Abstract Introduction For improved efficiency and security in heat application during hyperthermia, it is important to monitor tissue temperature during treatments. Photoacoustic (PA) pressure wave amplitude has a temperature dependence given by the Gruenesein parameter. Consequently, changes in PA signal amplitude carry information about temperature variation in tissue. Therefore, PA has been proposed as an imaging technique to monitor temperature during hyperthermia. However, no studies have compared the performance of different algorithms to generate PA-based thermal images. Methods Here, four methods to estimate variations in PA signal amplitude for thermal image formation were investigated: peak-to-peak, integral of the modulus, autocorrelation of the maximum value, and energy of the signal. Changes in PA signal amplitude were evaluated using a 1-D window moving across the entire image. PA images were acquired for temperatures ranging from 36oC to 41oC using a phantom immersed in a temperature controlled thermal bath. Results The results demonstrated that imaging processing parameters and methods involved in tracking variations in PA signal amplitude drastically affected the sensitivity and accuracy of thermal images formation. The sensitivity fluctuated more than 20% across the different methods and parameters used. After optimizing the parameters to generate the thermal images using an evolutionary genetic algorithm (GA), the percentage of pixels within the acceptable error was improved, in average, by 7.5%. Conclusion Optimization of processing parameters using GA could increase the accuracy of measurement for this experimental setup and improve quality of PA-based thermal images.

O trabalho foi realizado no Setor de Piscicultura do Departamento de Zootecnia da Universidade Federal de Santa Maria, em um sistema para criação de larvas com recirculação de água termoregulada. O objetivo foi avaliar a substituição de óleo de canola por lecitina de soja na alimentação de larvas de jundiá durante os primeiros 21 dias de vida. No experimento, testaram-se sete tratamentos com três repetições, usando-se diferentes proporções de óleo de canola (0 a 5%) e lecitina de soja (0 a 4%), incorporadas em uma ração preparada com fígado bovino e levedura de cana. Os melhores resultados foram obtidos no tratamento com 2% de lecitina de soja. Com ele, as larvas de jundiá apresentaram 80,25% de sobrevivência, peso médio individual de 184,89mg e 28,03mm de comprimento total, diferindo significativamente dos demais tratamentos. De acordo com os resultados obtidos no experimento, conclui-se que a lecitina de soja em nível de 2% é mais eficiente que a lecitina usada em combinação com óleo de canola na nutrição de larvas de jundiá.

This report was carried out at the Animal Sciences Department - Fish Culture Sector of the Federal University of Santa Maria, RS, Brazil, in a system for larvae raising with thermoregulation and recirculation of water, in order to assess the replacement of canola oil for soy lecithin in the feeding of south american catfish (Rhamdia quelen) larvae during their 21 days of life. In the experiment, seven treatments with three replications were tested by using different proportions of canola oil (0-5%) and soybean lecithin (0-4%), added to a diet prepared with beef liver and sugar canne yeast. The best results were obtained in treatment containing 2% of soy lecithin, in which catfish larvae presented 80.25% survival rate, 184.89mg average individual weight and 28.03mm total length, what significantly differs from the other treatments. According to the results obtained in the experiment, it is concluded that soy lecithin (2%) is more efficient as a lecithin - canola oil combination in south american catfish larvae nutrition.

O presente trabalho foi desenvolvido para avaliar a influência de diferentes fontes de lipídios sobre o desempenho de larvas de jundiá (Rhamdia quelen). Foi realizado no Setor de Piscicultura do Departamento de Zootecnia da Universidade Federal de Santa Maria, utilizando-se um sistema de criação de larvas com recirculação d'água, termorregulada. O experimento teve duração de 21 dias, testando-se 7 tratamentos com três repetições. Testaram-se diferentes fontes de lipídios: óleo de canola, óleo de soja, óleo de fígado de bacalhau, óleo de girassol e óleo de milho, incorporados na proporção de 5% de uma dieta base (fígado e levedura). O tratamento com óleo de canola resultou em 94% de sobrevivência e larvas com 19,97mm de comprimento total e 54,3mg de peso médio. De acordo com os resultados obtidos no experimento, conclui-se que os óleos de canola e fígado de bacalhau são mais eficientes como suplemento lipídico na nutrição de larvas de jundiá (Rhamdia quelen).

The present study was developed in order to evaluate the influence of different sources of fat on the Rhamdia quelen larvae performance. It was carried out at the Animal Husbandry Department - Fish culture Section of the Federal University of Santa Maria, using a system of larvae culture with thermoregulation and recirculation of water. There were seven (7) treatments, with three replicates each one and the different sources of fat tested during 21 days were: canola oil, soybean oil, cod liver oil, sunflower oil or corn oil incorporated in the rate of 5% of a basal diet (liver and yeast). The treatment with canola oil resulted in a 94% survival rate, and larvae with 19.97mm of total length and 54,3mg of individual body weight. According to the results obtained in the experiment, it was concluded that canola and cod liver oil are more efficient as fat supplement in Rhamdia quelen larvae nutrition.