ACR MR - Large Phantom
- Designed for simple and intuitive navigation
- Pass/Fail performance evaluation
- User can create Report Profiles to control Pass/Fail limits, output of images, overlays and graphs
- Instant trend analysis using our ‘Trend Report Links’
- Reports available in HTML and PDF formats
- Support local date and number formats
- Multiple language support
- Easy database export to Excel
- Supports compressed and enhanced DICOM images
- Self-service option for offline license activation
Image Quality Parameters Evaluated;
- High contrast spatial resolution
- Slice thickness accuracy
- Slice position accuracy
- Geometric distortion
- Image intensity uniformity
- Signal-to-noise ratio (SNR)
- Low contrast resolution (automatic and visual detection)
- Geometric distortion – Localizer
- High Contrast Spatial Resolution
- User input is required for this measurement. ‘High Contrast Spatial Resolution’ screen displays slice #1 with window/center (w/c) and magnification controls to support proper viewing for resolution determination. 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. Final w/c will be saved and used for the BMP image stored in the final report.
- 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 between approximately 2.5 – 3.1 mm’s.
- The integrated profile is first processed with a 5 pt smoothing kernel. The peak pixel value is determined for the TR and BR profiles and the FWHM is calculated with a baseline correction.
- 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 factor.
- Slice Position Accuracy- the difference between the endpoints of left and right wedge profiles are 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 from ghosting measurement.
- Low Contrast Resolution –
- 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 override automatic low contrast detection and manually input the number of spokes detected. Application Settings default to manual selection which turns on ‘Low Contrast Spatial Resolution’ screen for user input with controls similar to those available for the High Contrast Spatial Resolution screen.
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