Fig. 1. OBU index.

A. 1 (none): single open bronchus (arrow) in tumor periphery. B. 2 (low): multiple open bronchi in tumor periphery with adequate room to advance cutting needle into tumor. C. 3 (possible): centrally (arrow) and peripherally located open bronchi in tumor with space to advance cutting needle into tumor while evading open bronchi. D. 4 (probable): it is possible that open bronchi (arrows) in tumor are injured or penetrated by cutting needle. E. 5 (high): it is highly likely that open bronchi in tumor are penetrated by cutting needle. OBU = open bronchus unavoidability