RESUMO
Aim: The aim of this study was to estimate the spinal column dose for spinal Stereotactic body radiation therapy (SBRT) before patient treatment using the PTW dosimetry Octavius dose-volume histograms (DVH) four-dimensional (4D) feature. Materials and Methods: Twenty-three patients were included in the study, and a volumetric modulated arc therapy plan with 6MV flattening filter-free (6FFF) was generated for each patient in the Eclipse planning system using the Anisotropic Analytical Algorithm (AAA) algorithm (Varian Medical Systems, Palo Alto, CA) for the TrueBeam STx LINAC machine. The Octavius 4D system was used to estimate the spinal cord dose by delivering the plans to the 4D phantom. The measured dose was compared with the Eclipse treatment planning system (TPS) (Varian Medical Systems, Palo Alto, CA) dose. Results: The spinal cord max and mean doses estimated using Varisoft DVH 4D are in close agreement with the TPS calculated max and mean doses. The deviation between measured dose and TPS dose is ±5% for the spinal max dose, and the deviation between measured dose and TPS dose is ± 3% for the spinal mean dose. Conclusions: The study demonstrates that the PTW Octavius 4D phantom and DVH 4D feature can be used as a tool to estimate spinal cord dose before the treatment in spinal SBRT plans. The system provides an independent dose measurement that is comparable to the TPS dose. The close agreement between measured and calculated doses validates the use of this system as a critical organ dose verification tool.
RESUMO
Several related substances (RS4-RS10) were detected in lopinavir drug substance at levels ranging from 0.03% to 0.1% by employing gradient RP-HPLC. The related substances were identified by LC-MS analysis. These related substances were isolated and characterized by Mass, (1)H NMR and FT-IR spectral data. The separation was achieved on a YMC Pack ODS-AQ (250 mm x 4.6 mm, 5 microm) column thermostated at 45 degrees C using 0.02 M KH(2)PO(4) (pH 2.5): acetonitrile as a mobile phase in gradient elution mode. A PDA detector set at 210 nm was used for detection. The investigated validation elements showed the method has acceptable specificity, accuracy, linearity, precision, robustness and high sensitivity with detection limits and quantitation limits ranging from 0.028 microg/ml to 0.063 microg/ml and 0.084 microg/ml to 0.192 microg/ml respectively. The method can be used for routine quality control analysis and stability testing of lopinavir drug substance.