madan rehani, phd - aapm

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Radiation & Cataract: A New Challenge

Madan Rehani, PhD Radiation Protection of Patients Unit, IAEA, Vienna, Austria

Lawrence Dauer, PhDMedical Physics, Memorial Sloan-Kettering Cancer Center

[email protected]

What is cataract?

Clouding or opacification of the natural lens of the

eye and obstructing the passage of light

Rehani & Dauer AAPM/COMP 2011 2

Cataract

Lenticular Opacification

Risk Factors:

Corticosteroids

Diabetes Mellitus

Sunlight exposure (UVB)

Trauma

Infections

Nutritional deprivation

Age (~ 50% >65 yrs)

Heredity

Radiation

Rehani & Dauer AAPM/COMP 2011 4Rehani & Dauer AAPM/COMP 2011

mailto:[email protected]

2

What is treatment?

Easily treatable condition -surgery

Nothing to match naturalRehani & Dauer AAPM/COMP 2011 5

Phacoemulsification

• Eye's internal lens is emulsified with an

ultrasonic handpiece

• Aspirated from the eye.

• Aspirated fluids replaced with irrigation of

balanced salt solution



Dot Opacities

Latency depends on rate at

which damaged epithelial

cells undergo fibrogenesis

and accumulate.

Radiation & Cataract

HOT Topic in Occupational Radiation

Protection

Rehani & Dauer AAPM/COMP 2011

3

Unlike Patients where……..

Rehani & Dauer AAPM/COMP 2011 9 Rehani & Dauer AAPM/COMP 2011 10

nucleus

CapsuleEpithelium

Capsule

Epithelium

Capsule

Epithelium

Capsule

Epithelium

LENS

PSC

Cataract

CORNEA

a. b.

ANTERIOR

CHAMBER

Capsule

Epithelium

Capsule

Epithelium

Capsule

Epithelium

LENS

PSC

Cataract

CORNEA

a. b.

ANTERIOR

CHAMBER

4

• Cortical

• Nuclear

• Posterior SubCapsular (psc)

• Mixed

Major Cataract Subtypes

Rehani & Dauer AAPM/COMP 2011 13 14Rehani & Dauer AAPM/COMP 2011

History of radiation cataract

• Documented within 1 year of Roentgen’s

discovery of X rays

• H. Chalupecky, Ueber die wirkung der

Roentgenstrahlen. Centralblatt fuer

praktische Augenheilkunde (J. Hirschberg

Ed.), pp. 386–401. Veit, Leipzig, 1897.


History of radiation cataract-II

• However, cataract was long thought to result

from only high doses of radiation to the lens of

the eye.

• This was based on data from early cyclotron

workers with cataract after substantial

neutron doses and

• with early Japanese A-bomb studies that

reported excess cataracts among those who

received over 2–3 Gy.


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Up to early 1950’s

• W. Rohrschneider, Beitrag zur entstehung und morphologie der ro¨ntgenstrahlenkatarakt. Klin. Monatsbl. Augenheilkd. 81, 254–259 (1928).

• A. U. Desjardins, Action of Roentgen rays and radium on the eye and ear. Am. J. Roentgenol. 26, 643–679 (1931).

• P. J. Leinfelder and H. D. Kerr, Roentgen-ray cataract: An experimental, clinical, and microscopic study. Am. J. Ophthalmol. 19, 739–756 (1936).

• D. G. Cogan and K. K. Dreisler, Minimal amount of x-ray exposure causing lens opacities in the human eye. AMA Arch. Ophthalmol. 50, 30–34 (1953).


• G. R. Merriam and E. Focht, A clinical study of

radiation cataracts and the relationship to dose.

Am. J. Roentgenol. Radium Ther. Nucl. Med. 77,

759–785 (1957).

• G. R. Merriam and E. F. Focht, A clinical and

experimental study of the effect of single and

divided doses of radiation on cataract

production. Trans. Am. Ophthalmol. Soc. 60, 35–

52 (1962).


Beliefs based on data in late 1950’s

• Cataract has a dose threshold

• The severity increased and the latency decreased

as the radiation dose increased above that

threshold

• Latent period was strongly inversely correlated

with dose and that there was no cataract

induction below 2 Gy.


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Other major papers that influenced

• M. D. Nefzger, R. J. Miller and T. Fujino, Eye findings in atomic bomb survivors of Hiroshima and Nagasaki: 1963–1964. Am. J.Epidemiol. 89, 129–138 (1969).

