Cone Beam Computertomography (CBCT) in Interventional Chest Medicine - High Feasibility for Endobronchial Realtime Navigation

INTRODUCTION Currently there are several advanced guiding techniques for pathoanatomical diagnosis of incidental solitary pulmonary nodules (iSPN): Electromagnetic navigation (EMN) with or without endobronchial ultrasound (EBUS) with miniprobe, transthoracic ultrasound (TTUS) for needle approach to the pleural wall and adjacent lung and computed tomography (CT) -guidance for (seldom if ever used) endobronchial or (common) transthoracical approach. In several situations one technique is not enough for efficient diagnosis, therefore we investigated a new diagnostic technique of endobronchial guided biopsies by a Cone Beam Computertomography (CBCT) called DynaCT (SIEMENS AG Forchheim, Germany). METHOD AND MATERIAL In our study 33 incidental solitary pulmonary nodules (iSPNs) (28 malignant, 5 benign; mean diameter 25 +/-12mm, shortest distance to pleura 25+/-18mm) were eligible according to in- and exclusion criteria. Realtime and onsite navigation were performed according to our standard protocol.22 All iSPN were controlled with a second technique when necessary and clinical feasible in case of unspecific or unexpected histological result. In all cases common guidelines of treatment of different iSPNs were followed in a routine manner. RESULTS Overall navigational yield (ny) was 91% and diagnostic yield (dy) 70%, dy for all accomplished malignant cases (n=28) was 82%. In the subgroup analysis of the invisible iSPN (n=12, 11 malignant, 1 benign; mean diameter 15+/-3mm) we found an overall dy of 75%. For the first time we describe a significant difference in specifity of biopsy results in regards to the position of the forceps in the 3-dimensional volume (3DV) of the iSPN in the whole sample group. Comparing the specifity of biopsies of a 3D-uncentered but inside the outer one third of an iSPN-3DV with the specifity of biopsies of centered forceps position (meaning the inner two third of an iSPN-3DV) reveals a significant (p=0,0375 McNemar) difference for the size group (>1cm) of 0,9 for centered biopsies vs. 0,3 for uncentered biopsies. Therefore only 3D-centered biopsies should be relied on especially in case of a benign result. CONCLUSION The diagnostic yield of DynaCT navigation guided transbronchial biopsies (TBB) only with forceps is at least up to twofold higher than conventional TBB for iSPNs <2cm. The diagnostic yield of DynaCT navigation guided forceps TBB in invisible SPNs is at least in the range of other navigation studies which were performed partly with multiple navigation tools and multiple instruments. For future diagnostic and therapeutic approaches it is so far the only onsite and realtime extrathoracic navigation approach (except for computed tomography (CT)-fluoroscopy) in the bronchoscopy suite which keeps the working channel open. The system purchase represents an important investment for hospitals but it is a multidisciplinary and multinavigational tool with possible access via bronchial airways, transthoracical or vascular approach at the same time and on the same table without the need for an expensive disposable instrument use.