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Objective: To evaluate the performance of morning check device by comparing the dosimetric parameters of medical linear accelerators measured by radiation dosimeter, 3D water phantom and morning check device. Methods:The dosimetric parameters of the linear accelerator were measured and adjusted by using dosimeter and 3D water phantom so as firstly to ensure the stability of the beam system of accelerators. After the baseline was established, the dosimeter, 3D water phantom and morning check device were applied to measure central axis output dosage, and flatness and symmetry of the field, respectively. And then the data were collected and differences of the results were compared. And compared the results of morning check device with the baseline to evaluate performance of morning check device. Results: The results measured of morning check device were close to those measured by 3D water phantom. The maximum deviations of central axis output (CAX), flatness along LR direction, flatness along GT direction, symmetry along LR direction and symmetry along GT direction measured by morning check device were 0.87%, 0.96%, 0.48%, 0.40% and 0.59%, respectively, which were in the range of 3% and could meet the requirement of AAPM TG-142 report. Conclusion: It shows that the morning check device is effective and feasible to be used for daily quality control of linear accelerators, and it can be used as tool of daily quality control.
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Objective To compare the performances of four commercially available LINAC daily QA instruments.Methods The dosimetric stability of a LINAC including central axis output,flatness and symmetry were verified and fine-tuned using a 3-dimensional water phantom,dosimeters and ionization chambers.The baseline of the four instruments including LINA-C,QUICK-C,BEAM-C and QA3 were set thereafter.Daily measurements of LINAC were conducted with these instruments respectively and the results were compared.Arbitrary errors (CAX and SYM) beyond TG-142 tolerances were introduced to the LINAC to test the sensibilities of each instrument in detecting these changes.Results Relative to the baseline that were measured by the 3-dimensional water phantom and dosimeters,the results monitored by the four instruments were comparable.The maximum disparities of the CAX,FLAT,and SYM were 0.5％ (LINA-C),-0.45％ (QUICK-C),and 0.5％ (BEAM-C),respectively.All checkers detected the known errors successfully.Conclusions The stabilities of all the four evaluated instruments met the requirements of daily QA for LINAC.LINA-C verifies CAX only.QUICKE-C,BEAM-C and QA3 can be used to perform all the daily QA protocols as suggested by AAPM TG 142 report.They also provide unique additional functions.The setup of baseline determines if the morning checkers could measure the LINAC dosimetric parameters correctly.When an error is alarmed by the morning checker,it is recommended to verify the performance of the instrument first rather than recalibrating the LINAC immediately.
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One of the most important task in commissioning intensity modulated radiotherapy (IMRT) into a clinic is the characterization of dosimetry performance under small monitor unit delivery conditions. In this study, method of evaluating dose monitor linearity, beam flatness and symmetry, and MLC positioning accuracy using a diode array is investigated. Siemens Primus linear accelerator (LA) with 6 and 10 MV x-rays was used to deliver radiation and the characteristics were measured using a multi array diodes. Monitor unit stabilities were measured for both x-ray energies. The dose linearity errors for the 6 MV x-ray were 2.1, 3.4, 6.9, 8.6, and 15.4 % when 20 MU, 10 MU, 5 MU, 4 MU, and 2 MU was delivered, respectively. Greater errors were observed for 10 MV x-rays with a maximum of 22% when 2 MU was delivered. These errors were corrected by adjusting D1_C0 values and reduced to less than 2% in all cases. The beam flatness and symmetry were appropriate without any correction. The picket fence test performed using diode array and film measurement showed similar results. The use of diode array is a convenient method in characterizing beam stability, symmetry and flatness, and positioning accuracy of MLC for IMRT commissioning. In addition, adjustment of D1-C0 value must be performed when a Siemens LA is used for IMRT because factory value usually gives unacceptable beam stability error when the MU/segment is smaller than 20.
Subject(s)
Organothiophosphorus Compounds , Particle AcceleratorsABSTRACT
As a commonly used non-contact flatness detection method, laser triangular detection method is designed with low cost, but it cannot avoid measurement errors caused by strip steel vibration effectively. This paper puts forward a dynamic flatness image processing method based on improved laser triangular detection method. According to the practical application of strip steel straightening, it completes the image pre-processing, image feature curve extraction and calculation of flatness elongation using digital image processing technology. Finally it eliminates elongation measurement errors caused by the vibration.
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Confirmation of basic technological parameters of tension levellers is the most important factor of leveling strip. Up to now, most factories have used experts' experience to decide these parameters, without any established rule to follow. For better quality of strip, a valid method is needed to decide technological parameters precisely and reasonably. In this paper, a method is used based on neural network and genetic algorithm. Neural network has a good ability to extract rules from work process of tension levellers. Then using neural network, which has learned from a lot of working samples, to be the evaluation of fitness, genetic algorithm could easily find the best or better technological parameters. At the end of this paper, examinations are given to show the effect of this method.
ABSTRACT
As a commonly used non-contact flatness detection method, laser triangular detection method is designed with low cost, but it cannot avoid measurement errors caused by strip steel vibration effectively. This paper puts forward a dynamic flatness image processing method based on improved laser triangular detection method. According to the practical application of strip steel straightening, it completes the image pre-processing, image feature curve extraction and calculation of flatness elongation using digital image processing technology. Finally it eliminates elongation measurement errors caused by the vibration.
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It was known that lateral view of caucasian's face is projected roundly, however, that of Asian's face is flat relatively. The aim of this study was to investigate the facial depths of Korean and to find the existence of the difference with Caucasian. We used the standardized photographs of 852 individuals (559 men, 293 women) of Korean young adults between 20~39 years old and measured items using image analyzer. Measurement items were five anterior-posterior lengths between points from tragion to sellion, pronasale, subnasale, stomion, and gnathion. The facial depth of the Korean showed no significant difference based on laterality. Items such as tragion-sellion length, tragion-pronasale length, and tragion-subnasale length were showed minor difference according to gender. As results that compared upper, middle, and lower facial depths with caucasian, Korean had generally short facial depths. The lateral shape of face of Korean showed relatively flat, because the lower facial depth was longest due to projection of mandibular part especially.
Subject(s)
Humans , Male , Young AdultABSTRACT
The facial flatness was studied by the metric method which involves six measurements of breadth and projection of the midfacial skeleton, the calculation of three indices from the measurements. The indices of the modern Korean adult crania, Korea & Chosun Dynasty crania, the Iron Age Korean crania, and the late Neolithic Korean crania were investigated. The indices were compared to those of other published data on the Korean crania and those of neighboring asian races as well. All indices for facial flatness of Korea & Chosun Dynasty were similar to modern Korean. However, zygomaxillary index was different between modern and late Neolithic crania. The difference of zygomaxillary index was prominent in males than females. The difference of facial flatness between modern and ancient seems to be mainly due to zygomatic breadth. The frontal indices of modern Korean and Korea & Chosun Dynasty crania were relatively low and the simotic indices were relatively high among neighboring asian races. The zygomaxillary index is intermediate. Clustering analysis represented that the flatnesses of the modern Korean crania and Korea & Chosun Dynasty crania were closely related to those of the northern Chinese, modern Japanese, however, somewhat different from that of ancient Korean, Mongol, Siberian etc.