In our recent blog post, Endoscope Camera: Medical Imaging Camera Quality we have discussed the various camera sensors that could be incorporated into an endoscope and another post discussing the lighting methods available. In this blog we will discuss the mechanical components that will transition endoscope components into a complete medical camera assembly.
Medical endoscopes have historically been reusable, as the disposable medical camera market continues to develop and evolve, coupled with medical robotic imaging becoming more of a standard, the associated components and sub-components will progress and improve.
The market is seeing 400 x 400 resolution camera cubes that were housed in 1mm x 1mm square shells miniaturize into .63mm x .63mm housings and 720 x 720 resolution camera cubes take their place in the 1mm x 1mm square shell size.
Your opportunity is to transform the voice of customer from a theoretic idea to a functional, usable, ultimately beneficial disposable endoscope or another medical device.
Voice of Customer – how the customer wants the device to set in their hand, where they want their fingers to engage with the actuating components, and what they want the complete device to feel like. With the functional limitations of the components that they can’t see below the surface of the handle.
Articulating or Steerable tip
There are several methods for designing and articulating a distal end tip, including soft material driven, concentric tubes, conductive polymer driven, hydraulic pressure driven catheters, hybrid actuation, independently constrained geometrical “disks” or stacked sections, and notched hypo tube, to identify a few.
Engineers continue to innovate and push the limits and create new means of articulation. The world of magnetics is one area that continues to extend what is possible in articulation and manipulation.
Prior to considering your method of functionality an appropriate first step is to consider the desired functionality. Do you need 90°, 180°, or 270° deflection? Does your endoscope need to articulate in a single degree of freedom or more (left right, down-up, rotational, and back and forward)?
Will you have a central lumen or not?
These factors, as well as many others, will lead you to considering the method you will take to drive the tip functionality. How will the distal tip steering be manipulated and what do you need to know while determining your parameters?
Pull wire / tendon driven
Once you determine which method of articulation your device will be based on, you need to actuate the segment. One of the most popular practices for actuation is through pull cables or tendon driven.
This method of functionality can have one to four tendons, driving singular, dual, and quad articulation. With the added advantage of more tendons, the greater amount of movement that can be achieved.
Points of design consideration when using this method of functionality include tendon interval spacing and location, backbone shape, as well as tendon tension and torque.
Use case is the leading factor for device design and geometry. For example, will the disposable endoscope be a scope only or will it have a working channel.
If there is not a working channel the central lumen could be smaller than a device with a working channel where the central lumen and the subsequent geometry plays a much larger part in determining device design.
The central lumen doesn’t have to be “central”; it is common for articulating devices to have an offset working channel or lumen.
These and other design characteristics need to be considered when designing and developing the functionality of the pull wire / tendon driven mechanism.
Where internal functionality meets external functionality
You’ve designed the distal end articulation, connected the tendons, now you need to drive the functionality of both.
The interface between the distal end, the shaft, and the operator of the device comes in the shape of the handle and where the internal meets the external.
Your challenge is merging voice of customer with the functional limitations of the components that they can’t see below the surface of the handle.
Establishing voice of customer desires early in the design process will enable delivery of a device that meets those desires.
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