Evaluation of conversion coefficients relating air-kerma to H*(10) using primary and transmitted x-ray spectra in the diagnostic radiology energy range.

According to the International Commission on Radiation Units and Measurements (ICRU), the relationship between effective dose and incident air-kerma is complex and depends on the attenuation of x-rays in the body. Therefore, it is not practical to use this quantity for shielding design purposes. This correlation is adopted in practical situations by using conversion coefficients calculated using validated mathematical models by the ICRU. The ambient dose equivalent, H*(10), is a quantity adopted by the IAEA for monitoring external exposure. Dose constraint levels are established in terms of H*(10), while the radiation levels in radiometric surveys are calculated by means of the measurements of air-kerma with ion chambers. The resulting measurements are converted into ambient dose equivalents by conversion factors. In the present work, an experimental study of the relationship between the air-kerma and the operational quantity ambient dose equivalent was conducted using different experimental scenarios. This study was done by measuring the primary x-ray spectra and x-ray spectra transmitted through materials used in dedicated chest radiographic facilities, using a CdTe detector. The air-kerma to ambient dose equivalent conversion coefficients were calculated from these measured spectra. The resulting values of the quantity ambient dose equivalent using these conversion coefficients are more realistic than those available in the literature, because they consider the real energy distribution of primary and transmitted x-ray beams. The maximum difference between the obtained conversion coefficients and the constant value recommended in national and international radiation protection standards is 53.4%. The conclusion based on these results is that a constant coefficient may not be adequate for deriving the ambient dose equivalent.

Evaluation of mean conversion coefficients from air-kerma to H *(10) using secondary and transmitted x-ray spectra in the diagnostic radiology energy range.

Ambient dose equivalent H *(10) is an operational quantity recommended by the IAEA to establish dose constraints in area monitoring for external radiation. The direct measurement of H *(10) is not common due to the complexity in the calibration procedures of radiation monitors involving the use of expanded and aligned radiation fields. Therefore, conversion coefficients are used to assess H *(10) from the physical quantity air-kerma. Conversion coefficients published by international commissions, ICRU and ICRP, present a correlation with the radiation beam quality. However, Brazilian regulation establishes 1.14 Sv Gy-1 as unique conversion coefficient to convert air-kerma into H *(10), disregarding its beam quality dependence. The present study computed mean conversion coefficients from secondary and transmitted x-ray beams in order to improve the current assessment of H *(10). The weighting of conversion coefficients corresponding to monoenergetic beams with the spectrum energy distribution in terms of air-kerma was used to compute the mean conversion coefficients. In order to represent dedicated chest radiographic facilities, an anthropomorphic phantom was used as scatter object of the primary beam. Secondary x-ray spectra were measured in the diagnostic energy range at scattering angles of 30°, 60°, 90° 120° and 150° degrees. Barite mortar plates were used as attenuator of the secondary beam to produce the corresponding transmitted x-ray spectra. Results show that the mean conversion coefficients are about 43% higher than the recommended value accepted by Brazilian regulation. For secondary radiation measured at 100 kV the mean coefficient should be 1.46 Sv Gy-1, which represent the higher value in the mean coefficient set corresponding to secondary beams. Moreover, for transmitted x-ray beams at 100 kV, the recommended mean conversion coefficient is 1.65 Sv Gy-1 for all barite mortar plate thickness and all scattering angles. An example of application shows the discrepancy in the evaluation of secondary shielding barriers in a controlled area when the shielding goals is evaluated. The conclusion based on these results is that a unique coefficient may not be adequate for deriving the H *(10).

Developing and implementing a multi-modality imaging optimization study in paediatric radiology: Experience and recommendations from an IAEA coordinated research project.

Optimization of imaging examinations is a key requirement of both the International and European Basic Safety Standards, and the focus of much international activity. Although methodologies are well established in principle, there continues to be a variety of practical issues both in collecting and interpreting dose and image quality data and in making successful interventions to optimize exposures. A Coordinated Research Project, involving institutes from ten different countries, was established by the IAEA to assess the efficacy of recommended optimization methodologies in the field of paediatric radiology and to derive practical guidance on their implementation. The steps followed in this process were identification of the imaging process to be investigated (abdomen and chest x-rays, micturating cysto-urethrograms, and brain & thorax CT scans); collection of dose and image quality data; evaluation and comparison of the data between institutes and to standards; identification and implementation of interventions for optimization; and re-evaluation of dose and image quality parameters. The project succeeded both in achieving effective interventions for optimization of specific imaging tasks in individual institutes and in identifying key issues with potential to handicap this process. The main area in which problems were encountered was in the collation of reliable dose and image quality data. The reasons for this were explored and a series of recommendations have been made, summarized into 'ten practical tips' for optimization to assist institutes, particularly those in the early stages of addressing optimization issues.

