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Characterization of the Relation Between CT Technical Parameters and Accuracy of Quantification of Lung Attenuation on Quantitative Chest CT

¹ Department of Radiology, University of Virginia Medical Center, Charlottesville, VA.
² Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
³ Department of Radiology, Children's Hospital of Philadelphia, 34th St. and Civic Center Blvd., Philadelphia, PA 19104.

View larger version (79K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1 —Photograph shows urethane samples representing lung attenuation of –650 (left) and –820 H (right).

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —Anthropomorphic thoracic phantom. Photograph in anterior projection shows samples at apex (position 1) and base (position 2) of lungs.

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —Anthropomorphic thoracic phantom. Photograph shows posterior view of phantom.

View larger version (51K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with high-dose (200 mA) technique outside phantom (A), at lung base (B), and at lung apex (C).

View larger version (71K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with high-dose (200 mA) technique outside phantom (A), at lung base (B), and at lung apex (C).

View larger version (87K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3C —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with high-dose (200 mA) technique outside phantom (A), at lung base (B), and at lung apex (C).

View larger version (54K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3D —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with low-dose (30 mA) technique outside phantom (D), at lung base (E), and at lung apex (F). Degraded image quality is apparent in F.

View larger version (107K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3E —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with low-dose (30 mA) technique outside phantom (D), at lung base (E), and at lung apex (F). Degraded image quality is apparent in F.

View larger version (122K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3F —Sample materials in three environments tested in phantom. Slice thickness is 0.625 mm and tube voltage, 120 kVp. Axial CT images acquired with low-dose (30 mA) technique outside phantom (D), at lung base (E), and at lung apex (F). Degraded image quality is apparent in F.

View larger version (10K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A —Variation in mean attenuation in relation to tube current. Graph shows mean attenuation outside phantom. Error bars indicate SD, which is so small error bars are not evident. X, indicate 0 H; , –650 H; , –820 H; , –1,000 H.

View larger version (12K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B —Variation in mean attenuation in relation to tube current. Graph shows mean ± SD (error bars) attenuation at base of lung within phantom. To improve visualization of changes within samples of lung attenuation materials, water sample is not included. indicate –650 H; , –820 H; , –1,000 H.

View larger version (14K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C —Variation in mean attenuation in relation to tube current. Graph shows mean ± SD (error bars) attenuation at apex of lung inside phantom. indicate –650 H; , –820 H; , –1,000 H.

View larger version (10K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4D —Variation in mean attenuation in relation to tube current. Graph shows SD of mean attenuation of healthy lung (–650 H) at three locations. Similar results were obtained with other samples. indicate apex; , base; , outside of phantom.

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —Mean attenuation in relation to tube current at 15th percentile of attenuation. with solid line indicate mean attenuation of –650 H; with dashed line, attenuation of –650 H at 15th percentile; with solid line, mean attenuation of –820 H; with dashed line, attenuation of –820 H at 15th percentile; with solid line, mean attenuation of –1,000 H; with dashed line, attenuation of –1,000 H at 15th percentile. Graph shows mean and 15th percentile of attenuation outside phantom.

View larger version (11K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —Mean attenuation in relation to tube current at 15th percentile of attenuation. with solid line indicate mean attenuation of –650 H; with dashed line, attenuation of –650 H at 15th percentile; with solid line, mean attenuation of –820 H; with dashed line, attenuation of –820 H at 15th percentile; with solid line, mean attenuation of –1,000 H; with dashed line, attenuation of –1,000 H at 15th percentile. Graph shows mean and 15th percentile of attenuation at base of lung. 15th percentile of attenuation changes more with decreasing tube current than with mean attenuation.

View larger version (11K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C —Mean attenuation in relation to tube current at 15th percentile of attenuation. with solid line indicate mean attenuation of –650 H; with dashed line, attenuation of –650 H at 15th percentile; with solid line, mean attenuation of –820 H; with dashed line, attenuation of –820 H at 15th percentile; with solid line, mean attenuation of –1,000 H; with dashed line, attenuation of –1,000 H at 15th percentile. Graph shows mean and 15th percentile of attenuation at apex of lung. 15th percentile of attenuation changes more with decreasing tube current than with mean attenuation.

View larger version (7K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A —Percentage of pixels with attenuation less than –910 H in relation to tube current. indicates –650 H; , –820 H; , –1,000 H. Graph shows percentage of pixels with attenuation less than –910 H outside phantom for samples of normal lung (–650 H), borderline emphysematous lung (–820 H), and severely emphysematous lung (–1,000 H).

View larger version (8K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B —Percentage of pixels with attenuation less than –910 H in relation to tube current. indicates –650 H; , –820 H; , –1,000 H. Graph shows percentage of pixels with attenuation less than –910 H at base of lung for normal lung (–650 H) and borderline emphysematous lung (–820 H), which overlap, and severely emphysematous lung (–1,000 H).

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6C —Percentage of pixels with attenuation less than –910 H in relation to tube current. indicates –650 H; , –820 H; , –1,000 H. Graph shows percentage of pixels with attenuation less than –910 H at apex of lung for normal lung (–650 H), borderline emphysematous lung (–820 H) and severely emphysematous lung (–1,000 H) samples.

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