A Rimpler

D Delacroix

D Nikodemová

Felix M. Mottaghy

Filip Vanhavere

Gerrit J. Kemerink

Ilona Barth

M Tschurlovits

P Covens

English

PubMed

Crossref

European Journal of Nuclear Medicine

Extremity doses of nuclear medicine personnel: a concern

Springer - Publisher Connector

Kemerink, G.J.

Vanhavere, F.

Barth, I.

Mottaghy, F.M.

NARCIS 

Maastricht University Research Portal

EDITORIAL
Extremity doses of nuclear medicine personnel: a concern
Gerrit J. Kemerink & Filip Vanhavere & Ilona Barth &
Felix M. Mottaghy
Published online: 15 November 2011
# The Author(s) 2011. This article is published with open access at Springerlink.com
Introduction
Nearly one in five workers in nuclear medicine is likely to
receive more than the legal dose limit for the skin of
500 mSv per year according to a recently completed
ORAMED study [1, 2]. ORAMED (Optimization of
RAdiation protection of MEDical staff) was a European
FP7 project which aimed to develop methodologies for
better assessing and reducing the exposure to radiation of
personnel working in interventional radiology and cardiology
and nuclear medicine. One of the goals of the project was to
determine extremity doses of workers in nuclear medicine
during the preparation and administration of radiopharma-
ceuticals. Six countries participated in the study, and large
numbers of procedures using 99mTc (n=335), 18F (n=306)
and 90Y (n=127) were monitored.
In stark contrast with the finding of too high extremity
doses is the general lack of attention in nuclear medicine
paid to extremity dosimetry. The main purpose of this
contribution is therefore to emphasize that extremity
exposure is a real concern needing the attention of the
professional societies and the technical and medical staff. In
addition, some guidance is provided in measuring and
lowering the extremity dose.
Risks of commonly used radionuclides
The ORAMED project [1, 2] considered 99mTc, 18F and 90Y,
but did not include 68Ga and 124I. The latter two nuclides are
increasingly used in PET and they have relatively unfav-
ourable risk profiles. Here we consider all five radionuclides.
Their basic physical characteristics are summarized in
Tables 1 and 2 [3–5]; some of these are briefly discussed
to illustrate the relative radiation hazards of the nuclides.
According to Table 1, the 511 keV annihilation radiation
of 18F and 68Ga causes a nearly eightfold higher whole-
body dose than the 141 keV gamma photons from 99mTc
[3]. This is a result of the higher energy of the annihilation
radiation (511 keV versus 141 keV) and the formation of
two 511 keV photons per decay of these positron emitters,
whereas 99mTc emits only one photon per decay. Beta-
minus, positron and electron particles emitted by the
commonly used nuclides do not directly contribute to the
body dose as this is measured at a depth of 10 mm which is
too deep for these particles to reach.
When positrons are not completely stopped, e.g. by the
liquid in which they are present or the material surrounding
the activity, they contribute to the skin dose. In the case of
G. J. Kemerink (*) : F. M. Mottaghy
Department of Nuclear Medicine,
Maastricht University Medical Center,
P. Debyelaan 25,
6229HX Maastricht, The Netherlands
e-mail: gerrit.kemerink@mumc.nl
G. J. Kemerink
Department of Radiology, Maastricht University Medical Center,
Maastricht, The Netherlands
F. Vanhavere
Belgian Nuclear Research Centre SCK*CEN,
Mol, Belgium
I. Barth
Department of Radiation Protection and Health,
Federal Office for Radiation Protection (BfS),
Berlin, Germany
F. M. Mottaghy
Department of Nuclear Medicine,
University Hospital RWTH Aachen,
Aachen, Germany
Eur J Nucl Med Mol Imaging (2012) 39:529–532
DOI 10.1007/s00259-011-1973-z
point sources of 18F, 68Ga and 124I in air, at a distance of
30 cm, the positron contribution to the skin dose is about
66, 60 an 13 times the contribution of gamma radiation,
respectively [4]. This shows that radiation protection of the
skin against PET nuclides should in the first place be
directed at stopping the positrons.
For bare 5-ml syringes held with the fingers, the skin doses
for 18F, 68Ga and 124I are 8, 89 and 30 times higher than for
99mTc, respectively [4]. Note that positrons from 18F have a
lower energy (and range) than those of 68Ga and 124I, and
