Flexural and torsional rigidity of colonoscopes at room and body temperatures

Abstract

A series of experiments have been conducted to determine the flexural and torsional rigidity of an Olympus colonoscope CF-140S and torsional rigidity of a Pentax colonoscope EC-3870 and the dependency of these properties on temperature and on the presence of loops. Along the length of the colonoscope, the flexural rigidity of the Olympus colonoscope varied between 260 and 400 Ncm2 and the torsional rigidity varied between 68 and 88 Ncm2/deg, with an average of 76 Ncm2/deg for tests involving 0.86 Nm of anticlockwise torque. Results show a significant decrease of 10 per cent in torsional rigidity between clockwise and anticlockwise torque. For the Pentax colonoscope flexural rigidity was not tested; its torsional rigidity varied between 34 and 76 Ncm2/deg, with an average of 46 Ncm2/deg for tests involving 0.43 Nm of anticlockwise torque. An increase in temperature of the Olympus colonoscope from 24 to 37 °C reduced the flexural rigidity by an average of 17 per cent and torsional rigidity by an average of 7 per cent. A right-handed loop caused a significant increase in flexural rigidity, but other looping configurations had no significant influence.

Modeling and In Vitro Experimental Validation for Kinetics of the Colonoscope in Colonoscopy

“…The flexural rigidity EI of the colonsocope has been tested and can be found in the references. 8,15,16 [ U ] = represents a column matrix of displacements corresponding to force vector { F } (including external force F e and contact force F c ). Contact force computation is formulated into LCP by linearizing Signorini’s problem that is adapted into non-interpenetration with unilateral constraints.…”

Flexible Medical Devices: Review of Controllable Stiffness Solutions

“…In [4], the flexural and torsional stiffness of colonoscopes have been measured for different working temperatures. A reduction of 17% of the flexural stiffness is observed between 24 • C and 37 • C. In [205,206], the flexural stiffness of a colonoscope has been measured to 900 N cm 2 at 20 • C and to 540 N cm 2 at 40 • C.…”

“…The colonoscopes have to be very flexible, but also able to resist buckling [4]. The stiff shafts help for avoiding the loop formation, but not for traveling through a tortuous path (causing more pain when a loop happens), while the flexible shafts can ease the motion through a tortuous path, but cause more frequent apparition of loops.…”

A Variable Stiffness Spring–Sponge Composite Tube with Fast Response and Shape Recovery

“…Considering that the SSCT generally functioned under the bending force, three‐point bending tests with simple ends were carried out to investigate the range of stiffness variation (see more details in Supporting Information 2.1 about the test settings), the results are shown in Figure A. We figured out that the flexural modulus was 0.029 MPa in the soft state (corresponding deflection, 0 < δ < 8 mm) and 6.998 MPa in the stiff state (corresponding deflection, 0 < δ < 8 mm), about 240 times that of the former.…”