ABSTRACT
PURPOSE: Breast cancer is the most frequent cancer in women. Early and accurate detection of the disease is a major factor in patient survival. To this end, phase-contrast imaging has gained significant interest in recent years. The aim of this work was to validate the physics models of a Geant4 mammography imaging simulation (in the context of the XPulse project) by comparing to EGSnrc results. METHODS: We used three Geant4 electromagnetic physics lists of the version 10.4 of the toolkit: Standard, Livermore and Penelope. We calculated energy distributions in homogeneous and inhomogeneous phantoms and breast doses in DICOM images. The simulations used photon beams of energies 20-100â¯keV. The Geant4 calculations were compared with EGSnrc/DOSXYZnrc simulations. RESULTS: We found a very good agreement between the Standard Electromagnetic option 4 and Livermore Physics Lists (within 1% for all beam energies). Larger differences were found between Standard Electromagnetic option 4 and Penelope Physics Lists (about 4%). The agreement of longitudinal energy distributions between Geant4 Standard Electromagnetic option 4 and EGSnrc was good in water and light biological materials, but important discrepancies were found in heavy elements. We confirmed with both codes that dose to the breast is minimal at beam energy around 60â¯keV. CONCLUSIONS: Overall, we found good agreement between the option 4 of the Standard Electromagnetic physics list and Livermore physics lists of Geant4, as well as EGSnrc for materials relevant to mammography screening. Further investigations are needed for the case of heavier materials.
Subject(s)
Computer Simulation , Mammography/methods , Breast/diagnostic imaging , Breast/radiation effects , Breast Neoplasms/diagnostic imaging , Female , Humans , Monte Carlo Method , Phantoms, Imaging , Photons , Radiation Dosage , Time Factors , WaterABSTRACT
Coelioscopic surgery in children is today in constant progress and requires pharmacological agents which provide excellent surgical conditions for variable and unpredictable durations. The mivacurium-propofol association was clinically studied in this context in 30 ASA I patients aged from 6 to 16 years and appeared safe, efficient and easy to use. The orbicularis oculi and pollicis adductor stimulation allows simple and adapted neuromuscular blockade monitoring. Double-burst stimulation at the ulnar nerve improves the detection of a residual curarization.