• M. Otake and W. Schull, Radiation-related posterior lenticular opacities in Hiroshima and Nagasaki atomic bomb survivors based on the DS86 dosimetry system. Radiat. Res. 121, 3–13 (1990).


ICRP 60 and 103


…However, new data on the radiosensitivity of the eye with regard to visual impairment are expected.


NCRP

• Visually disabling cataracts of 2–10 Sv

for single brief exposures, and 0.8 Sv for

protracted exposures


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What is New?

Lens opacities being reported at

dose levels below the currently

mentioned threshold in ICRP,

NCRP


Odds Ratio

• Is a measure of effect size, describing the

strength of association or non-independence

between two binary data values.

• Odds ratio treats the two variables being

compared symmetrically, and can be estimated

using some types of non-random samples

• Ratio of the odds of an event occurring in one

group to the odds of it occurring in another group


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A-Bomb Survivors

Neriishi et al, Rad Research

168:2007

• Operative Cataract odds

ratio of

~1.4 at 1 Gy

• Dose threshold seen at

0.1 Gy (upper bound of

0.8 Gy).


A-Bomb Survivors

Minamoto et al, Int. J Rad Biol

80(5):2004

• Prevalence of cortical and

posterior subcapsular

opacities showed significant

correlation with radiation dose

• Odds ratios of

~1.3 at 1 Gy


http://en.wikipedia.org/wiki/Odds

8

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Chernobyl

Worgul et al, Rad Research

167:2007

• Dose effect threshold

< 1 Gy

• UN Chernobyl Forum 2006

• Even low doses of

0.25 Gy may also be

cataractogenic.


Airline Pilots

Rafnsson et al, Arch

Ophthalmol. 123:2005

• Cosmic radiation may

be a causative factor in

nuclear cataracts.

• Note – some have

disagreed with this

assertion


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Aviators / Astronauts

Jones et al, Aviat Space

Environ Med 78:2007

• Military aviators with

cataracts were found to have

a younger average age at

onset compared with

astronauts.

• Prevalence of cataracts was

found to be higher in

astronauts than aviators.


Astronauts

Cucinotta

2001 Rehani & Dauer AAPM/COMP 2011

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Astronauts

Cucinotta et al, Rad Research

156:2001

• Relatively low doses of space

radiation are causative of an

increased incidence and early

appearance of cataracts

• Increased risk with higher

lens doses > 8 mSv


Infancy Exposures

Hall et al, Rad Research

152:1999

• Children exposed to lenticular

doses during skin hemangioma

treatments 1920-1959

• Odds ratio for developing

posterior subcapsular cataract

1.5 at 1 Gy

• Odds ratio for developing

cortical opacity

1.35 at 1 Gy


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Chronic Low Dose Exposures

Chen et al, Rad Research 156:2001

• Contaminated buildings in Taiwan

• Minor lenticular changes in lenses of young subjects


Interventional Radiologists

Haskal & Worgul,

RSNA News 2004:14

• Radiologists

• 5/59 posterior

subcapsular cataracts

• 22/59 small dot-like

opacities (early signs

of radiation damage)

• 1/59 had undergone

cataract surgery in one

eye

Schueller et al, Radiographics 2006Rehani & Dauer AAPM/COMP 2011

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• Inspection of the Merriam and Focht papers

shows that the observation periods after

irradiation were mostly quite short (average of 8

years)

• They studied only 20 individuals who had

estimated lens doses under 2 Gy,


Strength of newer studies over earlier ones

• Negative aspects of earlier studies:

• short follow-up periods,

• failed to take into account increasing latent periods

with decreasing doses,

• relatively few subjects with doses below a few Gy.

• Positive aspects of newer studies: Long follow-

up, larger numbers, lower doses


Why longer follow-up?

• The latent period is dependent on the rate at

which damaged epithelial cells undergo aberrant

differentiation (fibergenesis) and accumulate in

the PSC region of the lens cortex .


