Cystoscope Redesign

Cystoscopy is a procedure that clinicians perform utilizing a cystoscope to visualize the inside of a patient's urethra and bladder. This procedure is performed while the patient is anesthetized and involves the insertion of the cystoscope's sheath into the urethra followed by an injection of water through the sheath to expand the walls of the urethra and the bladder to improve visualization. A current-day cystoscope is shown below.

IMG: Current-Day Cystoscope

The development of the next generation of medical devices has placed a heavy emphasis on moving procedures out of the OR and into outpatient clinics, as the laser eye procedure has already accomplished. The goal in redesigning the cystoscope was exactly this. The cystoscope redesign needed to contain all the key features including a sheath containing a camera and light source, channels for water flow, and valves to control water flow. The innovative design also needed to be comfortable to use for right and left handed clinicians and needed to be non-intimidating to patients (because they are conscious during the outpatient procedure). The redesign of the cystoscope began with a sketch.

Cystoscope Redesign - Sketch

The cystoscope redesign was first sketched and iterated to ensure a feasible design was produced that included all the key features. The key features were as follows:

Mount to accommodate 24F Sheath
M/F luer locks mount for water input/output
Valve control mount to manage water flow
Channel for water flow
Mount for 3-pole electrical connector for optics power supply
Mounts for widget to house optics within cystoscope

More information about the widget can be found here

The sketch was also crafted to make sure the design was comfortable to use for right and left handed clinicians and to ensure the device was non-intimidating to patients.

IMG: Final Sketched Cystoscope Design

Cystoscope Redesign - Model

The cystoscope was designed in Fusion 360 based on the design-intent of the initial sketch. The model was crafted to include all the key features listed above along with rubber grips to avoid slippage, screw bosses to allow for structurally sound connection of the two cystoscope halves, and an upstanding rib to prevent the rubbing of the two plastic cystoscope halves. Components such as the widget, water valve controls, water channel, electrical connector, wires, luer locks, and the sheath were also added to the design.

VID: Cystoscope Disassembly & Assembly Animation

IMG: Cystoscope Redesign External Model

IMG: Cystoscope Redesign Internal Model

IMG: Cystoscope Redesign Use

Cystoscope Redesign - Design for Manufacturing

Initially, the cystoscope redesign was not optimized for low-cost tooling and manufacturing during injection molding. The design was updated to add draft angles of three degrees to all surfaces. Potential areas for sink and short-fill were also updated by ensuring consistent material thickness throughout the cystoscope. The draft analysis of the cystoscope redesign is shown below.

IMG: Draft Analysis of Updated Cystoscope Redesign

Cystoscope Redesign - Finite Element Analysis

Finite Element Analysis (FEA) was performed on the cystoscope redesign to ensure the device could withstand stresses associated with use during cystoscopy. Safety factors above 1.2 were considered acceptable. In this study, the main part of the handle where the user grips was constrained in all directions, and a load case of 10 lbs of force was applied to the tip of the 24F sheath.

IMG: FEA Cystoscope Redesign Load Case

The resultant minimum safety factor was 1.44 with the main stress areas being concentrated near the mounting end of the 24F sheath. Since the minimum safety factor is above the acceptable threshold, the cystoscope redesign will withstand any forces associated with use.

IMG: FEA Cystoscope Redesign Safety Factor Results

IMG: FEA Cystoscope Redesign Stress Results