• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.172-174
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• 2003

화상평면내 미지호흡운동에 기인한 MRI 아티팩트를 제거하기 위한 후처리방법을 제안한다. 본 연구에서 호흡운동은 2차원의 선형확대축소운동으로 모델화 된다. 신체조직을 비압축성 유체모양의 물질로 가정할때, 화상위에서의 단위체적당 푸로톤 밀도는 일정하다고 가정한다. 사용한 모델에 따르면 호흡운동은 위상 오차와 비균일표본화 및 왜곡된 진폭변조를 MR 데이터에 부여한다. 운동 파라메타가 이미 알려져 있거나 추정 가능하다고 할 때, MRI 아티팩트를 제거하기 위하여 중첩법에 기초를 둔 재구성 알고리즘을 이용한다. 운동 파라매타가 미지인 경우 스팩트럼 이동법을 적용해서 호흡변동함수와 x 방향 확대계수 및 x 방향 확대중심을 추정한다. 다음으로 에너지 최소법을 이용해서 ｙ 방향 확대계수 및 ｙ 방향 확대중심을 추정한다. 시뮬레이션을 통해서 제안한 방법의 유효성을 확인한다.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.478-479
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• 2008

본 연구에서는 비접촉 방식으로 심박과 호흡을 측정하기 위해 2.4GHz 대역에서 동작하는 도플러 레이더 센서와 베이스밴드 모듈로 구성된 도플러 레이더 시스템을 설계하고 그 성능을 평가하였다. 설계된 도플러 레이더 시스템은 심폐활동에 의한 흉부 표면의 움직임에 의해 반사되는 레이더의 위상변화를 이용하여 심폐 활동을 측정한다. 도플러 레이더 센서의 출력은 베이스 밴드 모듈의 전처리 필터부, 증폭부, 오프셋 조정부를 통과하여 호흡과 심박 신호로 분리된다. 분리된 생체신호는 기존의 생체신호와 상관성을 확인하기 위해 기준신호로 호흡과 심전도를 동시에 측정하여 그 결과를 비교 및 분석하였다. 설계된 도플러 레이더 시스템에서 분리된 호흡 및 심박 신호는 측정 대상의 움직임이 없는 상태에서는 높은 검출률을 보였으며, 도플러 레이더에서 심박과 호흡 신호를 검출한 결과 거리, 호흡과 심박의 변이량, 호흡과 심박대역에 따라 검출률이 영향을 받는다는 것을 알 수 있었다.

• The Korean Journal of Nuclear Medicine
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• v.39 no.3
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• pp.174-181
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• 2005

Purpose: Reduction of respiratory motion artifacts in PET images was studied using respiratory-gated PET (RGPET) with moving phantom. Especially a method of generating simulated helical CT images from 4D-CT datasets was developed and applied to a respiratory specific RGPET images for more accurate attenuation correction. Materials and Methods: Using a motion phantom with periodicity of 6 seconds and linear motion amplitude of 26 mm, PET/CT (Discovery ST: GEMS) scans with and without respiratory gating were obtained for one syringe and two vials with each volume of 3, 10, and 30 ml respectively. RPM (Real-Time Position Management, Varian) was used for tracking motion during PET/CT scanning. Ten datasets of RGPET and 4D-CT corresponding to every 10% phase intervals were acquired. from the positions, sizes, and uptake values of each subject on the resultant phase specific PET and CT datasets, the correlations between motion artifacts in PET and CT images and the size of motion relative to the size of subject were analyzed. Results: The center positions of three vials in RGPET and 4D-CT agree well with the actual position within the estimated error. However, volumes of subjects in non-gated PET images increase proportional to relative motion size and were overestimated as much as 250% when the motion amplitude was increased two times larger than the size of the subject. On the contrary, the corresponding maximal uptake value was reduced to about 50%. Conclusion: RGPET is demonstrated to remove respiratory motion artifacts in PET imaging, and moreover, more precise image fusion and more accurate attenuation correction is possible by combining with 4D-CT.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.25-33
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• 2021

