pitch factor
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2021 ◽  
Vol 21 (2) ◽  
pp. 1-7
Author(s):  
Muhammad Ikhmal Naim Mohd Hilal ◽  
Rekha Ganesan ◽  
Norhashimah Mohd Norsuddin ◽  
Mohd Izuan Ibrahim ◽  
Said Mohd Shaffiq Said. Rahmat ◽  
...  

The eye is a radiosensitive organ that lies within the scan range during Computed Tomography (CT) of the head. The utilization of the head CT is increasing with growing concern about the chances of development of cataract which induces by ionising radiation. This research aimed to calculate eye absorbed dose and to study the potential occurrence of radiation induces cataracts between CT Brain and CT Temporal. A total of 399 set data were obtained retrospectively according to inclusion and exclusion criteria. 364 patients underwent CT Brain while 35 patients’ data obtained for CT Temporal. The scanning parameters such as tube current, tube potential, pitch factor, beamwidth, filter, revolution time, and filter were recorded. Eye absorbed dose was significantly different (p<0.05) between CT brain (49.07±10.08mGy) and CT temporal (25.72 ± 6.12mGy). None of the analysed data exceeded the eye threshold dose recommended by ICRP 2012. However, as expected, the cumulative eye absorbed dose was increased as the frequencies of the scan increase. The highest number of repeated scans is five times with cumulative dose was recorded as 278.27mGy. In conclusion, the eye absorbed dose is higher in CT Brain compared to CT Temporal and has potential for induction of cataract in the future especially with the patient that undergoes repeated CT examination.


PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250490
Author(s):  
Isabel Lange ◽  
Babak Alikhani ◽  
Frank Wacker ◽  
Hans-Juergen Raatschen

The objective of this study is to identify essential aspects influencing radiation dose in computed tomography [CT] of the chest, abdomen and pelvis by intraindividual comparison of imaging parameters and patient related factors. All patients receiving at least two consecutive CT examinations for tumor staging or follow-up within a period of 22 months were included in this retrospective study. Different CT dose estimates (computed tomography dose index [CTDIvol], dose length product [DLP], size-specific dose estimate [SSDE]) were correlated with patient’s body mass index [BMI], scan length and technical parameters (tube current, tube voltage, pitch, noise level, level of iterative reconstruction). Repeated-measures-analysis was initiated with focus on response variables (CTDIvol, DLP, SSDE) and possible factors (age, BMI, noise, scan length, peak kilovoltage [kVp], tube current, pitch, adaptive statistical iterative reconstruction [ASIR]). A univariate-linear-mixed-model with repeated-measures-analysis followed by Bonferroni adjustments was used to find associations between CT imaging parameters, BMI and dose estimates followed by a subsequent multivariate-mixed-model with repeated-measures-analysis with Bonferroni adjustments for significant parameters. A p-value <0.05 was considered statistically significant. We found all dose estimates in all imaging regions were substantially affected by tube current. The iterative reconstruction significantly influenced all dose estimates in the thoracoabdominopelvic scans as well as DLP and SSDE in chest-CT. Pitch factor affected all dose parameters in the thoracoabdominopelvic CT group. These results provide further evidence that tube current has a pivotal role and potential in radiation dose management. The use of iterative reconstruction algorithms can substantially decrease radiation dose especially in thoracoabdominopelvic and chest-CT-scans. Pitch factor should be kept at a level of ≥1.0 in order to reduce radiation dose.


Author(s):  
Р.М. Розенталь ◽  
С.В. Самсонов ◽  
А.А. Богдашов ◽  
И.Г. Гачев ◽  
А.Н. Леонтьев ◽  
...  

The multifrequency radiation in a pulsed gyro-resonance backward-wave oscillator (gyro-BWO) of the Ka-band based on a waveguide with helical corrugation are obtained. The radiation power achieved 30-35 kW with a pulse duration of about 120 μs and a repetition rate of up to 10 Hz. Due to the change in the magnetostatic field in the interaction region and the pitch factor of the particles, the center oscillation frequency and the distance between the main spectral lines are tuned in the 32–35.5 GHz and in the 360–550 MHz ranges, correspondingly.


