A novel method of transthoracic lung nodule localization

Abstract

Introduction: High-resolution computed tomography (CT) scans now detect smaller pulmonary nodules than were ever detected before, which has created new clinical challenges regarding the timing and method of obtaining a tissue diagnosis. Video-assisted thoracic excisional biopsy is the preferred method of obtaining tissue, but with smaller lesions that are not pleural-based, localization is necessary because tactile evaluation is limited. This study evaluated the feasibility of the deployment of suture-ligated vascular embolization microcoils (microcoils) as a method for localizing peripheral pulmonary nodules before video-assisted thoracoscopic surgery (VATS) and compared the microcoils with hookwires. MethodsSix 3-0 Prolene® microcoils and 6 hookwires were injected into 3 freshly harvested goat lungs. Fluoroscopy, CT, and direct visualization were utilized to evaluate the shape, location, and displacement characteristics of the deployed microcoils and hookwires. The forces required to displace these devices were measured by tensiometry. Displacement data were correlated with the force needed to deform a vascular embolization microcoil and hookwire out of tissue. An identical technique using a 4% agarose gel was performed to visualize the deformation characteristics. ResultsSignificantly different loads (0.29 ± .03 vs 0.72 ± .27 lbs, p < 0.006) were required to displace microcoils and hookwires, respectively, from lung tissue when a constant, slow displacement velocity of 0.5 in/min was applied. The loads for displacement from agarose gel of the microcoil and hookwire were 0.15 ± .04 and 0.32 ± .17 lbs, (p = 0.03), respectively. At a rapid velocity, an average force of 0.95 ± 0.41 lbs was required to displace a microcoil from agarose; an average of 0.74 ± 0.34 lbs of force was needed to displace a hookwire. To straighten a microcoil required 0.065 lbs of force, and 2.5 lbs of force was required to straighten a hookwire beyond 90°. Displacement of a hookwire causes lung tissue to tear, often with tissue remaining on the barb, whereas essentially no damage to lung tissue is observed with microcoil displacement. The observed gel disruption mimicked the lung tissue, demonstrating the tearing property of the wire and the straightening characteristic of the coil. ConclusionForces within the physiologic range will displace both microcoils and hookwires from lung tissue. The decreased rigidity of microcoils, their ability to be left in situ if necessary, and diminished disruption of lung parenchyma with displacement suggest that it is feasible to use this system in human subjects as a technique for pulmonary nodule localization before minimally invasive pulmonary resection.