Purpose : The purpose of this study is to evaluate the accuracy and usefulness of the Trigger mode for the Respiratory Gated Radiation Therapy (RGRT) Materials and methods : A QUASAR respiratory phantom that inserted a 3 mm fiducial marker (a gold marker) was used to estimate the accuracy of the Trigger mode. And the 20 bpm was used as reference respiration rate in this study. The marker that placed at the center of the phantom was contoured, and the lower threshold of a gating window was fixed at 2.0 mm using an OBI with Truebeam STx^TM. The upper threshold was measured every 0.5 mm from 1.0 mm to 3.0 mm. The respiration rates were changed every 10 bpm from 10 bpm to 60 bpm. We repeatedly measured five times to check the error rate of the trigger mode in the same condition. Result : The differences of a distance from a peak phase to upper threshold, 1.0 to 3.0 mm at a 20 bpm as a reference for 3 days in a row were 0.68±0.05 mm, 0.91±0.03 mm, 1.23±0.03 mm, 1.42±0.04 mm, and 1.66±0.06 mm, respectively. Measurement result of changes in respiratory rate compared to baseline respiratory rate in maximum absolute difference. The coefficient of determination (R2) to estimate the correlation between the respiration velocity and variation of absolute difference was on average 0.838, 0.887, 0.770, 0.850, and 0.906. The p-values of all the variables were below 0.05. Conclusion : Using Trigger mode during respiratory gated radiation therapy (RGRT), accuracy and usefulness of trigger mode at reference breathing rate were confirmed. However, inaccuracies depending on the rate of breathing it could be uncertain in case of respiration rate is faster than 20 bpm as a standard respiration rate compared to slower than 20 bpm. Consequently, when conducting a RGRT using the trigger mode, real time monitoring is required with well educated respiration.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10c
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• pp.432-434
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• 1998

임상진단에 있어서 종종 문제가 되고 있는 호흡에 따른 두뇌부분의 가상적인 상하이동을 고려해서 위상 엔코드 축인 Y 방향만의 강체의 평행이동을 취급한다. 종래의 발견적인 축차 근사 반복처리에 의한 제거방법과는 달리, 본 연구에서는 MRI 촬상과정과 화성특성의 해석에 근거한 MRI 신호증의 체동성분과 화상성분을 단순한 대수연산에 의해 분리할 수 있는 새로운 구속조건을 도출한다. MRI 신호에 대해서 X방향의 1차원 푸리에 변환을 행한 후의 Y 방향의 스펙트럼 위상값은 화상자신의 성분과 체동성분의 합이 되고 있다. 한편, 두뇌부위 등의 단상층에 있어서 주위의 피하지방 부위의 밀도는 거의 균일한 것으로 알려져 있어 이 부분위의 Y 방향의 1 라인 밀도 분포를 대칭이라고 간주할 수 있다. 밀도함수가 대칭인 경우 스펙트럼의 위상은 그 위치에 대하여 선형적으로 변화하며 이 선형함수로부터 벗어난 성분을 체동성분으로 분리할 수 있다. 이러한 구속조건에 기초를 둔 근거가 명확한 아티팩트의 제거방법을 제안한다.

• Progress in Medical Physics
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• v.27 no.2
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• pp.93-97
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• 2016

In this study, we evaluate the effect of respiration on the dose distribution in patient target volume (PTV) during intensity-modulated radiation therapy (IMRT) and research methods to reduce this impact. The dose distributions, homogeneity index (HI), coverage index (CVI), and conformity index of the PTV, which is calculated from the dose-volume histogram (DVH), are compared between the maximum intensity projection (MIP) image-based plan and other images at respiration phases of 30%, 60% and 90%. In addition, the reducing effect of complication caused by patient respiration is estimated in the case of a bolus and the expended PTV on the skin. The HI is increased by approximately twice, and the CVI is relatively decreased without the bolus at other respiration phases. With the bolus and expended PTV, the change in the dose distribution of the PTV is relatively small with patient respiration. Therefore, the usage of the bolus and expended PTV can be considered as one of the methods to improve the accuracy of IMRT in the treatment of breast cancer patients with respiratory motion.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.113-122
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• 2010

Purpose: To evaluate the accuracy of a target position at static and dynamic state by using Dynamic phantom for the difference between tumor's actual movement during respiratory gated radiation therapy and skin movement measured by RPM (Real-time Position Management). Materials and Methods: It self-produced Dynamic phantom that moves two-dimensionally to measure a tumor moved by breath. After putting marker block on dynamic phantom, it analyzed the amplitude and status change depending on respiratory time setup in advance by using RPM. It places marker block on dynamic phantom based on this result, inserts Gafchromic EBT film into the target, and investigates 5 Gy respectively at static and dynamic state. And it scanned investigated Gafchromic EBT film and analyzed dose distribution by using automatic calculation. Results: As a result of an analysis of Gafchromic EBT film's radiation amount at static and dynamic state, it could be known that dose distribution involving 90% is distributed within margin of error of 3 mm. Conclusion: As a result of an analysis of dose distribution's change depending on patient's respiratory cycle during respiratory gated radiation therapy, it is expected that the treatment would be possible within recommended margin of error at ICRP 60.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1010-1019
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• 2008

