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International Atomic Energy AgencyIAEA

Optimization of Radiation Optimization of Radiation Protection in CardiologyProtection in Cardiology

L 9

Lecture 9: Optimization of Radiation Protection in Cardiology 2 IAEARadiation Protection in Cardiology IAEA

Educational ObjectivesEducational Objectives

1. Optimization in interventional cardiology

2. Ways to improve the radiation protection aspect of procedure (balancing diagnostic information versus patient doses)

3. A single-centre’s (Udine, Italy) experience with optimization and flat panel detector


Is this statement “True” or “False”?Is this statement “True” or “False”?

1. Switching from old angiography machine with image intensifier to a new machine with flat-panel detector will definitely reduce patient radiation dose.


In room dosimetric indications

Have you ever paid attention to this?


Do you know how to interpret these data?Do you know how to interpret these data?


Reality check……Reality check…… Dose Information and Dose Reports Dose Information and Dose Reports

• Understanding the dose information available in the cath. lab.?

• Do you follow (and archive) patient dose reports?• Understanding the dose values in your occupational

dose report?

• Can you make out if the dose values as depicted in the monitor in cath. lab. are “normal” or “too high”?


Reality check……Reality check…… Knowing your X ray machine Knowing your X ray machine

• What is the “cost” in radiation dose you are “paying” for the image quality you want?

• Have you evaluated whether fewer images with lower image quality are acceptable?

• Do you know the dose rate values and dose/image for the different operation modes?

• Do you know the difference in dose for the different field of view (FOV) formats (magnification)?

• Do you know how to use the newer dose-reducing features?


Siemens Axiom ArtisCine normal mode

20 cm PMMA177 Gy/fr (entrance PMMA)

Siemens Axiom Artis, Fluoro low dose

20 cm PMMA13 Gy/fr (entrance PMMA)


Optimization means ...Optimization means ...

• To avoid acquiring more images than necessary:• Take care of the fluoroscopy time.

• Take care of the number of series.

• Take care of the number of frames per series.

• To avoid acquiring images with more quality (and more dose) than necessary:• It could be possible to accept sometimes some noisy

images in fluoroscopy and also in cine acquisitions.


Optimization of Radiation ProtectionOptimization of Radiation Protection

• Minimization of dose to patient and staff should not be the goal

• Must optimize dose to patient and minimize dose to staff

• Optimized patient dose rate should have sufficient dose rate to provide adequate image quality

If image quality is inadequate, then any radiation dose results in needless radiation dose!


One of the center's experience with One of the center's experience with new angiographic machine having new angiographic machine having

flat panel detectorflat panel detector


Motorized Iris

Video Camera

Image Intensifier

DE

TE

CT

OR

DE

TE

CT

OR

Photons

Cesium Iodide (CsI)

Light

Amorphous Silicon Panel(Photodiode/Transistor Array)

Digital DataDigital Data

Electrons

Read Out Electronics

Photons

Cesium Iodide (CsI)

Light

Photo-cathode

Video SignalVideo Signal

Electrons

Output screen

Light

CCD or PUT

Electrons

Readout Electronics

1

3,000

400

400,000

2,400

Particles #

ImageIntensifier

Flat-panel


Anticipated per-frame dose Anticipated per-frame dose reduction with Digital Flat reduction with Digital Flat Panel technology is 30%Panel technology is 30%


Coronary Angiography and AngioplastyCoronary Angiography and AngioplastyUdine,Udine, years 1990-2002years 1990-2002

0

500

1000

1500

2000

'90 '91 '92 '93 '94 '95 '96 '97 '98 '99 '00 '01 '02 '03

diagnosticPCI

Philips OM 200 (1983)

Philips Integris 3000 (1995)

performed by 3 interventionalists except in 1998


GE Innova 2000 (angiographic machine with GE Innova 2000 (angiographic machine with digital flat panel technology) at Udine Centerdigital flat panel technology) at Udine Center

• Activity started

04/12/2002

• Jan - Oct 2003

1421 procedures (79% of total)

• 1019 diagnostic coronary angiography

• 402 percutaneous coronary angioplasty


66

77

1.9

56

31.233.4

35.4

66

78

1.9

53

30.8

38.5

30.8

0

10

20

30

40

50

60

70

80

90

age (y) male sex (%) BSA (sqm) EF (%)

1 2 3

Comparison of Philips H 3000 and Innova 2000 in PCI

-- -- Characteristics of patientsCharacteristics of patients

diseased vessels (%)

H 3000: 588 pts, 90% of tot. treated in the year 2002

Innova: 274 pts, 67% of tot. treated between Jan-Oct 2003


65.9

22.9

11.314.8

6.12.6 3.2

56.5

25.5

15.3

10.2

3.6 2.96.6

0

10

20

30

40

50

60

70

H 3000

Innova


-- Characteristics of procedures & lesions (1)Characteristics of procedures & lesions (1)

%


29

22.2

6.2

18.1

4.8

12.8

37.2

22.3

4.7

16.1

3.6 3.3

0

5

10

15

20

25

30

35

40

H 3000Innova


-- Characteristics of procedures & lesions (2)Characteristics of procedures & lesions (2)

%


0

10

20

30

40

50

60

70

Fluoro T proced. T room occ. contrast (dl)

(m’)


-- Performance & complexity indexPerformance & complexity index

1,37

1

1,47

0,93

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

Comp.

