Page 416 - Flexible Robotics in Medicine

410 Chapter 18

18.3.2 Design failure mode and effect analysis

In addition to fulfilling the design criteria, EndoGoose has been analyzed using design
failure mode and effect analysis (DFMEA) (Table 18.3), showing the possible risks, type of
failure, and severity of the risk and corresponding mitigation of risks.

18.4 Analysis of needs and metrics

18.4.1 Design metrics

The prototype should have an actively bending section at the distal end that can be
manually controlled at the proximal end so as to conduct the biopsy precisely and quickly
to the operator needs. In order to translate the design requirements into quantifiable values,
a list of metrics was determined (Tables 18.4 and 18.5).

• Duration of the biopsy procedure: generally, the biopsy shall be conducted efficiently
and quickly. The total duration of a biopsy procedure is reduced through features that
aid in an actively bending section and the simplicity of using the prototype.
• Forceps to prevent contamination: the forceps tear out some tissue during the biopsy.
However, if the tissue torn out is too large and cancerous, it might come into contact
with other unaffected regions as it is being removed out of the body. This would result
in contamination and spreading of tumorous cells, causing unintended consequences.
As such, the forceps should be able to encapsulate the tissue removed as much as
possible, minimizing the amount of tissue exposed and reducing the possibilities of
contamination.
• Dimension and operator friendliness: the biopsy prototype should be thin and small as it
needs to enter the lumenal region. It also has to be small enough to accommodate the
small lumen of the endoscope. Next, if the prototype is going to be handheld, it should
be ergonomically comfortable and operator-friendly. Therefore, any mechanism or
buttons that are to be placed appropriately for easy accessibility. The prototype should
also be light enough to be carried by one hand.
• Shape and strength of forceps: forceps shall be strong enough to grab and tear the
tissues. This is dependent on the shape of the forceps and its design. The design should
not allow the forceps to break or deform easily, and it will determine the amount of
force to exert to remove samples of tissue. Also, the shape will determine if the forceps
is able to prevent contamination by properly encapsulating the tissue removed.
• Response time of bending section: As we control the actively bendable section, its
change in orientation and angle should respond to the controls quickly so that the
biopsy procedure can be completed with ease and efficiency. The response time, in this
case, is the time taken to bend 180 degrees along one plane. The metrics related to each
of the parameters in the biopsy procedure are shown in Table 18.4.