Uncertainty estimation and statistical comparative methodology for mammography x-ray energy spectra.

Numerical models are an alternative to measurements of x-ray energy spectra when validated by comparative methods that assess the similarity of experimental and calculated spectra. In this work, we compared x-ray energy spectra using several methodologies and determined the methodology with highest statistical power among them. Experiments and Monte Carlo (MC) simulations were used to generate a set of 65 experimental and simulated x-ray mammography spectra pairs typically used in mammography applications. They were generated using Tungsten and Molybdenum targets and Molybdenum and Rhodium filters. The x-ray beams were transmitted through breast tissue equivalent material (bTEM) plates with different glandularities and thicknesses, and the transmitted beam was detected using solid-state x-ray spectrometry with a Cadmium Telluride (CdTe) diode. The MC simulations used the PENELOPE code. Additional uncertainties, beyond that from counting, were propagated using the MC method. Quantitative comparative methods based on the [Formula: see text] statistics, the first and second half-value layers, the mean energy, the effective energy, and the non-parametric u-test were applied and their specificity (true negative rate) was assessed. The polyenergetic normalized glandular dose (DgNp) to a 6 cm breast of 50/50 glandularity was derived from the spectra. In this work, the [Formula: see text] statistics attained the highest score; therefore, it is the most indicated metric for the x-ray energy spectra comparative evaluations. The contribution of the additional uncertainties was important, being responsible for up to 98% of the spectra total uncertainty and shifting the mean of the evaluated [Formula: see text] to 1.2(1), compatible with its expected value. The use of non-parametric test is discouraged by our results, since it failed to distinguish spectra pairs that resulted in up to 72% discrepant DgNp.

Inhibition of the alpha1beta1 isoform of the Na, K-ATPase by 8-methoxycoumestrol without positive inotropic effect in human myocardium--novel aspects of cardiac glycoside pharmacology.

BACKGROUND: The Na,K-ATPase (NKA) is necessary for maintaining the resting membrane potential by transporting Na and K ions across the cell membrane. Although its 3 isoforms expressed in human heart (alpha1beta1, alpha2beta1, and alpha3beta1) possess similar biochemical properties, their specific functions in human tissues remain unknown. In our search for an isoform-specific agent, which can serve to identify isoform-specific functions, we examined 8-methoxycoumestrol in its ability to inhibit the NKA and to produce inotropism in connection with the possibility to identify the NKA isoform-specific functions. METHODS AND RESULTS: In radioligand binding experiments (membrane preparations of yeast expressing isoforms alpha1beta1, alpha2beta1, and alpha3beta1; backdoor phosphorylation; and [H]-ouabain, n = 3), 8-methoxycoumestrol (1-10 microM) produced no or only little inhibition of specific ouabain binding. However, when NKA activity of the alpha1beta1 isoform was measured in membrane preparations from human kidney (reduced form of nicotinamide adenine dinucleotide-coupled assay, n = 3), a concentration-dependent full inhibition of the activity was induced by 8-methoxycoumestrol (IC50: 90 +/- 97 nM), similar to that observed for classical cardiac glycosides digitoxin, digoxin, methyldigoxin, and beta-acetyldigoxin (IC50 = 287 +/- 190 nM, 409 +/- 171 nM, 282 +/- 482 nM, 587 +/- 135 nM, P > 0.05). However, unlike the classical cardiac glycosides, 8-methoxycoumestrol did not increase cardiac contractility of electrically stimulated human right atrial trabeculae. CONCLUSIONS: These results indicate that 8-methoxycoumestrol inhibits the human alpha1beta1 NKA by a mechanism different to that of cardiac glycosides. In addition, the inhibition of the alpha1beta1 NKA activity seems not sufficient to evoke positive inotropy in human trabeculae, indicating that either the positive inotropic effect of cardiac glycosides is not mediated via the alpha1beta1 isoform or the specific glycoside binding to alpha1beta1 is needed for positive inotropy.

