EXTREMITY DOSIMETRY IN NUCLEAR

MEDICINE

F. Vanhavere1, I. Barth2, A. Carnicer3, L. Donadille4, P. Ferrari5, M.

Fulop6, M. Ginjaume3, G. Gualdrini5, S. Krim1, X. Ortega3, A.

Rimpler2, N. Ruiz-Lopez7, S. Baechler7and M. Sans Merce7

1 Belgian Nuclear Research Centre (SCK-CEN), Mol, Belgium2 Bundesamt für Strahlenschutz (BfS), Berlin, Germany Universitat3 Politecnica de Catalunya (UPC), Barcelona, Spain4 Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France

5 ENEA Radiation Protection Institute, Bologna, Italy 6 Slovak Medical University (SMU), Bratislava, Slovakia7 University Hospital Center (CHUV), University of Lausanne, Switzerland

Tc-99mPure γ-emitter

Eγ = 140.5 keV (87%)

Y-90Pure β−-emitter

Eβ−max = 2280 keV (100%)

Y-90: ββββ−−−− spectrum

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

Energy (MeV)

Probability (a.u.)

F-18Mixed γ- and β+-emitter

Eγ = 511 keV (194%)

Eβ+max = 634 keV (97%)

F-18: ββββ++++ spectrum

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Energy (Mev)

Probability (a.u.)

� Diagnosis with Tc-99m and F-18

� Therapy with Y-90 (RIT with Zevalin®; PRRT with Dotatoc®)

Characteristics of the most frequently used radionuclides

Properties of the most common radionuclides

3

20

700

1

10

100

1000

Tc-99m

500 MBq

F-18

400 MBq

Y-90

1 GBq

mSv.m

in-1

Hp(0.07) rate (in mSv.min-1)

167

25

0.7

0.1

1.0

10.0

100.0

1000.0

Tc-99m

500 MBq

F-18

400 MBq

Y-90

1 GBq

min

Time (in min) to reach 500 mSv

Contact of an unshielded (5 ml) syringe

Dose rate at contact

Radiological risks: Sources of exposure of nuclear medicine workers

D0 / 202

�Risk of internal contamination•Valid for all radionuclides and specially for iodine (volatile)

and ...

Nuclear medicine implies the manipulation of unsealed radioactive sources

�Risk of external irradiation

• Whole body (WB) and extremities irradiation when manipulating radioactive sources

Labelling vialElution vialGenerator

Labelling with Tc-99m Injection in diagnostics

Radiological risks: Sources of exposure of nuclear medicine workers

The hands are particularly exposed in nuclear medicine

ICRP 60 recommendations :

Dose limit for the extremities for workers is the same as for the skin

500mSv for 12 months over 1cm2 independently of the exposed surface

European directive 96/29:

All workers likely to receive an extremity dose larger than 3/10 of the annual limit dose must wear an extremity dosemeter

Dose limits for the extremities

Good and bad

practices ?

Routine

monitoring?

Maximum

dose ?

Dose

distribution?

Level of

exposure?

Hp(0.07)/A manip(µSv/GBq)

Parameters

of influence?

ORAMED + EXDOS (Belgium)

Measurements Common protocol:

� A pair of gloves equiped with 11 TL dosemeters

each was worn by the worker

– 8 TLDs on palm side, 3 on nail side

– Only 1 type of radionuclide

– Only preparation or administration

– During: few days for Tc-99m~1 day for F-18

a single procedure for Y-90

� 1 pair of instrumented gloves = 1 measurement

� For diagnostic applications:

– At least: 5 measurements per worker2 workers per hospital

Palm side

Nail side

a

b c d e

f

g

h k

j

i

Measurements performed

Analyzed: 7 countries; 34 different hospitals; 124 different workers

Measurements Workers Hospitals

Preparation 178 36 21

Administration 157 32 20

Preparation 160 30 17

Administration 146 30 17

Total 641

Tc-99m

F-18

Preparation 49 20 16

Administration 45 27 15

Preparation 16 5 4

Administration 17 7 4

Total 127

PRRT Dotatoc®Y-90

Y-90 RIT Zevalin®

Overview on finger doses in diagnostic NM

• The preparation of the radiopharmaceutical involves higher finger doses per activity than the administration.• F-18 involves higher finger doses per activity than Tc-99m.

• Very large range of maximum finger doses among the same procedure.

Tc-99m

administration

Tc-99m

preparation

F-18

administration

F-18

preparation

Good practices

Bad practices

Tc-99m

administration

Tc-99m

preparation

F-18

administration

F-18

preparation

Overview on finger doses in diagnostic NM

� Are these finger doses a matter of concern from the point of view of radiation protection ?

Annual dose estimation

Tc-

99

m

ad

min

istr

ati

on

Tc-

99

m

pre

pa

rati

on

F-1

8

ad

min

istr

ati

on

F-1

8

pre

pa

rati

on

D < 150 mSv ���� 49%

150 mSv < D < 500 mSv ���� 31%

D > 500 mSv ���� 19%

Mo

re t

ha

n o

ne

pro

ced

ure

• Some workers were monitored for only one type of procedure

for the ORAMED project when actually they performed more. In

these cases, the estimation of the annual dose has been

calculated only considering the monitored procedures, from

which real measured values were available.