Inde

x

GIS

E Inde

x

r (with fluoro time)

0.30 0.29 0.34 0.26

11,6

11,5

40

48

59

84

24,1 21,

6

H 3000

Innova


67

1.9

72

99

71

20 1812

9

67

1.9

74

98

69

2024

19

9

0

20

40

60

80

100

120

Comparison of Philips H 3000 and Innova 2000 in Comparison of Philips H 3000 and Innova 2000 in diagnostic proceduresdiagnostic procedures

-- -- Characteristics of patients & proceduresCharacteristics of patients & procedures

(%)

H 3000: 1401 pts, 92% of tot. studied in the year 2002

Innova: 702 pt, 69% of tot. studied between Jan-Oct 2003

Lecture 9: Optimization of Radiation Protection in Cardiology 21 IAEARadiation Protection in Cardiology IAEAm’ Gy * cm2

measured

Comparison of Philips H 3000 and Innova 2000 in diagnostic procedures

-- performance indexes and exposure parametersperformance indexes and exposure parameters

calculated

4.2

24

54

15.6

20.39

10.67

31.06

4.4

28

54

15.8

27.05

18.83

45.88

35.32

0

10

20

30

40

50

60

Fluoro T

proced. T

room occ.

contrast (dl)

cine DAP

fluoro DAP

tot. DAP

1,3

H 3000

Innova


Entrance surface dose: H3000 and Innova 2000Entrance surface dose: H3000 and Innova 2000

0

10

20

30

40

50

60

70

Entrance dose rate

(mGy/min)

Low Normal High

Image quality

Entrance surface dose rates, FOV=17 cm, PMMA=20 cm

H3000

Innova2000

Entrance surface dose rates in Fluoro LOW for Innova is 30% less


Why Why the anticipated 30% per-frame dose the anticipated 30% per-frame dose reduction of digital flat panel technology reduction of digital flat panel technology does not translate into an effective dose does not translate into an effective dose

reduction to patientsreduction to patients


Differences in operating conditions of the two Differences in operating conditions of the two systemssystems

H 3000• field of view (cm)

23/18/14

• cine mode12,5/25 fps

• fluoro modelow/medium/high

• filterautomatic

Innova• field of view (cm)

20/17/15/12

• cine mode15/30 fps

pref 1/pref 2 (lower dose)

• fluoro modelow/normal

• filtermanual


20 cm23

cm 400 cm2

375 cm2

Detectors area are similar

H3000 Innova200


17 cm18

cm 290 cm2

230 cm2

area +26% DAP +26% !!!!

Using similar nominal field of view (FOV) sizes corresponds to very different area of the two X ray beams

H3000 Innova200


Other possibilities……Other possibilities……

patients may not be the same procedures may not be the same operators’ behavior

filters/collimation use of “difficult” projections (fluoro/cine) focus-detector mean distances

………


Collimators use in INNOVA to reduce exposure

FOV 15

dose reduction 25%

[still]


FOV 20

Collimators use in INNOVA to reduce exposure

[still]


proper filtering

improper filtering causes image deterioration

H 3000

Filtering prevents image saturation in low absorption areas


improper filtering does not cause image deterioration

INNOVAINNOVA


Skin exposure variation in exposure rate (DAP rate) with projectionanthropomorphic phantom (average-sized) measurements

Cusma JACC 1999

Projection Fluoroscopy entrance dose rate

(mGy/min)

Cine

entrance dose rate

(mGy/min)

AP 31 388

RAO 30° 19 203

LAO 40° 20 216

LAO 40°, Cran 30° 80 991

LAO 40°, Cran 40° 99 1236

LAO 40°, Caud 20° 29 341


Distance between patient and detector


d

2d

Because the same energy is spread over a surface 4 times larger at a doubled distance, the same object will receive only a fourth of the dose when moved away from “d” to “2d”

Source

Doubling the distance from the source divides the dose by a factor of 4

The inverse square law


The inverse square law


Collimation


Anti-scatter grid

Increase DAP and skin dose x 2 timesImprove image qualityTo be removed for pediatric patients !!


Coronary Angiography optimization DIMOND Quality Coronary Angiography optimization DIMOND Quality CriteriaCriteria

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

AAspects of an optimized angiographic techniquespects of an optimized angiographic technique


Innova 2000. Changes in exposure parameters over time

---- diagnostic procedures Jul 2003 - Feb 2004diagnostic procedures Jul 2003 - Feb 2004

0

1

2

3

4

5

Jul-Aug

Sept-Oct

Nov-Dec

Jan-Feb

Fluoro T (m')

25

26

27

28

29

30

31

32

33

34

Jul-Aug Sept-Oct

Nov-Dec

Jan-Feb

Tot DAP(Gy*cm2)


Optimization ProcessOptimization Process


Optimization requires……….Optimization requires……….