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Active collaborators

Eliseo Vano Norman Kleiman

Ariel Duran KH Sim Olivera Ciraj

A Minanoto

Raul Ramirez A Nader

Plus a team of local ophthalmologistsRehani & Dauer AAPM/COMP 2011 41

IAEA Cataract


Objective

To examine the prevalence of radiation-

associated lens opacities among interventional

cardiologists and technical staff and correlate

with occupational radiation exposure

• Not purely a doismetry or effect study

• Dose and effect


Background

• Since we are concerned with determination of effect, we need doses incurred in past, not prospective

• Non-availability of records of measured values from routine individual monitoring

• Non-availability of widely accepted methods for retrospective estimation


http://www.google.com/url?source=imgres&ct=tbn&q=http://www.rpm2010.org/images/speaker12.jpg&sa=X&ei=ObYyTbCkMdC6jAeImPSvCg&ved=0CAUQ8wc4Cw&usg=AFQjCNGaK66CoMsOAMdWykf_91aBRxnvag

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Interventional procedures

• Limited occupational dose data, USA/Canada??

• 20-30% of cardiologists do not use dosimeter

routinely (Vano et al, BJR, 2006, 79:383-388)

• In developing countries 40-90%

• Errors in use of dosimeters:

• Identification

• Interchange

• Use of protective devices??


Vano et al, Radiology, 2008:


Model Value Unit Source Remark

n/a 59 µSv/proc Tsapaki ate all, PMB, 2004 CA, 5 countries, shoulder

dose

n/a 89 µSv/proc Tsapaki ate all, PMB, 2004 PTCA, 5 countries,

Shoulder dose

Philips Optimus M

200 Poly C

260 mSv/y Vano, et al, BJR, 2006 5000 procedure/y

Philips

Integris HM 300


Philips

Integrtis N-5000


Philips

Integrtis Allura

3.5 mSv Kuipers et al, Cardiovas Int

Rad, 2008

4 weeks, TLD above the

apron

Philps

Polydiagnost C2

0.21-0.37 mSv/proc Steffino, et al BJR 1996 Ceiling screen in place

Not available 0.11 mSv/proc Pratt and Shaw, BJR, 1993 Ceiling screen and

Goggles in place

CGR DG 300 0.014 mSv/proc Marshall et al, BJR 1995 Eye dose, lead shield

Siemens

Angioskop D

0.28 mSv/proc Calkins et al, circulations,

1991

Eye, Ceiling screen in place

Philips Alura

10FD/20FD. GE

Advantix, Philips

Intergris 3000/5000,

Siemens Axiom bip A

Table 1 Sv//h Vano et al. Radiology 2008. Dose rate at 1 m. h=1.6 m

for different modes (fluoro.

cine..)

Dose information for various studies (I)


Model Value Unit Source Remark

Philips Integris Allura 3.85 mSv/4 weeksKuipers et al, J

Inte Card, 2008

TLD dose above the apron, mean value for 7

radiologists

Average 35 institutions 48 mSv/yNiklason at al,

Radiolgy, 1993972 procedures/y, dose above the apron

Philips Integris 3000, II

GE L-U, II6.55 mSv/month

Williams, BJR,

199746 procedures/month, neck dose

Not available Figure 2.b µGy/minWhitby, et al,

BJR, 2005PTCA

Different types of systems,

average values

0.5 (IC)

0.15 (nurses)mSv/proc

Vano et al, BJR ,

1998Without protective tools

Philips Integris V 3000 Figs 3.4,6,7 µGy/minWhitby, BJR,

2003Diagrams for PA, RAO, LAO projections

Different units Table 3 µ Sv/procVano, et al, BJR,

1998TLD dose, eyes, with and without protective screen

Philips Integris HM 3000Figs 4.5. 7-

11µGy/min

Morrish et al

BJR, 2008

Scatter dose rate for fluoroscopy and acquisition for

different projections

Dose information for various studies (II)


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Remarks

• Reported eye lens doses: • 0.3-11 mGy/study (without use of protective devices)

• 0.011-0.33 mGy/study (with protective devices)

• Multiple dosimetry quantities: air kerma, H*(10), Hp(10), Hp(3)…)

• Inaccuracy in dose assessment for nurses due to large variability of location and multiple tasks performed


Our Decision

• Typical doses if protective devices are not used

• 0.5 mGy/procedure for interventional cardiologists

• 0.15 mGy/procedure for and nurse

• This exposure corresponds to a typical procedure

of 10 min of fluoroscopy and 800 cine frames


Workload:

•number of procedures per week

•fluoroscopy time

•number of cine series per procedure

•number of frames per series

Radiation dose assessment

Typical doses if protective devices are not used:

•0.5 mGy/procedure for interventional cardiologists

•0.15 mGy/procedure for and nurse

Use of protective devices:

•ceiling suspended screens (factor: 0.1)

