Insertion method for minimizing fine needle deflection in bowel insertion based on experimental analysis

Accurate insertion of fine needles is difficult due to needle deflection. Needle deflection in the lower abdomen is particularly complex, as the needle has to pass through various tissues. As the area of the bowel is dominant in lower abdominal insertion, it is important to analyze the deflection during bowel insertion and to control the needle to minimize deflection. Few studies have focused on bowel insertion. We performed a fundamental deflection analysis of needle insertion in the bowel. Moreover, we have proposed an insertion method for minimizing the needle deflection based on our analysis. First, we performed needle insertion at various insertion positions and insertion angles into the hollow-shaped bowel, and determined the trend of the needle deflection during bowel insertion. The results revealed that the needle deflection was increased due to an increase in insertion angle, and therefore insertion angle should be minimized as much as possible. However, during actual bowel needle insertion, there are many situations in which the ideal path cannot be selected due to the arrangement of the bowel loops. We proposed an insertion method that can eliminate the total needle deflections during bowel insertion by controlling the needle tip direction at the breaching of each bowel wall. The results suggest that the needle deflection can be minimized by selecting the insertion path in which the sum of each insertion angle is zero. We verified the results of this insertion method in multiple bowels in in vivo experiments, and showed that it has the potential to be used in clinical practice.