EXTREMITY RING DOSIMETRY
INTERCOMPARISON IN REFERENCE AND
WORKPLACE FIELDS

Merce Ginjaume, Elefhteria Carinou, L Donadille, Jacek Jankowski, A Rimpler, Marta Sans Merce, Filip Vanhavere, M. Denoziere, Jean-Pierre Daurès, jean-marc bordy, et al.

► To cite this version:

Merce Ginjaume, Elefhteria Carinou, L Donadille, Jacek Jankowski, A Rimpler, et al. EXTREMITY RING DOSIMETRY INTERCOMPARISON IN REFERENCE AND WORKPLACE FIELDS. 12th International Congress of the International Radiation Protection Association, Oct 2008, Buenos Aires, Argentina. cea-05461846

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EXTREMITY RING DOSIMETRY INTERCOMPARISON IN REFERENCE AND WORKPLACE FIELDS

M. Ginjaume1*, E. Carinou2, L. Donadille3, J. Jankowski4, A. Rimpler5, M. Sans Merce6, F. Vanhavere7, M. Denoziere8, J. Daures8, J.M. Bordy8, C. Itie3 and P. Covens9

1 Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain

2Greek Atomic Energy Commission, Ag. Paraskevi, 15310, Greece

3 Institut de Radioprotection et de Sûreté Nucléaire, BP 17, 92262 Fontenay-aux-Roses Cedex, France

4Nofer Institute of Occupational Medicine, St. Teresa Street 8, 90-950 Lodz, Poland

5Bundesamt für Strahlenschutz, (BfS), Köpenicker Allee 120-130, 10312 Berlin, Germany

6 Institut Universitaire de Radiophysique Appliquée, rue du Grand Pré 1, 1007 Lausanne, Switzerland

7Belgian Nuclear Research Centre, Boeretang 200, 2400 Mol, Belgium

8CEA LIST Laboratoire National Henri Becquerel, CEA Saclay 91191 Gif sur Yvette Cedex, France

9University of Brussels and Academic Hospital AZ-VUB, Radiation Protection Department, Brussels, Belgium

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical
capabilities of available extremity dosemeters and focusing on their performance at clinical
workplaces with potentially high extremity doses. 24 services from 16 countries participated in the
intercomparison. The dosemeters were exposed to reference photon (137Cs) and beta (147Pm, 85Kr
and 90Sr/90Y) fields together with fields representing realistic exposure situations in interventional
radiology (direct and scattered radiation) and nuclear medicine (99mTc and 18F). It has been found
that most dosemeters provided satisfactory measurements of Hp(0.07) for photon radiation, both in
reference and realistic fields. However, only four dosemeters fulfilled the requirements given by the
trumpet curves for all radiation qualities. The main difficulties were found for the measurement of
low energy beta radiation. Finally, the results also showed a general under-response of detectors to
18F, which was attributed to the difficulties of the dosimetric systems to measure the positron
contribution to the dose.

INTRODUCTION

A coordinated network for radiation protection dosimetry, the CONRAD project, was founded in 2005 within the 6th EU Framework Programme. One of the working groups in the network dealt with the coordination and promotion of European research in the field of radiation protection dosimetry for medical staff. A thorough review of the literature on this topic was undertaken during the course of the project. The fact that extremity doses in interventional radiology (IR) and nuclear medicine (NM) could be high and even exceed occupational limits was highlighted(1,2) . It was also found that there was a wide range of recorded doses for similar situations together with an important lack of data for some identified critical working conditions.
In these medical applications, the extremities (hands and fingers) are often in contact or very close to the radiation beam or radiopharmaceuticals. Furthermore, a wide variety of radiation fields must be monitored, low and medium energy X-ray beams in interventional radiology and photon, positron and beta emitters in nuclear medicine. Therefore it is difficult to design a small dosemeter with an accuracy similar to that of a whole-body dosemeter for the whole range of interest. Moreover, there have been very few international intercomparisons for these types of dosemeters and none, to the best of our knowledge, specifically focused on the analysis of performance in typical workplaces both in interventional radiology and nuclear medicine.

The increasing number of such procedures has led to an increased interest in studying doses received by workers in nuclear medicine and radiology departments and also to the improvement of extremity dosemeter design. An intercomparison was organized within the CONRAD project from January to May 2007 in order to verify the performance of different extremity dosemeters in use in Europe, in radiation fields that represent exposure situations of staff in hospitals. This paper summarizes the main results of the intercomparison and completes the preliminary analysis presented in Carinou et al. (3).