Ambient dose equivalent and effective dose from scattered x-ray spectra in mammography for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations.

In this study, scattered x-ray distributions were produced by irradiating a tissue equivalent phantom under clinical mammographic conditions by using Mo/Mo, Mo/Rh and W/Rh anode/filter combinations, for 25 and 30 kV tube voltages. Energy spectra of the scattered x-rays have been measured with a Cd(0.9)Zn(0.1)Te (CZT) detector for scattering angles between 30 degrees and 165 degrees . Measurement and correction processes have been evaluated through the comparison between the values of the half-value layer (HVL) and air kerma calculated from the corrected spectra and measured with an ionization chamber in a nonclinical x-ray system with a W/Mo anode/filter combination. The shape of the corrected x-ray spectra measured in the nonclinical system was also compared with those calculated using semi-empirical models published in the literature. Scattered x-ray spectra measured in the clinical x-ray system have been characterized through the calculation of HVL and mean photon energy. Values of the air kerma, ambient dose equivalent and effective dose have been evaluated through the corrected x-ray spectra. Mean conversion coefficients relating the air kerma to the ambient dose equivalent and to the effective dose from the scattered beams for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations were also evaluated. Results show that for the scattered radiation beams the ambient dose equivalent provides an overestimate of the effective dose by a factor of about 5 in the mammography energy range. These results can be used in the control of the dose limits around a clinical unit and in the calculation of more realistic protective shielding barriers in mammography.

Changes in tissue biochemical composition and energy reserves associated with sexual maturation in the ommastrephid squids Illex coindetii and Todaropsis eblanae.

The aim of this study was to investigate the biochemical changes that occur during sexual maturation of the squids Illex coindetii and Todaropsis eblanae. In both species, amino acids and protein content increased in the gonad throughout maturation, but the allocation of these nitrogen compounds from the digestive gland and muscle was not evident. A significant (P < 0.05) increase in the content of lipids and fatty acids was observed in the gonad and digestive gland. It seems that both species take energy for egg production directly from food, rather than from stored products. Analyses for cholesterol revealed a significant (P < 0.05) increase in the gonad, and the lipid content differences between species are potentially related to different feeding ecologies. The glycogen reserves in the gonad increased significantly (P < 0.05), suggesting that glycogen has an important role in the maturation process. It was evident that sexual maturation had a significant effect upon the gonad energy content, but because the energy variation in the digestive gland and muscle was nonsignificant (P > 0.05), there was no evidence that storage reserves are transferred from tissue to tissue.

Evaluation of characteristic-to-total spectrum ratio: Comparison between experimental and a semi-empirical model.

Primary X-ray spectra were measured in the range of 80-150kV in order to validate a computer program based on a semiempirical model. The ratio between the characteristic and total air Kerma was considered to compare computed results and experimental data. Results show that the experimental spectra have higher first HVL and mean energy than the calculated ones. The ratios between the characteristic and total air Kerma for calculated spectra are in good agreement with experimental results for all filtrations used.

Monte Carlo simulation of the response functions of CdTe detectors to be applied in x-ray spectroscopy.

In this work, the energy response functions of a CdTe detector were obtained by Monte Carlo (MC) simulation in the energy range from 5 to 160keV, using the PENELOPE code. In the response calculations the carrier transport features and the detector resolution were included. The computed energy response function was validated through comparison with experimental results obtained with (241)Am and (152)Eu sources. In order to investigate the influence of the correction by the detector response at diagnostic energy range, x-ray spectra were measured using a CdTe detector (model XR-100T, Amptek), and then corrected by the energy response of the detector using the stripping procedure. Results showed that the CdTe exhibits good energy response at low energies (below 40keV), showing only small distortions on the measured spectra. For energies below about 80keV, the contribution of the escape of Cd- and Te-K x-rays produce significant distortions on the measured x-ray spectra. For higher energies, the most important correction is the detector efficiency and the carrier trapping effects. The results showed that, after correction by the energy response, the measured spectra are in good agreement with those provided by a theoretical model of the literature. Finally, our results showed that the detailed knowledge of the response function and a proper correction procedure are fundamental for achieving more accurate spectra from which quality parameters (i.e., half-value layer and homogeneity coefficient) can be determined.

