Respiratory motion phantom을 이용한 Flash mode 검사에서 motion artifact 감소로 인한 화질개선과 선량감소에 관한 연구

서경진(Kyeong Jin Seo),유흥준(Heung Joon Yoo),서동수(Dong Soo Suh),이기백(Ki Baek Lee) 대한CT영상기술학회 2012 대한CT영상기술학회지 Vol.14 No.2

목적 Chest CT는 호흡으로 인한 움직임의 영향을 많이 받기 때문에 호흡을 멈추고 검사를 한다. 호흡조절이 힘든 고령환자나 읍급중환자, 3세 이하 sedation이 필요한 소아환자의 CT검사에서 호흡에 의한 motion artifact를 줄여 질 좋은 영상을 얻는다면 더 정확한 진단과 재검사로 인한 불필요한 선량감소를 얻을 수 있다. 본 연구는 Chest CT에 Flash mode를 적용하여 빠른 tube rotation time과 pitch로 motion artifact를 줄여 image quality를 개선하고, 환자 선량을 낮출 수 있는지 알아보고자 한다. 대상 및 방법 CT 장비는 Somatom Definition Flash 128장비(Siemens, Erlangen, Germany)을 사용하였고, 팬텀은 ACR phantom(Model #462, Gamex RMI, USA과 Lung chest phantom(Model RS-330, Fluke Biomedical), 본원 방사선 종양학과에서 자체 제작한 respiratory moving phantom을 사용하였다. Spiral mode 1,1.5 pitch와 Flash mode 1.55, 2, 2.5, 3 pitch를 각각 검사하여 비교 평가하였다. Image quality 측정을 위하여 ACR phantom의 Noise, Uniformity, High contrast resolution의 visible lp/cm, MTF 10%, MTF 50%를 측정하였고, Respiratory motion phantom의 scan range는 성인은 32cm, 소아는 10cm으로 설정하였고, 호흡에 의한 움직임은 4초와 2초로 각각 설정하여 Lung chest phantom을 스캔 후 3명의 방사선사가 영상 평가를 시행하였다. 또한 Scan time과 CTDIvol도 비교하였다. 결과 Spiral과 Flash mode 각각 6가지 pitch실험에서 ACR phantom의 Noise, Uniformity, High contrast resolution visible lp/cm이 모두 허용범위 안에 있었고, MTF 10%와 MTF 50%도 큰 변화가 없었다. 하지만 Lung chest phantom의 정성적 평가에서 Flash mode의 pitch가 높아질수록 beam hardening artifacts가 심해졌다. Nodule 갯수와 선명도 폐실질 병변의 선명도 폐하부와 횡격막 사이 선명도, lung vessel의 선명도, 전체적인 image quality 등 5가지 항목에서 scan range가 32cm일 때 Spiral mode Chest 검사는 5점 만점이었으며, 성인환자의 호흡주기가 4초와 2초일 때 각각 Flash mode 1.55 pitch, 2.5 pitch 이상에서 병변 관찰이 가능하였고, 소아일 때는 Spiral mode 1.5 pitch 이상에서 병변 관찰이 용이하였다. Scan time은 32cm 검사 시 Flash mode의 pitch가 높아질수록 scan time이 짧아졌다. CTDIvol값은 Flash mode에서 19% 선량 감소가 있었다. 결론 호흡조절이 힘든 환자에서 호흡에 의한 motion artifact는 진단에 방해를 준다. ACR과 Lung chest phantom 평가에서 보았듯이 Flash mode를 사용하여 검사하면 image quality를 유지하면서 motion artifact가 줄어든 것을 확인할 수 있었고, CTDIvol이 19% 정도 줄어들어 환자 선량도 감소한 것을 알 수 있었다. 성인환자의 호흡주기가 4초와 2초일 때 모두 Flash 2.5pitch로 검사하는 것이 가장 좋았으며, 소아의 경우는 Flash의 모든 pitch에서 좋은 영상을 얻을 수 있다. Chest CT는 폐질환 진단 시 가치가 매우 뛰어나고 follow up검사가 많기 때문에 Flash mode를 적용한 Chest CT는 임상적으로도 굉장히 유용할 것이라 생각된다. I. Purpose Because irregular breathing has a bad effect on, Chest CT must be conducted in holding patient’s breath. CT exam of elderly patients, acute care patient and pediatric patients below 3 years who are difficult to breath needs to decrease breath holding time. Reducing Motion artifact according to irregular breathing can acquire excellent image quality and decrease unnecessary dose due to reexamination. This study adapts to Flash mode in Chest CT exam. By reducing motion artifact with fast