## METHOD

Organization of the intercomparison The scope of the intercomparison was limited to ring dosemeters because previous studies(2) demonstrated that, in general, they provide a better estimate of the maximum skin dose than wrist dosemeters. According to ICRP recommendations(4), the operational quantity used in the intercomparison was the personal dose equivalent at a depth of 0.07 mm, Hp(0.07), defined in ICRU 47 (5). Four types of irradiation fields were selected: reference gamma fields, reference beta fields and realistic interventional and nuclear medicine fields. The participants were selected on the basis of being a representative sample from different EU countries and of various types of dosimetric systems.

## Participants

Twenty-four dosimetric services from sixteen countries participated in the intercomparison. Participants included both small and large services. In total, they are responsible for monitoring of extremity exposure of 33,000 people a year.

Most of the dosemeters (21/24) used LiF phosphors as detectors with different types of dopants, isotopic concentration of 7Li and thicknesses. Two services used Li2B4O7 and another CaF2:Mn. The tested detector holders were manufactured by Rados, TLD Poland, Panasonic, Harshaw/ Thermo Instruments or by the service itself. The filter was plastic except for one service that used Cu+Sn. The overall thicknesses of the detectors and filters ranged between 12 and 300 mg/cm². More information on the types of dosemeters can be found in Carinou et al. (3).

Four services decided only to participate in the photon fields, the rest were tested in all the selected irradiation fields. In some cases, the dosemeters were irradiated in conditions in which they are probably not normally used, e.g. for beta radiation.

Most services used 137Cs for dosemeter calibration but only very few tested them with beta radiation.
## Irradiation fields

The irradiation programme was performed by four laboratories. All irradiations were performed on an ISO rod phantom (solid PMMA 30 cm cylinder, 19 mm diameter)(6, 7).

The Laboratory of Ionising Radiation Dosimetry at the Institute for Radiological Protection and Nuclear Safety (IRSN) (France) was in charge of the 137Cs irradiations at 0°, 60° and 180°. Hp(0.07) was determined according to the equation:

$$Hp(0.07) = h_{p,k}(0.07, \alpha) \cdot \text{Kair}, \quad (1)$$

where hp,K(0.07, α) is the conversion coefficient from kerma free in air to Hp(0.07) for an irradiation angle α provided by Grosswendt(8). The Kair value was measured at IRSN by using a secondary standard ionization chamber.

Reference values ranged between 4 and 6 mSv and the associated uncertainty was 4.8% (k=2). Uncertainty estimates included an uncertainty of 4.0% (k=2) for hp,K(0.07, α) as indicated in ISO 4037-3.

The beta irradiations were carried out at the Bundesamt für Strahlenschutz (BfS) (Germany). Reference sources from the series 1 specified in ISO 6980-1 (9), 90Sr/90Y, 85Kr and 147Pm were selected for the intercomparison. Irradiations were performed at 0° and 60° for each source. The reference values of Hp(0.07) were provided directly by the software of a BSS-2 type secondary standard, traceable to the primary laboratory at the PTB(10), according to expression (2):

$$Hp(0.07) = hp,D(0.07, \alpha) \cdot Dt(0.07), \quad (2)$$

where h<sub>p,D</sub>(0.07, α) is the conversion coefficient from absorbed dose in 0.07 mm of ICRU tissue, Dt(0.07), to personal dose equivalent, for an irradiation angle α. It was assumed that the conversion coefficient h<sub>p,D</sub>(0.07, 0°) is equal to 1 Sv/Gy. For an incidence of 60°, hp,D(0.07, 60°) from ISO 6980-3 (7) was used. Reference values ranged from 6 to 11 mSv and the uncertainty was equal to 2.3% for 90Sr/90Y and 85Kr, and 3% - 3.7% for 147Pm (k=2). By convention, no uncertainty was assigned to the conversion coefficient in this case.

