Feasibility of low dose chest CT for virtual bronchoscopy navigation in a porcine model

Abstract

Background: Virtual bronchoscopy navigation (VBN) is widely used for assistance in the histological examination of lung nodules. However, little is known about the optimal CT radiation dose for VBN. Therefore, we performed an animal study to evaluate the feasibility of low dose CT (LDCT) for VBN.

Methods: Ten pigs underwent standard dose CT (as a reference) and four different LDCT protocols: LDCT 1, 120 kVp, 15 mAs; LDCT 2, 120 kVp, 8 mAs; LDCT 3, 100 kVp, 7 mAs; and LDCT 4, 100 kVp, 4 mAs. As targets for the VBN, 10 mm virtual lesions were created in the central and peripheral bronchi. To assess the performance of the VBN, the navigation direction (direction of reconstructed pathways to the target) and the number of branching's (the number of peripheral bronchi to the target) were evaluated.

Results: The mean effective doses significantly differed across the four LDCTs (P < 0.001). For both central and peripheral virtual targets, there were significant differences in the accuracy of the navigation direction and the number of branching's of the VBNs across the four LDCTs (P < 0.001 for all). Regarding the accuracy of the navigation direction and the number of branching's, the areas under the curves of the ROCs were 0.9352 and 0.9324, respectively, for central virtual targets, and 0.8696 and 0.8783, respectively, for peripheral virtual targets. Youden's index indicated that the optimal effective CT scan dose for both central and peripheral virtual targets was 0.238 mSv.

Conclusions: LDCT is feasible for VBN.

Keywords: Bronchoscopy; Diagnosis; Lung neoplasms; Multisection computed tomography; Radiation.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1

Representative images of standard and low dose CT scans. a Standard dose CT. b-e Low dose CT scans 1–4

Fig. 2

Virtual targets for the virtual bronchoscopy navigation. a Creation of a three-dimensional virtual target (arrow) located on the peripheral bronchus (arrowhead) using LungPoint software. b Central (red circle) and peripheral (blue circle) virtual targets created in the middle and outer one-third of the lung parenchyma, respectively

Fig. 3

Guidance screen of the VBN. The red line represents all bronchial pathways and the blue line is the automatically searched-for route with the closest access to the virtual target. The navigation direction accuracy was defined as the concordance in the progression of the blue line between the VBN using low dose CT and that using standard dose CT. The number of branching’s was defined as the number of red lines that directly branched from the blue line, and the accuracy of the number of branching’s was defined according to the concordance of this number between the VBNs using low dose and standard dose CT. VBN = virtual bronchoscopy navigation

Fig. 4

ROC curves of the optimal effective low dose CT scan doses for VBN performance. a ROC curve of the navigation direction for central virtual targets. b ROC curve of the number of branching’s for central virtual targets. c ROC curve of the navigation direction for peripheral virtual targets. d ROC curve of the number of branching’s for peripheral virtual targets. VBN = virtual bronchoscopy navigation