Model-based iterative reconstruction technique for ultralow-dose chest CT: comparison of pulmonary nodule detectability with the adaptive statistical iterative reconstruction technique

• Published in: Investigative radiology Vol. 48; no. 4; p. 206
• Main Authors: Katsura, Masaki, Matsuda, Izuru, Akahane, Masaaki, Yasaka, Koichiro, Hanaoka, Shohei, Akai, Hiroyuki, Sato, Jiro, Kunimatsu, Akira, Ohtomo, Kuni
• Format: Journal Article
• Language: English
• Published: United States 01.04.2013
• Subjects: Aged; Female; Humans; Lung Neoplasms - diagnostic imaging; Male; Middle Aged; Models, Statistical; Radiation Dosage; Radiographic Image Interpretation, Computer-Assisted - methods; Radiography, Thoracic; Tomography, X-Ray Computed - methods
• ISSN: 1536-0210
• DOI: 10.1097/RLI.0b013e31827efc3a

The purpose of this study was to evaluate whether model-based iterative reconstruction (MBIR) enables dose reduction over adaptive iterative reconstruction (ASIR) while maintaining diagnostic performance. In this institutional review board-approved and Health Insurance Portability and Accountability Act-compliant study, 59 patients (mean [SD] age, 64.7 [13.4] years) gave informed consent to undergo reference-, low-, and ultralow-dose chest computed tomography (CT) with 64-row multidetector CT. The reference- and low-dose CT involved the use of automatic tube current modulation with fixed noise indices (31.5 and 70.44 at 0.625 mm, respectively) and were reconstructed with 50% ASIR-filtered back projection blending. The ultralow-dose CT was acquired with a fixed tube current-time product of 5 mA s and reconstructed with MBIR. Two radiologists evaluated 2.5- and 0.625-mm-slice-thick axial images from low-dose ASIR and ultralow-dose MBIR, recorded the pattern of each nodule candidate, and assigned each a confidence score. A reference standard was established by a consensus panel of 2 different radiologists, who identified 84 noncalcified nodules with diameters of 4 mm or greater on reference-dose ASIR (ground-glass opacity, n = 18; partly solid, n = 11; solid, n = 55). Sensitivity in nodule detection was assessed using the McNemar test. Jackknife alternative free-response receiver operating characteristic (JAFROC) analysis was applied to assess the results including confidence scores. Compared with the low-dose CT, a 78.1% decrease in dose-length product was seen with the ultralow-dose CT. No significant differences were observed between the low-dose ASIR and the ultralow-dose MBIR for overall nodule detection in sensitivity (P = 0.48-0.69) or the JAFROC analysis (P = 0.57). Likewise, no significant differences were seen for ground-glass opacity, partly solid, or solid nodule detection in sensitivity (P = 0.08-0.65) or the JAFROC analysis (P = 0.21-0.90). Model-based iterative reconstruction enables nearly an 80% reduction in radiation dose for chest CT from a low-dose level to an ultralow-dose level, without affecting nodule detectability.