The interventional radiology fields were reproduced at the Laboratoire National Henri Becquerel at the Comissariat à l'Energie Atomique CEA/LIST (LNHB) (France). A typical spectrum of 70 kVp with a filtration of 4.5 mm Al and 0.2 mm Cu produced in a medical X-ray generator MPH65 (GEMS) was used. Dosemeters were tested at two locations above the phantom, in the emission cone of the primary beam and outside the primary cone beam in the scattered field at the edge of the patient phantom. Hp(0.07) was determined using equation (1). The Kair value was measured at CEA using an ionization chamber traceable to primary standards. The photon spectra in terms of fluence were calculated with the MCNPX Monte Carlo Code(11,12) at the two points of tests. The average conversion coefficients from air kerma free in air to personal dose equivalent, hp,K(0.07, α), for the IR beams, were then derived from the calculated spectra folded with the individual conversion coefficients taken from ICRU 57(13). The reference personal dose equivalent values were equal to 2.6 mSv for the direct beam and to 0.61 mSv for the scattered field, the associated uncertainty was 6.5% (k=2). The uncertainty for the IR fields comes mainly from the uncertainty on the air kerma measurement (5%, k=2) and the uncertainty in the calculation of the conversion factors (4%, k=2).

The realistic nuclear medicine fields were simulated at the Free University of Brussels (UZ) (Belgium) with the collaboration of the Belgian Nuclear Research Center (SCK-CEN) - (Belgium). The dosemeters on the corresponding rod phantoms were situated at 14.05 cm from an unshielded
syringe filled, with 99mTc and 18F solutions, respectively. The reference values of Hp(0.07) were calculated using the MCNPX2.5.0 code(11). As compared with the experimental geometry shown in Figure 1, a simplified set-up was defined in the model. The radiopharmaceutical was simulated as a cylindrical water source limited by a 0.75 mm thick, 0.93 g cm⁻³ polyethylene syringe wall(14). The whole geometry was surrounded by 1.205 g cm⁻³ dry-air(14). For each solution (99mTc and 18F), decay data were taken from Brown and Firestone(15) and Stabin and da Luz(16). For the 18F problem, 511 keV annihilation gamma-rays were taken into account as created where each positron (beta-ray) came to rest. The dose equivalent Hp(0.07) was estimated as the dose deposited in a 0.5 cm height water cylindrical cell at 7±1 mg cm⁻² depth within the phantom (2 mg cm⁻² thick). The rod phantom was simulated as a 10 cm high, 1.9 cm thick water cylinder, with the front wall located at 14.05 cm from the centre of the source cell.

Photons and electrons were transported in the calculations, following the method recommended by Schaart et al. (17). For 18F it was observed that 57% of the total Hp(0.07) value is due to direct exposure to positrons and 43% to annihilation gamma-rays. Calculated deposited doses were expressed in terms of Sv per 99mTc or 18F disintegration, as appropriate. Subsequently, they were normalized by the measured total number of disintegrations during the irradiation. The latter parameters were obtained from measurements of the initial activities of radioactive solutions in a radioisotope calibrator and the irradiation times. The reference values ranged from 4 to 6 mSv for 99mTc and from 10 to 15 mSv for 18F, with an uncertainty (k=2) of 10.5% and 8%, respectively. This uncertainty includes the component due to activity measurement (4.5% for k=2) and the simulation. The latter is calculated as the square root of the variance of the statistical uncertainty (2% for k=2) plus the variance associated with the simulated model (9.2% for 99mTc and 6% for 18F, for k=2), which was estimated by comparing the influence of a different set-up and of different Monte Carlo codes in the results.

## Performance criteria

The performance requirements of passive extremity dosemeters are described in ISO 12794(18). This standard specifies the recommended type tests and dosimetric requirements for extremity individual monitoring purposes. The scope of the standard includes measurements of photon beams with energies from 15 keV to 3 MeV and beta radiation with a maximum energy ranging from 0.5 MeV to 3 MeV. As regards the performance criteria, the standard requires that the energy response of the dosemeter for reference qualities defined in ISO 4037-1 (19) and ISO 6980-1 (9), within the energy range of the scope, shall not vary by more than ± 50%. The standard defines performance criteria for the angular response of 60 kV photon beams but does not detail requirements for angular beta response.

The main aim of the intercomparison was not to verify if the services fulfilled the ISO 12794, but to analyse the dosemeter performance in radiation fields of interest in some medical applications. Therefore, it only included some of the ISO type-tests and it was completed with additional simulated work-place fields.

In the overall analysis of the results, the general dosimetric requirements established by ICRP(4,20) and represented by the so-called "trumpet curves"(21) were applied.

## RESULTS AND DISCUSSION
In each field, two dosemeters from each service were irradiated. Services were requested to read the dosemeters and to evaluate Hp(0.07) and its uncertainty for each dosemeter. The services had no information about irradiation conditions except for the fact that the dosemeters irradiated with 137Cs and X-rays were labelled as photon fields and the rest were identified as mixed beta/gamma fields.