• Knowledge of factors contributing to patient and staff radiation dose

patient factors

procedural factors

equipment (machine) factors

• Knowledge of dose reduction capabilities of our X ray system

• Periodic update of our clinical and technical working protocols


Optimization process involves ............Optimization process involves ............

• Data collection

• procedures, DAP, fluoro time

• Data analysis

• reliability of data

• Discussion & processes review

• collimators/filters use, FOV, projections

• Implementation of changes

• more precise data collection, collimators/filters use, FOV 17 whenever

possible, avoiding LAO projections

• Data verification


Reference levels Reference levels

3rd level “Patient risk”

2nd level “Clinical protocol”

1st level“Equipment performance”

Dose rate and dose/image

(BSS, CDRH, AAPM)

Level 1 + No. images + fluoroscopy time

Level 2 + DAP + Maximum Skin Dose (MSD)

Reference levels: an instrument to help operators to conduct optimized procedures with reference to patient exposure

Required by international (IAEA) and national regulations

For complex procedures reference levels should include:

• more parameters

• and, must take into account the protection from stochastic and deterministic risks

(Dimond)


• Modern X ray systems display dosimetric indications directly on the console in the control room and inside the catheterization laboratory, allowing cardiologists to know the level of radiological risk during the procedure.

• Typically Dose Area Product and Cumulative Dose (*) are displayed.

(*) Cumulative Dose (CD) is the air kerma accumulated for a procedure at a specific point in space relative to the fluoroscopic gantry for a procedure (it does not include tissue backscatter). It can give an indication of the skin dose.


1 CARD FIXED Coro ND 1k 7s 15F/s 15-Jan-03 09:16:21A 81kV 744mA 6.0ms 200CL small 0.3Cu 17cm 211.4µGym² 36.2mGy 0LAO 0CRA 105F

2 CARD FIXED Coro ND 1k 6s 15F/s 15-Jan-03 09:17:01A 86kV 734mA 6.0ms 600CL small 0.2Cu 17cm 376.9µGym² 63.8mGy 29RAO 0CRA 94F

3 CARD FIXED Coro ND 1k 5s 15F/s 15-Jan-03 09:17:43A 124kV 553mA 8.0ms ****** small 0.2Cu 17cm 490.3µGym² 94.1mGy 48RAO 22CRA 75F

4 CARD FIXED Coro ND 1k 6s 15F/s 15-Jan-03 09:18:16A 115kV 591mA 8.0ms ****** small 0.2Cu 17cm 460.4µGym² 97.8mGy 48RAO 22CRA 84F

5 CARD FIXED Coro ND 1k ***** 15F/s 15-Jan-03 09:19:05A 96kV 714mA 8.0ms ****** small 0.2Cu 17cm 9.3µGym² 1.9mGy 15RAO 30CRA 2F

6 CARD FIXED Coro ND 1k ***** 15F/s 15-Jan-03 09:19:07A 102kV 666mA 8.0ms ****** small 0.2Cu 17cm 17.2µGym² 3.5mGy 15RAO 30CRA 3F

Example of the data included in the study report (Siemens)


The proposed reference levels for Coronary Angiography and PTCA were DAP 45 Gy•cm2 and 75

Gy•cm2; fluoroscopy time 7.5 min and 17 min and number of frames 1250 and 1300, respectively.


Procedure optimization in the cath. lab.Procedure optimization in the cath. lab.patients and staff share a lot……patients and staff share a lot……

• correct indications

• fluoro time reduction

• frame rate reduction (25 12,5/sec)

• collimation/filtering

• LAO cranial projection limitation

• distance from X ray source

• lead apron and thyroid protection

• protective glasses and suspended screen

(staff)

(patient)


• Optimization is especially important in more complex PTCA procedures

chronic total occlusion bifurcation lesion degenerated saphenous

vein graft lesion lesion in severely

tortuous vessel ostial lesion


Procedure optimizationProcedure optimizationannual hand dose (cardiologist)annual hand dose (cardiologist)

0

10

20

30

40

50

60

1994 1995 1996 1997 1998

n. procedurex10dose mSv

- 27%

+ 2%

- 49% - 23%

Cardiologia & Fisica Sanitaria - Udinem

Sv

1994-1998 - 71%


0

10

20

30

40

50

60

70

1998 1999 2000 2001 2002

DAP cineDAP fluoroDAP totalG

y*cm

2Procedure optimization Procedure optimization DAP measurements at Udine Hospital (aDAP measurements at Udine Hospital (all proceduresll procedures))


X-Ray

Scatterradiation

Measures taken to reduce radiation exposure to patient will also benefit the operator/cath. lab. staff

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