• Even considering this hypothesis, it is found that the

extrapolated doses reach the annual limit for 19% of the

workers.

Statistically significant differences

Syringe shield: higher doses with unshielded syringe?

Not enough data

Mean and median doses at each measuring position for preparation

Dose distribution across the hand

F-18

Mean and median doses at each measuring position for administration

Dose distribution across the hand

F-18

Dose distribution across the hand

Ad

min

istr

ati

on

Highest

dose

Lowest

dose

ND hand

ND hand

Pre

pa

rati

on

Dominant hand

Dominant hand

Index tip and thumb of the ND hand are the most exposed.

Index tip and thumb of the ND hand and index tip and thumb of the D hand.

Highest

dose

Lowest

dose

thumb

7

22%

index tip

14

44%middle tip

1

3%

ring tip

1

3%

index nail

1

3%

THUMB

2

6%

INDEX TIP

3

9%

RING TIP

2

6%

INDEX NAIL

1

3%

thumb

3

12%

index tip

16

64%

middle tip

1

4%

THUMB

1

4%

INDEX TIP

3

12%

INDEX NAIL

1

4%

Pre

pa

rati

on

Ad

min

istr

ati

on

70% ND

30% D52% ND

48% D

53% ND

47% D

77% ND

23% D

Maximum dose – frequency (with shield)Tc-99m F-18

thumb

3

18%

index tip

4

24%

middle tip

2

12%ring tip1

6%

THUMB

1

6%

MIDDLE

1

6%

RING TIP

2

12%

INDEX NAIL

1

6%

MIDDLE NAIL

1

6%

RING NAIL

1

6%

thumb

1

3%

index

1

3%

middle

1

3%

index tip

10

33%

middle tip

2

7%

index nail

1

3%

THUMB

2

7%

INDEX

1

3%

INDEX TIP

10

33%

INDEX NAIL

1

3%

Usually the ND hand receives the highest dose, in particular the index tip

52% ND

48% D

53% ND

47% D

thumb

2

15%

index tip

4

31%

middle tip

1

8%

ring tip

1

8%

THUMB

3

23%

RING

1

8%

MIDDLE

NAIL

1

8%

thumb

1

13%middle tip

1

13%

index nail

1

13%

THUMB

4

50%

INDEX TIP

1

13%

index tip

2

50%

middle tip

2

50%

Pre

pa

rati

on

Ad

min

istr

ati

on

100% ND

0% D

62% ND

38% D

37% ND

63% D

Maximum dose – frequency (unshielded)Tc-99m F-18

� General ratios considering all data independently of the procedure.

22 18

6.09.4

3.12.5

5.5 10

Ratios for diagnostics procedures

• The recommended monitoring position is the base of the index finger of

the ND hand (low ratio, high correlation with the maximum) which

underestimates the maximum dose by a factor of 6.

(outliers

excluded)

�

� Aims:

– To analyze separately the parameters influencing the doses

� Sensitivity study to understand intra- and inter-operator

variabilities

– To calculate surface dose distributions (dose mapping) for some selected cases

� 6 scenarios were defined

Considered as representative of different manipulation stages

Simulations

1. Defining the case 2. Creating a moulding

3. Scanning the moulding 4. Generating a voxel phantom

5. Adding the source and dosemeters

From real to numerical world

Example 1: variation of the active volume Example 2: rotation of the syringe

The sensitivity study

Parameters studied:

– Radionuclide

– Shielding

– Displacement of the source

– Orientation of the source

– Volume of the source

The doses were evaluated at

the 11 points on the voxel

hand model corresponding to

the TLDs positions.

Injection scenarios

F-18

� F-18: (best is 8 mm W) 5 mm W provide a factor of 10

Preparation scenarios

� 3 cm Pb provides 2 orders of magnitude in dose

reduction

F-18Dose mapping of the hand’s surface:

The location of the maximum can be at a different place to that of the dosemeters.

� How large is the underestimation?

Dose mapping

Injecting F-18 without shielding

�Wide ranges of individual exposures (min/max) for similar

procedures, different equipment, radiation protection

means and tools.

�Skin dose limit (500 mSv/y) can be exceeded by numerous

workers in hospitals where RP standard is low

�There is adequate potential to further improve radiation

protection and decrease exposures

�Adequate skin dose monitoring is urgently needed in

nuclear medicine

Conclusions

�Shielding of vials and syringes are essential and a

precondition but not a guarantee for low exposures.

�Other RP tools and measures (e.g. pincers, forceps,

time etc.) significantly influence the exposure.

�Also subjective factors e.g. risk awareness and

training affect exposures..

� Working fast is often not sufficient

�Ring dosemeters (base of index finger non-dominant

hand) are recommended, and need a correction factor

of around 6

�Series of practical recommendations available

Conclusions

Thank you

for your

attention

Special thanks to all the workers

and hospitals that have

collaborated

More info: www.oramed-fp7.eu

ACKNOWLEDGMENT

The research leading to these results has received funding from the European Atomic Energy

Community's Seventh Framework Programme (FP7/2007-2011) under grant agreement n° 211361.

The measurements in Belgium have partially been financed by the FANC under the EXDOS project