For each tested field, i, the response of the services, Ri, was calculated as:

$$ \frac{1,2, ( )}{2} (0.07) \text{i i i p ref i L L Bk R H + - = (3)} $$

Where:

Li1 and Li2 are the two readings of irradiation field i, Bki is the measured background of irradiation field i, calculated as the mean value of the background dosemeter readings. Hp(0.07)ref,i is the reference personal dose equivalent in i.

Table 1 shows the response of the participants, for each irradiation field, classified in the following categories:

(1) Category I: participants that comply with the trumpet curve in the 13 tested fields. Four services belong to this group. A sub-category I Ph is considered in this group to include three of the four services that only were tested for photons and presented results within the requirements of the intercomparison.

(2) Category II: participants that comply with ISO 12794 and with the trumpet curves limits in the realistic fields, but do not belong to the first category. There are three services in this group; they are outside the limits for the 147Pm and for the 85Kr at 60°.

(3) Category III: participants that do not belong to categories I and II, but that are within the limits for photon fields and 90Sr normal incidence. There are ten services in this group.

(4) Category IV: participants outside the previous categories. There are four services in this group, who had difficulties in the measurement of the tested photon beams. The service that uses CaF2:Mn (id: 15) belongs to this category and presented an important over-estimate for X-rays compared with the response to 137Cs.

Each service is identified by an anonymous number, id. Values outside the trumpet curve limits are indicated in Table 1 in italic-bold case. Table 2 provides a general overview of the performance of the participants and summarises the main results: mean response, response range and number of services that failed to fulfil trumpet curve criteria.

Results show that, for 137Cs, at all tested angles, with two exceptions, all reported doses are very close to 1. The average relative response is 0.93. For 90Sr/90Y, normal incidence, the results are also satisfactory except in one case, the average relative response is 1.00. The performance is slightly worse at 60°, with an average relative response of 0.63 and half of the services are below the trumpet curve lower limit. For 85Kr and 147Pm, normal incidence, Hp(0.07) is underestimated, the average relative responses are 0.45 and 0.25, respectively. Only dosemeters with thin filters and thin detectors provided appropriate results, 8 out of 20 for 85Kr and 5 out of 20 for 147Pm. Responses were even lower for the 60° angle of incidence.

In realistic interventional fields, both within and outside the beam, two services reported very high doses and one underestimated the given dose. The rest of services were within the limits. The average relative response was 1.86, taking into account the 24 participants but it was reduced to
1.29 if the two services with a large overestimation (id: 3 and 8) were excluded. It was shown that, generally, there was an overestimation of 30% of the reported doses by the services that use LiF detectors and an underestimation of 15% for those that use Li2B4O7.

The results obtained for the 99mTc irradiation were satisfactory in 19 out of 20 cases and the average relative response was 1.08. On the other hand, in the case of 18F irradiation, there was a general underestimation of the dose. The average relative response was found to be 0.55 and only 7 services were within the trumpet curve for this field. It must be mentioned that the services that had a good relative response to betas also presented a good response for 18F dose.

The uncertainties assigned by the services to their results varied substantially among them. From the 24 services, 3 reported that they had not evaluated their uncertainties. Four others reported their 'total' uncertainties, but did not give any specification on how they were calculated. All the others gave some information, and, as expected, the description on how it was calculated varied significantly.

The technical recommendations for monitoring individuals occupationally exposed to external radiation (EUR 14852)(22) consider as main sources of uncertainties in TL individual monitoring energy and directional dependence, the non-linearity of the response, calibration errors and uncertainty in individual calibration factors. Only three services reported that they took all these parameters into account. However, in the intercomparison, the main source of uncertainty is expected to be energy dependence and, therefore, the 13 services that took energy dependence into account, should provide an acceptable estimate of the uncertainty. Of course, in the intercomparison, the uncertainty associated with energy dependence should consider the behaviour of the dosemeters in all the reference tested fields but this, as mentioned above, was not the case for most services.

When dividing the participants in two groups: those that included energy dependence in their uncertainty budget (13), and those who did not include it (8), the uncertainties (k=2) ranged from 12 to 50% in the first group and, from 5 to 21% for the second group. These uncertainties did not justify some of the measurements outside the trumpet curve limit, in either of the two groups.

## CONCLUSION

Analysis of the intercomparison fulfilled the expected objectives since it provides a large overview of the capabilities and the difficulties of extremity dosemeters in measuring the quantity Hp(0.07) in photon and beta reference fields and in realistic workplace fields characteristic from interventional radiology and nuclear medicine.