In this paper, we present a noise analysis and measurement results of a bio-radar system that can detect human heartbeat and respiration signals. The noise analysis including various phase noise effects is very important in designing the bio-radar system, since the frequency difference between the received signal and local oscillator is very small and the received power is very low. All of the noise components in a bio-radar system are considered from the point of view of SNR. From this analysis, it can be concluded that the phase noise due to antenna leakage is a dominant factor and is a function of range correlation. Therefore, the phase noise component with range correlation effect, which is the most important noise contribution, is measured using the measurement setup and compared with the calculated results. From the measurement results, our measurement setup can measure a closed-in phase noise of a free-running oscillator. Based on these results, it is possible to design a 2.4 GHz bio-radar system quantitatively which has a detection range of 50 cm and low power of 1 mW without additional PLL circuits.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1204-1212
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• 2008

The paper proposes a new signal model which is revised from the commonly used signal model. Recently, many research institutions had a research about CW bio-radar for detecting he heartbeat and respiration. However, when the bio-radar detects the heartbeat using the previous signal model, the bio-radar has a disadvantage of weakness about he residual phase and AWGN. Also, the model is inappropriate in ergonomics because this signal model supposes hat the heart and lung are located at a same place. In this paper, the modified signal model, which is appropriate n ergonomics, is proposed. This paper analyzes and compares with the performance for detecting the heartbeat and respiration using the previous model and revised model in AWGN and multi-path environment.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.123-135
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• 2012

Purpose: It is essential to minimize the movement of tumor due to respiratory movement at the time of respiration controlled radiotherapy of non-small cell lung cancer patient. Accordingly, this Study aims to evaluate the usefulness of restricted respiratory period by comparing and analyzing the treatment plans that apply free and restricted respiration period respectively. Materials and Methods: After having conducted training on 9 non-small cell lung cancer patients (tumor n=10) from April to December 2011 by using 'signal monitored-breathing (guided- breathing)' method for the 'free respiratory period' measured on the basis of the regular respiratory period of the patents and 'restricted respiratory period' that was intentionally reduced, total of 10 CT images for each of the respiration phases were acquired by carrying out 4D CT for treatment planning purpose by using RPM and 4-dimensional computed tomography simulator. Visual gross tumor volume (GTV) and internal target volume (ITV) that each of the observer 1 and observer 2 has set were measured and compared on the CT image of each respiratory interval. Moreover, the amplitude of movement of tumor was measured by measuring the center of mass (COM) at the phase of 0% which is the end-inspiration (EI) and at the phase of 50% which is the end-exhalation (EE). In addition, both observers established treatment plan that applied the 2 respiratory periods, and mean dose to normal lung (MDTNL) was compared and analyzed through dose-volume histogram (DVH). Moreover, normal tissue complication probability (NTCP) of the normal lung volume was compared by using dose-volume histogram analysis program (DVH analyzer v.1) and statistical analysis was performed in order to carry out quantitative evaluation of the measured data. Results: As the result of the analysis of the treatment plan that applied the 'restricted respiratory period' of the observer 1 and observer 2, there was reduction rate of 38.75% in the 3-dimensional direction movement of the tumor in comparison to the 'free respiratory period' in the case of the observer 1, while there reduction rate was 41.10% in the case of the observer 2. The results of measurement and comparison of the volumes, GTV and ITV, there was reduction rate of $14.96{\pm}9.44%$ for observer 1 and $19.86{\pm}10.62%$ for observer 2 in the case of GTV, while there was reduction rate of $8.91{\pm}5.91%$ for observer 1 and $15.52{\pm}9.01%$ for observer 2 in the case of ITV. The results of analysis and comparison of MDTNL and NTCP illustrated the reduction rate of MDTNL $3.98{\pm}5.62%$ for observer 1 and $7.62{\pm}10.29%$ for observer 2 in the case of MDTNL, while there was reduction rate of $21.70{\pm}28.27%$ for observer 1 and $37.83{\pm}49.93%$ for observer 2 in the case of NTCP. In addition, the results of analysis of correlation between the resultant values of the 2 observers, while there was significant difference between the observers for the 'free respiratory period', there was no significantly different reduction rates between the observers for 'restricted respiratory period. Conclusion: It was possible to verify the usefulness and appropriateness of 'restricted respiratory period' at the time of respiration controlled radiotherapy on non-small cell lung cancer patient as the treatment plan that applied 'restricted respiratory period' illustrated relative reduction in the evaluation factors in comparison to the 'free respiratory period.