Equipment Dose Research Articles

SU-E-T-104: Development of 3 Dimensional Dosimetry System for Gamma Knife

Purpose: The aim of this study was to develop a new 3 dimensional dosimetry system to verify the dosimetric accuracy of Leksell Gamma Knife-Perfexion™ (LGK) (Elekta, Norcross, GA). Methods: We designed and manufactured a lightweight dosimetry instrument to be equipped with the head frame to LGK. It consists of a head phantom, a scintillator, a CCD camera and a step motor. The 10×10 cm2 sheet of Gd2O3;Tb phosphor or Gafchromic EBT3 film was located at the center of the 16 cm diameter hemispherical PMMA, the head phantom. The additional backscatter compensating material of 1 cm thick PMMA plate was placed downstream of the phosphor sheet. The backscatter plate was transparent for scintillation lights to reach the CCD camera with 1200×1200 pixels by 5.2 um pitch. With This equipment, 300 images with 0.2 mm of slice gap were acquired under three collimator setups (4mm, 8mm and 16mm), respectively. The 2D projected doses from 3D distributions were compared with the exposured film dose. Results: As all doses normalized by the maximum dose value in 16 mm setup, the relative differences between the equipment dose and film dose were 0.2% for 4mm collimator and 0.5% for 8mm. The acquisition of 300 images bymore » the equipment took less than 3 minutes. Conclusion: The new equipment was verified to be a good substitute to radiochromic film, with which required more time and resources. Especially, the new methods was considered to provide much convenient and faster solution in the 3D dose acquisition for LGK.« less

400 V class high-speed current limiting circuit breaker for electric power system

In Japan, a new network distribution system with advanced protective and operational functions designed to meet the needs of today's information society is being studied. For this new distribution system, the authors have developed high-speed current limiting equipment using gate turn-off thyristors (GTOs), to lower the breaking capacity of switches and to suppress instantaneous voltage drops. The main components of this equipment are a high-speed vacuum switch and a GTO switch connected in parallel. The usual load current is carried by the vacuum switch. In the case of a system fault, the fault current is commutated to and interrupted by the GTO switch by opening the vacuum switch. The time from fault occurrence to current interruption is less than 1 ms. This response time is about 100 times as fast as that of mechanical breakers. This equipment dose not require a large cooling system and is compact compared with conventional solid-state equipment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A qualitative assessment of developmental toxicity within a series of structurally related dopamine mimetics

A qualitative assessment of developmental toxicity within a series of 12 structurallu related compounds, 11 of which were active dopamine mimetics and one was inactive, was conducted in rats treated orally by gavage during the major periodof organogenesis. Doses were chosen where possible to be equipotent in terms of pharmacological activity. The series was typified by the compound BRL 16644 (2-[[3,4-dihydro-2,2-dimethyl-4-3-(triflruomethyl)phenyl]-2 H-1-benzopyran-7yl]- N, N-dimethyl-ethanamine: Chemical Abstracts No. 59257-24-8). Five of these compounds were clearly teratogenic producing specific abnormalities typified by anasarca, brachygnathia and clefy palate. Similar levels of maternal toxicity, particularly stereotypic behaviour, and foetotoxicity were seen in both teratogenic and non-teratogenic compounds suggesting that neither maternal nor foetotoxicity plays a role in the aetiology of the abnormalities. Four of the teratogenic componds contained a trifluromethyl group in the 4-phenyl ring and, within this series of compounds, substitution with this group appears to confer teratogenicity. Although equipment doses were used this only pertained to the adult and as only limited pharmacokinetic data were available, including the extent of placental transfer, the influence of this group is not clear. Investigations have been undertaken to relate the teratogenic potential of these compounds to a number of their chemical descriptors, including electronic, steric, quantum chemical and hydrophobicity parameters, to try and clarify of the trifluoromethyl group.