2020 ◽  
pp. 85-89
Author(s):  
О.Г. Несиоловский ◽  
Р.Д. Адакин ◽  
И.М. Соцкая

Рассмотрен вопрос интенсификации процесса теплоотдачи хлебопекарного теплообменного аппарата (ТА). ТА хлебопекарной печи имеет дополнительную конструктивную особенность – направляющий кожух. Предложено разместить на нём дефлекторы и направляющие пластины, которые изготовлены из нежаропрочных сталей, поскольку они напрямую не контактируют с продуктами горения, а лишь со вторичным теплоносителем. Дефлекторы – это небольшие пластины, установленные перпендикулярно стенке кожуха. Они позволяют образовывать локальные турбулентные завихрения теплоносителя, приводящие к увеличению теплоотдачи. Пластины направляют холодный теплоноситель на обтекание жаровой трубы камеры сгорания, дополнительно повышая его температуру. В результате численных моделирований установлены оптимальные зазоры между дефлекторами и трубками ТА, а также угол атаки направляющих пластин. Данная методика может быть применена к любым размерам трубок ТА, при соблюдении углов пластин и коэффициента шага между дефлектором и трубкой ТА. Установка на кожухе дефлекторов и пластин, как показывает моделирование, не приводит к существенному увеличению гидравлического сопротивления. Предложенные конструктивные доработки приводят к повышению значений теплоотдачи от 10 до 40%, в зависимости от скорости теплоносителя. Использование дефлекторов и направляющих пластин ведёт к повышению КПД ТА, снижению расхода топлива, более эффективному использованию выработанного тепла для выпечки хлебобулочных изделий. The issue of intensification of heat transfer process of bakery heat exchanger (HE) is considered. The baking oven HE has an additional structural feature – a guiding jacket. It is proposed to place deflectors and guide plates on it which are made of non-high-temperature steels, since they do not directly contact the combustion products, but only with the secondary coolant. Deflectors are small plates installed perpendicular to the wall of the casing. They allow the formation of local turbulent swirls of the coolant, leading to an increase in heat carrier. Plates direct cold heat carrier to flow around flame tube of combustion chamber, additionally increasing its temperature. As a result of numerical simulations, optimal gaps between deflectors and HE tubes are installed, as well as angle of attack of guide plates. This technique can be applied to any size of the HE tubes, in accordance with plate angles and pitch factor between the deflector and the HE tube. Installation of deflectors and plates on the casing, as the simulation shows, does not lead to a significant increase in flow friction. The proposed structural modifications lead to an increase in heat transfer values from 10 to 40%, depending on the coolant speed. The use of deflectors and guide plates leads to an increase in the coefficient of efficiency of HE, a decrease in fuel consumption, and a more efficient use of the generated heat for baking bakery products.


Author(s):  
Issahaku Shirazu ◽  
Y. B. Mensah ◽  
Cyril Schandorf ◽  
S. Y. Mensah ◽  
Theophilus Sackey ◽  
...  

In medical exposure dose to patients are determine by input parameters including mAs, kVp, pitch factor among other factors. The aim of this study is to provide procedure and protocol of how to assess patients’ dose (organ and effective dose) estimates with preset eff mAs and standard kVp. This is to determine a tradeoff between patient’s dose and the image quality before imaging. In addition to providing appropriate clinical recommendation for clinicians for dose management during CT scan. MVL DICOM application software was used to access image data during abdominal CT scan. Organ and effective dose estimates were estimated as developed by ICRP 103 recommendations. Where on the image data, using MVL platform detail information of the mAs, kVp, CTDI<sup>vol</sup> and DLP were available for recording. <span style="background:white">The weighted CTDI (CTDI<sup>W</sup>) was estimated by multiplying the volume CTDI (CTDI<sup>VOL</sup>) by the pitch factor. Which was used to estimate organ dose using </span>the normalized organ dose factor <span style="background:white">and the effective dose was estimated by</span> the product of the region-specific normalizing constant and the dose length product.<span style="background:white"> The </span>mAs is the effective Milliameter per second, which were calculated by dividing the mAs by the pitch factor. The relationship between input and output parameters were modeled as the final component of the modeling process in a form of GUI applications format. This was done to establish the various process and procedures involve in abdominal scan for dose managements. The coding process involve the use of written visual basic code to design an interface and integrated on the MVL application platform for clinical application. The GUI has been recommended for use by various stake holders in CT operations.


2008 ◽  
Vol 51 (10) ◽  
pp. 772-779 ◽  
Author(s):  
E. V. Ilyakov ◽  
I. S. Kulagin ◽  
V. N. Manuilov ◽  
A. S. Shevchenko

2008 ◽  
Vol 15 (8) ◽  
pp. 1069-1074 ◽  
Author(s):  
Tatsuro Suzuki ◽  
Takamasa Ota ◽  
Tatsuo Maeda ◽  
Yasuhiro Noshi ◽  
Satoru Nakanishi ◽  
...  

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