Automated continuous quantitative measurement of proximal airways on dynamic ventilation CT: initial experience using an ex vivo porcine lung phantom

Abstract

BackgroundThe purpose of this study was to evaluate the feasibility of continuous quantitative measurement of the proximal airways, using dynamic ventilation computed tomography (CT) and our research software.MethodsA porcine lung that was removed during meat processing was ventilated inside a chest phantom by a negative pressure cylinder (eight times per minute). This chest phantom with imitated respiratory movement was scanned by a 320-row area-detector CT scanner for approximately 9 seconds as dynamic ventilatory scanning. Obtained volume data were reconstructed every 0.35 seconds (total 8.4 seconds with 24 frames) as three-dimensional images and stored in our research software. The software automatically traced a designated airway point in all frames and measured the cross-sectional luminal area and wall area percent (WA%). The cross-sectional luminal area and WA% of the trachea and right main bronchus (RMB) were measured for this study. Two radiologists evaluated the traceability of all measurable airway points of the trachea and RMB using a three-point scale.ResultsIt was judged that the software satisfactorily traced airway points throughout the dynamic ventilation CT (mean score, 2.64 at the trachea and 2.84 at the RMB). From the maximum inspiratory frame to the maximum expiratory frame, the cross-sectional luminal area of the trachea decreased 17.7% and that of the RMB 29.0%, whereas the WA% of the trachea increased 6.6% and that of the RMB 11.1%.ConclusionIt is feasible to measure airway dimensions automatically at designated points on dynamic ventilation CT using research software. This technique can be applied to various airway and obstructive diseases.

Asynchrony in respiratory movements between the pulmonary lobes in patients with COPD: continuous measurement of lung density by 4-dimensional dynamic-ventilation CT

“…Using the wide volume mode (non-helical mode), dynamic scanning was performed at a fixed point without bed movement, resulting in fluoroscopic images of 160 mm in length 19,20. Scanning field of view (FOV) was selected from two settings based on patient body habitus: 320 (medium, n=14) or 400 mm (large, n=18).…”

Hyperinflated lungs compress the heart during expiration in COPD patients: a new finding on dynamic-ventilation computed tomography

“…Dynamic scanning was performed at a fixed point without bed movement (non-helical scanning), resulting in fluoroscopic images of 160 mm in length. 26 , 27 Scanning and reconstruction parameters for the dynamic-ventilation CT were as follows: tube current =40 mA (n=27) or 20 mA (n=4); tube voltage =120 kVp; rotation time =0.35 s; total scanning time =4.5–6.5 s; scanning field of view (FOV) =320 (medium, n=12) or 400 mm (large, n=19); imaging FOV =320 mm; collimation =0.5 mm; slice thickness =1 mm; reconstruction kernel = FC15 (for mediastinum); reconstruction interval =0.5 s/frame (total 9–13 frames); reconstruction method = half reconstruction. Scan data were converted to CT images using an iterative reconstruction method (adaptive iterative dose reduction using three-dimensional processing [AIDR3D], mild setting).…”

“…Recently, 320-row and 256-row multi-detector CT scanners have been developed that can continuously scan the thorax under normal breathing conditions, allowing visualization of thoracic respiratory movements. 26 , 27 Although dynamic-ventilation CT cannot cover the entire lung (≤160 mm in the z -axis), continuous mean lung density (MLD) values of the scanned lung can be obtained. A strong correlation between MLD and lung volume has previously been reported.…”

Continuous quantitative measurement of the proximal airway dimensions and lung density on four-dimensional dynamic-ventilation CT in smokers

“…Detailed information of the software was described in our technical note. 8 In brief, the software automatically created a tree of the centerlines from the trachea to all traceable peripheral bronchi throughout the cine-CT, on which the anatomical information of the measurement point was sustained and reproduced in each frame. Thus, once the operator set a measurement point on the airway centerline in a single frame, the corresponding measurement points in other frames were simultaneously determined ( Figure 1 ; Video S2 ).…”

“…Recently, novel research software was developed that can track and measure an airway point throughout the dynamic-ventilation CT scan. 8 Although the scanned lung is limited to a part of the whole lung (≤160 mm in length), the continuous mean lung density (MLD) values of the dynamic CT are also measurable using different software that can separate the airways and lungs.…”