2007 International Nuclear Atlantic Conference - INAC 2007
Santos, SP, Brazil, September 30 to October 5, 2007
ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN
ISBN: 978-85-99141-02-1
INTERCOMPARISON PROGRAM OF ACTIVITY MEASUREMENTS IN
NUCLEAR MEDICINE IN RECIFE, PE
Flávio Chiappetta Paes Barreto, Alberto Teodósio, Marcus Aurélio P dos Santos, Fabiana
Farias de Lima and Mércia L Oliveira
Centro Regional de Ciências Nucleares (CRCN/CNEN-PE)
Av. Professor Luiz Freire, 200
50740-540, Recife/PE
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
ABSTRACT
Intercoparison is an important tool for quality assessment, since not only the equipment performance but also
the procedures are evaluated and compared. This tool is wide utilized to evaluate the ability of nuclear medicine
services (NMS) to measure activities of radiopharmaceuticals. Since 1998, the Laboratório Nacional de
Metrologia das Radiações Ionizantes (LNMRI/IRD/CNEN) has been conducting intercomparison programs at
Rio de Janeiro and surroundings, and, after successive rounds of comparison, an improvement in the
performance of the radionuclide calibrators have been observed in this region. Similar results were observed
worldwide. The Centro Regional de Ciências Nucleares (CRCN-NE/CNEN) was designated by the LNMRI to
establish the intercomparison program of activity measurementsin NMS in the Brazilian northeast. The aim of
this work is to present the results of the first round of comparison measurements of activity of 99mTc and 131I.
This round was carried out in Recife/PE. Six NMS participated in this intercomparison. Additionally to the
activity measurement, some information about equipments (calibration and quality control program) and human
resources was obtained. All NMS participants complied with the limit established by CNEN for the accuracy of
measurement (±10%) for 99mTc and 131I. Measurements will be repeated for 99mTc and 131I, and additional rounds
will be performed including different radionuclides.
1. INTRODUCTION
Radioactive materials are widely used for therapeutic or diagnostic medical purposes. As an
example, there is the nuclear medicine. In this case, the determination of the activity managed
to the patient plays an important role for the success of the therapy or the diagnostic.
Various regulations have been published worldwide limiting values for the maximum
uncertainties permissible in activity measurements, as for an example the guide published
recently by the National Physical Laboratory (NPL), United Kingdom [1]. The aim of this
publication is to present the quality controls that should be undertaken on a routine basis for
medical radionuclide calibrators to ensure the accuracy and traceability of measurements of the
activities of radiopharmaceuticals [1].
In Brazil, these values were established by the Comissão Nacional de Energia Nuclear in the
CNEN-NE-3.05 standard [2]. Following this standard, the correct value of the activity of a
radiopharmaceutical should be known with the maximum uncertainty of 10%. The most
popular instrument to measure the activity of radioactive materials in Nuclear Medicine
Services (NMS) is the radionuclide calibrator because of its simple and fast utilization. To
guarantee the administration of the correct value of radiopharmaceutical activity to the patient,
the appropriate use of the radionuclide calibrators is indispensable. This equipment is capable
to carry through accurate activity measurements if adequate procedures are followed.
Intercomparison programs are important tools for evaluation of the quality of the
radiopharmaceutical activity measurements, because it can evaluate the equipment accuracy
and the technical procedure or method employed. Since 1998, the Laboratório Nacional de
Metrologia das Radiações Ionizantes (LNMRI/IRD) has been conducting intercomparison
programs at Rio de Janeiro and surroundings [3-4]. The Centro Regional de Ciências Nucleares
(CRCN-NE/CNEN) was designated by the LNMRI to establish this program in the Brazilian
northeast.
The aim of this work is to present the results of the first round of intercomparison
measurements performed at Recife, PE.
2. MATERIAL
A radionuclide calibrator, Capintec, model CRC-15 was established as the standard instrument.
There was established a quality control program at the laboratory, and repetitivity and
reproducibility measurements have been done regularly, in addition to diary verification of
voltage, auto zero and background radiation contribution.