tube rotation time and pitch, we evaluate improvement of image quality and patient’s dose reduction II. Meterial and Methods CT scans were performed with a Somatom Definition Flash 128-slice MDCT (Siemens, Erlangen, Germany), ACR Phantom(Model #462, Gamex RMI, USA), Lung chest phantom(Model RS-330, Fluke Biomedical) and respiratory moving phantom which is made by Department of radiation oncology, Asan Medical Center. Each exam adapting spiral mode(1 and 1.5 pitch) and flash trode(1.55, 2, 2.5 and 3 pitch) was respectively evaluated. Noise, Uniformity, visible lp/cm of High contrast resolution, MTF 10% and MTF 50% were measured for image quality. Scan range of Respiratory motion phantom was 32 cm for adult and 10 cm for child and respiratory range was 4 second and 2 second respectively. Three radiologic technologist assessed image quality and scan time, CTDIvol were compared respectively. III. Result All six measurement items(Noise, Uniformity, visible lp/cm of High contrast resolution, MTF 10% and MTF 50%) using both Spiral and Flash mode were within a permissible range and there were no significant differences in MTF 10% and MTF 50%. But visible assessments of Lung chest phantom images showed a bad effect on images. The higher a pitch was increased, the worse an image were showed because of rising beam hardening artifacts. Nodule figure & visibility, visibility of lesion, resolution between lower margin of lung and diaphragm, lung vessel definition and overall image quality were evaluated. When scan range was 32 cm, Spiral mode chest exam scored five points out of five, which is the highest score recorded. When the respiratory range in adult patients was both 4 and 2 second, lesion observation was possible with Flash mode of 1.55 and 2.5 pitch and in pediatric patients, only Spiral mode over 1.5 pitch can catch lesion. The higher a pitch of Flash mode used 32cm was, the more scan time was decreased. In Flash mode, CTDIvol value was 19% dose reduction. IV. Conclusions Motion artifact of irregular breathing has a bad effect on diagnostic images. Our experiments show that when Flash mode is adapted in exam, this artifacts are remarkably decreased with high image quality. Also, there is 19% dose reduction. When the respiratory range in adult patients was both 4 and 2 second, it was the best to adapt 2.5 pitch of Flash mode. For pediatric patients, we got the best image on all pitch of Flash mode. Chest CT exam is very critical about lung disease as diagnostic image and shows a significant increase because of f/u(follow up) role. Thus, Chest CT using Flash mode is considered to be very useful in diagnostic imaging.

