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Radiation Measurements 46 (2011) 1299e1302

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Radiation Measurements

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Investigation of radiation exposure of medical staff: Measurements supportedby simulations with an articulated hand phantom

Frank Becker*, Christoph BlunckInstitute for Nuclear Waste Disposal, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

a r t i c l e i n f o

Article history:Received 28 February 2011Received in revised form19 July 2011Accepted 22 July 2011

Keywords:Monte CarloMCNPXHand phantomBeta emittersNuclear medicineRadiation protection

* Corresponding author.E-mail address: frank.becker@kit.edu (F. Becker).

1350-4487/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.radmeas.2011.07.029

a b s t r a c t

To evaluate and optimise extremity doses in nuclear medicine, work package 4 of the ORAMED project(ORAMED, 2011) focussed on investigating skin doses of nuclear medicine worker hands (Carnicer, 2010).In addition to a measurement campaign, selected scenarios were simulated by means of hand waxphantoms. The phantoms were modelled according to the scenario of radiopharmaceutical syringehandling. The wax phantoms in the position of interest were scanned and introduced as lattice (voxel)geometry into the simulation input geometry. In this article the mathematical articulated hand modeldeveloped at KIT (Blunck et al., 2009) is compared to these models. This mathematical hand phantomconsists of rigid and flexible elements, allowing for an adaptable anatomy and flexible hand poses. Incontrast to the static voxel models obtained by a complex procedure based on CT-scanned images, thearticulated hand phantom can be used comparably simply for differing scenarios.

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1. Introduction

With the growing use of beta emitters in nuclear medicinetherapies, detailed research relating to the radiation protection ofthe staff working with these emitters is gaining importance. In thisstudy we report on extremity doses of medical staff, with the mainfocus on a mathematical hand model (Blunck et al., 2009).

For safe handling and adequate shielding measures for nuclearmedicine staff, analysis of the radiation field and possible dose atrelevant positions in the working area is necessary. Since theradiation field may be very inhomogeneous and in some casesdifficult or not possible to measure, simulation of specific scenariosoffers an efficient means to analyse the radiation fields and deter-mine potential exposures.

2. Materials and methods

Within the European ORAMED project (ORAMED, 2011) and atthe Karlsruhe Institute of Technology (KIT), dose measurementsduring preparation and application of radiopharmaceuticals forseveral radionuclide therapies were performed. Thin-layer lithiumfluoride thermoluminescence detectors (TLDs) were employed for

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extremity dose determination. The TLDs used at KIT (Bilski et al.,1995) enable measurement of beta and photon exposure and arecalibrated in a Sr-90/Y-90 reference field of a Beta SecondaryStandard with respect to the personal dose equivalent Hp(0.07). Inaddition to themeasurements, Monte Carlo simulations of differentradiation scenarios were performed mainly using the MCNPX code(Pelowitz, 2005). Investigations at KIT assessing medical staffextremity doses focused on selective internal radiation therapy(Stubbs et al., 2001) and radiosynoviorthesis (RSO) (Gratz et al.,2000). In these therapies, the beta-emitting nuclide Y-90 is used.Exemplary results for a syringe employed in the RSO case study willbe presented here. The top of Fig. 1 shows the KIT experimental set-up with a hand phantom provided by the LPS Berlin (LPS, 2008),TLDs in their plastic wrapping and a syringe containing a Y-90solution placed in the hand. This scenario, not typical for RSO, waschosen as simple experimental set-up for validation of the simu-lation method. The lower part of Fig. 1 shows the same scenariomodelled by the articulated hand phantom in the simulations (forsimulation details see (Blunck et al., 2010)). The highest possibleaccuracy of detector position placement in the simulationscompared to experiment is �2 mm.

3. Results and discussion

Fig. 2 compares the KITmeasurements with the simulations. Themeasured dose values are within 50% of the simulation data

Fig. 1. Top: set-up for the KIT dose measurements e TLDs (wrapped in plastic bags)and syringe placed on the hand phantom, bottom: the corresponding scenario asmodelled by the mathematical hand phantom for the simulations.

F. Becker, C. Blunck / Radiation Measurements 46 (2011) 1299e13021300

(average uncertainty of the measured values is about 15%) exceptfor the thumb andwrist with deviations of about a factor of two andtwenty, respectively. This may be explained by differences in TLDspositioning (see discussion below) and/or due to the fact thatexperimental data are single TLD measurements.

