A phantom study investigating the relationship between ground‐glass opacity visibility and physical detectability index in low‐dose chest computed tomography. (8th July 2015)

• Record Type: Journal Article
• Authors: Ichikawa, Katsuhiro; Kobayashi, Takeshi; Sagawa, Motoyasu; Katagiri, Ayako; Uno, Yukiko; Nishioka, Ryo; Matsuyama, Jun
• Is Part Of: Journal of applied clinical medical physics. Volume 16:Number 4(2015)
• Page Start: 202
• Page End: 215
• Publication Date: 2015-07-08
• Subjects: computed tomography -- ground‐glass opacity -- detectability -- dose index -- lung cancer screening; Medical physics -- Periodicals; Clinical medicine -- Periodicals; Health Physics; Clinical Medicine; Electronic journals; Periodicals; Periodicals; Fulltext; Internet Resources; 610.153
• DOI: 10.1120/jacmp.v16i4.5001
• Languages: English
• ISSNs: 1526-9914

Abstract

Abstract : In this study, the relationship between ground‐glass opacity (GGO) visibility and physical detectability index in low‐dose computed tomography (LDCT) for lung cancer screening was investigated. An anthropomorphic chest phantom that included synthetic GGOs with CT numbers of ‐ 630 Hounsfield units (HU; high attenuation GGO: HGGO) and ‐ 800 HU (low attenuation GGO: LGGO), and three phantoms for physical measurements were employed. The phantoms were scanned using 12 CT systems located in 11 screening centers in Japan. The slice thicknesses and CT dose indices ( CTDI vol ) varied over 1.0–5.0 mm and 0.85–3.30 mGy, respectively, and several reconstruction kernels were used. Physical detectability index values were calculated from measurements of resolution, noise, and slice thickness properties for all image sets. Five radiologists and one thoracic surgeon, blind to one another's observations, evaluated GGO visibility using a five‐point scoring system. The physical detectability index correlated reasonably well with the GGO visibility ( R 2 = 0.709, p < 0.01 for 6 mm HGGO and R 2 = 0.646, p < 0.01 for 10 mm LGGO), and was nearly proportional to the CTDIvol . Consequently, the CTDI vol also correlated reasonably well with the GGO visibility ( R 2 = 0.701, p < 0.01 for 6 mm HGGO and R 2 = 0.680, p < 0.01 for 10 mm LGGO). As a result, the CTDI vol was nearly dominant in the GGO visibility for image sets with different reconstruction kernels and slice thicknesses, used in this study. PACS numbers: 81.70.Tx, 87.57.Q‐