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Special Requirements for CR QC  In film screen systems the film is changed for every image  With CR the IP is read up to 10,000 times  Almost all plates.

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Presentation on theme: "Special Requirements for CR QC  In film screen systems the film is changed for every image  With CR the IP is read up to 10,000 times  Almost all plates."— Presentation transcript:

1 Special Requirements for CR QC  In film screen systems the film is changed for every image  With CR the IP is read up to 10,000 times  Almost all plates suffer from wear artifacts  If you are suspicious about an artifact take an image using the same plate and no patient  Make sure there is a QC program to detect wear before you detect it clinically Hammerstrom et al J Digital Imaging :226

2 Observations

3  Sharp particulates embedded in the felt lining under a plastic clip etched phosphor surface to create density on radiograph  Not enough pressure beside plastic clip to cause 2 nd wear mark to effect radiograph

4 Observations  Yellowing of phosphor  Virox

5 Observations Dust Scratches

6 CR QC Recommendations  Quality Control (QC) - perform monthly Inspection – cassette and IP Visual Radiographic CR Cassette cleaning CR IP cleaning Benefits Fewer image artifacts and repeated exposures Increased life cycle of cassettes, IPs, and readers Compliance with vendor warranties

7 Retake Analysis  Facilities must maintain records of every retake, including the reason and any corrective actions  An analysis must be done to identify and correct any errors or trends

8 Retake Analysis  Optional Retake Analysis software Agfa - NX Quality Assurance (2008 vers.) Fuji - Retake Analysis Kodak - Administrative Analysis and Reporting Software Software records all exposures and rejected images and produce charts / graphs

9 Retake Analysis - Fuji  Image is rejected (X’d)  Reject reason is assigned by technologist to rejected image  Image information is saved in an exposure log

10 CR Reject/Repeat Analysis By Body Part and Menu Name

11 CR – Repeat/Reject Analysis One month intervals (Feb, 2007 – Oct, 2008)

12 CR – Repeat/Reject Analysis UBCH - IPs Usage (Nov 1 – Dec 31, 2007)

13 Retake Analysis - Fuji  Retake Analysis  Select reject reason  Export as.csv for further data manipulation if desired

14 Retake Analysis - DR  Philips – have electronic retake analysis capture software  Siemens – have promised retake analysis capture software for summer 2009 Until then, use logsheet and manually record rejected images and reason for reject Unreliable data due to “honor system” May need to involve RIS team to supply period stats

15 Digital System QC DetectorReading Viewed Display Digital Processing Stored PACS  Images are used to follow disease processes so it important that the whole digital chain is linear  Linearity should be checked after changes to software/hardware in any component

16 Overview Session 1 Requirements for all systems20 Radiation Protection10 Questions10 Radiography DR/CR20 Radioscopy (Fluoroscopy, Angio), DF20 Questions10 LUNCH

17 Radioscopy (RF + Angio) QC Quality Control ProceduresDFRadioscopic System Weekly Quality Control Tests Visual Inspection of Cleanliness of Imaging Systems W1 Laser Film Printer OperationW3 Digital Subtraction Angiography System Performance Use phantom to check consistency (W7) Quarterly Quality Control Tests Protective devices (Q6)Lead skirts, lead glass etc Table angulation and motion (Q3) Compression devices (Q4) Timer (Q5) Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

18 Annual Radioscopy QC (1) Quality Control ProceduresDFRadioscopic System Annual Quality Control Tests Safelight TestY1 Film/Screen ContactY2 Accuracy of Loading FactorsY3mAs Linearity Radiation Output ReproducibilityY4Reproducibility Radiation Output LinearityY5Output with mAs X-ray Beam FiltrationY6HVL X-ray Field and Light Field Alignment Y8Congruency of x-ray beam and light field edges X-ray Beam CollimationY9Congruency of x-ray beam and light field centres Phantom Dose MeasurementsY18Measure dose at surface of standard phantom eg 20 cm PMMA Typical Image Intensifier Air Kerma Rate Y19eg 20 cm PMMA, Al or Cu Maximum Image Intensifier Air Kerma Rate Y20With detector blocked by lead Automatic Intensity ControlY21Tracking of detector dose with phantom thickness Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