Obesity and vitamin D deficiency: a systematic review and meta-analysis.

Over the past decade, there have been an increasing number of studies on the association between vitamin D deficiency and anthropometric state. However, we did not identify any meta-analyses of the relationship between obesity and vitamin D deficiency in different age groups. Thus, we evaluated the association between obesity and vitamin D deficiency. We searched for observational studies published up to April 2014 in PubMed/Medline, Web of Science and Scopus databases. We performed a meta-analysis in accordance with the random-effects model to obtain the summary measurement (prevalence ratio, PR). Among the 29,882 articles identified, 23 met the inclusion criteria. The prevalence of vitamin D deficiency was 35% higher in obese subjects compared to the eutrophic group (PR: 1.35; 95% CI: 1.21-1.50) and 24% higher than in the overweight group (PR: 1.24; 95% CI: 1.14-1.34). These results indicate that the prevalence of vitamin D deficiency was more elevated in obese subjects. The vitamin D deficiency was associated with obesity irrespective of age, latitude, cut-offs to define vitamin D deficiency and the Human Development Index of the study location.

Azole resistance among oral Candida species isolates from AIDS patients under ketoconazole exposure.

This is a prospective study designed to investigate species distribution and azole susceptibility profile among Candida spp. isolated from the oral cavities of AIDS patients. One hundred thirty-two AIDS patients sequentially admitted at a teaching tertiary care hospital were enrolled in this study. Samples were obtained by swabbing the oral cavities of the patients. Yeast isolates were identified by classical methods and the antifungal susceptibility profile was further determined according to the NCCLS microbroth assay. Among all patients with prescriptions of systemic antifungal drugs, ketoconazole had been elected to treat 56% of patients. We found 82% of oral yeast carriage, 22% of them harboring non-albicans species. Overall rates of susceptibility dose dependent/resistance to azoles was 16% for itraconazole, 13% for ketoconazole, and 10% for fluconazole with a high agreement rate among the susceptibility profiles of all isolates tested against the triazoles.

Determination of the voltage applied to x-ray tubes from the bremsstrahlung spectrum obtained with a silicon PIN photodiode.

This work describes a methodology for the obtainment of the electron accelerating potential (kVp) applied to an x-ray tube, through the determination of the end point of the energy spectrum of the radiation emitted by the tube. The measurements have been performed utilizing alternatively two silicon PIN photodiodes, directly irradiated by the x-ray beam. Both were operated at room temperature, with low bias, so avoiding the drawbacks presented by photomultiplier tubes and germanium detectors. The energy calibration of the system was performed with X- and gamma-emitter radioactive sources, which makes the method absolute. Each kVp value was determined by means of a linear regression in the end of the spectrum, to give, simultaneously, a good fit of the straight line to the experimental data and a low standard deviation for the kVp value. Results of the measurements carried out with an x-ray tube connected to a three-phase generator, using additional filtration between 1.5 and 4.0 mm of Cu, are presented. This filtration was used in order to minimize the contribution of low energy photons and to reduce pulse pile-up. Errors determined for the values of kVp are between 0.06 and 0.16 kV, in the potential range from 50 to 100 kV. As an example, the methodology has been applied in the verification of the secondary calibration of a voltage divider, utilized, by its turn, in the tertiary calibration of noninvasive kVp meters. All intrinsic sources of errors involved in the process are discussed and evaluated.

Comprehensive analysis of the spectrometric determination of voltage applied to X-ray tubes in the radiography and mammography energy ranges using a silicon PIN photodiode.

This work describes the analysis of factors which affect the results of estimation of the electron accelerating potential (kVp) applied to an X-ray tube, through determination of the end point of the energy spectrum of the emitted radiation beam. Measurements have been performed utilizing two spectrometers each with a silicon PIN photodiode: one operating at room temperature, and the other, a high resolution spectrometer, with a Peltier cooler. Both were directly irradiated by different X-ray beams. Both systems work at low voltage and without liquid nitrogen cooling, thus avoiding the drawbacks presented by germanium detectors. Each kVp value was determined by linear regression of the end of the spectrum, so as to give, simultaneously, the best fit to the experimental data and low standard deviation for the kVp value. Detector energy resolution and calibration, counting statistics and high voltage waveform ripple have been investigated in order to establish better experimental conditions and to optimize measurement time. Results of measurements carried out with X-ray tubes connected to single-phase, three-phase or constant potential units, using additional filtration of Cu, Al or Mo (for mammographic beams), are presented. The variations resulted in kVp uncertainties up to 0.1 kV.