•leaded glass eyewear (factor: 0.1)

Angulations (factor: 1.8)

Radial access (factor: 2.0)


Materials and methods

• Interventional cardiologists and nurses

• Control group


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Dose related parameters (I)

Parameter Source

Number of years in interventional cardiology form

Model of fluoroscopy system used (in the past/now) form

Use of ceiling suspended screens (in % of time period), S form

Use of goggles (in % of time period), G form

Workload: number of procedures/week form

Fluoroscopy time/procedure form

No of frames/procedure

(no of frames/series and series/ procedure)form


Dose related parameters (II)

Parameter Source Value Factor

Attenuation of goggles, A literature 90%

Attenuation of ceiling suspended screen, B literature 90%

Distance from isocenter literature 75 cm ISL

For particular procedure. for different models

of interventional systems at eye level scatter

dose:

• Dose rate [Sv/h]

• Normalized dose rate [Sv/mAs]

• Total dose for typical procedure [Sv/study]

literature;

different

sources to

match the

model of the

system

Angulations

literature:

Vano, 2006

Batsou, 1998

Morrish, 2008

1.8

Radial access

literature:

IAEA, 2004

Vano, 2008

2

100

)1(1

AG

100

)1(1

BS


Dose assessment

Scenario Calculation

Information about model of the

unit, workload and typical

procedure parameters are available

•Scattered dose rate

•Correction for distance, use of protective

devices, angulation, radial access

•Dose ate eye level for typical procedure

•Annual dose/dose for the whole period use

of a particular system

Information about model and

workload is available

(procedure parameters are not

available)

•Typical exposure parameters from the

literature for a particular or similar type if

system (10 min fluoroscopy time and 800

cine frames)

•Same a previous


Angulation for typical procedure (CA)

Betsou et al.

BJR, 1998

Vano et al.

Radiology, 2008.Average

PROJECTION TIME (%) mSv/h mSv/h

PA 11.50 1.00 0.12

PA CD 0.50 1.00 0.01

PA CR 5.90 1.00 0.06

RAO 7.50 1.00 0.08

RAO CD 15.80 1.00 0.16

RAO CR 4.20 1.00 0.04

LAO 26.30 2.00 0.53

LAO CD 11.90 2.50 0.30

LAO CR 15.10 3.00 0.45

L LAT 1.30 5.00 0.07

100.00 1.8


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Assessment of lens change

• Dilatated slit lamp

examination

• Merriam-Focht scoring

system

• Scores: 0-3.0

• Scores >2.0 correlate

with visual acuity




Results


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CCI has the highest impact factor of all journals

focusing on interventional/invasive therapies.

IF≈ 2.5


PSC changes (score > 0.5)

Interventional cardiologists:

• Prevalence 52% (29/56. 95%

CI: 35-73)

• Significance (Fisher exact

test): p<0.001

• Relative risk: 5.7 (95% CI:

1.5-22)

Nurses:

• Prevalence 45% (5/11. 95%

CI: 15-100)

• Significance (Fisher exact

test): p<0.05

• Relative risk: 5.0 (95% CI:

1.2-21)


Subjects NoAge*

(y)

No of years in

interventional

cardiology

Cumulative dose

to the lens (Gy)*

Interventional

cardiologists56

42 ± 7

(31-64)

9.2 ± 6.9

(1.0-33)

3.7 ± 7.5

(0.02-43)

Nurses 1138 ± 11

(25-53)

6.0 ± 4.6

(1.0-14)

1.8 ± 3.1

(0.01-8.5)

Control group 2244 ± 9

(29-57)n/a n/a

*mean ± standard deviation; values in parentheses are ranges

Subjects and cumulative radiation dose

to the lens of the eye


Dose response for posterior lens changes in cardiologists and

nurses and associated odds ratios (OR). relative risk (RR)

and 95% confidence intervals (CI)

Dose (Gy)Number of

subjects

Number of subjects

with posterior lens

changes*

OR 95% CI RR 95% CI

0 (Control) 22 2 (9%) 1.0 n/a 1.0 n/a

<1 31 12 (39%) 6.3 1.2-32 4.3 1.0-17

1<2 11 5 (45%) 8.3 1.3-54 5.0 1.1-22

2-<3 9 5 (55%) 12.5 1.7-89 6.1 1.4-26

≥3 16 12 (75%) 30 4.7-189 8.3 2.1-32

34 (51%) 10.3 2.2-48 5.6 1.4-21

*cataract grade 0.5 or higher in one eyeRehani & Dauer AAPM/COMP 2011 68

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Number of interventional cardiologists with posterior lens changes graded by

severity of lens changes with associated cumulative doses to the lens of the eye

Score N (%)