이론적 모델을 이용한 4DCT에서의 Motion Artifact 분석

김태호,윤제웅,강성희,서태석,Kim, Tae-Ho,Yoon, Jai-Woong,Kang, Seong-Hee,Suh, Tae-Suk 한국의학물리학회 2012 의학물리 Vol.23 No.3

본 연구에서는 호흡에 의한 표적의 움직임 모사가 가능한 팬톰을 이용, 나선형 4DCT 영상에서 발생되는 위상 내 모션 아티팩트(residual motion artifact)의 경향을 분석했으며, 그 특성 및 원인 분석을 위한 이론적 모델을 제시하였다. 표적의 움직임은 SI 방향의 1차원 사인파형을 적용하였으며, 주기는 4s로 고정, 진폭은 10, 20, 30 mm로 변화를 주었다. 표적의 움직임과 동조를 이루는 호흡신호를 얻은 후 이를 기반으로 최대흡기(Inhale peak, 0%)로부터 10% 위상간격(phase bin)으로 재분류하여 총 10개의 4DCT 영상을 재구성하였다. 각각의 진폭(10, 20, 30 mm)별로 획득된 총 30 사례의 영상은 RTP 시스템(CorePLAN, SC&J)에서 분석을 수행하였으며, 경계설정 시 오류를 줄이기 위해 contour window를 고정 값으로 설정한 후 SI 방향의 표적 지름변화를 측정하여 왜곡 정도를 평가 하였다. 각 위상 별 표적의 지름 변화를 측정한 결과 일정한 변화 경향을 확인할 수 있었다. 3 사례(10, 20, 30 mm) 모두 50% 위상(phase) 영상에서 비교적 작은 지름 변화가 관찰 되었는데 10 mm 진폭에서는 정지 영상 대비 변화가 없었고, 20 mm 진폭에서는 0.1 cm (5%)의 변화, 30 mm 진폭에서는 0.1 cm (5%) 변화를 확인할 수 있었다. 반면 30% 위상(phase) 또는 80% 위상 영상에서는 다른 위상 영상에 비해 표적 지름의 변화가 비교적 크게 나타남을 확인할 수 있었다. 10 mm 진폭에서는 정지 영상대비 최대 0.2 cm (10%) 지름 변화가 나타났고 20 mm 진폭에서는 최대 0.7 cm (35%)의 변화, 30 mm 진폭에서는 최대 0.9 cm (45%)의 지름 변화가 나타났다. 이상의 실측결과를 이론모델의 시뮬레이션 결과와 비교해 봤을 때 변화의 양적인 측면에서는 다소 차이가 발생되었지만 변화의 경향성을 확인하는 측면에서는 의미 있는 결과를 얻을 수 있었다. 본 연구의 결과를 통해 규칙적인 1차원 표적 움직임(sine motion)이 적용된 나선형 4DCT 영상에서도 위상 내 움직임에 의한 표적 지름변화가 발생될 수 있음을 확인했고 각 위상(phase)에서의 영상왜곡 정도가 위상 내 움직임의 속도에 비례함을 증명할 수 있었다. 또한 이상의 실측 결과를 이론모델에 적용하여 분석함으로써 위상 내 모션 아티팩트(residual motion artifact)의 발생원인 및 경향성 분석에 직관적 이해를 도울 수 있었고 이론모델에 기초한 분석 프로그램을 개발하여 특정 CT 파라미터(parameter) 상에서 영상왜곡을 줄이기 위한 최적의 위상(phase) 선택에 도움을 줄 수 있었다. In this study, we quantify the residual motion artifact in 4D-CT scan using the dynamic lung phantom which could simulate respiratory target motion and suggest a simple one-dimension theoretical model to explain and characterize the source of motion artifacts in 4DCT scanning. We set-up regular 1D sine motion and adjusted three level of amplitude (10, 20, 30 mm) with fixed period (4s). The 4DCT scans are acquired in helical mode and phase information provided by the belt type respiratory monitoring system. The images were sorted into ten phase bins ranging from 0% to 90%. The reconstructed images were subsequently imported into the Treatment Planning System (CorePLAN, SC&J) for target delineation using a fixed contour window and dimensions of the three targets are measured along the direction of motion. Target dimension of each phase image have same changing trend. The error is minimum at 50% phase in all case (10, 20, 30 mm) and we found that ${\Delta}S$ (target dimension change) of 10, 20 and 30 mm amplitude were 0 (0%), 0.1 (5%), 0.1 (5%) cm respectively compare to the static image of target diameter (2 cm). while the error is maximum at 30% and 80% phase ${\Delta}S$ of 10, 20 and 30 mm amplitude were 0.2 (10%), 0.7 (35%), 0.9 (45%) cm respectively. Based on these result, we try to analysis the residual motion artifact in 4D-CT scan using a simple one-dimension theoretical model and also we developed a simulation program. Our results explain the effect of residual motion on each phase target displacement and also shown that residual motion artifact was affected that the target velocity at each phase. In this study, we focus on provides a more intuitive understanding about the residual motion artifact and try to explain the relationship motion parameters of the scanner, treatment couch and tumor. In conclusion, our results could help to decide the appropriate reconstruction phase and CT parameters which reduce the residual motion artifact in 4DCT.