Biochemical dynamics of spermatogenesis and oogenesis in Eledone cirrhosa and Eledone moschata (Cephalopoda: Octopoda).

The effect of spermatogenesis and oogenesis on protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Eledone cirrhosa and Eledone moschata tissues (gonad, digestive gland and muscle) was investigated. A significant (p<0.05) increase in the amino acids and protein content of the gonad throughout sexual maturation (namely in oogenesis) was observed, but the allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids (EAA) in the three tissues were leucine, lysine and arginine. The major nonessential amino acids (NEAA) were glutamic acid, aspartic acid and alanine. A significant increase in lipid and fatty acid contents of gonad and digestive gland was observed. There was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production Eledone species use energy directly from food, rather than from stored products. Most of saturated fatty acid (SFA) content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid (MUFA) content as 18:1 and 20:1 and polyunsaturated fatty acid (PUFA) content as 20:4n-6, 20:5n-3 and 22:6n-3. Cholesterol and glycogen contents significantly increased in gonad and digestive gland throughout maturation while the muscle revealed no obvious pattern. If Eledone's component sterols are of a dietary origin, a considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. Although spermatogenesis and oogenesis had a significant effect (p<0.05) in gonad and digestive gland energy content, the biochemical composition of digestive gland and muscle may not be primarily influenced by sexual maturation, but rather by other biotic factors such as feeding activity, food availability, spawning and brooding.

Surgical pathology of aorta and arteries of the lower limbs in the elderly.

From 1.1.1988 tot 31.8.1991, 42 surgical revascularisations of the aorta and the lower limbs were performed on patients aged 75 and more (men: 24--women: 18; extreme ages: 75-84; average age: 80). In all cases surgery was absolutely indicated: for advanced arteriopathy in the lower limbs (stage III or IV of Fontaine's classification) (37 cases) and ruptured abdominal aortic aneurysm (5 cases). No primary major amputation was performed in the peripheral vascular group stages III and IV. Peripheral vascular occlusive disease (30 cases) was operated under locoregional anaesthesia and consisted of the femoro-distal popliteal bypass with in situ saphenous vein (23 cases). Patients with proximal lesions preferably underwent an extra-anatomic bypass under general anaesthesia (7 cases). Ruptured infrarenal aortic aneurysm also needs a general anesthesia and represents a high surgical risk (5 cases). For the 42 patients, we observed 38 good immediate functional results and 4 peri-operative deaths. Of the 38 immediate good results, we observed 6 secondary obliterations of the bypass within a period of 5 to 18 months, among which 2 were successfully disobliterated. The other 4 patients underwent lower limb amputation.

Babesia spp. no líquido peritoneal em cão com ascite - relato de caso / Babesia spp. in the peritoneal fluid in dog with ascites - case report

Babesia canis é um protozoário cosmopolita que parasita eritrócitos de cães domésticos e selvagens. O diagnóstico é realizado mediante a observação direta do microrganismo em hemácias no esfregaço de sangue periférico, métodos sorológicos e técnicas moleculares. O objetivo deste trabalho é relatar pela primeira vez a presença de merozoítos de Babesia spp. no líquido peritoneal de um cão com ascite. No Hospital Veterinário da Universidade Federal de Viçosa, foi atendido um cão, macho, sem raça definida, de sete meses de idade, com histórico de emaciação, apatia e abaulamento abdominal. No exame físico, foram evidenciadas mucosas hipocoradas, ascite, sopro sistólico grau IV/V e taquipneia. Nos exames laboratoriais, evidenciou-se anemia normocítica/normocrômica, trombocitopenia e hipoproteinemia. No esfregaço sanguíneo, foram observadas estruturas intraeritrocitárias compatíveis com Babesia spp. A avaliação do líquido ascítico foi compatível com transudato modificado e observaram-se inúmeras estruturas intra e extracelulares compatíveis com merozoítas de Babesia spp. A presença de microrganismos intra e extracelular poderia estar relacionada a uma lesão no baço com extravasamento do conteúdo para a cavidade abdominal. A coleta do líquido peritoneal pode ser uma alternativa para o diagnóstico de babesiose quando o animal com suspeita da infecção apresentar ascite.(AU)

