Transcript IAEA Training Material on Radiation Protection in Cardiology

International Atomic Energy Agency
Image Quality in Cardiac
Angiography
L 8.1
Educational Objectives
1. How can image quality of
cardiac angiographic images be
assessed?
2. How useful can the quality
criteria be?
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Lecture 8.1: Image quality in cardiac angiography
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Interventional cardiology in Europe 1992-1999
+112%
+204%
+75%
Rotter, EHJ 2003
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Lecture 8.1: Image quality in cardiac angiography
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PCI in some European Countries
(1994-1999)
160000
140000
1994
1996
1999
120000
100000
80000
60000
825
20000
239
1443
242
763
484
800
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Fra
UK
Ita
818
Nl
OL
A
Ger
GE
R
0
per million
2081
GB
40000
1200
Lecture 8.1: Image quality in cardiac angiography
267
858
Spa
EHJ 2001, 2003
4
Quality of cardiac images
• background
• cardiac cine-angiographic images
•
•
•
•
should allow the cardiologist to evaluate
the anatomic (and sometimes functional)
details which are relevant for clinical
decision making
variables
technical performance of the imaging
system
patient cooperation
angiographic technique
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the interventional cardiologist and quality…
quality it’s me !!
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Quality in invasive cardiology and
scientific societies
Scientific societies implemented guidelines to guarantee adequate
level of quality and performance of invasive cardiology
•
•
•
training of operators
quantitative standards to maintain the expertise in coronary
angiography or angioplasty
quality-assurance programme
Pepine, J Am Coll Cardiol 1995;25:14–6
Miller, Can J Cardiol 1996;12:470–2
Cowley, Cathet Cardiovasc Diagn 1993;30:1–4
Heupler, Cathet Cardiovasc Diagn 1993;30:191–200
Scanlon, J Am Coll Cardiol 1999;33:1756–824
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Lecture 8.1: Image quality in cardiac angiography
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Quality of cardiac images and scientific
societies
the specific problem of achieving and
maintaining high-quality standards in
angiographic imaging
• responsibility of cardiac catheterization laboratory
directors
• involves periodic cine-angiograms review
• lesion quantification (QCA, calipers)
precise criteria have never been stated for
coronary procedures
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Lecture 8.1: Image quality in cardiac angiography
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do we need a method for
image quality assessment
in the routine practice of
diagnostic (and
interventional) cardiology
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Types of technical deficiencies in 308
cineangiograms (Leape, Am Heart J 2000;139:106-13)
No technical deficiencies
No reference segment
Inadequate separation from background
Inadequate lesion/vessel separation
Inadequate opacification flow
Inadequate opacification technique
Inadequate radiographic procedure
Totally inadequate
Epicardial vessel not injected
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Lecture 8.1: Image quality in cardiac angiography
N
%
153
32
35
67
48
68
10
7
5
49.6%
11.4%
11.4%
22%
15.6%
22%
3.2%
2.3%
1.6%
10
Percentage of inadequate studies by
different hospitals (Leape, Am Heart J 2000;139:106-13)
In 12/29 hosp.
50% of studies had
deficencies
6 of these are
teching hosp.
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mean fluoroscopy time, frame number and dose-area
product (DAP) in some European centers during coronary
angiography
+ 288%
Country
DAP (Gy×cm2)
FT (min)
median mean median
No. of frames
mean
median
mean
Greece
38.6
46.7
5.5
7.1
1620
960
Spain
27.8
39.4
6.4
9.4
903
1596
Italy
28.2
33.5
3.0
4.2
570
610
England
28.2
33.5
3.0
4.2
570
610
Ireland
33.3
37.5
3.2
4.4
580
585
Finland
39.6
52.7
4.1
4.8
417
803
+ 41%
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+ 113%
Neofotistou, ER 2003
Lecture 8.1: Image quality in cardiac angiography
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DIMOND 3 data
mean number of series
18,0
15,4
16,0
13,8
14,0
Series
12,0
12,4
11,5
9,2
10,0
projections’ distribution
7,5
8,0
6,0
4,0
50
2,0
45
0,0
Udine
Dublin
Leuven
Greece
Treviso
Spain
40
35
1045,1
SIID (cm)
1050,0
30
LEFT-CR (+,+)
% 25
LEFT-CAU (+,-)
20
RIGHT-CR (-,+)
15
RIGHT-CAU (-,-)
1040,0
10
1030,0
5
1020,0
0
1010,0
Dublin %
Leuven %
Athens %
Madrid %
1000,4
1000,0
990,0
982,4
980,0
970,0
960,0
950,0
Dublin
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Greece
Spain
focus-detector mean distances
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quality evaluation of angiographic images
objective methods
based on measurement of some physical parameters
• system transfer factor K
• spatial resolution (MTF, modulation transfer function)
• detective quantum efficiency (DQE)
• noise
they are rather complex and rarely applied to daily practice
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quality evaluation of angiographic images
subjective methods
 test objects or phantoms
• they are able to simulate the same radiation
conditions as the part of the body
• they describe behaviour of radiology equipment
in specific operating condition
 evaluation of clinical images
• allow evaluation of the overall performance
including patient’s collaboration and technique
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Lecture 8.1: Image quality in cardiac angiography
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test objects
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quality evaluation of angiographic images clinical images produced in
different conditions
 binary classification
• pre-defined feature identification, normal vs. abnormal
(this is typically used with test objects )
• correct answer must be known
• borderline visibility
 progressive judgement in terms of quality
• variable level quality (clarity of thoracic calcification,
arrange images in order of preference)
• strength of agreement by different observers gives
indications on superiority
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“lossy” compression
1:1
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Lecture 8.1: Image quality in cardiac angiography
1:80
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improper filtering
proper filtering
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quality evaluation of angiographic images
limitations
 set of reference images difficult to obtain
 use limited settings where perceptibility of
abnormal feature is under experimenter’s
