Lecture presented in Archamps (Salève Building) by :
2012 :15th SESSION of ESMP
Elly CASTELLANO (London)
European School of Medical Physics - Archamps
Quality control in x-ray imaging and CT
Elly Castellano
2European School of Medical Physics - Archamps
Objectives• the quality assurance programme
• the quality control cycle
• physics testing of the imaging chain
• is QC worth it?
3European School of Medical Physics - Archamps
Quality assurance programme• defined as (EU 1997)
All those planned and systematic actions necessary to provide adequate
confidence that a structure, system, component or procedure will perform
satisfactorily in compliance with agreed standards.
• comprises
– quality management
• quality manual
• audit
• training
– quality control
• scheduling and coordinating tests
• making measurements
• analysing and reporting results
4European School of Medical Physics - Archamps
The quality control cycle• required under BSS in EU
– IRR 99 in UK
Clinical use
Radiation safety checks Acceptance testing Commissioning
Routine QCService
Equipment fault
X-ray tubes,
detectors,
software?
5European School of Medical Physics - Archamps
Radiation safety tests• required under BSS
– room shielding
– warning signs and lights
– engineering controls
• deadman operation
• AEC termination
• x-ray tube housing leakage
• x-ray tube filtration
• how do we do it?
– IPEM report 79
– BIR report Radiation shielding for diagnostic x-rays
– IPEM report 32
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Acceptance testing
• manufacturer’s specifications
• how do we do it?
– manufacturer’s protocol
– IPEM report 32
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Commissioning
• opportunity to learn
• pre-requisite for optimisation
• how do we do it?
– no guidance
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Routine Testing
• Guidance in
– IPEM 91
• Simple, frequent tests
• Complex, annual tests
• How do we do it?
– IPEM report 32
• parts I-VII
– IPEM report 89
– IAEA technical reports
• mammography, CT in development
9European School of Medical Physics - Archamps
Physics testing of the imaging
chain
• component tests
– x-ray production
– x-ray detection
– image processing
– image display
• system tests
– doses to phantoms
– image quality
10European School of Medical Physics - Archamps
X-ray productiontest R&F mammo CT test equipment
kV and exposure
time calibration� � � kVp meter
tube output � � � ionisation chamber or solid state
dosimeter
HVL � � � ionisation chamber or solid state
dosimeter, Al filters
focal spot size � � � pinhole, star test object
x-ray field/light
field and beam
alignment
� � alignment test tool
tube leakage � � � ionisation chamber, film cassettes or CR
plates
dose indicator
calibration� � � ionisation chamber, film cassettes or CR
plates, phantoms
11European School of Medical Physics - Archamps
X-ray production: kVp calibration
to CRO
detectors
X-ray
beam
filter pack
• two or more solid state detectors
• filters placed over detectors
• modality specific
0
20
40
60
80
100
120
-0.02 0 0.02 0.04 0.06 0.08 0.1 0.12
Time (Second)
kV
p
50
60
70
80
90
100
110
0.005 0.006 0.007 0.008 0.009 0.01
Time (Second)
kV
p
Frequency ~ 5kHz
12European School of Medical Physics - Archamps
X-ray production: tube output
www.radcal.com
• AK-calibrated dosimeters
• small volume < 10 cm3
• modality specific
• free-in-air measurements
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
4.00 4.20 4.40 4.60 4.80 5.00
ln kV)
ln Y
(d)
0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
13European School of Medical Physics - Archamps
X-ray production: multi-meters• solid state dosimeters
• combined modalities
– e.g. R/F, mammo
• simultaneous parameters
– tube output
– kVp
– HVL
– exposure time
• automatic input to spreadsheet
Unfors Xi
RTI Piranha
14European School of Medical Physics - Archamps
X-ray detection: radiography and
fluoroscopytest FS
