Quantification of airway dimensions using a high‐resolution CT scanner: A phantom study

Abstract

Small airways with inner diameters less than 2 mm are sites of major airflow limitations in patients with chronic obstructive pulmonary disease (COPD) and asthma. The purpose of this study is to investigate the limitations for accurate assessment of small airway dimensions using both high-resolution CT (HRCT) and conventional normal-resolution CT at low dose levels. Methods:To model the normal human airways from the 3rd to 20th generations, a cylindrical polyurethane phantom with 14 airway tubes of inner diameters (ID) ranging from 0.3 to 3.4 mm and wall thicknesses (WT) ranging from 0.15 to 1.6 mm was placed within an Anthropomorphic QRM-Thorax phantom.The Aquilion Precision (Canon Medical Systems Corporation) HRCT scanner was used to acquire images at 80, 100, and 120 kV using high resolution mode (HR, 0.25 mm × 160 detector configuration) and normal-resolution (NR) mode (0.5 mm × 80 detector configuration). The HR data were reconstructed using a 1024 × 1024 matrix (0.22 × 0.22 × 0.25 mm voxel size) and the NR data were reconstructed using a 512 × 512 matrix (0.43 × 0.43 × 0.50 mm). Two reconstruction algorithms (filtered back projection; FBP and an adaptive iterative dose reduction 3D algorithm; AIDR 3D) and three reconstruction kernels (FC30, FC52, and FC56) were investigated. The CTDI vol dose values ranged from 0.2 to 6.2 mGy. A refined automated full-width half-maximum (FWHM) method was used for the measurement of airway dimensions, where the density profiles were computed by radial oversampling using a polar coordinate system. Both ID and WT were compared to the known dimensions using a regression model, and the root-mean-square error (RMSE) and average error were computed across all 14 airway tubes. Results:The results indicate that the ID can be measured within a 15% error down to approximately 0.8 and 2.0 mm using the HR and NR modes, respectively. The overall RMSE (and average error) of ID measurements for HR and NR were 0.10 mm (−0.70%) and 0.31 mm (−2.63%), respectively. The RMSE (and average error) of WT measurements using HR and NR were 0.10 mm (23.27%) and 0.27 mm (53.56%), respectively. The WT measurement using HR yielded a factor of two improvement in accuracy as compared to NR.

Accuracy of Nodule Volume and Airway Wall Thickness Measurement Using Low-Dose Chest CT on a Photon-Counting Detector CT Scanner

“…In the current study, for PCD-CT–derived nodule volume measurements at the dose level studied (0.8 mGy), volume accuracy was consistent or improved compared with Zhou et al 19 potentially due to the differences in the PCD-CT scanner platform, acquisition parameters, dose, and reconstruction including kernels, matrix size, and slice thickness. The study by Zhao et al 14 cited nearly a factor of 3 improvement of airway wall thickness measurement accuracy (RMSE) between standard and high-resolution EID-CT images with CTDI vol of 6.2 mGy. In the current study, the RMSEs of the airway tubes similar in size to those used Zhao et al in MK PCD-CT and USK PCD-CT images (CTDI vol = 7.35 mGy) were 0.43 mm and 0.11 mm, respectively.…”

“…Recently, deep learning reconstruction methods have been applied to chest CT and pulmonary nodule detection, 13 aiding in noise reduction. High-resolution CT has been used to measure the dimensions of small structures such as airways for the purpose of monitoring for COPD and asthma 4,14 …”

Diagnostic Value of Coronary Computed Tomography Angiography Image under Automatic Segmentation Algorithm for Restenosis after Coronary Stenting

“…The calculation method was shown in ( 15 ). In ( 16 ), the segmentation effect of the overall segmentation algorithm was measured by the average voxel error [ 21 ]. …”

Standardization and Quantitative Imaging With Photon-Counting Detector CT

“…65 In addition, high-resolution CT has been used to measure the dimensions of small structures such as airways for the purpose of monitoring for chronic obstructive pulmonary disease and asthma. 66,67 High-resolution PCD-CT has been shown to improve nodule volume quantification, shape characterization, and image quality compared with standard-resolution PCD-CT. 54,58,68,69 Photon-counting detector CT has been applied to nodule volume, emphysema, and airway quantification. [69][70][71][72] In the context of interstitial lung disease, PCD-CT technology maintained diagnostic performance at reduced dose compared with EID-CT. 73,74 Dunning et al 75 showed that PCD-CT improved nodule volume estimation (volume quantification error reduced Gadobutrol (Gadavist; Bayer Healthcare, NJ) contrast agent was first injected intravascularly, followed by an iohexol (Omnipaque 350; GE Healthcare, WI) injection 17.5 seconds from the initial injection.…”

“…Lung cancer CT screening is used to detect lung nodules, and estimate of their volumes are used clinically to assess the need for follow-up and/or to monitor nodule growth 65 . In addition, high-resolution CT has been used to measure the dimensions of small structures such as airways for the purpose of monitoring for chronic obstructive pulmonary disease and asthma 66,67 …”