Article Figures & Data
Figures
- Fig 1.
CNR in nonenhanced (A) and contrast-enhanced (B) head CT with the use of various tube currents and reconstruction of data by FBP or IR. In the boxplot diagrams, the line across the middle of the box identifies the median sample value; boxes extend from the 25th to the 75th quartile, and whiskers, down to the lowest and highest values.
- Fig 2.
Regression plot of CNR against tube current with IR and FBP. According to linear regression equation, the x-intercept is at a tube current of 255 mAs when y is at a standard 1.98 CNR (320-mAs FBP).
- Fig 3.
Subjective grading of WM-GM differentiation in nonenhanced (A) and contrast-enhanced (B) head CT with use of various tube currents and reconstruction of data by FBP or IR. Data are presented as means and ranges.
- Fig 4.
Example of image quality at 320 (A and D), 275 (B and E), and 225 (C and F) mAs. At all dose levels, use of IR (D−F) is associated with a considerable reduction of noise and enhancement of image quality. As demonstrated in our study, this is achieved without significant loss of image sharpness. While image quality at 85% dose and IR (E) is similar to the standard of reference (A), a 30% dose reduction results in substantial increase of noise despite using IR (F).
Tables
- Table 1:
Patient characteristics and radiation dose in CT protocols with various tube currents
Characteristic 320 mAs 275 mAs 225 mAs P Age 63 ± 14 67 ± 13 66 ± 12 .54 Sex (male/female) 12/18 14/16 19/11 .17 CTDIvol (mGy) 60.1 51.8 42.3 — DLP (mGy.cm) 1043 ± 53 890 ± 34 733 ± 52 <.0001 Effective dose (mSv) 2.2 ± 0.1 1.8 ± 0.07 1.5 ± 1.0 <.0001 Tube Current 320 mAs Tube Current 275 mAs Tube Current 225 mAs IR FBP IR FBP IR FBP Non-Enhanced WM 8.8 ± 2.1 7.9 ± 1, P = 0.01 8.0 ± 1.7 7.0 ± 1.3, P < .0001 7.6 ± 1.5 6.7 ± 1.4, P = .006 GM 10.9 ± 2 9.4 ± 1.4, P < .0001 9.8 ± 1.4 8.3 ± 1.3, P < .0001 9.7 ± 1.8 8.4 ± 1.6, P < .0001 LQ 1.4 ± 0.5 1.2 ± 0.4, P < .0001 1.3 ± 0.4 1.0 ± 0.3, P < .0001 1.2 ± 0.3 1.0 ± 0.3, P < .0006 BG −448 −302, P < .0001 −385 −210, P < .0001 −295 −244, P < .0001 Contrast-Enhanced WM 8.9 ± 1.8 7.6 ± 1.4, P < .0001 7.9 ± 1.5 6.8 ± 1.1, P < .0001 7.8 ± 1.4 6.5 ± 1.0, P < .0001 GM 11.2 ± 1.7 10.2 ± 1.6, P = .001 10.2 ± 1.7 9.0 ± 1.4, P = .0008 9.4 ± 2.1 8.6 ± 1.7, P = .02 LQ 1.3 ± 0.6 1.0 ± 0.4, P < .0001 1.2 ± 0.5 1.0 ± 0.4, P = 0.004 1.1 ± 0.3 0.9 ± 0.4, P < .001 BG −385 −328, P < .0001 −222 −192, P < .008 −221 −191, P < .0001 -
Note: —LQ indicates liquor; BG, background.
-
↵a Data are shown for WM, GM, LQ, and BG measurements in air outside the skull. P values refer to differences between IR and FBP.
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- Table 3:
Mean and median of qualitative image scores in various CT protocols with either IR or FBPa
Tube Current 320 mAs Tube Current 275 mAs Tube Current 225 mAs IR FBP IR FBP IR FBP Non-Enhanced Noise 1.2 (1) 1.6 (1.5), P = .003 1.6 (2) 1.9 (1.75), P = .001 2.0 (2) 2.5 (2.5), P < .0001 GM/WM 1.4 (1) 1.8 (2), P = .002 1.6 (1.5) 2.2 (2.25), P = .009 2.2 (2) 2.9 (3.0), P < .0001 SS 1.4 (1) 1.7 (2), P = .007 1.6 (2) 2.0 (2), P = .01 2.1 (2) 2.7 (3), P = .0006 PF 1.6 (2) 2.0 (2), P = .1 2.0 (2) 2.7 (2.5), P = .001 2.8 (3) 3.4 (3), P = .0002 DA 1.3 (1) 1.7 (2), P = .002 1.7 (2) 2.2 (2), P = .0005 2.2 (2) 2.8 (2.5), P < .0001 Contrast-Enhanced Noise 1.2 (1) 1.4 (1.5), P = .02 1.4 (1) 1.8 (1.75), P = .003 2.1 (2) 2.5 (2.5), P = .0002 GM/WM 1.3 (1) 1.6 (2), P = .002 1.6 (1.5) 2.1 (2), P = .001 2.1 (2) 2.7 (3), P = .0004 SS 1.3 (1) 1.6 (2), P = .004 1.5 (1.75) 1.9 (2), P = .008 2.0 (2) 2.6 (3), P < .0001 PF 1.6 (2) 2.0 (2), P = .01 2.2 (2) 2.5 (2.5), P = .09 2.8 (3) 3.0 (3), P = .2 DA 1.2 (1) 1.8 (2), P = .007 1.6 (2) 2.0 (2), P = .008 2.1 (2) 2.6 (2.5), P = .0003 -
Note:—SS indicates subarachnoid space margins; PF, distinctness of posterior fossa contents; DA, overall diagnostic acceptability.
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↵a Image-quality grading is provided for noise, GM-WM matter differentiation, sharpness of SS, PF, and overall DA. Median is in parentheses.
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