Summarising the main results of the study, it can be pointed out that, in general, there is a satisfactory response for photon fields: 137Cs, IR direct and scattered fields and 99mTc. Major difficulties were encountered in the measurement of beta radiation (Category III services). The study highlights the fact that this limitation is also a matter of concern when handling 18F because in this case the contribution of positrons to the dose cannot be neglected. The importance of dosemeter design, in particular, the thickness of the filter and the detector has been shown. Four services performed within established criteria for all tested fields and seven services fulfilled requirements in the tested medical fields.

It was confirmed that CaF2:Mn is not a good detector to be used for extremity dosimetry in the medical field because it presents a high over-response for X-ray fields. Finally, the collected data show a large variation of the reported uncertainties, which ranged between 5% and 50% (k=2). These
differences were due to the different components of uncertainty considered by the services, thus indicating that there is a need for harmonization in this field. Results also highlight the fact that the contribution of energy response dependence on the measurement uncertainty cannot be neglected and has to be estimated for all fields of interest. The calibration procedures should also be reviewed depending on the fields where the dosemeters will be used.

## ACKNOWLEDGMENTS

The authors would like to thank all the irradiation laboratories (IRSN, BfS, CEA and AZ-VUB/SCK-CEN) and the participating services for their collaboration in the intercomparison.

## REFERENCES

1. Vanhavere, F., Carinou, E., Donadille, L., Ginjaume, M., Jankowski, J., Rimpler, A. and Sans Merce, M. An overview on extremity dosimetry in medical applications. Accepted for publication in Radiat. Prot. Dosim. (2007).

2. Donadille, L., Carinou, E., Ginjaume, M., Jankowski, J., Rimpler, A., Sans Merce, M. and F. Vanhavere. An overview of the use of extremity dosemeters in some European countries. This issue in Radiat. Prot. Dosim.

3. Carinou, E., Donadille, L., Ginjaume, M., Jankowski, J., Rimpler, A., Sans Merce, M., Vanhavere, F., Denozière, M., Daures, J., Bordy, J.M., Itié, C. and Covens, P. Intercomparison on measurements of the personal dose equivalent, Hp(0.07), by extremity ring dosemeters in medical fields. Accepted for publication in Radiat. Prot. Dosim. (2007).

4. International Commission on Radiological Protection. 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60, Annals of the ICRP 21(1-3) (Oxford: Pergamon Press) (1992).

5. International Commission on Radiations Units and Measurements. Determination of dose equivalents from external photon and electron radiations. ICRU Report 47 (Bethesda, MD 20814: ICRU Publications) (1992).

6. International Organization for Standardization. X and gamma reference radiation for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy - Part 3: Calibration of area and personal dosemeters and the measurement of their response as a function of energy and angle of incidence. ISO 4037-3, Geneva, (1999).

7. International Organization for Standardization. Reference beta-particle radiation – part 3: calibration of area and personal dosimeters and the determination of their response as a function of beta radiation energy and angle of incidence. ISO 6980-3, Geneva, (2006).

8. Grosswendt, B. Angular dependence factors and air kerma to dose equivalent conversion coefficients for cylindrical phantoms irradiated by plane-parallel extended monoenergetic photon beams. Radiat. Prot. Dosim. 59, 165-179, (1995).

9. International Organization for Standardization. Nuclear energy - Reference beta-particle radiation – Part 1 Method of production. ISO 6980-1, Geneva, (2006).

10. Helmstädter, K., Buchholz, G., Ambrosi P. Das PTB Beta-Sekundärnormal BSS 2 für den Strahlenschutz. Report PTB-Dos-50, Braunschweig, (2006).
11. MCNPX User's manual, version 2.5.0. D.B. Pelowitz (ed.). Los Alamos, NM: Los Alamos National Laboratory, Report LA-CP-05-0369, (2005).

12. Struelens, L., Donadille, L., Bordy, J.M., Schultz, F.W., Fülöp, M., Carrapiço, C., Ennow, K., Itie, C., Denoziere, M., Daures, J. Monte Carlo Modelling for Medical Staff Dosimetry, Paper submitted for the proceedings of the CONRAD-WP4 workshop on 'Uncertatinty assessment in computational dosimetry'. 8-10 October 2007, Bologna (2007).

13. International Commission on Radiations Units and Measurements. Conversion Coefficients for use in Radiological Protection Against External Radiations. ICRU Report 57 (Bethesda, MD 20814: ICRU Publications) (1998).