A motion artifact reduction method for dental CT based on subpixel-resolution image registration of projection data

Eldib, Mohamed Elsayed,Hegazy, Mohamed A.A.,Cho, Myung Hye,Cho, Min Hyoung,Lee, Soo Yeol Elsevier 2018 Computers in biology and medicine Vol.103 No.-

<P><B>Abstract</B></P> <P>High-resolution imaging is essential in three-dimensional (3D) CT image-based digital dentistry. A small amount of head motion during a CT scan can degrade the spatial resolution of the images to the extent where the efficacy of 3D image-based digital dentistry is greatly compromised. We introduce a retrospective motion artifact reduction (MAR) method for dental CTs that eliminates the necessity for any external motion tracking devices. Assuming that rigid-body motions are dominant in a dental scan of a human head, we extracted motion information from the projection data. By taking the cross-correlation between two successive projection data for every projection view, we determined the displacement of the projection data at each view. We experimentally found that any motion of the imaging object during the scan resulted in displacement of the projection data proportional to the motion amplitude. We decomposed the displacement into two components, one caused by translational motion and the other caused by rotational motion. The displacement components were used to correct the projection data before CT image reconstruction. We experimentally verified the MAR method using the projection data of a few phantoms acquired through a clinical dental CT machine. When the MAR performance was evaluated by the structural similarity index (SSIM) and the normalized absolute error (NAE) in reference to the motion-less images, the SSIM improved to 99% while the NAE was reduced by 80–90%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We introduce a retrospective motion artifact reduction (MAR) method for a dental CT. </LI> <LI> A subpixel image registration technique is used to estimate the motion-induced displacements. </LI> <LI> The proposed method can estimate all the motion components including translation and rotation. </LI> <LI> Actuator-controlled and manual motions have been applied on phantoms using a clinical dental CT. </LI> <LI> The experimental results demonstrate the high performance of the proposed method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

용량성 전극의 동잡음 측정 장치 연구

임용규,Lim, Yong Gyu 대한의용생체공학회 2017 의공학회지 Vol.38 No.3

The indirect-contact bio-electric measurements using capacitive electrodes show large motion artifacts in comparison with conventional direct-contact measurements. It is necessary to measure the motion artifacts quantitatively, for the researches of reducing the motion artifacts. In this study, a device for quantitative measurement of motion artifacts was built. Using the device, an electrode was rubbed against some cloth(cotton) and the voltage variation of the electrode was measured as motion artifact in several environmental conditions(temperature and relative humidity). The measured waveforms agreed with that expected by the triboelectricity and the prior observations of the motion artifacts. Therefore, the results demonstrated the usability of the measurement system built in this study. The measurement system will be a great contribution to future research for reducing motion artifact.

