[en] As dosing oxygenated water by using polarography has been envisaged within the framework of water purity controls for the Melusine pile, the objective of the authors is here to see whether the polarographic method could be satisfying for routine analyses, and would result in a higher dosing sensitivity. They describe the polarography principle, indicate devices which are used, specify and comment conditions under which polarography is performed

[en] Bladder-filling reconstruction artifacts have a detrimental effect on the image quality of pelvic bone single photon emission computed tomography (SPECT). Using a simple protocol consisting of forced diuresis coupled with intravenous (IV) hydration, this study was undertaken to obtain an artifact-free pelvic SPECT after discarding the residual urinary activity. Thirty patients were enrolled. In group I, pelvic SPECT was performed directly after normal void, whereas in group II, SPECT was preceded by IV injection of 0.5 mg/kg furosemide (maximum 40 mg) coupled with IV infusion of 500 cc of physiologic saline. Bladder-filling reconstruction artifacts were analyzed in group I patients, who had their images reconstructed using both filtered backprojection and iterative algorithms, both qualitatively and quantitatively by means of regions of interest (ROIs) drawn around the artifact-bearing bone areas as well as the corresponding contralateral sites. For group II patients, besides visual analysis, ROIs were placed over the sites corresponding to those of the group I patients. In every patient, total counts of each ROI were normalized to a reference ROI placed over the sacrum, and a ratio was created. Using filtered backprojection, two forms of anti-facts were identified in group I patients: first, a streak pattern that extended to the sacro-iliac joint in nine (60%) patients, the hip joint in five (33%), the superior pubic rami in four (27%), the sacrum in three (20%), and the ischium in one (6%); second, a count loss subtype which extended to the hip joints in nine (60%) patients. Corresponding values after iterative reconstruction were two (13%) for the sacro-iliac joint, three (20%) for the hip joint, one (6%) for the superior pubic ramus, and one (6%) for the sacrum. In five (33%) patients, residual count loss artifacts were still identifiable after iterative reconstruction. However in group II, no such effects were observed because the bladder activity reached near background level in 14 (93%) of 15 patients after three successive voids with a 3.5-fold decrease in the mean value of total bladder count in comparison with group I patients. A statistically significant difference was found between artifact- and non-artifact-harboring ROIs in group I whichever the method used for reconstruction, whereas the values of right and left hemi-pelvis ROIs/sacrum in group II were almost identical. Forced diuresis coupled with parenteral hydration facilitates the acquisition of an artifact-free pelvic SPECT. Especially for clinical questions that focus on femoral heads and pubic bones, applying the aforementioned protocol may improve the diagnostic accuracy of pelvic bone SPECT. (author)

[en] The recent growth of the applications of positron emission tomography modality has led to a drastic increase in the number of units installed in western countries, prompting public health authorities to define a strategy concerning acceptance and regular tests (i.e. status tests and stability tests) to be performed on these systems. In parallel, standards concerning the qualification of PET systems have been updated (introduction of body scan characterization conditions) and appeared to be useful to set legal requirements, in spite of the fact that this is not their goal. The aim of this study is first to choose a set of tests described in the standards to define measurements to be performed at the acceptance of the systems after the regular maintenance (at least once every six months) and for assuring the stability of the systems. To verify the feasibility from technical and time requirements points of view, the quality assurance programme proposed has been applied on PET systems (Philips Gemini and GE Discovery LS). This study will present the feasibility and time requirements of the quality assurance programme proposed based on measurements performed independently from manufacturers. Introduction. In its Ordinance related to the use of the unsealed radioactive sources (November 1997), the Swiss Public Health Authority requires the supplier to carry out an acceptance test on all imaging devices used in the field of nuclear medicine before they can be used on patients. Moreover, a maintenance procedure of the imaging device has to be performed at least every six months by properly trained staff. This maintenance has to be followed by a status test that assures the integrity of the system before it can be used for further clinical applications. Daily and weekly stability tests under the responsibility of the users of the system are also defined. According to this Ordinance, all the measurements required for the acceptance and status tests should follow the international standards set by either the NEMA (National Electrical Manufacturers Association) or IEC (International Electrotechnical Commission). In order to set the list of tests required to accept a PET unit to be used on patients and to assure its stability over time, a working group has been created by the Swiss Public Health Authority involving manufacturers and medical physicists. On the basis of the two standards recently published within the framework of the qualification of PET (NEMA-NU-2, 2001 and IEC 61675-1, 1998), this group has proposed a set of recommendations which will be presented in this paper. The results of the measurements performed on two PET systems (Philips Gemini and GE Discovery LS) will be reported. Content of the tests. The background documents of this work are the standards NEMA NU-1994 and NEMA NU- 2001. Table 1 summarizes the tests required in the framework of the acceptance and status tests (RT: acceptance (or reception) tests and ST: Status tests (six month frequency). Conclusion This introduction of the proposed protocol should allow an objective qualification of the systems. However, the main problem that remains to be solved is to decide whether (a) ¹⁸F has to be provided by the centre to the manufacturers staff, who should then perform NEMA type tests or (b) if these tests have to be performed by in site medical physicists