many more of them are therefore stopped in the syringe and
do not contribute to the skin dose. A 5-ml syringe with
1 GBq of 68Ga causes a skin dose rate of 8.7 mSv/s, which
means that the annual dose limit of 500 mSv would be
reached in less than 1 min of contact. For such high-energy
positron emitters in a syringe or vial the contribution of
positrons to the skin dose is dominant, and protection against
these positrons should again be the first goal.
In the case of skin contamination, the ratios of the skin
doses with respect to 99mTc are 90, 143 and 41 (Table 1). In
this situation also for 18F only a few positrons are stopped
in the very thin source forming the contamination.
The beta-minus emitter 90Y is extensively used in therapy.
It has a high maximum beta energy (Table 2) causing many
beta particles to escape from a vial or syringe, resulting in a
high skin dose from holding a bare container (12 mSv/s for a
5-ml syringe containing 1 GBq). Note that this is only
slightly higher than for 68Ga (8.7 mSv/s per GBq, a value
dominated by the contribution of positrons). In other words,
a high-energy positron emitter such as 68Ga combines the
risks of 18F as far as annihilation radiation is concerned and
(nearly) the risk of 90Y as far as positrons are concerned.
In conclusion, these considerations show that the risk of an
elevated skin dose is much higher for the beta (beta-minus and
positron) emitters considered here than for 99mTc, the nuclide
many workers in nuclear medicine first encountered.
Data on extremity dose
When handling unsealed radiopharmaceuticals, the skin of
the hands of nuclear medicine personnel is the organ most
at risk. The ICRP has recommended that the personal dose
equivalent Hp(0.07), the dose at a depth of 0.07 mm, be used
as a measurable proxy for the equivalent skin dose [6]. The
annual dose limit of 500 mSv applies to the average over the
single square centimetre with the highest exposure [6].
Assessment of compliance with the skin dose limit of
500 mSv/year is difficult in practice as the area with the
highest exposure has to be monitored. This location is not
known in advance, and it can vary from procedure to
procedure, but most often it is the tip of one of the fingers
or the thumb [1, 2]. Unfortunately, it is not practical to put a
dosimeter at the tip of a digit, as this would affect the digit’s
use, and also because the fragile dosimeter would easily
fracture. Furthermore, the dose must be measured at the
tissue depth equivalent to 0.07 mm. This is not trivial for
beta particles and positrons, because it requires very thin
detectors with thin covers. So far extremity dosimetry has
Table 1 Exposure parameters of some radionuclides [3, 4]
Nuclide Body dosea due to
point source in air
[mSv.m2/(GBq.h)]
Skin doseb due to
contact with 5-ml syringe
[mSv/(MBq.h)]
Skin doseb due to
contamination with
50 μl on 1 cm2
[mSv/(kBq.h)]
Lead shielding (mm)
To lower
transmission
to one-half
To lower
transmission
to one-tenth
99mTc 0.02168 0.354 0.00877 0.3 1
18F 0.1655 2.88 0.788 6 17
68Ga 0.1580 31.4 1.25 6 17
124I 0.1745 10.7 0.36 8 31
90Y 0 43.5 1.35 Total β-absorption in 9.2 mm plastic
a Strictly ambient dose equivalent, H*(10), effectively due to gamma radiation.
b Personal dose equivalent, Hp(0.07), in principle due to electrons, beta and gamma radiation
Table 2 Some radionuclides and their decay properties relevant to
occupational exposure [5]
Nuclide Energy gamma
(intensity)
[keV, (per decay)]
Maximum energy beta
particle (intensity)
[keV, (per decay)]
99mTc 141 (89%) –
18F 511 (193%) 634 (97%)
68Ga 511 (178%) 1,899 (88%)
124I 511 (45%), 603 (63%),
723 (10%)
1,535 (12%), 2,138 (11%)
90Y - 2,284 (100%)
The 511 keV gammas originate from positron annihilation; their
intensity is taken as two times the positron intensity, assuming local
annihilation
530 Eur J Nucl Med Mol Imaging (2012) 39:529–532
mostly been performed using ring finger or wrist dosimeters,
which has been found to result in severe underestimation of
the extremity dose [1, 2]. Even worse, in most hospitals
extremity dosimetry is not being performed at all.
We only mention the most relevant findings from the
ORAMED study; for the complete results we refer to the
website [1] and publications [2]. In the study, detailed doses
were measured on the fingers, thumb and wrist using thin