For the ORAMED project, the following scenario was simulatedwith the articulated hand phantom: injecting a Y-90 solution withan unshielded syringe. The 1ml syringe filled with 0.57ml of a Y-90solution having an activity of 0.194 GBq used in this scenariocorresponds to the ORAMED validation report (Carnicer, 2010).

Fig. 2. Dose measurement results compared to simulation results from the set-upsshown in Fig. 1 (0.2 GBq Y-90 activity).

Measured data (single TLD measurement) were taken from theORAMED report and modelling of the articulated hand phantomwas based on voxel data provided by the ORAMED collaboration(Carnicer, 2010). The Voxel2MCNP software (Hegenbart, 2010) wasemployed to extract 3D coordinates of characteristic points of thevoxel model, in order to adjust the articulated hand phantom. Thesyringe was modelled manually based on pictures of the experi-mental set-up (Carnicer, 2010).

A photograph of the experimental set-up with wax hand,syringe, and TLDs at different positions of the hand, the corre-sponding voxel model and the articulated mathematical handphantom, are shown in Fig. 3.

Fig. 4 compares the ORAMED measurement results with thetwo simulations e that from the voxel model and from themathematical hand phantom. The measured data were restrictedto significant dose values, i.e. Hp(0.07) > 1 mSv/(GBq$s). Theagreement is good, except for values for the middle finger; thedose values from simulations using the mathematical handphantom are significantly higher. The differences between thevoxel and mathematical model likely result mainly from variationsin positioning of the monitoring points. Differences betweenmeasurement and the two simulations also likely stem from thepositional accuracy of monitoring points, of TLDs and of thesyringe.

In order to assess the sensitivity of measurements and simula-tions to positional accuracies, simulations with both phantomswere performed for four investigated scenarios, with the syringe

Fig. 3. The mathematical hand phantom (bottom) based on photographs of themeasurement set-up and the imported voxel phantom according to the ORAMEDvalidation report.

Fig. 4. Comparison of the ORAMED measurements with simulations using the voxel phantom and the mathematical hand model shown in Fig. 3.

Fig. 5. Four different syringe positions/orientations in the hand phantom used to studythe influence of source position on simulation results. The displacement vector in cm,together with the syringe axis rotation angle (with respect to the reference positionshown in Fig. 3), are given in parentheses.

Fig. 6. Simulated dose values for the four different syringe positions/ori

position and orientation varied as shown in Fig. 5. The above modelconsisting of the syringe filled with a Y-90 solution placed in thehand was used again to simulate the dose at different points of thehands.

Fig. 6 displays the results of the different simulations comparedto the ORAMED measurements. In the extreme case for the middlefinger nail, the dose variation due to the different positions/orientations of the syringe can be nearly an order of magnitude.Differences between simulation dose values from the voxelphantom compared to those obtained using the mathematicalhand phantom might be attributed to differences in the geometryand the position of the dose calculation volumes. Obviously,variations in position influence the simulation and measurementresults strongly.

entations on the hand (see Fig. 5) in comparison to measurements.

F. Becker, C. Blunck / Radiation Measurements 46 (2011) 1299e13021302

4. Summary and outlook

We have shown that the articulated mathematical handphantom is a useful tool to estimate radiation exposure of medicalstaff. The main advantage of using such a simulation is the easyhandling compared to the CT-scan procedure of the wax handmodels and facile change in geometry for varying simulation inputs.

However, both measurements and simulations are sensitive topositioning accuracy of monitoring points and source location. Thisshould be particularly true for strong field gradients in mixedphoton-beta fields.

On-going studies (Blunck et al., 2010) and future activities willaddress modelling action sequences from video recordings. In thisway, simulations with the articulated hand phantom can provideinformation about handmotions in radiation fields, thus potentiallyimproving radiation protection of medical staff by revealing poseswith the highest doses and by optimising individual radiophar-maceuticals handling procedures.

Acknowledgement

The authors would like to thank Dr. E. Martini and Dr. J. Engel-hardt from the LPS Berlin (Personal Monitoring Service & Educationand Training in Radiation Protection) for providing the handphantom for the KIT measurements.

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