Microdosimetric calculations of the Auger electron emitter (123)I were done in liquid water spheres using the Geant4 toolkit. The electron emission spectrum of (123)I produced by Geant4 is presented. Energy deposition and corresponding S-values were calculated to investigate the influence of the sub-cellular localization of the Auger emitter. It was found that S-values calculated by the Geant4 toolkit are generally lower than the values calculated by other Monte Carlo codes for the (123)I radionuclide. The differences in the compared S-values are mainly due to the different particle emission spectra employed by the respective computational codes and emphasizes the influence of the spectra on dosimetry calculations.
Auger electron emitters are considered to be a promising strategy for targeted radionuclide therapy of metastatic diseases, given their high linear energy transfer (LET) and short range in tissue which could potentially limit normal tissue toxicity. Particularly Auger electron emitters that can be targeted into the DNA of tumor cells have been considered as an attractive cancer therapy in the past decade. In this study, the efficiency of the Auger electron emitter 123 I (half-life 13.2 h) to induce chromosomal damage was investigated by using the cytokinesis-block micronucleus assay. A stannylated deoxyuridine was synthesized and radiolabeled with 123 I, resulting in 123 IUdR that carried the Auger electron emitter across the nuclear membrane and allowed its incorporation into newly synthesized DNA. The DNA damage caused by the 123 I Auger cascade was estimated by evaluating the induced micronuclei frequencies in human peripheral blood lymphocytes obtained from three different donors. The isolated lymphocytes were stimulated with phytohemagglutinin (1 mg/ml) for 48 h before pulse labeling with 123 IUdR and the S-phase fraction was determined using flow cytometry. Geant4 Monte Carlo calculations were performed to determine the absorbed dose in cells by the Auger emitter. The relative biological effectiveness (RBE) was calculated by comparing the dose response curves for 123 IUdR with the reference dose response curves, obtained with 60 Co γ-ray irradiation in this study, for lymphocytes of the same donors. This resulted in a range of individual RBE values from 3 up to 10, depending on the donor and the radiation dose. In addition, dose limiting RBE values (RBE Max) were calculated for each donor and ranged from 5 to 11, dependent on the inherent radiosensitivity of the donors. This study provides valuable information on the RBE of Auger electron emitter 123 I, which is identified as a promising theranostic radionuclide for future targeted radionuclide therapy.
Where must a clinician turn when straightforward schizophrenia suddenly turns out to be just the opposite? Fortunately, these days, there are protocols for just about everything. But how much value do these add? This article outlines the journey of our attempt to follow one such protocol.
Risperidone treatment of amphetamine psychosis Amiodaroneinduced depression Psychological treatments for hypochondriasis Antipsychotic polypharmacy and early death rn Shotguns and blunderbusses: suicide in farmers Satisfaction ofcarers at home Hair analysis for substance use Risperidone treatment of amphetamine psychosis Sir: Risperidone is an atypical antipsychotic drug indicated for psychoses in which both positive and negative symptoms are prominent. Misra & Kofoed (1997) have reported for the first time a case of methamphetamine-associated psychosis responding to risperidone. In that report risperidone was prescribed after the discontinuation of methamphetamine. We report another case of amphetamine psychosis responding to risperidone while still on amphetamine.
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