Determination of uncertainties associated to the in vivo measurement of iodine-131 in the thyroid.

Intakes of radionuclides can be estimated through in vivo measurements, and the uncertainties associated to the measured activities should be clearly stated in monitoring program reports. This study aims to evaluate the uncertainties of in vivo monitoring of iodine 131 in the thyroid. The reference values for high-energy photons are based on the IDEAS Guide. Measurements were performed at the In Vivo Monitoring Laboratory of the Institute of Radiation Protection and Dosimetry (IRD) and at the Internal Dosimetry Laboratory of the Regional Center of Nuclear Sciences (CRCN-NE). In both institutions, the experiment was performed using a NaI(Tl) 3''3″ scintillation detector and a neck-thyroid phantom. Scattering factors were calculated and compared in different counting geometries. The results show that the technique produces reproducibility equivalent to the values suggested in the IDEAS Guide and measurement uncertainties is comparable to international quality standards for this type of in vivo monitoring.

Determination of the centesimal composition and characterization of flours from fruit seeds.

Fruit seeds, common byproducts of the food industry, are generally discarded despite their potential use as a source of nutrients in the human diet. The dietetic use of the flour made from fruit seeds depends on their centesimal composition and other characteristics. In this work the centesimal compositions were determined of six fruits seeds. The flours obtained from these seeds were characterized by infrared absorption spectrometry, X-ray diffraction, thermogravimetric analysis, and low-field nuclear magnetic resonance. The protein content of the seeds ranged from a low of 10% (Surinam cherry) to a high of 32% (orange). The lipid content varied from 3% (Surinam cherry) to 39% (peach). The highest ash content was 3.9% (melon and peach). The X-ray diffraction analyses showed that the starches from jackfruit and Surinam cherry seeds presented A-type crystallinity and the thermogravimetric tests showed they were the most thermally resistant. The relaxometry studies of the hydrogen nucleus determined the mobility domains of each sample.

Biokinetics and dosimetric studies about 99mTc(V)-DMSA distribution.

Research for radiodiagnostic agents should considerate biological critical parameters which will give own contribution on the absorbed dose. The dimercaptosuccinic acid (DMSA) labeled with (99m)Tc(V) is a radiopharmaceutical which has well established role in medullar thyroid carcinoma and has been proposed in evaluation of bone metastasis. This work studied the biokinetics and dosimetry of (99m)Tc(V)-DMSA by animal model. The (99m)Tc(V)-DMSA was prepared from a (III)DMSA kit alkalized. Mice (n=5) received (99m)Tc(V)DMSA i.v., they were sacrificed (30 min, 1h, 5h and 12h), the organs excised and the activities measured by a gamma counter. The results were evaluated based on %activity/g and the absorbed dose was estimated (MIRDOSE 3.0 program) by extrapolation of data from animal to human scale. The results showed the majority of organs reached the top uptake at 30 min, the greatest kidney uptake was (4.81 +/- 1.38)% activity/g, while the bone presented its highest uptake at 1h (5.49+/- 0.47)% activity/g, after 1h all the organs had activity exponential decrease. The biokinetic profile of (99m)Tc(V)-DMSA was well established, allowing quantifying of residence time, and the radiation dose estimates were made for this agent. About the absorbed dose, the preliminary results showed higher value to bone, being the soft tissue dose relatively low.

Radiation exposure from diagnostic nuclear medicine in Alagoas (Brazil) in 2002-2005.

Use of radionuclides in medical practice has grown steadily in recent years due to the introduction of new radiopharmaceuticals and new equipments. This paper presents a survey of nuclear medicine procedures performed in Alagoas, State of Brazil, in order to help establish reference levels for nuclear medicine patients. Data were gathered on the type of radiopharmaceuticals used and administered activity of each kind of examination, and the age and sex of the patients involved over the period 2002-2005. Based on ICRP-60, the effective dose (E) and collective effective dose (Ecol) have been calculated. The results showed an annual increase in the nuclear medicine examinations during the period of study and cardiac scintigraphy are the most common procedure. The results also indicated that the activities administered to patients are higher than the guidance levels of the Basic Safety Standards (BSS) in most of the kind of examinations. The differences found in the administered activities may reflect the differences in the quality assurance programs implemented. It was observed that the Ecol and E/inhabitant are higher than other countries. Therefore, it is suggested that the protocols have been revised in order to reduce the patient dose without reduce the image quality.

Preliminary results of 3D dose calculations with MCNP-4B code from a SPECT image.

Interface software was developed to generate the input file to run Monte Carlo MCNP-4B code from medical image in Interfile format version 3.3. The software was tested using a spherical phantom of tomography slides with known cumulated activity distribution in Interfile format generated with IMAGAMMA medical image processing system. The 3D dose calculation obtained with Monte Carlo MCNP-4B code was compared with the voxel S factor method. The results show a relative error between both methods less than 1 %.