Article Figures & Data
Figures
- Fig 1.
A, Positioning of the sheep, a 4-year-old 72-kg hornless white Dorper ewe, in the CT scanner. B, Sample coronal head CT images with ROIs marking the cortical gray matter (yellow) and deep white matter (blue) for quantitative analysis.
- Fig 2.
Benchmark coronal head CT images for rating scales of gray-white differentiation: 982 mAs with FBP for score = 4 (A), 573 mAs with FBP for score = 3 (B), 327 mAs with FBP for score = 2 (C), and 82 mAs with FBP for score = 1 (D).
- Fig 3.
Benchmark coronal head CT images for rating scales of image texture: 409 mAs with FBP for score = 4 (A), 982 mAs with FBP for score = 3 (B), 982 mAs with ADMIRE-3 for score = 2 (C), and 982 with ADMIRE-5 for score = 1 (D).
- Fig 4.
Heat maps of qualitative ratings of gray-white differentiation (A), image texture (B), and combined scores (C). Note that scores of 2 in the bottom left corner of the texture heat map were reclassified from original scores of 4 as explained in the Materials and Methods section. Most important, the low scores in the top right corner of texture heat map reveal the inadequacy of the high-dose and high-strength combination. The greatest dose reduction (58%) that preserves comparable gray-white differentiation and texture to the reference FBP (blue outline) is achieved at 409 mAs with ADMIRE-5 (green outline).
- Fig 5.
Sample coronal head CT images comparing FBP (left column) and ADMIRE-5 (right column) at the reference dose (A), 8% dose reduction (B), 58% dose reduction (C), and 75% dose reduction (D). Gray-white detectability and image texture were subjectively scored as equivalent between the reference dose with FBP (left, A) and a 58% dose reduction with ADMIRE-5 (right, C) as marked with an asterisk.
- Fig 6.
SD (ie, noise) of the white matter (A), signal-to-noise of the white matter (B), and contrast-to-noise of the cortex (C) for each run, from the highest (982 mAs) to lowest (82 mAs) effective dose; FBP followed by ADMIRE 1–5 for each dose level. Noise, SNR, and CNR all improve with higher IR strength but worsen with dose reduction. Noise, SNR, and CNR equivalent to the reference image (ie, highest dose with FBP) as illustrated by red horizontal line can be maintained with a 67% dose reduction at the highest IR strengths. Equivalent noise, SNR, and CNR cannot be preserved at further dose reductions regardless of IR strength. The last graph (D) relates CNR of the cortex to the radiation dose for each reconstruction technique. In each case, the CNR decreases with progressive dose reduction. However, for any given radiation dose, higher IR strengths improve the CNR. If the CNR is to be preserved, dose reduction must be complemented by higher IR strength.
