International Atomic Energy Agency Image Quality in Cardiac Angiography L 8.1

International Atomic Energy Agency

Image Quality in Cardiac Image Quality in Cardiac AngiographyAngiography

L 8.1

Lecture 8.1: Image quality in cardiac angiography 2Radiation Protection in Cardiology

Educational ObjectivesEducational Objectives

1. How can image quality of cardiac angiographic images be assessed?

2. How useful can the quality criteria be?


Rotter, EHJ 2003

+112%

+204%

+75%

Interventional cardiology in Europe 1992-1999


EHJ 2001, 2003

PCI in some European Countries(1994-1999)

0

20000

40000

60000

80000

100000

120000

140000

160000

Ger Fra UK Ita Nl Spa

1200 2081

825 1443

242 484

239 763

800 818267 858

1994

1996

1999

per million


Quality of cardiac imagesQuality 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


quality it’s me !!

the interventional cardiologist and quality…


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;25:14–6Miller, Can J Cardiol 1996;12:470–2Cowley, Cathet Cardiovasc Diagn 1993;30:1–4Heupler, Cathet Cardiovasc Diagn 1993;30:191–

200Scanlon, J Am Coll Cardiol 1999;33:1756–824

Quality in invasive cardiology and Quality in invasive cardiology and scientific societiesscientific 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

Quality of cardiac images and scientific Quality of cardiac images and scientific societiessocieties


do we need a method for do we need a method for image quality assessment image quality assessment in the routine practice of in the routine practice of

diagnostic (and diagnostic (and interventional) cardiologyinterventional) cardiology


No technical deficiencies 153 49.6%

No reference segment 32 11.4%

Inadequate separation from background 35 11.4%

Inadequate lesion/vessel separation 67 22%

Inadequate opacification flow 48 15.6%

Inadequate opacification technique 68 22%

Inadequate radiographic procedure 10 3.2%

Totally inadequate 7 2.3%

Epicardial vessel not injected 5 1.6%

Types of technical deficiencies in 308 Types of technical deficiencies in 308 cineangiogramscineangiograms (Leape, Am Heart J 2000;139:106-13)(Leape, Am Heart J 2000;139:106-13)

N %


Percentage of inadequate studies by Percentage of inadequate studies by different hospitals different hospitals (Leape, Am Heart J 2000;139:106-13)(Leape, Am Heart J 2000;139:106-13)

In 12/29 hosp. 50% of studies had deficencies

6 of these are teching hosp.


Country DAP (Gy×cm2) FT (min) No. of frames

median mean median 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

mean fluoroscopy time, frame number and dose-area product (DAP) in some European centers during coronary angiography

Neofotistou, ER 2003+ 41%

+ 113%

+ 288%


0

5

10

15

20

25

30

35

40

45

50

%

Dublin % Leuven % Athens % Madrid %

LEFT-CR (+,+)

LEFT-CAU (+,-)

RIGHT-CR (-,+)

RIGHT-CAU (-,-)

projections’ distribution

11,5

9,2

7,5

15,413,8

12,4

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

16,0

18,0

Udine Dublin Leuven Greece Treviso Spain

Se

rie

s

mean number of series DIMOND 3 data

1000,4

1045,1

982,4

950,0

960,0

970,0

980,0

990,0

1000,0

1010,0

1020,0

1030,0

1040,0

1050,0

Dublin Greece Spain

SII

D (

cm)

focus-detector mean distances


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

quality evaluation of angiographic imagesquality evaluation of angiographic images objective methodsobjective 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

quality evaluation of angiographic imagesquality evaluation of angiographic images subjective methodssubjective methods


test objects


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

quality evaluation of angiographic images quality evaluation of angiographic images clinical images produced in clinical images produced in different conditionsdifferent conditions


1:801:501:1

““lossy” compressionlossy” compression



proper filtering

improper filtering


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

quality evaluation of angiographic imagesquality evaluation of angiographic images limitationslimitations


quality of images is assessed in comparison to pre-

specified 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)

quality evaluation of angiographic imagesquality evaluation of angiographic images

method of quality criteriamethod 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 for

Optimizing Radiological INformation Content and Dose)

contracts FI 4P-0042DG12-WSMN, FIGM-CT-2000-00061-DIMOND

http://www.dimond3.org/

development of Quality Criteriadevelopment of Quality Criteria


Diagnostic requirementsDiagnostic requirementsadapted from EUR 16260 ENadapted 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 detailsProvide 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)


Objectivesto 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’

ModelEuropean guidelines on quality criteria for

diagnostic radiographic images (EUR 16260 EN) where the diagnostic requirements and image criteria are settled


What was not intendedto 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

Warningsunder no circumstances should an image

which fulfils all clinical requirements but does not meet all image criteria ever be rejected*

*EUR 16260 EN


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

definition of termsdefinition of terms


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)


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

clinical criteria for RCA projections based on operator’s choice


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)

technical criteriatechnical criteria


aspects of an optimised angiographic techniqueaspects 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 90-

100 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


Are these criteria, derived from a model

studied for static radiological imaging,

suitable for the more complex cine-

angiogram examinations ?

Based on these criteria, is it possible to

evaluate and quantify quality in an objective

way ?

questions on DIMOND Quality Criteriaquestions on DIMOND Quality Criteria


problems related to subjective evaluation of images ……


problems related to subjective evaluation of images ……


the method of image quality evaluation based on DIMOND Quality Criteria






example of quality score calculation (QS) for RCA



sum of scores = 91 (actual score)

maximum theoretical score = 96

QS = actual score/theoretical score %

= 65/88x100 = 94%

example of QS calculation for RCA


total score (mean and std dev.)total score (mean and std dev.)15 angio, 65 readings, 3 european centers15 angio, 65 readings, 3 european centers

75

80

85

90

95

100

Italy

4

Italy

3

Italy

1

Gre 4

Italy

5

Spa 2

Spa 5

Spa 1

Gre 1

Italy

2

Gre 2

Gre 3

Gre 5

Spa 4

Spa 3

0

2

4

6

8

10

12

14

16

18

20

med

std dev

Linear (med)

% within pts variability = 0.08

Lin’s coeff = .76 (CI .67-.84)

AJC, 1999 (abs)


total score (mean and std dev.)total score (mean and std dev.)30 angio, 160 readings, 6 european centers30 angio, 160 readings, 6 european centers

0

10

20

30

40

50

60

70

80

90

100

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

-4

1

6

11

16

21

med

std dev

Linear (med)

%


good (33 readings) (mean SD)

acceptable (28 readings) (mean SD)

P

total score 96 4 93 9 0,11

total scores compared to subjective opinion “good” and “acceptable”

two cases lacking


what is ?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


RemarksRemarks

the method based on Quality Criteria applies to cardiac angiography

reproducibility is goodmeasure of clinical acceptability seems

improved in comparison to subjective opinion

the method “forces” to a systematic and

standardized analysis of the imagesspecific training not requested (but it may

improve agreement)


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

Quality CriteriaQuality Criteria published paperspublished papers


closing remarksclosing 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.

Documents

International Atomic Energy Agency Image Quality in Cardiac Angiography L 8.1