• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.811-817
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• 2020

This study aims to evaluate the Modulation Transfer Function (MTF) according to the change in the number of channels of the CT examination device by changing the posture of the patient to the X-axis and Y-axis in the wrist joint CT examination. Using a CT device and a wrist phantom, the test was performed by moving 0 (matched), 5, 10, and 15 cm in the X-axis around the isocenter, and the Z-axis was rotated by -20° and -40°. For the test, 16, -40 and 64 channels were used to check whether there was a difference for each number of channels. The examined images were compared by measuring the MTF values of the ulna and left and right sides of the radius. In the experiment where the isocenter was moved along the X-axis, the MTF value decreased with an increase in the moving distance, and the MTF value was found to be unaffected by the number of channels. In the experiment in which the wrist joint was rotated by -20° and -40° on the Z-axis, the degree of deviation and MTF were found to be irrelevant. It was not related to the number of channels either. In conclusion, the movement of the wrist along the X-axis should be restrained as much as possible for a wrist joint CT scan, whereas deviation around the Z-axis depending on the environment for the patient would not affect the MTF of the image.

• Journal of radiological science and technology
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• v.29 no.3
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• pp.167-175
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• 2006

With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can't be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner's design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.123-133
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• 2007

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.97-101
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• 2012

The TC&R(Telemetry, Command & Ranging) antennas should have the hemispherical omni antenna patterns to make sure that the communication link between the satellite and the ground station can be established under whatever satellite attitude during after launch to on-orbit mission. The hemispherical omni-antennas are typically placed on the +z axis and -z axis of the satellite to provide the spherical omni patterns. The S-band qaudrifilar helix antennas having RHCP and LHCP hemispherical omni pattern are designed to meet the antenna gain and the axial ratio requirements. To investigate the omni-antenna pattern characteristics depending on four cases of antenna polarization combination placed on the +z axis and -z axis, the antenna pattern of each case is analyzed. Based on the result, after installing the designed RHCP and LHCP S-band omni-antennas on the +z axis and -z axis of the satellite, the combined antenna gain is obtained and finally analyzed in conjunction with the communication link influence.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.67-74
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• 2019

Purpose: The purpose is to correct for position errors caused by long treatment times. By correcting the target motion that can occur during lung SBRT using IntraFraction CBCT. Methods and materials: We analyzed retrospectively the IFM data of 14 patients with two treatment arc in the treatment plan for lung cancer with stereotactic radiotherapy. An IntraFraction Motion was applied to the Arccheck phantom to acquire the Gamma index data. Results : IntraFraction Motion during the first treatment arc is in the left-right(LR), superiorinferior(SI), anterior-posterior(AP) directions were $0.16{\pm}0.05cm$, 0.72 cm(max error), $0.2{\pm}0.14cm$, 1.26 cm, $0.24{\pm}0.08cm$, 0.82 cm and rotational directions was $0.84{\pm}0.23^{\circ}$, $2.8^{\circ}$(pitch), $0.72{\pm}0.23^{\circ}$, $2.5^{\circ}$(yaw), $0.7{\pm}0.19^{\circ}$, $2^{\circ}$(roll). IntraFraction Motion during the second treatment arc is in the LR, SI, AP directions were $0.1{\pm}0.04cm$, 0.37 cm, $0.14{\pm}0.17cm$, 2 cm, $0.12{\pm}0.04cm$, 0.5 cm and rotational directions was $0.45{\pm}0.12^{\circ}$, $1.3^{\circ}$, $0.37{\pm}0.1^{\circ}$, $1^{\circ}$, $0.35{\pm}0.1^{\circ}$, $1.2^{\circ}$. Gamma index pass rates were $82.64{\pm}10.51%$, 48.4 %. Conclusions : In this study, we examined the validity of IntraFraction Motion correction in lung SBRT and the efficiency of IntraFraction CBCT. Due to the nature of SBRT treatment, IFM may increase due to the increased treatment time. It is believed that the increase in IFM with the increase in treatment time can be improved with the use of FFF Beam and additional position correction using CBCT during treatment.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.181-188
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• 2000