19 Annual Radioscopy QC (2) Quality Control ProceduresDFRadioscopic System Annual Quality Control Tests Image Quality Grid PerformanceY10Check uniformity and movement of grid Exposure IndexY12 Exposure Index versus Dose 1 to 50  Gy Noise, Uniformity and Image ArtifactsY14For above range of dose measure noise in center and each quadrant Check for artifacts Spatial ResolutionY15Line-pair or Leeds phantom Contrast DetectabilityY16Leeds phantom Digital Detector Residual ImagesY17 Take image at 50  Gy then zero; check for artifacts Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

20 Consistency Checks  Weekly/daily Simple phantom to test reproducibility To use if there seems to be a problem

21 Vancouver Phantom  This phantom we have developed for routine constancy QC of digital systems Field collimation Standard operating conditions Resolution Contrast Low contrast circles High contrast mesh

22 Overview Session 1 Requirements for all systems20 Radiation Protection10 Questions10 Radiography DR/CR20 Radioscopy (Fluoroscopy, Angio), DF20 Questions10 LUNCH

23 Overview Session 2 CT20 Equipment Purchase/ Acceptance Testing 15 Patient dose15 Questions10 Personnel qualifications20 Education and training10 Questions20

24 Weekly/Monthly CT QC Quality Control ProceduresCT Systems Weekly QC Tests CT Number AccuracyCheck CT number water 0 ± 4 HU (W4) CT Noise Image noise in center of water phantom ± 10% from baseline value (W5) CT Uniformity Check CT number in center and 4 quadrants ± 10% from baseline value (W6) Monthly QC Tests Electronic Display Devices Performance All device used to display digital images – use pattern SMPTE CT Tomographic Section ThicknessSlice thickness should be ± 0.5 mm from baseline value (M8) Calibration of CT NumberCheck CT number water 0 ± 4 HU and air 1000 ± 10 HU (M9) CT Number LinearityCheck CT number over CT range to (M10) Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

25 3 and 6 monthly CT QC Quality Control ProceduresCT System Quarterly QC Tests Interlocks (Q2)Error? Interlocks are seldom used on CT scanner doors CT Patient Support Movement Check table movement corresponds to digital display ±1 mm (Q8) CT Spatial ResolutionMeasure MTF or line pair phantom (Q9) CT Low Contrast DetectabilityQ10 Semi-annual QC Tests CT Laser Light AccuracyCheck laser light vs X-ray beam with phantom(SY1) CT Accuracy of Automatic Positioning of Tomographic Plane (using the scanned projection radiograph) Check localization scan corresponds to digital display ±2 mm (SY2) CT Accuracy of Gantry TiltSY3 CT Patient DoseCheck CTDI ± 20% from baseline values (SY4) Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

26 Annual CT QC Quality Control ProceduresCT System Annual QC Tests CT Number Dependence on Phantom Position Check CT number water 0 ± 5 HU for possible patient positions in the gantry(Y23) CT Radiation Dose ProfileY24 CT Radiation Dose—Scout Localisation Image Radiation Dose for Localisation Image within 20% of baseline value (Y25) General Preventive MaintenanceBiomed PMs must be performed (Y29) Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS ( annual)

27 QC in CT - Daily  In-air calibration of scanner every 24 hours Adjusts sensitivity of all detectors May be required for each collimation Important to do this – build into schedule.

28 RPS CT QC Frequency FunctionTestWeeklyAnnually MechanicalScan plane congruenceX Couch movementX Collimated beam widthX Image QualityNoise and uniformityXX CT numberXX Spatial resolutionX Imaged slice thicknessX Image linearityX DoseCTDI 100 in airX

29 Dosimetry  CT Dose Index - CTDI  Measured using special cylindrical acrylic phantoms for head and abdomen(FDA)  Special pencil ion chamber has uniform response  One or several slices can be measured

30 QC Phantoms  ACR CT Accreditation Phantom (Gammex 464) Alignment, noise, uniformity, CT number, resolution, MTF, low contrast, image slice width  Scanner QC phantoms GE: noise, uniformity, resolution, MTF, low contrast Siemens: noise, uniformity, MTF


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