Browsing by Author "Chen, Chien-An"

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Patient delivery quality assurance for linac-based IMRT and helical tomotherapy using solid state detectors
(2011-12-01)
Chong, Ngot Swan
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Lee, Jason J. S.
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Kung, Wei-Hsiang
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Chen, Chien-An
;
Hsieh, Chen-Hsi
The purpose of this study is to demonstrate how to perform and define appropriate action levels for the intensity-modulated radiation therapy (IMRT) delivery quality assurance (DQA) for both linear accelerator (linac) and helical tomotherapy (HT) plans using a 2D array diode detector. MapCHECK (Sun Nuclear, Melbourne, FL, USA) was used to perform the DQA measurements of patient plans at various sites: brain, head and neck, chest, abdomen, pelvis, spine, bone and others. The measured and planned doses were compared using gamma analysis with a total dose discrepancy of 3% or a gradient difference of 3 mm criteria. DQAs for 507 HT and 380 linac-based IMRT plans were performed, and the mean diode percentage passing rates for 3%/3 mm criteria were 93.8% and 95.1% respectively. For HT delivery, 4.6% and 9.5% of the plans had the passing rates below 80% and 85%, while for linac-based IMRT, 7.4% of the plans had the passing rates lower than 90%. Applying confidence limit with multiplier of 1, action levels for passing rates of 87% and 90% are recommended for HT and IMRT plans respectively. (C) 2011 Elsevier Ltd. All rights reserved.
Tuning the Morphology of Isoindigo Donor-Acceptor Polymer Film for High Sensitivity Ammonia Sensor
(2018-10-04)
Lu, Chun-Fu
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Shih, Cheng-Wei
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Chen, Chien-An
;
Chin, Albert
;
Su, Wei-Fang
Monitoring the ammonia gas is of great interest to both environmental benefits and human health. The recent advance in polymer thin film transistors (TFTs) can realize high sensitivity and low-cost gas sensors. Ammonia gas interacts with charge carrier channels and polymer/dielectrics interface through Coulomb force. This is the first report of high sensitivity and reusable ammonia sensor fabricated from thiophene-isoindigo donor-acceptor conducting polymer. This kind of polymer has advantages of simple synthesis and excellent air stability. The systematic study is carried out to investigate relationship among chemical structure variation and morphology control of polymer to the performance of ammonia sensor. High crystallinity, favored crystal orientation, and direct percolation routes for analytes are found to be essential to increase the susceptibility of polymers to ammonia gas. By strengthening edge-on morphology, the sensitivity can be enhanced fivefold for the same polymer. The idea can put forward the development of sensor array in a time-efficient manner by employing the morphology effect.