관상동맥 CT검사 시 운동 인공물 감소를 위한 SnapShot Freeze Mode의 유용성 평가

김지원(Ji Won Kim),이상우(Sang Woo Lee) 대한CT영상기술학회 2013 대한CT영상기술학회지 Vol.15 No.1

Ⅰ. Purpose Few many technologies are developed for decrease of radiation exposure by increasing usage of CTCA. Among the before, EKG gating technique is used mostly that able to correct images; using prospective EKG gating which can edit images of other phase if non-diagnostic image is acquired. But, it has disadvantages that correction is impossible when pitch is false or heart-rate is irregular. Thus, not only additional contrast medium injection, but also radiation dose exposure is used by reexamination. We have evaluated the useful of the developed Snapshot Freeze mode for overcoming this limitation. Ⅱ. Meterial and Methods Discovery CT750 HD (GE Healthcare, Milwaukee, Wisconsin, USA), Low-contrast Artery Insert Phantom (Model76-715), and respiratory moving phantom (private product) are used. Low-contrast Artery Insert is located on moving phantom moving above and below. Phantom is scanned on the supposition that heart-rate is 40~70 bpm, and pitch is altered 0.18, 0.20, 0.22, 0.24. The standard of correction is evaluated by measure artery diameter. Snapshot Freeze Mode applied to twenty six patients who get non-diagnostic image of coming to AMC Health Screening Center. Ⅲ. Result In phantom study, the more artery diameter is increased as heart-rate increases, the more pitch and heart-rate are mismatches. It is mostly corrected by Snapshot Freeze Mode, but limited in case of severe artifacts. In clinical study, images corrected by Snapshot Freeze Mode are better than prospective ECG gating images. Results shows better correction degree in more than 67 bpm, but it couldn’t apply to all of frequency heart-rate. Axial images good at motion artifacts correction, but most sagittal images are inadequate for diagnosis because of step stair artifacts. Ⅳ. Conclusions The motion artifacts due to inappropriate respiration and irregular heart-rate have a bad effect on diagnosis using CTCA. For this reason, the prospective ECG gating technique which requires considerable radiation dose has been used, Meanwhile, Snapshot Freeze Mode available to dose reduction is used. Not Snapshot could decrease all of artifacts, but if we solve stair-step artifact on sagittal and shorten image reconstruction time, it is probably a valuable software on CTCA. 목적 CTCA검사 시 심전도 동기화 기법이 많이 사용되어지는 데, 진단에 부적합한 영상을 얻었을 경우 후향적 심전도 동기화를 이용하여 다른 심주기의 영상을 재구성해 어느 정도 보정이 가능하다. 그러나 Pitch 사용이 맞지 않거나 환자의 심박수가 일정하지 않을 경우 보정이 불가능하여 추가적인 조영제 투여와 추가선량으로 재검사를 시행해야 한다는 단점이 있다. 이러한 한계를 보완하기 위해 개발된 기술 중, SnapShot Freeze 모드를 이용하여 그 유용성을 평가하였다. 대상 및 방법 CT 장비는 GE사의 Discovery CT750 HD(GE Healthcare, Milwaukee, Wisconsin, USA)을 사용하였고, Phantom은 Low-contrast Artery Insert(Model 76-715), 본원 방사선 종양학과에서 자체 제작한 respiratory moving phantom을 사용하였다. Phantom연구는 Moving Phantom위에 Low-contrast Artery Insert를 위치시키고, Moving Phantom을 상하(inferior-superior) 방향으로 움직이게 하여 심박수가 40~70 bpm일 때를 가정해 Pitch만 0.18, 0.20, 0.22, 0.24로 변경하며 촬영, Artery의 두께를 측정하여 보정정도를 평가하였다. 임상 연구는 본 원에 내원한 건진 환자 중 진단에 부적합한 영상을 얻은 26명을 대상으로 SnapShot Freeze Mode를 적용해, 후향적 심전도 동기화 영상과 비교 평가하였다. 결과 Phantom연구에서, 설정한 심박수와 Pitch값이 맞지 않을수록, 심박수가 높을수록 영상에서 측정한 Artery의 두께가 증가되었다. 대부분의 경우에서 Snapshot Freeze Mode에 의해 보정되었으며, 인공물의 정도가 심한 경우는 보정에 한계가 있었다. 임상연구에서 Snapshot Freeze Mode에 의해 보정된 영상은 비교대상이었던 후향적 심전도 동기화 영상과 비교하였을 때, 비슷하거나 더 좋은 결과를 보여주었다. 67 bpm 이상의 높은 심박수의 영역에서 더 나은 보정정도를 보여주었으나, 모든 경우의 심박수에서 SnapShot Freeze Mode 영상이 후향적 심전도 동기화 영상보다 월등하다 보기는 어려울 것으로 보인다. Axial 영상의 경우 motion artifact의 보정에 탁월한 효과를 보였으나, Sagittal 영상은 대부분 Stair-step artifact가 심해 임상적 진단 효율이 낮았다. 결론 호흡조절의 실패나 불규칙한 심박동수의 변화로 생기는 Motion artifact는 CTCA의 진단에 어려움을 준다. 이를 위해 사용되었던 후향적 심전도 동기화 기법은 많은 선량을 필요로 하였으나, SnapShot Freeze Mode를 사용함으로써 환자의 피폭선량 감소에 많은 도움이 되었다. 그러나 SnapShot Freeze Mode가 모든 경우의 artifact을 감소시킬 수 있는 것은 아니었으며, Sagittal 영상에서 생기는 stair-step artifact 보정문제를 해결하고, 영상재구성 시간을 단축시켜 적용한다면 CTCA검사에서 아주 유용한 소프트웨어가 될 것으로 사료된다.

