[Nuclear medicine and radiopharmaceuticals]. / Medicina nuclear y radiofármacos.

Nuclear Medicine is a medical specialty that allows modern diagnostics and treatments using radiopharmaceuticals original radiotracers (drugs linked to a radioactive isotope). In Europe, radiopharmaceuticals are considered a special group of drugs and thus their preparation and use are regulated by a set of policies that have been adopted by individual member countries. The radiopharmaceuticals used in diagnostic examinations are administered in very small doses. So, in general, they have no pharmacological action, side effects or serious adverse reactions. The biggest problem associated with their use are the alterations in their biodistribution that may cause diagnostic errors. Nuclear Medicine is growing considerably influenced by the appearance and development of new radiopharmaceuticals in both the diagnostic and therapeutic fields and primarily to the impact of new multimodality imaging techniques (SPECT-CT, PET-CT, PET-MRI, etc.). It's mandatory to know the limitations of these techniques, distribution and eventual physiological alterations of radiopharmaceuticals, contraindications and adverse reactions of radiological contrasts, and the possible interference of both.

[Analysis of variability in determining intact parathyroid hormone (iPTH) according to the method used to process the sample]. / Análisis de la variabilidad en la determinación de la hormona paratiroidea (PTH-i) según el método empleado para procesar la muestra.

BACKGROUND: The measurement of i-PTH circulating is not easy due to its analytical variablity. Variability that appears in the process that goes from the sample collection to the final result determination. There are several important aspects that can influence within the pre-test variability: type of sample (serum o plasma), temperature, time elapses from blood extraction to freezing and from freezing to i-PTH quantification. Blood coming from centres far from our laboratory do not always meet the required processing conditions. Our aim was to study the stability of i-PTH with varying conditions of temperature and time until freezing in patients with chronic kidney disease (CKD). METHODS: We have analyzed 294 blood samples of 49 patients with chronic kidney disease (18 transplantated patients (36.7%) and 31 patients in haemodyalisis (63.3%)). The blood samples were collected using tubes treated with ethylenediaminotetraacetic acid (EDTA); these samples were subjected to different conditions of temperature and time before they were frozen, constituting 6 groups: blood centrifuged and plasma immediately frozen (group A or reference group); blood maintained 1 hour at room temperature and plasma stored at 2-8 masculineC during 0, 8 and 24 hours (groups B,C,D); blood maintained 3 hours at room temperature and plasma stored at 2-8 masculineC during 0 and 8 hours (groups E,F). The intact PTH (i-PTH) was measured using the immunoradiometric assay (IRMA Total Intact Scantibodies assay). We have analyzed the differences between the PTH-i mean values in the referenced groud and the others. We have applied the tests of homogeneity variance and normality and we have perform a comparation by pairs with the t-test including the Bonferroni correction. RESULTS: The mean value of intact-PTH in the referente Group was 202.5+/-199.72 pg/ml. The means values of intact-PTH in the other groups were 196 +/- 203.23 pg/ml, 202.8 +/- 200.2 pg/ml, 200.06 +/- 194.87 pg/ml, 204.08 +/- 204.073 pg/ml, 197.94 +/- 182.31 pg/ml. The results were practically identical for each group. We did not find important differences with respect to the reference group (p = 0.87, p = 0,99, p = 0,95, p = 0,96, p = 0,90 when comparing with groups 2a, 2b, 2c, 3a y 3b). CONCLUSIONS: The use of EDTA maintain the PTH stability during a longer period without the necessity of freezing the samples immediately. These results can help to state strategies to management the samples in patients with ERC.

[Determination of dose calibrator setting of the capintec CRC-35R for samarium-153]. / Determinación del factor de calibración para el samario-153 en el activímetro de dosis CRC-35R.

OBJECTIVE: The aim of this work is to determine the calibration factor for Sm-153 and evaluate the influence of the geometry in the activity measurements in order to administer accurately the activity to the patient. METHODS: The calibration factor for Sm-153 was determinated using the Sm-153 sources commonly used in clinical practice and the calibrator response in a known calibration setting. The geometry correction factor for the vial and the plastic syringe was calculated using the real activity indicated by the manufacturer and the activity measured in the vial and in the plastic syringe. RESULTS: The calibration factor obtained is 239 +/- 4 and the correction factor which takes in consideration the geometry is 0,87 +/- 0,07. The activity measured in the syringe is eighteen percent higher to activity measured in the vial. CONCLUSION: This method allows to measure accurately the activity of Sm-153 in vial and syringe applying this geometry correction factor to determine accurately the activity administered to the patient.