Table 2.
Comparison of the Mean (Standard Deviation, SD) of the Contrast to Noise Ratio (CNR), Signal to Noise Ratio (SNR) and Artifact Index (AI) of the polymer and gold fiducials in CT and MRI imaging. The means (SD) relate to the CT number for CT scans and gray-scale for the MRI. Two comparative Backgrounds were used for CNR and SNR, i.e. distant to the artifact for “Phantom”, and the 50 mm square region of interest (ROI) containing the artifact for the “ROI”.
| Statistic: Mean (SD) | Polymer | Gold |
|---|---|---|
| CT | ||
| CNR (Phantom) | 89.4 (25.4) | 491.9 (24.7) |
| CNR (ROI) | 54.2 (3) | 30.1 (7.9) |
| SNR (Phantom) | 103.5 (3.3) | 97 (5.2) |
| SNR (ROI) | 65.6 (15.3) | 5.9 (1.3) |
| AI | 13.7 (5.6) | 191.6 (41.4) |
| MRI | ||
| CNR (Phantom) | 27.3 (5.1) | 29.4 (4.4) |
| CNR (ROI) | 21.2 (1.2) | 24 (3.5) |
| SNR (Phantom) | 70.2 (9.8) | 106.9 (9.1) |
| SNR (ROI) | 52.8 (1.3) | 85.4 (12.1) |
| AI | 5.8 (0.9) | 4.1 (1) |
CNR = Contrast/Noise = (Fiducial mean − Background mean)/(Background SD). SNR = Signal/Noise = (Background mean excluding fiducial)/(Background SD excluding fiducial).
AI = .