Cancellation of MRI Motion Artifact in Image Plane

Kim Eung-Kyeu The Korea Institute of Convergence Signal Processi 2000 융합신호처리학회 논문지 (JISPS) Vol.1 No.1

In this study, a new algorithm for canceling a MRI artifact due to the translational motion In the image plane is described. Unlike the conventional iterative phase retrieval algorithm, in which there is no guarantee for the convergence, a direct method for estimating the motion is presented. In previous approaches, the motions in the x(read out) direction and the y(phase encoding) direction were estimated simultaneously. However, the feature of x and y directional motions are different from each other. By analyzing their features, each x and y directional motion is canceled by the different algorithms in two steps. First, it is noticed that the x directional motion corresponds to a shift of the x directional spectrum of the MRI signal, and the non-zero area of the spectrum just corresponds to the projected area of the density function on the x axis. So the motion is estimated by tracing the edges between non-zero area and zero area of the spectrum, and the x directional motion is canceled by shifting the spectrum in an reverse direction. Next, the y directional motion is canceled by using a new constraint condition, with which the motion component and the true image component can be separated. This algorithm is shown to be effective by using a phantom image with simulated motion.

Seismic fragility analysis of sliding artifacts in nonlinear artifact-showcase-museum systems

Pei Liu,Zhi-Hao Li,Wei-Guo Yang 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.3

Motivated by the demand of seismic protection of museum collections and development of performance-based seismic design guidelines, this paper investigates the seismic fragility of sliding artifacts based on incremental dynamic analysis and three-dimensional finite element model of the artifact-showcase-museum system considering nonlinear behavior of the structure and contact interfaces. Different intensity measures (IMs) for seismic fragility assessment of sliding artifacts are compared. The fragility curves of the sliding artifacts in both freestanding and restrained showcases placed on different floors of a four-story reinforced concrete frame structure are developed. The seismic sliding fragility of the artifacts within a real-world museum subjected to bi-directional horizontal ground motions is also assessed using the proposed IM and engineering demand parameter. Results show that the peak floor acceleration including only values initiating sliding is an efficient IM. Moreover, the sliding fragility estimate for the artifact in the restrained showcase increases as the floor level goes higher, while it may not be true in the freestanding showcase. Furthermore, the artifact is more prone to sliding failure in the restrained showcase than the freestanding showcase. In addition, the artifact has slightly worse sliding performance subjected to bi-directional motions than major-component motions.

체표 변화에 기반한 심전도 모니터링 의류의 센싱 위치 연구

조하경 ( Ha Kyung Cho ),조상우 ( Sang Woo Cho ) 한국의류산업학회 2015 한국의류산업학회지 Vol.17 No.5

Recently, according to change of lifestyle and increase of concerning in health, needs of the smart clothing based on the vital sign monitoring have increased. Along with this trend, smart clothing for ECG monitoring has been studied various way as textile electrode, clothing design and so on. Smart clothing for ECG monitoring can become a comfortable system which enables continuous vital sign monitoring in daily use. But, smart clothing for ECG monitoring has a weakness on artifact during motion. One of the motion artifact caused by shifting of the electrode position was affected skin change by motion. The aim of this study was to suggest electrode locations for clothing of ECG monitoring to reduce of motion artifacts. Therefore, change of skin surface during the movement were measured and analyzed in order to find location to minimize motion artifacts in ECG monitoring clothing by 3D motion capture. For the experiment, the subjects consisted of 5 males and 5 females in their 20’ with average physique. As a result, the optimal location for ECG monitoring was deducted under the bust line and scapula which have least motion artifact. These locations were abstracted to be least affected by movement in this research.