14. International Commission on Radiations Units and Measurements. Tissue Substitutes in Radiation Dosimetry and Measurement, ICRU Report 44. Bethesda, MD: International Commission on Radiation Units and Measurements (Bethesda: ICRU Publications), (1989).

15. Browne, E. and Firestone, R.B. Table of Radioactive Isotopes. Virginia S. Shirley, Ed., (1986) ISBN 0-471-84909-X

16. Stabin, M.G. and da Luz, L.C.Q.P Decay data for internal dose assessment. Health Phys. 83(4), 471-475, (2002). See also http://www.doseinfo-radar.com/.

17. Shaart, D.R., Jansen, J.Th., Zoetelief, J. and A de Leege, P.F. A comparison of MCNP4C electron transport with ITS 3.0 and experiment at incident energies between 100 keV and 20 MeV: influence of voxel size, substeps and energy indexing algorithm, Phys. Med. Biol. 47, 1459-1484, (2002).

18. International Organization for Standardization. Nuclear energy -Radiation protection- Individual thermoluminiscence dosemeters for extremities and eyes. ISO 12794, Geneva, (2000).

19. International Organization For Standardization, X and Gamma Reference Radiation for Calibrating Dosemeters and Dose Rate Meters and for Determining their Response as a Function of Photon Energy - Part I: Characteristics of the Radiations and their Methods of Production. ISO 4037-1, Geneva, (1996).

20. International Commission on Radiological Protection, General Principles for the Radiation Protection of Workers, Publication 75, Annals of the ICRP 27, 1-3, Pergamon Press, New York (1997).

21. Böhm J., Ambrosi P., Mandatory type tests of solid state dosimetry systems as an appropriate aid to quality assurance in individual monitoring. Radiat. Prot. Dosim. 34, 123-126 (1990).

22. European Commission, Technical recommendations for monitoring individuals occupationally exposed to external radiation, (EUR 73). EUR 14852 EN (1994).

## Captions:

Figure 1: Photograph of the experimental set-up to simulate nuclear medicine workplace conditions.

Table 1: Participant response for each tested radiation quality. Services are classified in four categories and responses outside trumpet curve limits are highlighted in bold-italic case. (Each service is identified by an anonymous number from 1 to 24).

