Bending Section Endoscopes essentially consist of an insertion tube having a bending portion located at a distal end and an elongate portion proximal to the bending portion. The bending portion is designed to allow the insertion tube to conform to the interior shape of a body lumen or orifice that most prior art insertion tubes could not accommodate. This is particularly true in the case of body regions, such as esophagus, stomach, small and large bowel, intestines, bile ducts, large and small respiratory airways, nasal cavities, urethras, fallopian tubes and similar.
In many prior art insertion tubes, the outer surface of the insertion tube is circular in cross-section. As a result, the insertion tube cannot be used to view body regions with non-circular internal lumen shapes (e.g., lobular internal lumens).
To overcome this problem, a number of variations of the bending tube have a plurality of joint pieces connected to each other so as to be rotatable with respect to each other and an outer skin that covers an outer periphery of the bending tube. The protrusions of the outer skin enable the bending tube to be bent along a longitudinal direction, and the degree of bending can be set by defining the width of the protrusions.
Another variation of the bending tube has a non-circular outer Bending Section Endoscope perimeter of cross-section, which matches the geometry of the region of the body into which it is inserted. This type of insertion tube is particularly useful for use with a wide variety of body regions, including esophagus, stomach, intestines, bile and other ducts, large and small respiratory airways, urethras and other urinary tract structures and similar.
For this purpose, the bending tube is equipped with four angulation wires that run the length of the insertion tube, and are firmly attached to the tip of the bending tube at the 3 o’clock, 6 o’clock, 9 o’clock, and 12 o’clock positions. When pulled, the angulation wires cause the bending tube to bend in a certain direction, such as up.
In addition, the bending tube is configured to be a non-circular endoscope. This is because the bending tube can be bent more rapidly at the distal end side of Bending Section Endoscope the outer skin than at the proximal end side, which is a significant improvement in flexing capabilities.
Flat surface
A Bending Section Endoscope is a device used in diagnostic and therapeutic procedures to insert into a body channel. The insertion tube includes a bending section near the distal tip that is steerable by a physician to provide orientation and position of the endoscope tip for optimal viewing of objects inside the patient’s body.
Generally, the bending section is constructed differently than other parts of the insertion tube to provide a deflectable portion that can be manipulated by the physician. In one embodiment, the bending section is composed of a series of oddly shaped metal rings that are connected to each other by a freely moving joint. This mechanism permits the ring on each side of the bending section to move independently and to be selectively displaced from the ring on the other side by 90 degrees.
The individual vertebrae of the bending section are D-shaped to provide a non-round, non-planar bending section. A first pair of protrusions extending from one surface of the vertebrae defines a horizontal bending axis, and a second pair of protrusions extending from a second surface of the vertebrae defines a vertical bending axis. The apex of each protrusion is flat to provide a flat contact surface between adjacent vertebrae.
To enable the bending section to be steered, control wires are selectively retracted and extended through apertures of each of the individual vertebrae. The resulting movement of each control wire is symmetrically matched to achieve a desired bending of the bending section.
In our experiments, 20 flexible colonoscopes and five gastroscopes were evaluated in a bench top setup (Fig. 3). We measured maximal tip bending and tip angulation. The resulting hysteresis plot was used to determine cable slackness and the virtual play that is involved in the tip bending response.
We found that the slackness and virtual play were minimal in our measurements, but the maximal bending angles of the slackest colonoscopes and gastroscopes varied significantly from the manufacturer’s prescribed settings. In particular, the maximum bending angles of the slackest gastroscopes were significantly higher than the maximal bending angles of the slackest colonicoscopes.
Light source
Bending section endoscopes require a light source to illuminate the area to be viewed. The light sources can be small and portable or large standalone devices. The selection of the best type of light source depends on several factors, including the area of use and the budget available for the operation.
Most conventional light sources are xenon or halogen lamps with heat sinks, infrared filters and forced-air cooling systems. These devices typically produce considerable heat, which must be dissipated to prevent damage to the fiber bundle of the endoscope.
The light source is often positioned near the tip of the bending section. In some cases, the light source may be inserted into the handle of the endoscope. The heat is dissipated by the larger surface of the handle, but the generated light still has to be transported to the tip of the instrument for illumination.
In order to minimize the heat produced by the lamp, an infrared absorbing material is usually incorporated into the light guide lens at the distal tip of the instrument. This infrared absorbing material absorbs the light from the light source and directs it to the endoscope’s fiber bundle. The light is then guided to the distal end of the bending section and spreads over the visual field.
An advantage of this design is that it reduces the likelihood of arcing from the insertion unit to the operation unit, which could cause the universal cord extending out of the operation unit to be pulled or twisted. This is especially an issue in the case of a heavy torsion.
A second benefit of the insertion unit-operating unit structure is that an operator can advance, withdraw or twist the insertion unit to angle the operation unit for inserting work. This operation can be performed by changing the way in which the hand-held unit is held or pressing switches. The angling knob 137 of the operation unit can also be adjusted and controlled by the operator.
A third advantage of the insertion unit-operating unit design is that the light guide connector is not led out of the proximal unit but rather leads to the light source apparatus or video processor disposed outside of the endoscope. This configuration obviates the necessity of the universal cord and greatly improves the maneuverability or use-friendliness of the operation.
