Transcript QC in a Digital World

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 2006 19:226
Observations
Observations
 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 2nd wear mark to
effect radiograph
Observations
 Yellowing of
phosphor
 Virox
Observations
Dust
Scratches
CR QC Recommendations
 Quality Control (QC) - perform monthly
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Inspection – cassette and IP
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Visual
Radiographic
CR Cassette cleaning
CR IP cleaning
Benefits
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Fewer image artifacts and repeated exposures
Increased life cycle of cassettes, IPs, and readers
Compliance with vendor warranties
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
Retake Analysis
 Optional Retake Analysis software
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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
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
CR Reject/Repeat Analysis
By Body Part and Menu Name
CR – Repeat/Reject Analysis
One month intervals
(Feb, 2007 – Oct, 2008)
CR – Repeat/Reject Analysis
UBCH - IPs Usage (Nov 1 – Dec 31, 2007)
Retake Analysis - Fuji
 Retake
Analysis
 Select reject
reason
 Export as
.csv for
further data
manipulation
if desired
Retake Analysis - DR
 Philips – have electronic
retake analysis capture
software
 Siemens – have promised
retake analysis capture
software for summer 2009
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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
Digital System QC
Detector
Reading
Digital
Processing
Stored
PACS
Viewed
Display
 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
Overview Session 1
Requirements for all systems
20
Radiation Protection
10
Questions
10
Radiography DR/CR
20
Radioscopy (Fluoroscopy, Angio), DF 20
Questions
LUNCH
10
Radioscopy (RF + Angio) QC
Quality Control Procedures
DF
Radioscopic System
Visual Inspection of Cleanliness of Imaging
Systems
W1
W1
Laser Film Printer Operation
W3
W3
Weekly Quality Control Tests
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
Annual Radioscopy QC (1)
Quality Control Procedures
DF
Radioscopic System
Safelight Test
Y1
Y1
Film/Screen Contact
Y2
Y2
Accuracy of Loading Factors
Y3
mAs Linearity
Radiation Output Reproducibility
Y4
Reproducibility
Radiation Output Linearity
Y5
Output with mAs
X-ray Beam Filtration
Y6
HVL
X-ray Field and Light Field
Alignment
Y8
Congruency of x-ray beam and light field edges
X-ray Beam Collimation
Y9
Congruency of x-ray beam and light field centres
Phantom Dose Measurements
Y18
Measure dose at surface of standard phantom eg
20 cm PMMA
Typical Image Intensifier Air
Kerma Rate
Y19
eg 20 cm PMMA, Al or Cu
Maximum Image Intensifier Air
Kerma Rate
Y20
With detector blocked by lead
Automatic Intensity Control
Y21
Tracking of detector dose with phantom thickness
Annual Quality Control Tests
Normal Font – Required Test (“must do”)
Italics - Recommended Test (“recommended”)
Required Tests currently recommended by RPS
Annual Radioscopy QC (2)
Quality Control Procedures
DF
Radioscopic System
Grid Performance
Y10
Check uniformity and movement of grid
Exposure Index
Y12
Exposure Index versus Dose 1 to 50 mGy
Noise, Uniformity and Image Artifacts
Y14
For above range of dose measure noise in
center and each quadrant
Check for artifacts
Spatial Resolution
Y15
Line-pair or Leeds phantom
Contrast Detectability
Y16
Leeds phantom
Digital Detector Residual Images
Y17
Take image at 50 mGy then zero;
check for artifacts
Annual Quality Control Tests
Image Quality
Normal Font – Required Test (“must do”)
Italics - Recommended Test (“recommended”)
Required Tests currently recommended by RPS
Consistency Checks
 Weekly/daily
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Simple phantom to test reproducibility
To use if there seems to be a problem
Vancouver Phantom
 This phantom we have
developed for routine
constancy QC of
digital systems
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Field collimation
Standard operating
conditions
Resolution
Contrast
Low contrast
circles
High contrast
mesh
Overview Session 1
Requirements for all systems
20
Radiation Protection
10
Questions
10
Radiography DR/CR
20
Radioscopy (Fluoroscopy, Angio), DF
20
Questions
10
LUNCH
Overview Session 2
CT
20
Equipment Purchase/ Acceptance Testing
15
Patient dose
15
Questions
10
Personnel qualifications
20
Education and training
10
Questions
20
Weekly/Monthly CT QC
Quality Control Procedures
CT Systems
Weekly QC Tests
CT Number Accuracy
Check 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 Thickness
Slice thickness should be ± 0.5 mm from baseline value (M8)
Calibration of CT Number
Check CT number water 0 ± 4 HU and air 1000 ± 10 HU (M9)
CT Number Linearity
Check CT number over CT range -1000 to +1000 (M10)
Normal Font – Required Test (“must do”)
Italics - Recommended Test (“recommended”)
Required Tests currently recommended by RPS
3 and 6 monthly CT QC
Quality Control Procedures
CT 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 Resolution
Measure MTF or line pair phantom (Q9)
CT Low Contrast Detectability
Q10
Semi-annual QC Tests
CT Laser Light Accuracy
Check 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 Tilt
SY3
CT Patient Dose
Check CTDI ± 20% from baseline values (SY4)
Normal Font – Required Test (“must do”)
Italics - Recommended Test (“recommended”)
Required Tests currently recommended by RPS
Annual CT QC
Quality Control Procedures
CT 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 Profile
Y24
CT Radiation Dose—Scout Localisation
Image
Radiation Dose for Localisation Image within 20%
of baseline value (Y25)
General Preventive Maintenance
Biomed PMs must be performed (Y29)
Normal Font – Required Test (“must do”)
Italics - Recommended Test (“recommended”)
Required Tests currently recommended by RPS ( annual)
QC in CT - Daily
 In-air calibration of scanner every 24 hours
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Adjusts sensitivity of all detectors
May be required for each collimation
Important to do this – build into schedule.
RPS CT QC Frequency
Function
Mechanical
Image Quality
Dose
Test
Weekly
Annually
Scan plane congruence
X
Couch movement
X
Collimated beam width
X
Noise and uniformity
X
X
CT number
X
X
Spatial resolution
X
Imaged slice thickness
X
Image linearity
X
CTDI100 in air
X
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
QC Phantoms
 ACR CT Accreditation Phantom
(Gammex 464)
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Alignment, noise, uniformity, CT
number, resolution, MTF, low contrast,
image slice width
 Scanner QC phantoms
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GE: noise, uniformity, resolution, MTF,
low contrast
Siemens: noise, uniformity, MTF