We report a mathematically rigorous formulation for the qualitative evaluation of beam matching between linear accelerators.

The angular distribution of preequilibrium nucleons emitted in low-and medium-energy heavy-ion reactions is determined from the kinematics of nucleon-nucleon scattering inside the nuclear matter. In calculating the scattering kernels the excitation of the nuclear matter has been taken into account through a finite-temperature Fermi distribution of the nucleons. Neutron angular distribution in 12 Cϩ 165 Ho reaction at 300 MeV incident energy and 20 Nϩ 165 Ho reaction at 600 MeV is calculated from two-body scattering kinematics and compared with the experimental data. The present calculations reproduce the experimental data fairly well in both cases.

The aim of this study was to assess the performance of a gantry‐mounted detector system and a couch set detector system using a systematic multileaf collimator positional error manually introduced for volumetric‐modulated arc therapy. Four head and neck and esophagus VMAT plans were evaluated by measurement using an electronic portal imaging device and an ion chamber array. Each plan was copied and duplicated with a 1 mm systematic MLC positional error in the left leaf bank. Direct comparison of measurements for plans with and without the error permitted observational characteristics for quality assurance performance between detectors. A total of 48 different plans were evaluated for this testing. The mean percentage planar dose differences required to satisfy a 95% match between plans with and without the MLCPE were 5.2% ± 0.5% for the chamber array with gantry motion, 8.12% ± 1.04% for the chamber array with a static gantry at 0°, and 10.9% ± 1.4% for the EPID with gantry motion. It was observed that the EPID was less accurate due to overresponse of the MLCPE in the left leaf bank. The EPID always images bank‐A on the ipsilateral side of the detector, whereas for a chamber array or for a patient, that bank changes as it crosses the ‐90° or +90° position. A couch set detector system can reproduce the TPS calculated values most consistently. We recommend it as the most reliable patient specific QA system for MLC position error testing. This research is highlighted by the finding of up to 12.7% dose variation for H/N and esophagus cases for VMAT delivery, where the mere source of error was the stated clinically acceptability of 1 mm MLC position deviation of TG‐142.PACS numbers: 87.56.‐v, 87.55.‐x, 07.57.KP, 29.40.‐n, 85.25.Pb

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Energy distributions of emitted neutrons were measured for 7.2A MeV 16 O ions incident on a thick 181 Ta target. Measurements were done at 0°, 30°, and 60°with respect to the projectile direction using the proton recoil scintillation technique. Comparison with calculated results from equilibrium and preequilibrium ͑PEQ͒ nuclear reaction models suggests the emission of PEQ neutrons at this projectile energy. This model also implies that PEQ emissions take place only before any scattering between target and projectile nucleons start. The paper discusses the method for selecting the initial exciton configuration with the help of measured data, and the stage at which the PEQ process is completed.

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