Babesia canis is a cosmopolitan protozoan that parasites erythrocytes of domestic and wild dogs. The diagnosis is performed by direct observation of the microorganism in red blood cells in the peripheral blood smear, serological methods and molecular techniques. The aim of this work is to report for the first time the presence of merozoites of Babesia spp. in the peritoneal fluid of a dog with ascites. At the Veterinary Hospital of the Federal University of Viçosa was attended a Mixed-breed seven month old dog, male, with history of emaciation, apathy and abdominal bulging. Pale mucous membranes, ascites, grade IV/V systolic murmur and tachypnea were evidenced in the physical examination. Laboratory tests revealed normocytic/normochromic anemia, thrombocytopenia, and hypoproteinemia. Intra-erythrocyte structures compatible with Babesia spp. were observed in the blood smear. The evaluation of the ascites fluid was compatible with modified transudate where numerous intra and extracellular structures compatible with Babesia spp. merozoites were observed. The presence of intra and extracellular microorganisms could be related to an injury of the spleen with extravasation of the contents into the abdominal cavity. Collection of the peritoneal fluid may be an alternative for the diagnosis of babesiosis when the animal with suspected infection has ascites.(AU)

Evaluation of metoclopramide and ranitidine on the prevention of gastroesophageal reflux episodes in anesthetized dogs.

This research aimed to evaluate the effect of metoclopramide and ranitidine in the prevention of gastroesophageal reflux episodes during anesthetic procedures. Ninety healthy female dogs were submitted to elective ovariosalpingohisterectomy, randomly divided into three groups of 30 animals. The control group received only the anesthetic protocol. The metoclopramide group received an intravenous bolus of 1mg/kg, and continuous infusion (1 mg/kg/h intravenously) immediately after anesthetic induction. The ranitidine group received an intravenous bolus of 2 mg/kg, 6 h before anesthesia. Anesthesia (acepromazine, propofol and isofluorane) was standardized and the esophageal pH variations were recorded. Esophagoscopy was carried out after surgery. No difference (p<0.05) was verified in the reflux episodes between the groups. Seven animals presented reflux. Metoclopramide in bolus and continuous infusion, as well as ranitidine, 6 h before anesthesia, did not influence the reduction of the incidence of gastroesophageal reflux.

Matrix effect on paralytic shellfish toxins quantification and toxicity estimation in mussels exposed to Gymnodinium catenatum.

Paralytic shellfish toxins were quantified in whole tissues of the mussel Mytilus galloprovincialis exposed to blooms of the dinoflagellate Gymnodinium catenatum in Portuguese coastal waters. A validated liquid chromatography method with fluorescence detection, involving pre-chromatographic oxidation was used to quantify carbamoyl, N-sulfocarbamoyl and decarbamoyl toxins. In order to test for any matrix effect in the quantification of those toxins, concentrations obtained from solvent and matrix matched calibration curves were compared. A suppression of the fluorescence signal was observed in mussel extract or fraction in comparison to solvent for the compounds dcGTX2 + 3, GTX2 + 3 and GTX1 + 4, while an enhancement was found for C1 + 2, dcSTX, STX, B1, dcNEO and NEO. These results showed that a matrix effect varies among compounds. The difference of concentrations between solvent and matrix matched calibration curves for C1 + 2 (median = 421 ng g⁻¹) exceeded largely the values for the other quantified compounds (0.09-58 ng g⁻¹). Those differences were converted into toxicity differences, using Oshima toxicity equivalence factors. The compounds C1 + 2 and dcNEO were the major contributors to the differences of total toxicity in the mussel samples. The differences of total toxicity were calculated in ten mussel samples collected during a 10-week blooming period in Portuguese coastal lagoon. Values varied between 53 and 218 µg STX equivalents kg⁻¹. The positive differences mean that the estimated toxicity using solvent calibration curves exceed the values taking into account the matrix. For the toxicity interval 200-800 µg STX equivalents kg⁻¹ an increase was found between 44 and 28%.