OBJECTIVE: To assess the performance of radionuclide calibrators in 55 Brazilian nuclear medicine services in the measurement of 99Tc m radiopharmaceutical activity. Proficiency tests were applied to data sets with 63 results originated from the comparison program developed by Laboratório Nacional de Metrologia das Radiações Ionizantes of Instituto de Radioproteção e Dosimetria. MATERIALS AND METHODS: The calibrators' performance was evaluated in compliance with the acceptance criterion of ±10% accuracy required by the Brazilian standards and also the criteria established by the ISO/IEC Guide 43-1, and classified as either "acceptable" or "non-acceptable". The samples of 99Tc m utilized in the comparison were supplied by some of the participants and calibrated at Laboratório Nacional de Metrologia das Radiações Ionizantes for determining the activity reference value. RESULTS: The present study utilizing 99Tc m has shown that 82.5% of the calibrators were considered as acceptable according to the Brazilian standards, while by the criteria established by ISO/IEC 43-1, 81.0% were considered as acceptable. On the other hand, radionuclide calibrators with Geiger-Müller detectors presented unsatisfactory performance when compared with calibrators with ionization chambers. CONCLUSION: The performance evaluation based on the ISO/IEC 43-1 criteria, which are applied to analytical laboratories, in spite of being more restrictive, has demonstrated to be quite consistent with the accuracy criterion established by the Brazilian standard.

Keywords: Proficiency test, Radionuclide calibrator, Nuclear medicine, 99Tc m

OBJECTIVE: To develop of a software tool for evaluation and control of sensitometric curves. MATERIALS AND METHODS: A method was developed for obtaining high- and low-contrast films sensitometric values, with no need to define wedge steps. RESULTS: The software named Sensito was implemented and tested utilizing data of sensitometric strips from conventional radiology, hemodynamics, and mammography departments. The feasibility of analyzing sensitometric curves from these areas remained evidenced with no need of user-dependent adjustments, and with no deviation in the evaluated sensitometric parameters and variations. CONCLUSION: The software allows the creation of a database including sensitometric curves from different processors in a same institution, easily generating gamma curves of a register and constant charts of the evaluated sensitometric characteristics, constituting an important tool for sensitometric control.

Keywords: Automatic processor, Sensitometric curve, Sensitometry

The evaluation of film processing using the STEP test (sensitometric test for the evaluation of processing) is based on the identification of significant deviations in the processor-chemicals-film system. Ideal processing conditions are established for this type of evaluation. A standard film is processed according to the manufacturer's recommendations, i.e. standard processing at 100. The film is exposed to the light of a calibrated sensitometer and the sensitometric steps are read with the use of a densitometer. A standard curve (OD × STEP) is therefore obtained. The percentual deviation should be lower than 20% compared to the standard curve. This method is useful to identify processing problems. We tested processors from several public/university hospitals and found that approximately 33% of the equipments had inadequate processing conditions.

Keywords: Automatic processors, Radiographic films, Sensitometry, STEP test

Quality control of automatic processors is an important issue in the implementation of quality assurance programs in diagnostic radiology. A pilot program of quality control for automatic processors using the sensitometric method was implemented in the Radiodiagnosis Service of a University Hospital in Rio de Janeiro, RJ, Brazil. An initial survey of the darkrooms showed that they had high temperature and humidity and several light leaks; fog levels were excessively high requiring an increase in mAs of up to 24% to compensate for contrast loss; dry to dry processing time was out of control with errors of up to 56%; developer temperature was as high as 39°C (4°C higher than the recommended by the manufacturers); replenishment rates presented values as high as 417% above manufacturer's recommendations; and rejection rates of radiographic films were of the order of 21% in the mammography service. Sensitometric measurements performed before the implementation of the quality control showed values of base + fog as high as 0.24 optical density and speed and contrast outside recommended limits. The radiographic films presented several artifacts that resulted in low quality images. The pilot program consisted of the implementation of the quality control in the mammography service. Several initiatives were taken including training of the technicians, improvement of maintenance of the processors and increase in the number of patients/day from 7 to 12. This procedure allowed replenishment rates to be lowered to acceptable levels. The implementation of the quality control maintained chemical products stable keeping the sensitometric parameters under control. However, the most significant result of the program was better image quality, free from artifacts, a significant reduction in costs to the hospital and especially lower doses imparted to the patients due to the reduction in rejection rates to 7.7%.

Keywords: Quality control, Automatic processors, Sensitometric method

OBJECTIVE: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. MATERIALS AND METHODS: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. RESULTS: Values for multiple scan average dose values corresponded to 13.6 ± 0.7, 13.5 ± 0.7 and 18.7 ± 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. CONCLUSION: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil.

Keywords: Kerma profiles; Computed tomography; Radiochromic films; MSAD.

OBJECTIVE: The present study was aimed at evaluating the viability of replacing ¹⁸F with ^99mTc in dose calibrator linearity testing. MATERIALS AND METHODS: The test was performed with sources of ^99mTc (62 GBq) and ¹⁸F (12 GBq) whose activities were measured up to values lower than 1 MBq. Ratios and deviations between experimental and theoretical ^99mTc and ¹⁸F sources activities were calculated and subsequently compared. RESULTS: Mean deviations between experimental and theoretical ^99mTc and ¹⁸F sources activities were 0.56 (± 1.79)% and 0.92 (± 1.19)%, respectively. The mean ratio between activities indicated by the device for the ^99mTc source as measured with the equipment pre-calibrated to measure ^99mTc and ¹⁸F was 3.42 (± 0.06), and for the ¹⁸F source this ratio was 3.39 (± 0.05), values considered constant over the measurement time. CONCLUSION: The results of the linearity test using ^99mTc were compatible with those obtained with the ¹⁸F source, indicating the viability of utilizing both radioisotopes in dose calibrator linearity testing. Such information in association with the high potential of radiation exposure and costs involved in ¹⁸F acquisition suggest ^99mTc as the element of choice to perform dose calibrator linearity tests in centers that use ¹⁸F, without any detriment to the procedure as well as to the quality of the nuclear medicine service.

Keywords: Nuclear medicine; Dose calibrator; Linearity test; Nuclear instrumentation.