A Bronchial Puncture Mechanism for Transoral Access to the Lung Parenchyma1

摘要

More people die from lung cancer each year than any other form of cancer. Over 150,000 lives are lost to the disease each year in the U.S. alone [1]. Early detection is critical in reducing the mortality rate, and despite advances in imaging, biopsy remains the only definitive diagnostic tool. The most common lung biopsy approaches are percutaneous and transoral. Percutaneous biopsy punctures the pleura (the membrane surrounding the lung) in order to reach the suspicious nodule and risks pneumothorax (lung collapse), which is a serious complication and can be deadly for patients with poor baseline lung function. Transoral lung biopsy is preferable due to the fact that the biopsy device never traverses the pleura.However, current bronchoscopes cannot access the majority of the peripheral lung, due to their large diameter in relation to bronchi diameter. While smaller diameter endoscopes and endoscopelike devices are under development, there will always remain locations where a path that exits the bronchi and travels through the parenchyma is desirable, either because it is shorter or because the nodule lies away from a usable bronchial access path. To facilitate the biopsy tool exiting the bronchi to reach such targets, we have developed the puncture mechanism described in this paper.In addition to biopsy with a straight-line biopsy needle, our device may enable the use of steerable needles in the lung parenchyma. Recent advances in robotics such as concentric tube robots (CTRs) [2] and bevel-tip steerable needles [3] (among other new needle steering technologies) may be useful in reaching targets through controllable curved paths. But these technologies require the means of exiting the bronchi that we provide in this paper.Inspired by the prior work showing that fast needle insertion can controllably transit tissue with minimal deformation [4–6], in this paper we develop a bronchoscope-deployed system that can drive the needle tip through the bronchial wall and surrounding cartilage and connective tissue, providing a port for subsequent deployment of biopsy needles and/or steerable needles into the lung parenchyma.Our concept is to deploy a stylet and CTR (both made from superelastic nitinol) through the tool port typically available in bronchoscopes (see Fig. 1). The CTR is curved, such that when it is deployed from the tip of the bronchoscope, it will naturally deflect toward the bronchial wall in a direction defined by the physician (set based on its axial rotation). The stylet is elastic, yet straight, and has a sharp tip.Based on this overall concept, our design challenge in creating a puncture mechanism was to construct a device capable of delivering adequate axial actuation to the back of the stylet, such that when it is placed against the bronchial wall by the CTR, it is capable of controllably puncturing the bronchial wall. The stylet can then be withdrawn through the CTR and removed, allowing the steerable needle to be deployed through the CTR into the lung parenchyma.To make our device adjustable to a variety of surgeon-desired puncture dynamics and depths, we used a spring-based concept in which stylet dynamics can be adjusted by exchanging a replaceable spring and enabled user-specified puncture depth. We also sought a design that was compatible with a range of needle diameters, enabling the surgeon to create entry ports of different sizes in the bronchial wall, allowing a diverse set of steerable needles and other instruments to enter the parenchyma. Finally, it was determined that the device should be compact, lightweight, and detachable from the system after puncturing.The mechanism's basic function is to compress a spring and then release it to propel the stylet rapidly forward, causing its tip to puncture the bronchial wall. The spring compression and shaft travel (setting puncture depth) are controlled with a motor. The mechanism is fired mechanically by pressing the trigger lever. The mechanism (shown in Fi