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Subtle Lung Nodules: Influence of Local Anatomic Variations on Detection¹

¹ From the Departments of Radiology, Physics, and Biomedical Engineering, Duke University Medical Center, DUMC 3302, Durham, NC 27710 (E.S.); and Departments of Radiology (E.S., M.J.F., W.R.E.) and Biostatistics and Research Epidemiology (E.P.), Henry Ford Health System, Detroit, Mich. Received May 15, 2002; revision requested July 12; revision received August 7; accepted September 26. Supported in part by a small project grant from the Henry Ford Health Sciences Center, Detroit, Mich, and by the NIH, R21 CA91806. Address correspondence to E.S. (e-mail: samei@duke.edu).

View larger version (25K): [in a new window]   Figure 1. Five locations (L0-L4) where simulated nodules were superimposed near the center of the lung images. To prevent the observers from learning the exact locations of the nodules, the locations were sequentially rotated by 15° on the images. As examples, black circles represent locations in image 1; dark gray circles, locations in image 2; and light gray circles, locations in image 3.

View larger version (139K): [in a new window]   Figure 2a. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (158K): [in a new window]   Figure 2b. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (150K): [in a new window]   Figure 2c. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (167K): [in a new window]   Figure 2d. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (148K): [in a new window]   Figure 2e. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (156K): [in a new window]   Figure 2f. (a-f) Each of the six images used in the study, with a 6.4-mm-diameter (ie, 0.4-mm contrast-diameter-product) nodule (arrow) inserted at the center.

View larger version (40K): [in a new window]   Figure 3. Graph illustrates mean observer scores as a function of nodule contrast-diameter products for the six images used in the study. The error bars represent ±1 SD of the mean score. For reference, the mean and SD of the scores for the control images (ie, with no nodules inserted) are shown at the point where the nodule contrast-diameter product equals 0.06 mm (logCD = -1.2). The data points for the different images were slightly shifted for better visualization of the data.

View larger version (67K): [in a new window]   Figure 4. Contour plots depicting observer scores as a function of nodule location and contrast-diameter product for each of the six images used in the study. The location scale (L0-L4) indicates a path from the center (ie, location 0 [L0]) around the circumference of a 12-mm-diameter central region, as illustrated in Figure 1.

View larger version (42K): [in a new window]   Figure 5. Plotted t test results show significant pairwise differences in nodule detectability between any two locations on each image (see Fig 1). Each solid circle represents a statistically significant difference in the detectability of nodules between the two locations according to Holm ordered rejection P values: solid circles in the 0,1 location column represent P < .005; solid circles in the 0,2 column, P < .010; solid circles in the 0,3 column, P < .015; solid circles in the 0,4 column, P < .020; solid circles in the 1,2 column, P < .025; solid circles in the 1,3 column, P < .030; solid circles in the 1,4 column, P < .035; solid circles in the 2,3 column, P < .040; solid circles in the 2,4 column, P < .045; and solid circles in the 3,4 column, P < .050. All open circles represent marginally significant differences at P < .05. Blank areas indicate no significant difference in nodule detectability between the two locations.