LiF:Mg,Cu,P thermoluminescence dosimeters. The meas-
urements were complemented by Monte Carlo simulations.
For all procedures, in diagnostics as well as in therapy, the
difference between minimum and maximum extremity
doses was huge, as is illustrated by Table 3. Evidently
bad practices were also observed, e.g. holding bare vials
and syringes with the fingers. The authors estimated that
between 15% and 20% of those working with both 99mTc
and 18F may exceed the annual skin dose limit of 500 mSv.
Similar finger doses have been reported by Covens et al. [7]
in a review and by Rimpler and Barth [8].
For 124I, the highest skin dose (on the thumb) measured
for preparation was 9.5, 3.1 and 1.0 mSv/GBq, depending
on the degree of optimization of the procedure [9].
However, the first method was already rather well opti-
mized, and much higher skin doses will be incurred if
protection is poor. For 68Ga no experimental data are
available as far as we know.
The ORAMED study paid special attention to the
estimation of the maximum skin dose in daily practice.
For all three nuclides studied the authors concluded that the
dose measured by a ring dosimeter with the detector on the
palmar base of the forefinger of the nondominant hand gave
an acceptable estimate of the maximum skin dose, provided
a correction factor of about 6 was applied.
Covens et al. also investigated skin contamination (this
work is also presented in reference [1]). Of the 300
procedures monitored, 9% revealed a contamination, while
all workers were unaware of it. Skin doses up to 30 mSv
due to a single contamination were estimated.
Shielding
The differences in gamma radiation emitted by 99mTc, 18F,
68Ga and 124I also affect shielding requirements, as is
illustrated in Table 1. Shielding should be used whenever
possible and it should be adapted to the radionuclide that is
being handled. The ORAMED study assessed the benefit of
shielding using Monte Carlo simulations. For 99mTc,
shielding with 2 mm tungsten or lead should usually be
sufficient. For 18F, syringe shields of tungsten (or lead) of
5 mm or preferably 8 mm thickness should be used. For
90Y, shielding with tungsten is best, as a shield of 5 mm
tungsten has been shown to give better protection than
10 mm acrylic in recent studies [10–12]. For syringes with
less than 200–300 MBq 90Y the cheaper acrylic is
satisfactory, however. The studies [10–12] also indicate
that a shield of just tungsten is the best choice for the high-
energy positron emitters 68Ga and 124I, as it both stops the
positrons and attenuates the gamma radiation and brems-
strahlung. However, syringe shields do not provide protec-
tion near the syringe bottom.
Conclusions
Radiation exposure of the hands of personnel in nuclear
medicine is a real concern and needs to be addressed
urgently. The high doses, and the large spread of doses, are
most likely due to lack of radiation awareness and
optimization. Some recommendations can be formulated:
1. Professional societies should address extremity dosim-
etry at their meetings to disseminate information on
radiation risks and how these risks can be countered.
2. Technical and medical staff have to take responsibility
for their personnel by improving awareness of the
existing risks, and by providing education and training.
Educational material developed as part of the ORAMED
project [1], or available at the IAEA [13], may be
helpful.
3. Extremity doses should routinely be measured with a ring
dosimeter suitable for beta and gamma radiation, worn on
the palmar side of the proximal phalanx of the forefinger
of the nondominant hand. A correction factor of 6 should
be applied to obtain an estimate of the actual maximum
skin dose. The use of dosimeters worn on the ring finger
or on the wrist should be discontinued.
4. Performing a study within the workers’ own depart-
ment, aiming at the optimization of a procedure used in
Table 3 Maximum skin doses of both hands in nuclear medicine
procedures measured within the ORAMED project [1, 2]
Procedure Skin dose (μSv/GBq)
Mean Minimum Maximum
99mTc preparation 432 33 2,062
99mTc administration 233 12 951
18F preparation 1,205 97 4,433
18F administration 933 139 4,113
90Y DOTATOC preparation 2,100 100 7,400
90Y DOTATOC administration 1,900 400 4,900
90Y Zevalin preparation 11,000 700 63,700
90Y Zevalin administration 4,800 700 24,600
