CT evaluation of patient deep inspiration self-breath-holding: How precisely can patients reproduce the tumor position in the absence of respiratory monitoring devices?

The aim of the present study was to evaluate the reproducibility of tumor position under patient deep inspiration self-breath-holding in the absence of respiratory monitoring devices, as well as to compare the reproducibility of deep inspiration self-breath-holding on the verbal command of a radiation technologist (Passive mode) with that initiated by patients’ own estimation (Active mode). Twenty patients with lung cancer were shown how the tumor and diaphragm move during the respiration cycle. Patients were instructed to hold their breath during deep inspiration and reproduce identical tumor position as well as possible either by the Active mode or by the Passive mode. After patients had practiced self-breath-holding during deep inspiration, a set of three CT scans was obtained for each of the two modes of self-breath-holding (6 CT scans total) to obtain randomly timed images of 2 mm thickness in the vicinity of the tumor. The first three scans were performed during breath-hold using the Active mode, and next three scans were using the Passive mode. Maximum difference in tumor position for the three CT scans was then calculated along three axes: cranial-caudal (C-C); anterior-posterior (A-P); and right-left (R-L). In the 20 patients who underwent analysis of self-breath-holding, mean maximum difference in tumor position obtained under breath-hold using the Active and the Passive modes were: 2.2 and 3.1 mm along the C-C axis; 1.4 and 2.4 mm along the A-P axis; and 1.3 and 2.2 mm along the R-L axis, respectively. These differences in all axes were significantly smaller (p