Post on 06-Feb-2021
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