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Effects of spatial resolution and tube current on computer-aided detection of polyps on CT colonographic images: phantom study

Cited 18 time in Web of Science Cited 20 time in Scopus
Authors
Kim, Se Hyung; Lee, Jeong Min; Shin, Cheong-Il; Kim, Hyo Chul; Lee, Joon-Goo; Kim, Jong Hyo; Choi, Jin Young; Eun, Hyo Won; Han, Joon Koo; Lee, Jae Young; Choi, Byung Ihn
Issue Date
2008-02-10
Publisher
Radiological Society of North America (RSNA)
Citation
Radiology. 2008;248(2):492-503
Keywords
AlgorithmsAnimalsColonic Polyps/*radiography*Colonography, Computed TomographicFalse Positive Reactions*Phantoms, ImagingProspective Studies*Radiographic Image Interpretation, Computer-AssistedSensitivity and SpecificitySwine
Abstract
PURPOSE: To prospectively evaluate the effects of z-axis spatial resolution and tube current on the sensitivity of a commercially available computed tomographic (CT) colonography computer-aided diagnosis (CAD) system for polyp detection by using pig colon phantoms. MATERIALS AND METHODS: Ninety-six polyps were created and analyzed in 14 pig colon phantoms. CT colonography was performed by using a 16-detector CT scanner at 0.75-mm collimation; 10, 50, 100, and 160 mAs; and a pitch of 1.5. At each milliampere-second setting, the CT images were reconstructed with a section thickness (ST) of 1.5 mm and a reconstruction increment (RI) of 1.3 mm. To evaluate the effect of z-axis spatial resolution, CT images were also reconstructed at 100 mAs with various SI and RI combinations (respectively: 1.0 and 0.7 mm, 3.0 and 2.0 mm, 3.0 and 3.0 mm, 5.0 and 5.0 mm). The phantom data were then analyzed by using a CAD program. CAD performance with different CT parameters was calculated and compared in terms of per-polyp sensitivity and number of false-positive (FP) findings per data set. RESULTS: At a constant tube current of 100 mAs, the polyp detection rate was significantly higher in data sets obtained with SI and RI combinations of 1.0 and 0.7 mm, respectively (81% [78/96]), and 1.5 and 1.3 mm, respectively (75% [72/96]), than in those obtained with the three thicker ST-RI settings (27% [26/96] to 64% [61/96]) (P < .01). A similar trend was observed, regardless of polyp size or morphology. However, the number of FP findings at the 1.0 mm and 0.7 mm setting (8.9 per phantom) was also significantly greater than that at the thicker ST-RI settings (4.0-6.1 per phantom) (P < .05). At a constant z-axis spatial resolution (1.5-mm ST, 1.3-mm RI), CAD polyp detection rate and number of FP findings per phantom remained nearly constant-close to 78% (75/96) and 6.1, respectively-at various tube current settings. CONCLUSION: CAD performance in polyp detection at CT colonography is highly dependent on z-axis spatial resolution. However, tube current is not an influencing factor in CAD performance at a given z-axis spatial resolution. Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2482071025/DC1.
ISSN
1527-1315 (Electronic)
0033-8419 (Print)
Language
English
URI
http://hdl.handle.net/10371/67877
DOI
https://doi.org/10.1148/radiol.2482071025
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College of Medicine/School of Medicine (의과대학/대학원)Radiology (영상의학전공)Journal Papers (저널논문_영상의학전공)
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