Rad
CR
Rad
DR
Rad
fluoro-
scopy
fluoro-
graphy
FS CR DR
test equipment
AEC
performance� � � � � phantoms, densitometer
detector dose
under AEC� � � � � ionisation chamber or SS
dosimeter, attenuator
detector
matching� � attenuator, densitometer
detector
response� � � � (DR) ionisation chamber or SS
dosimeter, attenuator
detector
resolution� � � � *high contrast grating
detector
artifacts� � � � � attenuator, mesh
beam spillover � film or CR cassettes
15European School of Medical Physics - Archamps
X-ray detection: detector dose
under AEC• contact measurement
• AK calibrated ionisation
chambers
– medium volume < 100 cm2
– detect backscatter
• AK calibrated dosimeters
– must not occlude AEC sensor
16European School of Medical Physics - Archamps
X-ray detection: mammography
and CTtest mammo
FS
mammo
CR
mammo
DR
CT test equipment
AEC
performance� � � � phantoms, densitometer
detector dose
under AEC
detector
matching� �
detector
response� � ionisation chamber or SS
dosimeter, attenuator
detector
resolution� � � *high contrast grating
detector artifacts � � � attenuator, mesh
beam spillover � � � film or CR cassettes
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Image processing
test FS
Rad
CR
Rad
DR
Rad
fluoro mammo CT test equipment
dark room
lightproofing� � (FS) � (FS)
processor tests –
developer temp
replenish rate
pH
� � (FS) � (FS) *
CR reader tests –
calibration
laser function
erasure cycle
efficiency
� � (CR) � (CR) dosimeter, test
objects
processing
algorithms�
18European School of Medical Physics - Archamps
Image display
test F/S
Rad
CR
Rad
DR
Rad
fluoro mammo CT test
equipment
film tests –
sensitometry,
resolution
� � � � sensitometer,
densitometer,
test patterns
light box tests –
luminance� (film) lightmeter
monitor tests
(acquisition) –
luminance response
resolution
� lightmeter, test
patterns
monitor tests
(reporting) –
luminance response
resolution
� � � � � lightmeter, test
patterns
19European School of Medical Physics - Archamps
System tests
test F/S
Rad
CR
Rad
DR
Rad
fluoro mammo CT test equipment
dose to
phantoms� � � ionisation chamber,
phantoms
image
uniformity� � � � � � phantoms
contrast detail
performance� � � � � phantoms, test objects
system
response� phantoms, test objects
system
resolution� � phantoms, test objects
20European School of Medical Physics - Archamps
System tests: dose to phantoms
• phantoms
– modality-specific
– Perspex slabs, cylinders
• AK calibrated ionisation
chambers
– modality specific
– detect backscatter
• typical exposure geometry
21European School of Medical Physics - Archamps
System tests: image quality
• test objects
– modality-specific
– used with/in phantoms
• image quality parameters
– uniformity
– contrast detail performance
– system resolution
fluoroscopy
Leeds TOR 18FG
Leeds TO 10
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System tests: image quality in
mammography
Leeds TOR MAM Leeds TOR MAX
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System tests: image quality in CT
Catphan
GE
24European School of Medical Physics - Archamps
Is QC worth it?
• acceptance
– CT scanner table in wrong place
– filtration too low
– mammo collimator in wrong place
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Is QC worth it?• routine testing
– fault in stator rotation
– incorrect Cu filter in fluoroscopy unit
– drift in CT scanner calibration
-10
-8
-6
-4
-2
0
2
4
6
8
10
10/12/2002 28/06/2003 14/01/2004 01/08/2004 17/02/2005
QA date
CT
nu
mb
er
ca
l
0.5 mm row 1
0.5 mm row 2-10
-8
-6
-4
-2
0
2
4
6
8
10
10/12/2002 28/06/2003 14/01/2004 01/08/2004 17/02/2005
QA date
CT
nu
mb
er
un
ifo
rmit
y0.5 mm row 1
0.5 mm row 2
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Summary• QA and QC introduced
• overview of physics testing of the imaging chain
provided
• merits of QC testing discussed
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Acknowledgements
• Claire Skinner