[en] Like in the field of radiology, digital systems are also becoming the standard in the field of nuclear medicine. This offers not only the possibility to process, transmit and archive data from patients more easily but also to introduce quantitative measurements for quality controls. In this framework standards concerning the qualification of gamma camera systems have been updated and appeared to be useful to set legal requirements, in spite of the fact that this is not their goal. The aim of this study was first to choose a set of tests described in standards to define measurements to be performed at the acceptance of the systems, after the regular maintenances (at least once every six months; status test) and for assuring the stability of the systems. To verify the feasibility, from the point of view of technical and a time requirements, the quality assurance programme proposed has been applied on three gamma camera systems. The results of this study show that, based on international standards, new requirements concerning the quality assurance of the gamma camera of the Swiss Public Health Authority make it necessary to slightly modify some procedures to reduce the time required for the acceptance and status tests. In the Ordinance related to the use of unsealed radioactive sources (November 1997) the Swiss Public Health Authority requires the supplier to carry out a reception test on all imaging devices used in the field of nuclear medicine before they can be used on patients. Moreover, a maintenance procedure of the imaging device has to be performed at least every six months by properly trained staff. This maintenance has to be followed by a status test that assures the integrity of the system before it can be used for further clinical applications. Daily and weekly stability tests, under the responsibility of the users of the system, are also defined. According to the Swiss Ordinance, all the measurements required for the acceptance and status tests should follow International standards set by either the National Electrical Manufacturers Association (NEMA) or the International Electrotechnical Commission (IEC). In practice, it appeared that the standards available at that time were not sufficiently precise to allow the technical staff from the manufacturers to perform these tests. Thus, acceptance and status tests performed were manufacturer dependent and could not allow the comparison of performances of different systems. This study presents these recommendations, shows their feasibility, evaluates the time and the material required and proposes slight modifications to simplify a few measurements. The background document of this work is the standard NEMA NU-1. The tests required in the framework of reception and status test (RT: acceptance (or reception) test and ST: Status test (six month frequency) are summarized. These new requirements will permit a uniform qualification of the gamma camera systems. A set of minimal acceptance tests is now available and requires two and a half hour acquisition time per head. For status test, the acquisition time can be reduced to one hour and a half per head, taking into account that the longer test (intrinsic homogeneity) is often required in the process of the maintenance. The main problem encountered during this study is the manipulation of very high activities when dealing with the assessment of the counting rate behaviour. To reduce exposure, manufacturer staff should be properly trained and the strict respect of the standard (let the source decrease) should be preferred since this test is only required for reception of the unit where time constraint is less of a problem. Concerning stability tests, one should control the homogeneity at least weekly and should check the picking and contamination of the system on a daily basis

[en] Like in the field of radiology, digital systems are also becoming the standard in the field of nuclear medicine. This offers not only the possibility to process, transmit and archive data from patients more easily but also to introduce quantitative measurements for quality controls. In this framework, standards concerning the qualification of gamma camera systems have been updated and appeared to be useful to set legal requirements, in spite of the fact, that this is not their goals. The aim of this study was first to choose a set of tests described in standards to define measurements to be performed at the acceptance of the systems and after the regular maintenance (at least once every six months). Reference values are then established to control the stability of the system. To verify the feasibility, from a technical and a time requirements points of view, the tests proposed for the quality assurance programme have been applied on three gamma camera systems. The results of this study show that new requirements concerning the quality assurance of gamma camera of the Swiss Federal Office of Public Health based on international standards required to slightly modify some procedures to reduce the time necessary for the acceptance and status tests. (authors)