Input shaping is a method fur reducing residual vibration. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with the desired system command. It has been applied to robot with a flexible manipulator. But it can be applied to the reduction of residual vibration far overhead crane. In this paper, input shaping shows good performance for anti-sway of overhead crane. In the z-domain, we designed an input shaper and calculated the sensitivity of it. If sensitivity is calculated in the z-domain, the shapes of sensitivity curves are expected easily. Accordingly, it is easy to design an input shaper in the z-domain. We compared the response of a system with shaper to it without that. Also, we compared El shaper to ZV shaper in view of robustness.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.202-206
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• 1997

항공기 부품, 터빈형 임펠라나 브레이드, 자동차나 가전제품용의 대형금형류의 정밀가공과 생산성 향상에는 5축의 NC가공이 기존 3축의 NC 가공보다 많은 이점을 갖고 있다. 제1차 선도기술개발사업을 통해 C 형의 5축머시닝센터를 성공적으로 개발한 실적을 바탕으로 제2차 선도기술개발사업을 통해 작업이송거리 12,000*3,500*1,500(X*Y*Z), 위치정밀도 $\pm0.005mm/M$, 주축동력 30/45Kw의 대형, 강력, 정밀형의 문형5축머시닝센터 개불을 목표로 추진하고 있다.

• Journal of radiological science and technology
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• v.33 no.2
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• pp.127-132
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• 2010

The purpose of this study is to measure scattered ray which is occurred except for Z-axis range of the detector in MDCT's iso-center and present the basic data about the standard for reduction of scattered ray. The development of MDCT brings out the enlargement of beam thickness to the patient's Z-axis, which distributes to the increase in exposure dose according to the rise of scattered ray. Also MDCT brings out the increase of scattered ray about 4times more than SDCT. To evaluate scattered ray according to the change of beam thickness on MDCT, we measured scattered ray of MDCT's Z-axis beam thickness by using one 16-slice CTs and two 64-slice CTs. We used the ionization chamber 60ml 2026C as the equipment of measurement. In our results, we found out that the change of scattered ray according to the beam thickness in the same kVp has increase of scattered ray. Secondly we found out the increase of scattered ray according to the increase of kVp. Lastly we found out the decrease of scattered ray according to the increase of the distance from the ionization chamber.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.19-26
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• 1997

The manufacture of an impeller typically requires the 5-axis CNC machining, since the impeller is usually under working conditions such as high speed, high temperature, and high pressure. Thus, this study contributes to development of an exclusive CAM system for effective 5-axis CNC machining of a ruled surface type impeller. In this study, the sampled impeller is made of blades and a body and the blade consists of ruled surfaces between hub curve and shroud curve. In the post processing for 5-axis NC part program, the cutter axis direction vector is the straighten vector on ruled surface. The position of ball center in ball end mill cutter is decided on the interference check between the cutter and body surface of impeller using with the modified z-map method that z-axis is the same of cutter axis direction vector. The exclusive CAM system for an impeller developed in this study was very effective for designs and 50-axis machining of a ruled surface type impeller.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.175-178
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• 1999

원형단면을 갖는 수신용 하이드로폰과 같은 면적의 정사각형 단면을 가정하여, 상온의 증류수를 매질로 초음파 변환기에서 방사되는 음장의 공간적 분포를 모의실험하였다. 이러한 "정사각형 평면 근사 평균법(이후 평면 근사 평균법)"을 이용하여, x-축 주사, z-축 주사, xy-평면 주사 및 xz-평면 주사를 모의실험하여 실제 실험에서 나타날 수 있는 여러 가지 현상을 조사하였다. z-축 주사 모의 실험 결과는 Beissner의 이론과 비교하여 비교적 잘 일치하였다