control
 quality measurement is only relative
 clinical adequacy not evaluated
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quality evaluation of angiographic images
method of quality criteria
quality of images is assessed in comparison to prespecified criteria to comply with
effective and relevant in clinical practice
• radiographic images (Maccia, Radiat Protect
Dosim
1995; Vañò, Br J Radiol 1995, Radiat Prot Dosim 1998;
Perlmutter, Radiat Prot Dosim 1998)
• CT scan (Calzado, Radiat Prot Dosim 1998)
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development of Quality Criteria
1995-1996: GISE Società Italiana di Cardiologia
Invasiva and AIFM Associazione Italiana di
Fisica Biomedica
1996–2003: European Concerted Action DIMOND
Cardiology Group
(Digital
Imaging:
Measures
Optimizing Radiological INformation Content and Dose)
contracts FI 4P-0042DG12-WSMN, FIGM-CT-2000-00061-DIMOND
http://www.dimond3.org/
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for
Diagnostic requirements
adapted from EUR 16260 EN
Image criteria
In most cases specify important anatomical structures that
should be visible on an image to aid accurate diagnosis. Some of
these criteria depend fundamentally on correct positioning and
cooperation of the patient or good angiographic technique,
whereas others reflect technical performance of the imaging
system
Important image details
Provide quantitative information on the minimum sizes at which
important anatomical details should become visible on the
image. Some of these anatomical details may be pathological and
therefore may not be present (ex. mitral insufficiency)
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Objectives
to
set guidelines and give methods for the
evaluation of image quality in
– Left Ventriculography
– Left Coronary Angiography
– Right Coronary Angiography
– Angiography of Venous Graft or Arterial Free Graft
– Angiography of Left Mammary Artery ‘In Situ’
Model
European
guidelines on quality criteria for
diagnostic radiographic images (EUR 16260 EN)
where the diagnostic requirements and image
criteria are settled
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What was not intended
to repeat what has already been included in
the manuals of Coronary Angiography, but
to give some guidelines about how an
angiogram should appear provided that
good equipment and a correct angiographic
technique are used
Warnings
under
no circumstances should an image
which fulfils all clinical requirements but
does not meet all image criteria ever be
rejected*
*EUR 16260 EN
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definition of terms
 Clinical criteria are defined as important anatomical features that should
be visible; the level of visualisation is as follows
 visualization: characteristic features are detectable, but details are not
fully reproduced (features just visible)
 reproduction:
details of anatomical structures are visible, but not
necessarily clearly defined (details emerging)
 visually
sharp reproduction: anatomical details are clearly defined
(details clear)
 Technical criteria
 help to asses the technical quality of the procedure
 features not necessarily impair the clinical information content
(panning, arms position, etc.)
 Aspects of an optimised angiographic technique
 set of technical information
 aimed to an optimised radiological technique
 not mandatory
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visualization: characteristic features are detectable,
but details are not fully reproduced (features just
visible)
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reproduction: details of anatomical structures are visible,
but not necessarily clearly defined (details emerging)
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visually sharp reproduction: anatomical details are clearly
defined (details clear)
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clinical criteria for RCA projections based on operator’s
choice
1) Visually sharp reproduction of the origin, proximal,
mid (especially the crux region) and distal portion in
at least two orthogonal views, with minimal
foreshortening and overlap
2) Visually sharp reproduction of side branches  1.5
mm in at least two orthogonal views, with minimal
foreshortening and overlap. The origin should be seen
in at least one projection
3) Visually sharp reproduction of lesions in vessels  1.5
mm in at least two orthogonal views, with minimal
foreshortening and overlap
4) Visualization of collateral circulation when present
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technical criteria
1) Simultaneous and full opacification of the vessel
lumen at least until the first flow-limiting lesion (in
general ~ 90-95% by visual estimation)
2) Performed at full inspiration if necessary to avoid
diaphragm superimposition or to change anatomic
relationship (in apnoea in any case)
3) Arms should be raised clear of the angiographic field
4) Panning should be limited. If necessary, pan in steps
rather than continuously, or make subsequent cine
runs to record remote structures
5) When clinical criteria 1-4 have been fulfilled, avoid
extra projections (mainly LAO semi-axial)
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aspects of an optimised angiographic technique
1) Use of the wedge filter on bright peripheral areas
2) 2-3 sequences (except for difficult anatomic details)
3) 12.5-15 frames/s (25-30 only if heart rate exceeds 90100 bpm or in paediatric patients)
4) 60 images per sequence at average (12.5-15 fr/s)
except if collaterals have to be imaged or in case of
slow flow
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questions on DIMOND Quality Criteria
Are
these criteria, derived from a model
studied for static radiological imaging,
suitable for the more complex cineangiogram examinations ?
Based
on these criteria, is it possible to
evaluate and quantify quality in an objective
way ?
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problems related to subjective evaluation of
images ……
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problems related to subjective evaluation of
images ……
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the method of image quality
evaluation based on
DIMOND Quality Criteria
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the method of image quality
evaluation based on
DIMOND Quality Criteria
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the method of image
quality evaluation based on
DIMOND Quality Criteria
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example of quality score calculation (QS) for
RCA
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
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