Table 2: Summary of the intercomparison results for each tested radiation quality: mean response, response range and number of services outside the trumpet curve
<table><caption>Table 1: Participant response for each tested radiation quality. Services are classified in four categories and responses outside trumpet curve limits are highlighted in bold-italic case. (Each service is identified by an anonymous number from 1 to 24).</caption><thead><tr><th rowspan="2">Category</th><th rowspan="2">ID</th><th colspan="6">Beta reference fields</th><th colspan="2">NM workplace</th><th colspan="2">Gamma reference fields</th><th colspan="2">IR workplace</th></tr><tr><th><sup>90</sup>Sr-<sup>90</sup>Y</th><th><sup>85</sup>Kr</th><th><sup>147</sup>Pm</th><th><sup>13</sup>F</th><th><sup>90</sup>Tc</th><th>0°</th><th>60°</th><th>180°</th><th>in beam</th><th>outside beam</th></tr><tr><th></th><th>0°</th><th>60°</th><th>0°</th><th>60°</th><th>0°</th><th>60°</th><th><sup>13</sup>F</th><th><sup>90</sup>Tc</th><th>0°</th><th>60°</th><th>180°</th><th>in beam</th><th>outside beam</th></tr></thead><tbody><tr><td rowspan="4">I</td><td>10</td><td>1.02</td><td>0.93</td><td>0.89</td><td>0.79</td><td>0.49</td><td>0.69</td><td>0.75</td><td>0.81</td><td>0.60</td><td>0.73</td><td>0.75</td><td>1.12</td><td>1.20</td></tr><tr><td>11</td><td>0.94</td><td>0.67</td><td>0.88</td><td>0.72</td><td>0.81</td><td>0.51</td><td>0.73</td><td>1.14</td><td>0.59</td><td>0.79</td><td>0.80</td><td>1.36</td><td>1.11</td></tr><tr><td>12</td><td>1.39</td><td>1.28</td><td>1.24</td><td>0.94</td><td>1.18</td><td>0.63</td><td>1.06</td><td>1.11</td><td>0.78</td><td>0.79</td><td>1.12</td><td>1.42</td><td>1.55</td></tr><tr><td>13</td><td>1.27</td><td>0.89</td><td>1.00</td><td>0.65</td><td>0.87</td><td>0.88</td><td>0.92</td><td>0.95</td><td>0.89</td><td>0.95</td><td>0.90</td><td>1.51</td><td>1.42</td></tr><tr><td rowspan="3">I Ph</td><td>4</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>1.02</td><td>1.03</td><td>1.04</td><td>1.67</td><td>1.57</td></tr><tr><td>17</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.65</td><td>0.61</td><td>0.67</td><td>1.10</td><td>1.06</td></tr><tr><td>19</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.70</td><td>0.81</td><td>0.88</td><td>0.76</td><td>0.64</td></tr><tr><td rowspan="3">II</td><td>2</td><td>1.33</td><td>0.78</td><td>0.70</td><td><strong>0.39</strong></td><td><strong>0.01</strong></td><td><strong>0.01</strong></td><td>0.69</td><td>1.01</td><td>0.81</td><td>0.81</td><td>0.80</td><td>1.25</td><td>1.36</td></tr><tr><td>14</td><td>1.17</td><td>1.06</td><td>0.88</td><td><strong>0.50</strong></td><td><strong>0.08</strong></td><td><strong>0.04</strong></td><td>0.73</td><td>0.93</td><td>0.78</td><td>0.77</td><td>0.83</td><td>1.27</td><td>1.00</td></tr><tr><td>22</td><td>1.22</td><td>1.05</td><td>0.99</td><td>0.66</td><td>0.42</td><td><strong>0.25</strong></td><td>0.84</td><td>0.89</td><td>0.77</td><td>0.85</td><td>1.22</td><td>1.83</td><td>1.45</td></tr><tr><td rowspan="10">III</td><td>1</td><td>0.84</td><td><strong>0.46</strong></td><td>0.74</td><td><strong>0.31</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.45</strong></td><td>1.14</td><td>1.03</td><td>0.68</td><td>0.90</td><td>1.38</td><td>1.81</td></tr><tr><td>6</td><td>1.15</td><td>0.63</td><td><strong>0.20</strong></td><td><strong>0.11</strong></td><td><strong>0.01</strong></td><td><strong>0.01</strong></td><td><strong>0.51</strong></td><td>1.27</td><td>1.08</td><td>1.07</td><td>1.00</td><td>1.50</td><td>1.40</td></tr><tr><td>7</td><td>1.09</td><td><strong>0.44</strong></td><td><strong>0.10</strong></td><td><strong>0.03</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.43</strong></td><td>0.85</td><td>1.05</td><td>0.96</td><td>0.99</td><td>0.89</td><td>0.94</td></tr><tr><td>9</td><td>1.05</td><td>0.76</td><td><strong>0.48</strong></td><td><strong>0.33</strong></td><td><strong>0.09</strong></td><td><strong>0.05</strong></td><td><strong>0.47</strong></td><td>1.04</td><td>0.79</td><td>0.78</td><td>0.82</td><td>1.41</td><td>1.58</td></tr><tr><td>16</td><td>1.14</td><td>0.55</td><td><strong>0.15</strong></td><td><strong>0.06</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.50</strong></td><td>1.03</td><td>1.07</td><td>1.09</td><td>1.05</td><td>1.28</td><td>1.43</td></tr><tr><td>18</td><td>0.82</td><td><strong>0.43</strong></td><td><strong>0.10</strong></td><td><strong>0.02</strong></td><td><strong>0.00</strong></td><td><strong>-0.01</strong></td><td><strong>0.42</strong></td><td>1.06</td><td>0.88</td><td>0.85</td><td>0.97</td><td>1.50</td><td>1.23</td></tr><tr><td>20</td><td>0.94</td><td><strong>0.48</strong></td><td><strong>0.07</strong></td><td><strong>0.07</strong></td><td><strong>0.00</strong></td><td><strong>0.01</strong></td><td><strong>0.48</strong></td><td>1.17</td><td>1.00</td><td>0.96</td><td>0.95</td><td>1.42</td><td>1.52</td></tr><tr><td>21</td><td>1.00</td><td><strong>0.46</strong></td><td><strong>0.13</strong></td><td><strong>0.04</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.37</strong></td><td>0.73</td><td>0.77</td><td>0.76</td><td>0.75</td><td>0.71</td><td>0.68</td></tr><tr><td>23</td><td>0.59</td><td><strong>0.10</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.26</strong></td><td>1.29</td><td>0.99</td><td>0.97</td><td>0.95</td><td>1.57</td><td>1.53</td></tr><tr><td>24</td><td>1.03</td><td><strong>0.43</strong></td><td><strong>0.17</strong></td><td><strong>0.04</strong></td><td><strong>0.00</strong></td><td><strong>0.01</strong></td><td><strong>0.42</strong></td><td>1.11</td><td>0.92</td><td>0.92</td><td>0.89</td><td>1.46</td><td>1.43</td></tr><tr><td rowspan="4">IV</td><td>3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td><strong>2.3</strong></td><td><strong>2.2</strong></td><td><strong>2.4</strong></td><td><strong>3.5</strong></td><td><strong>2.6</strong></td></tr><tr><td>5</td><td><strong>0.42</strong></td><td><strong>0.36</strong></td><td><strong>0.06</strong></td><td><strong>0.04</strong></td><td><strong>0.00</strong></td><td><strong>0.00</strong></td><td><strong>0.26</strong></td><td>0.56</td><td>0.63</td><td><strong>0.43</strong></td><td><strong>0.42</strong></td><td><strong>0.46</strong></td><td>0.51</td></tr><tr><td>8</td><td>0.70</td><td><strong>0.44</strong></td><td><strong>0.13</strong></td><td><strong>0.03</strong></td><td><strong>0.01</strong></td><td><strong>0.01</strong></td><td><strong>0.43</strong></td><td>1.19</td><td>1.03</td><td>1.06</td><td>1.10</td><td>1.56</td><td><strong>2.0</strong></td></tr><tr><td>15</td><td>0.94</td><td><strong>0.47</strong></td><td><strong>0.11</strong></td><td><strong>0.07</strong></td><td><strong>0.01</strong></td><td><strong>0.01</strong></td><td><strong>0.40</strong></td><td><strong>2.3</strong></td><td>0.87</td><td>0.87</td><td>0.90</td><td><strong>12</strong></td><td><strong>11</strong></td></tr></tbody></table>