Dose (Gy)

mean median min max

0 in both eyes 27 48 1.6 0.94 0.02 7.4

0.5 in one eye 8 14 2.4 1.8 0.04 8.4

0.5 in both eyes 18 32 7.4 1.3 0.02 43

>1 in one eye

(0.5 or more in the other eye)3 5 3 2.8 0.24 4.5



Vano, E., Kleiman, N.J., Duran, A, Rehani MM, D Echeverrie,

M Cabreraf. Radiation cataract risk in interventional

cardiology personnel. Radiat. Res. 174, 490-5 (2010). IF≈3.1

• 116 exposed individuals and 93 similarly aged

non-exposed controls

• Relative risk of psc opacities in IC was 3.2 (38%

compared to 12%; p<0.005).

• 21% of nurses and technicians

• Cumulative median values of lens doses were

estimated at 6.0 Sv for cardiologists and 1.5 Sv

for associated medical personnel.


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Conclusions from IAEA studies

• Threshold value, if any, is much lower that

current guidelines indicate

• Dose-response relationship between

occupational exposure and the prevalence of

radiation-associated posterior lens changes

• There is a need to find better means for eye

lens dosimetry

• First ever report among this group


Limitations

• Opacities that had not progressed to cause

significant visual disability

• Preliminary investigation of the dose response

relationship

• A study of a larger cohort is needed


• Lens of the eye, threshold in absorbed dose is

now considered to be 0.5 Gy (against 0.5 to 2 for

detectable opacities and 5 for visual impairment) .

• Occupational Exposure Lens of Eye Limit

• 20 mSv in a y (against 150), averaged over

defined periods of 5 y, with no single y exceeding

50 mSv

75Rehani & Dauer AAPM/COMP 2011 76

Shielding & Positioning Use Barrier Shielding for Body and Eye Protection

Be aware of Staff Location


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77

Shielding & Positioning Eye Shielding Imperative

• Leaded Ceiling Shield 98% reduction.

• Leaded Glasses Shield ~74-91%

• Differences in performance related to operator position, likely representing interplay of design and fit.

• Sports wraparound or side shields important.

Rehani & Dauer AAPM/COMP 2011 78Rehani & Dauer AAPM/COMP 2011

Training & Self-Evaluations

• Operators and Staff should be trained in the

machine operation and radiation protection.

• Free Training Programs:

• IAEA has free training program • http://rpop.iaea.org/RPOP/RPoP/Content/-

AdditionalResources/Training/1_TrainingMaterial/Radiology.htm

• MARTIR (Multimedia and Audiovisual

Radiation Protection Training in Interventional

Radiology)• http://ec.europa.eu/energy/wcm/nuclear/cd_rom_martir_project.zip

• Perform frequent Self-Evaluations / Audits

79Rehani & Dauer AAPM/COMP 2011 80

Mitigation Efforts (Training, Behavior Modification & Shielding)

~45% drop in 3 years

Average IR LDE by Year

0

10

20

30

40

50

60

2003 2004 2005 2006 2007 2008

Years

LD

E (

mS

v)

Lieto and Jackson, 2000.

Dauer, 2008


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http://rpop.iaea.org/RPOP/RPoP/Content/-AdditionalResources/Training/1_TrainingMaterial/Radiology.htm



http://ec.europa.eu/energy/wcm/nuclear/cd_rom_martir_project.zip

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Additional Resources

81

CVIR-JVIR, 2010


Additional Resources

82

• http://rpop.iaea.org = IAEA Radiation Protection of Patients

• http://rpop.iaea.org/RPOP/RPoP/Content/Documents/TrainingRadiolo

gy/Lectures/RPDIR-L16.2_Fluoroscopy_doses_WEB.ppt


Learning Objectives

1. To understand the basic information about

radiation cataractogenesis

2. To understand the efficacy of protective tools

3. To become aware about the most recent changes

in recommendation by the ICRP on reduction in

eye lend dose limit


d

IAEA


http://www.rpop.iaea.org/

http://rpop.iaea.org/RPOP/RPoP/Content/Documents/TrainingRadiology/Lectures/RPDIR-L16.2_Fluoroscopy_doses_WEB.ppt




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