Eur J Nucl Med Mol Imaging (2012) 39:529–532 531
the preparation and administration of activity for
imaging or therapy, is an excellent way to achieve
radiation awareness, to educate and train workers, and
to show compliance with dose limits.
5. Working with positron emitters, especially with high-
energy ones, should only be initiated after adequate
education and training of workers.
6. Frequent checks for contamination should be per-
formed during all handling of radioactivity.
7. Sufficient shielding materials should be provided for all
stages of handling activity where skin exposure is
possible. In addition, suitable forceps, pincers, tweezers
and possibly other equipment should be available to keep
activity at a distance while handling it. Using automated
systems may also help.
8. Direct contact of the fingers with unshielded vials,
syringes, tubing or valves containing radionuclides
must be avoided. This should become a basic principle
when handling beta emitters.
Finally, an important and reassuring conclusion from the
ORAMED project and the 124I study [9] is that acceptable
levels of radiation exposure can be achieved when workers
are trained and procedures have been optimized.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
References
1. Belgian Nuclear Research Centre (SCK•CEN), Optimization of
Radiation Protection of Medical Staff.http://www.oramed-fp7.eu/
en/Presentations. Accessed 27 Oct 2011
2. Radiation Measurements, Volume 46 Issue 11; Special Issue:
International Workshop on Optimization of radiation Protection of
Medical Staff, ORAMED 2011.
3. Tschurlovits M, Leitner A, Daverda G. Dose rate constants for
new dose quantities. Radiat Prot Dosimetry. 1992;42:77–82.
4. Delacroix D, Guerre JP, Leblanc P, Hickman C. Radionuclide and
radiation protection data handbook 2002. Radiat Prot Dosimetry.
2002;98:1–168.
5. National Nuclear Data Center (NNDC). Evaluated Nuclear Structure
Data File (ENSDF), Brookhaven: National Nuclear Data Center
(NNDC). http://www.nndc.bnl.gov/chart/decaysearchdirect.jsp?
nuc=124I&unc=nds. Accessed 27 Oct 2011 (note the nuclide 90Y
instead of 124I is for instance chosen by replacing “124I” by “90Y”).
6. International Commission on Radiological Protection. ICRP
Publication 103: Recommendations of the ICRP. Annals of the
ICRP, vol. 37/2-4. Elsevier; 2008
7. Covens P, Berus D, Vanhavere F, Caveliers V. The introduction of
automated dispensing and injection during PET procedures: a step
in the optimisation of extremity doses and whole-body doses of
nuclear medicine staff. Radiat Prot Dosimetry. 2010;140:250–8.
8. Rimpler A, Barth I. Beta radiation exposure of medical staff and
implications for extremity dose monitoring. Radiat Prot Dosimetry.
2007;125:335–9.
9. Kemerink GJ, Franssen R, Visser MG, Urbach CJ, Halders SG,
Frantzen MJ, et al. Hard beta and gamma emissions of 124I.
Impact on occupational dose in PET/CT. Nuklearmedizin 2011;50
(6). [Epub ahead of print].
10. Aubert B, Guilabert N, Lamon A, Richard M. Which protection
against radiation for new protocols of internal radiotherapy by
Yttrium 90? Proceedings of the 6th European ALARA Network
Workshop “Occupational Exposure Optimisation in the Medical
Field and Radiopharmaceutical Industry”, Madrid. 23–25 October
2002, pp 47–9.
11. Coulot J, Ricard M. Radiation protection against yttrium 90:
comparison between measurements and Monte-Carlo calculations.
50th Annual Meeting of the Society of Nuclear Medicine, New
Orleans. 21–25 June 2003.
12. Chéa M, Donadille L, Trompier F. Etude des performances
des protège-seringues utilisés dans un service de médecine
nucléaire pour procéder à des injections de radiopharmaceu-
tiques marqués à l’yttrium 90. IRSN Report DRPH/SDE, no.
2005-28, 2005.
13. IAEA, Radiation Protection of Patients (RPOP).Training material.
https://rpop.iaea.org/RPOP/RPoP/Content/AdditionalResources/
Training/1_TrainingMaterial/index.htm. Accessed 27 Oct 2011.
532 Eur J Nucl Med Mol Imaging (2012) 39:529–532


Extremity doses of nuclear medicine personnel: a concern

Abstract

Similar works

Full text

Available Versions

Crossref

Springer - Publisher Connector

NARCIS

Maastricht University Research Portal

Springer - Publisher Connector

Maastricht University Research Portal

Publikationsserver der RWTH Aachen University

RWTH Publications