연구논문 : 비접촉식 심장활동 모니터링 기능 의복형 웨어러블 시스템의 모듈 효과 탐색

구혜란 ( Hye Ran Koo ),이영재 ( Young Jae Lee ),지선옥 ( Sunok Gi ),이승표 ( Seung Pyo Lee ),김경남 ( Kyeng Nam Kim ),강승진 ( Seung Jin Kang ),이정환 ( Jeong Whan Lee ),이주현 ( Joo Hyeon Lee ) 한국의류학회 2015 한국의류학회지 Vol.39 No.3

Various forms of wearable bio-signal monitoring systems have been developed recently. Acquisition of stable bio-signal data for health care purposes needs to be unconscious and continuous without hindrance to the users`` daily activities. The garment type is a suitable form of a wearable bio-signal monitoring system; however, motion artifacts caused by body movement degrade the signal quality during the measurement of bio-signals. It is crucial to stabilize the electrode position to reduce motion artifacts generated when in motion. The problems with motion artifacts remain unresolved despite their significant effect on bio-signal monitoring. This research creates a foundation for the design of garment-type wearable systems for everyday use by finding a method to reduce motion artifacts through modular design. Two distinct garment-type wearable systems (tee-shirt with a motion artifact-reducing module (MARM) and tee-shirt without a MARM) were designed to compare the effects of modular design on the measurement of heart activity in terms of electrode position displacement, signal quality index value, and morphological quality. The tee-shirt with MARM showed superior properties and yielded higher quality signals than the tee-shirt without MARM. In addition, the tee-shirt with MARM showed a better repeatability of the heart activity signals. Therefore, a garment design with MARM is an efficient way to acquire stable bio-signals while in motion.

U-헬스케어 시스템을 위한 개선된 PMAF 기반의 PPG 신호의 동잡음 제거

이한욱(Hanwook Lee),이주원(Juwon Lee),정원근(Wongeun Jeong),전재철(Jaechul Jun),이건기(Gunki Lee) 대한전자공학회 2008 電子工學會論文誌-SC (System and control) Vol.45 No.5

유비쿼터스 헬스케어 환경의 실현을 위해 실시간의 생체 정보 모니터링은 매우 중요한 요소이다. 이러한 생체 정보 모니터링을 위한 장치는 대부분 PPG 신호를 얻어 피측정자의 상태 모니터링에 활용하고 있다. PPG 신호를 얻기 위해서는 핑거프로브를 손가락에 착용해야 하기 때문에 일상생활을 하기에 불편할 뿐만 아니라, 핑거 프로브 착용자의 움직임에 의한 동잡음으로 인하여 정확한 PPG신호를 얻기가 매우 힘들다. 본 논문에서는 핑거프로브를 없앤 U-헬스케어를 위한 손목형 생체 정보모니터링 시스템을 개발하고, 생체 정보 모니터링 시스템의 감시 요소 중 하나인 PPG 신호의 동잡음 제거를 위해 새로운 알고리즘을 제안한다. 개발한 시스템은 핑거프로브를 없앤 대신 밴드스트립에 LED와 포토센서를 장착하여 손목의 동맥혈관의 혈류 변화량으로부터 PPG를 얻도록 설계하였다. 그러나 밴드스트립에 위치한 센서는 핑거프로브에 위치한 센서에 비해 많은 동잡음에 노출되어 있으므로, 그 동잡음들을 제거하기 위하여 최근 제기된 PPG 신호의 유사 주기성을 이용한 PMAF(Periodic Moving Average Filter) 방법을 개선한 새로운 동잡음 제거 방법을 제안한다. The real-time biomedical signal monitoring is a very important factor to realize the ubiquitous healthcare environment. Most of these devices for monitoring the biomedical information get the PPG signal from the user, and these signals are utilized for monitoring their health. It is inconvenient to get the PPG because the user should wear the finger probe with his finger for measuring the PPG signal. Also it is difficult to get the PPG correctly, because of the motion artifacts from the movement of the user. In this paper, we develop the watch type biomedical signal monitoring system without the finger probe, and propose the new algorithm for reducing the motion artifacts from the PPG signal. We designed the system which gets the PPG from the sensor on the wrist band strip. As compared with the finger probe type, this system we proposed is more affected by the motion artifacts. So to filter this motion artifacts, we propose the new method; the improved PMAF(Periodic Moving Average Filter) method.