<table><caption>Table 2: Summary of the intercomparison results for each tested radiation quality: mean response, response range and number of services outside the trumpet curve</caption><thead><tr><th>H<sub>g</sub>(0.07) [mSv]</th><th>Radiation quality</th><th>Mean response</th><th>Response range</th><th>N° services outside the trumpet curve</th></tr></thead><tbody><tr><td>8.2</td><td><sup>90</sup>Sr-<sup>90</sup>Y, 0°</td><td>1.00</td><td>0.38 – 1.42</td><td>1/20</td></tr><tr><td>9.0</td><td><sup>90</sup>Sr-<sup>90</sup>Y, 60°</td><td>0.63</td><td>0.03 – 1.30</td><td>10/20</td></tr><tr><td>10.3</td><td><sup>85</sup>Kr, 0°</td><td>0.45</td><td>0 – 1.31</td><td>12/20</td></tr><tr><td>11.0</td><td><sup>85</sup>Kr, 60°</td><td>0.29</td><td>0 – 0.95</td><td>15/20</td></tr><tr><td>5.8</td><td><sup>147</sup>Pm, 0°</td><td>0.25</td><td>0 – 1.34</td><td>15/20</td></tr><tr><td>8.3</td><td><sup>147</sup>Pm, 60°</td><td>0.16</td><td>0 – 0.95</td><td>16/20</td></tr><tr><td>10.1</td><td><sup>13</sup>F</td><td>0.55</td><td>0.02 – 1.08</td><td>13/20</td></tr><tr><td>4.2</td><td><sup>90</sup>Tc</td><td>1.08</td><td>0.48 – 2.36</td><td>1/20</td></tr><tr><td>4.5</td><td><sup>137</sup>Cs, 0°</td><td>0.92</td><td>0.35 – 2.35</td><td>1/24</td></tr><tr><td>4.8</td><td><sup>137</sup>Cs, 60°</td><td>0.91</td><td>0.38 – 2.37</td><td>2/24</td></tr><tr><td>5.2</td><td><sup>137</sup>Cs, 180°</td><td>0.96</td><td>0.37 – 2.52</td><td>2/24</td></tr><tr><td>2.6</td><td>IR in beam</td><td>1.86</td><td>0.27 – 12.5</td><td>3/24</td></tr><tr><td>0.7</td><td>IR outside beam</td><td>1.86</td><td>0.21 – 11.7</td><td>3/24</td></tr></tbody></table>

<figure><img src="image_2.png" /><figcaption>Figure 1:</figcaption></figure>