ABSTRACT
Hadron therapy for malignant tumor is becoming increasingly popular. There are many factors which effect on implementation of a proper treatment planning. The purpose of this work is to investigate the inhomogeneity effects as affecting factor on proton range, Full width at half maximum [FWHM] and 20% position of penumbra [P20] by MCNPX code. An inhomogeneous tissue [Bone or Adipose] with a variable thickness [0.1 cm, 0.5cm and 1.0 cm] was inserted into a phantom. Then this phantom was irradiated by 108.8 MeV proton beam located at 10 cm away from it. Particle energy deposition [PEDEP] in mesh tally card was used for simulation of Bragg curve and obtaining the proton range, FWHM and 20% position of penumbra [P20]. Finally, the MCNPX results were compared with GEANT4. The results of MCNPX for water phantom including 1cm adipose for range and P20 were 8.87 and 9.10 cm respectively, and for 1cm bone, range and P20 were 8.52 and 8.58 cm. By increasing the adipose thickness, range and P20 were reduced but it was vice versa for increasing the bone thickness. Also FWHM does not show a regular variation in both bone and adipose tissues. The results show that the location of the inhomogeneous tissues does not affect the variation of the whole shape of the Bragg curve, while it radically affects the dose in the Bragg curve. The comparison between MCNPX and GEANT4 results showed that the MCNPX results have the closer values than GEANT4 to references
ABSTRACT
Introduction: the endotracheal route for drug delivery is a valuable alternative in emergency conditions in which intravenous access is difficult or impossible. Liodcaine is an antiarrhythmic agent with tracheal absorbency, commonly used in cardiac emergenices
Objective: the purpose of this study was to investigate Lidocaine pharmacokinetic behavior following endotracheal administration in critically ill patients
Materials and Methods: 14 mechanically ventilated critically ill patients received 2mg/kg lidocaine 2% [diluted as necessary with 0.9% Saline up to total volume of 5-10 ml] via an endotracheal tube. Five positive pressure breaths were provided immediately after instillation of the drug into the airway and then patients connected to the ventillator again. Venous blood samples were drawn for 4 hours after lidocaine administration and plasma concentrations determined by HPLC method
Results: after 5 min, average lidocaine concentrations reached the therapeutic range [1.5-5 ?g/ml] and remained in this range for 30 minutes. Volume of distribution [Vd] was found to be 0.7 +/- 0.3 L/Kg, and clearance [Cl] 4.29 +/- 1.4 ml/min /kg. These valuse are lower than those described previously for healthy volunteers [P< 0.001], but similar to those described in ICU patients [P > 0.05]. Half life was 113.1 +/- 34.1 min and was not different from parameters published previously for healthy and ICU patients [P > 0.05]
Conclusion: in conclusion, endotracheal administration of Lidocaine can provide therapeutic levels in critically ill patients.It is not definitely clear that the technique of endotracheal drug administration or the unstable physiologic condition of the patients alters the pharmacokinetics of lidocaine