ACR Large phantom
- High contrast spatial resolution (visual only)
- Slice thickness accuracy
- Slice position accuracy
- Geometric distortion
- Image intensity uniformity
- Signal-to-noise ratio (SNR)
- Low contrast detectability (automatic and visual detection)
Output Available As;
- HTML, PDF
- NoSQL database
- Query database and export to spreadsheet application
- Trend analysis links embedded in HTML file
- User enabled Pass/Fail and user defined limits (default values based on ACR limits)
- Sample report in PDF format
- Chinese, Japanese and Spanish translation supported
- Database shared location user defined
- Self-serviced ‘Off-line’ license activation supported.
- Easy license deactivation if license needs to be moved and used on a different system
- High Contrast Spatial Resolution
- User input is required for this measurement. ‘Report Options’ screen provides a BMP image of the high contrast resolution section. User needs to assess the upper left (UL) and lower right (LR) resolution for the 1.1 mm, 1.0 mm, 0.9 mm sections, and identify the minimum hole size with a row (UL) or column (LR) of holes distinguishable from adjacent holes.
- Slice Thickness Accuracy-
- Horizontal count density profiles are sampled and integrated for the top ramp (TR) and bottom ramp (BR) measurements.
- Sample size is matrix dependent, with sampling width of between approximately 2.5 – 3.1 mm’s.
- The integrated profile is processed with a 5 pt smoothing kernel. The peak pixel value is determined for the TR and BR profiles and the FWHM is calculated.
- Slice Thickness Accuracy reported is the average of the TR and BR FWHM measurements divided by 10.
- Slice Offset – is the difference between the TR and BR ramp centers multiplied by the ramp angle magnification
- Slice Position Accuracy- the difference between the endpoints of left and right wedge profiles were computed and reported according to the instructions provided in the ACR Large Phantom Guidance documentation.
- Geometric Accuracy – reported distance measurements from single pixel profile samples.
- Image Uniformity Intensity- reported measurements calculated according to the instructions provided in the ACR Large Phantom Guidance documentation.
- Ghosting- reported measurements calculated according to the instructions provided in the ACR Large Phantom Guidance documentation
- Signal-to-Noise (SNR) – reported measurement uses the large mean ROI calculated from the Image Intensity Uniformity measurement and the same two background noise (SD) measurements used in ghosting.
- Low Contrast Detectability –
- Automated low contrast target detection is based on maximizing the target means using ROI diameters approximately equal to the target diameters.
- Optimization methods make adjustments in centering and rotation angles of expected target locations.
- Target visualization threshold is >1.0 SD of the target and background mean difference. The mean and standard deviation for background ROI’s were averaged for each target; ROI’s tangential to target for outer two rings and radial to the target for the inner ring.
- Contrast to noise ratio (CNR) is calculated and reported for each Low Contrast image (#8- #11) using 3 targets found in spoke #1 ( 7mm targets.
- Manual Low Contrast – User can over-ride automatic low contrast detection and manually input the number of spokes detected