The 99mTc and 131I samples utilized were contained in glass vials with 5 ml of solution. The
reference value of activity was determined by measurements performed with the Capintec,
CRC-15, radionuclide calibrator.
3. METHODOLOGY
The intercomparison program was divided in two steps:
1. The measurement at the nuclear medicine service (NMS) under evaluation:
At the NMS, a technician, designed by the NMS manager, is asked to make three
measurements for background radiation and five measurements of activity with the
radiopharmaceutical-test; after, the three repeated measurements of background
radiation are performed.
A special questionnaire was written to standardize the measurements procedure; besides
the results of the activity measurements, some information concerning the activimeter
itself (manufacturer, model, serial number, calibration date and operational voltage) are
checked.
2. Measurements at CRCN:
The measurement procedure at CRCN is the same that followed at the NMS under
evaluation. A Capintec (model CRC-15R) activimeter was utilized as the standard
INAC 2007, Santos, SP, Brazil.
equipment. A quality control program was established at the laboratory in order to
guarantee the adequate behavior of the standard instrument.
According to Brazilian National Regulatory Agency, the acceptable value for the accuracy on
activity measurements for radionuclides utilized in Nuclear Medicine is ±10%.
4. RESULTS
Six private and public NMS from Recife, PE, participated in the first round of the
intercomparison program. Each participant received an identifying code (A, B, C, D, E and F)
in order to guarantee the anonymity.
It was observed that all participants utilized Capintec radionuclide calibrator models, and all
participants affirmed that they have a quality control program established in their routine
measurements based on CNEN recommendations [2]. However, no one perform diary tests as
suggested by NPL [1].
The same 131I and 99mTc samples were utilized to perform all the measurements at the NMS and
at CRCN. All measurements were corrected for decay to the time when the measurements at
CRCN were executed. The results are showed in Figures 1 and 2. All NMS participants of the
first round of the intercomparison program complied with the limit established by CNEN for
the accuracy of measurement (±10%) for 99mTc and 131I [2].
1,2
NMS/CRCN Activity Ratio
1,15
1,1
1,05
1
0,95
0,9
0,85
0,8
A
B
C
D
E
F
NMS
Figure 1. NMS/CRCN activity ratio for
and lower limits.
INAC 2007, Santos, SP, Brazil.
99m
Tc intercomparison. Dashed lines represent upper
1,2
NMS/CRCN Activity Ratio
1,15
1,1
1,05
1
0,95
0,9
0,85
0,8
A
B
C
D
E
F
NMS
Figure 2. NMS/CRCN activity ratio for 131I intercomparison. Dashed lines represent upper and
lower limits.
5. CONCLUSIONS
As an important quality tool, the activity measurements intercomparison program was
established in Recife, PE. In the first round, activity measurements of 99mTc and 131I were
performed. All NMS participants demonstrated a very good capability to determine the activity
of these two nuclides.
Further efforts will be done in order to evaluate the uncertainties involved in the measures
performed at NMS.
INAC 2007, Santos, SP, Brazil.
ACKNOWLEDGMENTS
The authors are thankful to all participating institutions. The authors are grateful to Dr Akira
Iwahara for his continuous help. The authors also acknowledge the partial financial support of
the Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE).
REFERENCES
1. NPL, Protocol for Establishing and Maintaining the Calibration of Medical Radionuclide
Calibrators and their Quality Control. No. 93, United Kingdom (2006).
2. CNEN, Requisitos de radioproteção e segurança para serviços de medicina nuclear, CNENNN 3.05, Rio de Janeiro, Brasil (1996).
3. A. Iwahara, A. E. Oliveira, L. Tauhata, C. J. da Silva, R. T. Lopes, “Intercomparison of 131I
and 99mTc activity measurements in Brazilian nuclear medicine services,” Applied
Radiation and Isotopes, 54, pp. 489-496 (2001).
4. A. Iwahara, A. E. Oliveira, L. Tauhata, C. J. da Silva, C. P. G. da Silva, A. M. S.
Braghirolli, R. T. Lopes, “Performance of dose calibrators in Brazilian hospitals for activity
measurements,” Applied Radiation and Isotopes, 56, pp. 361-367 (2002).
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