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example of QS
calculation for RCA










sum of scores = 91 (actual score)

maximum theoretical score =

96
QS = actual score/theoretical score %
= 65/88x100 = 94%



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total score (mean and std dev.)
15 angio, 65 readings, 3 european centers
100
20
18
95
16
14
90
12
med
10
%
within pts variability = 0.08
85
Linear (med)
8
6
Lin’s coeff = .76 (CI .67-.84)
80
std dev
4
2
75
ly
Ita
0
4
ly
Ita
3
ly
Ita
1
re
G
4
ly
Ita
5
S
pa
2
S
pa
5
S
pa
1
re
G
1
ly
Ita
2
re
G
2
re
G
3
re
G
5
S
pa
4
S
pa
3
AJC, 1999 (abs)
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total score (mean and std dev.)
30 angio, 160 readings, 6 european centers
100
21
90
80
16
70
60
11
med
50
%
std dev
Linear (med)
40
6
30
20
1
10
0
-4
1
3
5
7
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11
13
15
17
19
21
23
25
Lecture 8.1: Image quality in cardiac angiography
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29
44
total scores compared to subjective
opinion “good” and “acceptable”
good (33 readings)
(mean  SD)
acceptable (28 readings)
(mean  SD)
P
96  4
93  9
0,11
total score
two cases lacking
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what is ?
good
I get all the information needed to treat the patient
and I like this examination
acceptable
I get all the information needed to treat the patient
but I don’t like very much this examination
unacceptable
I don’t get all the information needed to treat the
patient and I don’t like this examination at all
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Remarks
the method based on Quality Criteria applies
to cardiac angiography
reproducibility is good
measure of clinical acceptability seems
improved in comparison to subjective
opinion
 the method “forces” to a systematic and
standardized analysis of the images
specific training not requested (but it may
improve agreement)
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Quality Criteria published papers
Criteri di Qualità dell’Immagine Cineangiografica (documento
preliminare). Emodinamica 1997; 10 (suppl.): 9-11
Quality criteria of imaging in diagnostic and interventional
cardiology. TCT-196: Am J Cardiol, 1999:84(6A):73P-74P
A method based on DIMOND Quality Criteria to evaluate imaging
in diagnostic and interventional cardiology. Radiat Prot Dosim
2001;94:167-172
Quality Criteria for cardiac images in diagnostic and
interventional cardiology. Br J Radiol 2001; 74:852-855
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closing remarks
 image quality is not warranted in coronary angiography
 a great variability is found in common practice among different
operators and radiological exposure varies considerably
 image quality assessment plays a pivotal role in the optimisation
of angiographic procedures
 optimisation implies a continuous process of research and audit
which should involve
 Scientific Societies
 single operators
 cooperation of all professionals in the Cath. Lab.
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