Motion Planning in Deformable Soft Tissue with Applications to Needle Insertion

Abstract

Minimally invasive medical procedures such as brachytherapy, biopsies, and treatment injections often require inserting a rigid needle to a specific target location inside the body to implant a radioactive seed, extract a tissue sample, or inject a drug. In all cases, the needle tip should be inserted as close as possible to a predetermined target inside soft tissue. Unfortunately, inserting and retracting a needle causes the surrounding soft tissue to displace and deform: ignoring these deformations can result in substantial placement error, as illustrated in figure 3.1. Although real-time imaging such as ultrasound is available during the procedure, it does not provide crisp tissue boundaries and cannot be used to precisely monitor the tissue deformations. Physicians must therefore learn to compensate for the effects of tissue deformations in order to insert the needle to the correct location within the tissue.