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The biological tissue has been mimicked and replaced
by other materials, which have shown certain radiological similarity determined by attenuation coefficient (μ), density and atomic
number. Specifically, in molecular imaging and radiation therapy have been developed multifunctional radiopharmaceuticals which contain
beta/gamma and/or light emitters to chronic degenerative diseases treatment.
Therefore, it is necessary to develop phantoms that allow optical and radiometric characterization. Since the agar gel has shown to be a medium which allows to model biological tissue in
phototherapy studies, the aim of this study is to determine whether the agar gel may be used as biological tissue substitutes in 99mTc
dosimetry. Agar gel was
prepared to 1% and 2.3% (water:agar)
and its radiologicalproperties as: linear attenuation coefficient obtained by
narrow beam geometry and XCOM software, density and effective atomic number (Zeff) were determined.
Using the determined μ, photontransmission was calculated by Monte
Carlosimulation. The 99mTc source region was immersed in a water phantom, two source regions were used, one source region was filled with water and another with agar gel. For both cases; the cumulated activity () by
conjugate view method, the absorbed doseper unitcumulated
activity (S) and absorbed dose (D) were determined. The 2.3% concentration
gel consistency facilitated its handling during a bigger irradiation time. A was obtained
and also this value was corroborated with the XCOM software. The agar gel density was and . The calculated cumulated
activity presented 1%
difference in both phantoms. The absorbed doseper unitcumulated activity was the same in both media, therefore the D too.
Agar gel showed to be equivalent to water in terms of radiological
properties for 140 keV photons, thus it can substitute soft tissue in 99mTc dosimetry.
This paper reports the effects of different culture conditions for Dunaliella salina SA32007 from Salar de Atacama (second Region, northern ofChile) over
biomass, lipid production and triglycerides synthesis. A maximum value of
microalgae density (8.2 × 109 Cells/L) and an intrinsic growth rate (0.17 d-1),
were obtained using a culture with 0.5 mol/L of NaCl and a nitrogen/phosphorous
(N/P) limitation of 14/1. The triglycerides production was significantly
favoured under nitrogen deficiency conditions (Mann-Whitney test; p = 0.0043).
However there was a nitrogen-limiting threshold for the stimulation and
accumulation of triglycerides (N/P: 14/1), lower than that limit, these
compounds would not be accumulated. It was also observed that triglyceride
content was not proportional to the total lipid content and the maximum number
of cells. The aeration system employed stimulated the growth and synthesis of
structural organic molecules. Regarding microalgae growth stage subjected to
nitrogen deficiency, when the deficit was applied before the lag phase, the
negative effect on the biomass and the triglycerides production decreased.