Lorad FFDM QC Procedures for Medical Physicist Tao Wu, Ph.D. Hologic, Inc.
Lorad Selenia FFDM
Tests Following Lorad QC Manual Collimation Assessment Artifact Evaluation System Resolution Phantom Image Quality Evaluation Automatic Exposure Control Function Performance Automatic Exposure Control Reproducibility Signal-To-Noise and Contrast-To-Noise Measurements Softcopy Workstation QC
Acquisition Workstation Software
OS Login Medical Physicist username: phys password: phys
Detector Warm-Up After logging in OS, a dialog showing detector warm-up status appears If the system has been running - Dismiss If the system has been shut down - Wait for 30-40 min (or dismiss it and start with tests in which detector is not involved, e.g. HVL, tube output)
Application Login Username:Andrea Password: Andrea
Turn Off Auto-decompression
Send Images to Output Devices
Send Images to Output Devices
Send Images to Output Devices
Non-Imaging Mode
Create a New Patient Account Select No Output
Create a New Patient Account
Create a New Patient Account
Selenia QC Tests
Tests Following Lorad QC Manual Collimation Assessment Artifact Evaluation System Resolution Phantom Image Quality Evaluation Automatic Exposure Control Function Performance Signal-To-Noise and Contrast-To-Noise Measurements Softcopy Workstation QC
Order of Testing Artifact Evaluation Phantom Image Quality Evaluation SNR and CNR Measurements AEC Function Performance Other Tests
Artifact Evaluation Evaluation of detector, x-ray tube, filter etc 4 cm thick acrylic block No compression paddle Four flat field images Mo/Mo, contact mode, LFS with grid Mo/Rh, contact mode, LFS with grid Mo/Mo, mag mode, SFS without grid Mo/Rh, mag mode, SFS without grid Review the images on acquisition workstation monitor Window width = 500, Level = 350
Artifact Evaluation
Artifact Evaluation
Evaluation of Printer Artifact Evaluation Select a computer-generated flat-field image Print the image and evaluate it Repeat the test for each printer If a printer is connected to multiple Selenia systems, it only needs to be tested once from one Selenia.
Artifact Evaluation
Phantom Image Quality Evaluation ACR phantom with acrylic disc AEC position 2 Print film Measure film densities - Background density > 1.20, with control limit ± 0.20 - Density difference over the acrylic disk > 0.40, with control limit ± 0.05 Phantom scoring (hard copy and softcopy station) 5 fibers, 4 speck groups, 4 masses
Phantom Image Quality Evaluation
SNR and CNR Measurements
SNR and CNR Measurements SNR 40 Establish the reference CNR value during the acceptance test CNR should stay within ±15% of the reference
Automatic Exposure Control (AEC) AEC modes Auto-Filter: Auto-kV: Auto-Time: filter, kvp, mas all automatically determined filter manually selected kvp and mas automatically determined filter and kvp manual selected mas automatically determined AEC Method - Filter and kvp are determined by breast thickness (in Auto- Filter and Auto-kV modes) - A pre-exposure is used to determine mas AEC positions Auto-AEC (The densest tissue gets enough exposure) Seven manual positions (marked on compression paddle)
AEC Function Performance 1. Performance at different thickness and imaging modes 2. Performance at different compensation levels
AEC Function Performance 1. Performance at different thickness and imaging modes Acrylic or BR-12 blocks AEC position 2 Contact mode (LFS, grid): 2, 4, 6, 8 cm phantom Mag mode (SFS, no grid): 4 cm phantom Variation of target pixel values 10% of the mean target pixel value
AEC Function Performance
AEC Function Performance 2. Performance at different compensation levels 4 cm acrylic or BR-12 Compensation levels: Step -5 to Step +5 Use average target count at Step 0 as reference Compare target count at other steps to the reference Step -5 0.23 0.28 Step -4 0.36 0.44 Step -3 0.50 0.61 Step -2 0.63 0.77 Step -1 0.77 0.94 Step +1 1.04 1.27 Step +2 1.17 1.43 Step +3 1.31 1.60 Step +4 1.44 1.76 Step +5 1.58 1.93
Collimation Assessment 1. X-Ray Field to Light Field 2. X-Ray Field to Image Receptor 3. Compression Paddle to Image Receptor
Collimation Assessment One test for 24 29 cm imaging mode Three tests for 18 24 cm imaging modes Left imaging position Center imaging position Right imaging position L M R
Collimation Assessment Use coin method as described in ACR manual
Collimation Assessment 1. X-Ray Field to Light Field Measure deviations between the edges of the light field (exterior edge of the coin) and the x- ray field at al four sides Sum of the magnitude of deviations on opposite sides 2% of the SID SID = 66 cm 2% of the SID = 1.32 cm
Collimation Assessment 2. X-Ray Field to Image Receptor d 1 : measured on film distance from the inner edge of the coin to the edge of the x-ray field d 2 : measured on digital image distance from the inner edge of the coin to the edge of the detector (d 1 1.06 ) - d 2 The x-ray field shall extend beyond the chest wall side of the image receptor The x-ray field must NOT extend >2% of the SID at any of the four sides of the image receptor
Collimation Assessment 3. Compression Paddle to Image Receptor Measure distance from the outer edge of the coin to the edge of the image The anterior edge of the compression paddle must be aligned just beyond the chest wall edge of the image receptor, but 1% of the SID
Collimation Assessment
Collimation Assessment
Collimation Assessment
Evaluation of System Resolution Line pair phantom 4 cm acrylic block Line pair phantom placed at 45º to the detector row
Evaluation of System Resolution Limiting spatial resolution 7 c/mm (lp/mm)
Detector Ghosting (Optional) 1. Create ghosting effect 2. Quantify ghosting effect
Detector Ghosting (Optional) 1. Create ghosting effect Ghosting area
Detector Ghosting (Optional) 2. Quantify ghosting effect Ghosting area
Detector Ghosting (Optional) 2. Quantify ghosting effect Ghosting factor 0.3 ROI 1 in background without ghosting Ghosting Factor = ROI 2 in Al filter without ghosting mean region2 -mean region3 mean region1 -mean region2 ROI 3 in Al filter with ghosting
Thank you! Tao Wu twu@hologic.com Tel: 203-207-4574