Deep-learning reconstruction for ultra-low-dose lung CT: Volumetric measurement accuracy and reproducibility of artificial ground-glass nodules in a phantom study

• Published in: British journal of radiology Vol. 95; no. 1130; p. 20210915
• Main Authors: Mikayama, Ryoji, Shirasaka, Takashi, Kojima, Tsukasa, Sakai, Yuki, Yabuuchi, Hidetake, Kondo, Masatoshi, Kato, Toyoyuki
• Format: Journal Article
• Language: English
• Published: England The British Institute of Radiology 01.02.2022
• Subjects: Deep Learning; Humans; Lung Neoplasms - diagnostic imaging; Phantoms, Imaging; Radiation Dosage; Radiation Exposure - prevention & control; Radiographic Image Enhancement - methods; Solitary Pulmonary Nodule - diagnostic imaging; Tomography, X-Ray Computed - methods; Tumor Burden
• ISSN: 0007-1285; 1748-880X
• DOI: 10.1259/bjr.20210915

The lung nodule volume determined by CT is used for nodule diagnoses and monitoring tumor responses to therapy. Increased image noise on low-dose CT degrades the measurement accuracy of the lung nodule volume. We compared the volumetric accuracy among deep-learning reconstruction (DLR), model-based iterative reconstruction (MBIR), and hybrid iterative reconstruction (HIR) at an ultra-low-dose setting. Artificial ground-glass nodules (6 mm and 10 mm diameters, -660 HU) placed at the lung-apex and the middle-lung field in chest phantom were scanned by 320-row CT with the ultra-low-dose setting of 6.3 mAs. Each scan data set was reconstructed by DLR, MBIR, and HIR. The volumes of nodules were measured semi-automatically, and the absolute percent volumetric error (APEvol) was calculated. The APEvol provided by each reconstruction were compared by the Tukey-Kramer method. Inter- and intraobserver variabilities were evaluated by a Bland-Altman analysis with limits of agreements. DLR provided a lower APEvol compared to MBIR and HIR. The APEvol of DLR (1.36%) was significantly lower than those of the HIR (8.01%, = 0.0022) and MBIR (7.30%, = 0.0053) on a 10-mm-diameter middle-lung nodule. DLR showed narrower limits of agreement compared to MBIR and HIR in the inter- and intraobserver agreement of the volumetric measurement. DLR showed higher accuracy compared to MBIR and HIR for the volumetric measurement of artificial ground-glass nodules by ultra-low-dose CT. DLR with ultra-low-dose setting allows a reduction of dose exposure, maintaining accuracy for the volumetry of lung nodule, especially in patients which deserve a long-term follow-up.