Improvement in the Accuracy of Respiratory-gated Radiation Therapy Using a Respiratory Guiding System

강승희,김동수,김태호,서태석,윤제웅 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.1

The accuracy of respiratory-gated radiation therapy (RGRT) depends on the respiratory regularity because external respiratory signals are used for gating the radiation beam at particular phases. Many studies have applied a respiratory guiding system to improve the respiratory regularity. This study aims to evaluate the effect of an in-house-developed respiratory guiding system to improve the respiratory regularity for RGRT. To verify the effectiveness of this system, we acquired respiratory signals from five volunteers. The improvement in respiratory regularity was analyzed by comparing the standard deviations of the amplitudes and the periods between free and guided breathing. The reduction in residual motion at each phase was analyzed by comparing the standard deviations of sorted data within each corresponding phase bin as obtained from free and guided breathing. The results indicate that the respiratory guiding system improves the respiratory regularity, and that most of the volunteers showed significantly less average residual motion at each phase. The average residual motion measured at phases of 40, 50, and 60%, which showed lower variation than other phases, were, respectively, reduced by 41, 45, and 44% during guided breathing. The results show that the accuracy of RGRT can be improved by using the in-house-developed respiratory guiding system. Furthermore, this system should reduce artifacts caused by respiratory motion in 4D CT imaging.

IGRT를 위한 비침습적인 호흡에 의한 장기 움직임 실시간 추적시스템

김윤종,윤의중,Kim, Yoon-Jong,Yoon, Uei-Joong 대한의용생체공학회 2007 의공학회지 Vol.28 No.5

A non-invasive respiratory gated radiotherapy system like those based on external anatomic motion gives better comfortableness to patients than invasive system on treatment. However, higher correlation between the external and internal anatomic motion is required to increase the effectiveness of non-invasive respiratory gated radiotherapy. Both of invasive and non-invasive methods need to track the internal anatomy with the higher precision and rapid response. Especially, the non-invasive method has more difficulty to track the target position successively because of using only image processing. So we developed the system to track the motion for a non-invasive respiratory gated system to accurately find the dynamic position of internal structures such as the diaphragm and tumor. The respiratory organ motion tracking apparatus consists of an image capture board, a fluoroscopy system and a processing computer. After the image board grabs the motion of internal anatomy through the fluoroscopy system, the computer acquires the organ motion tracking data by image processing without any additional physical markers. The patients breathe freely without any forced breath control and coaching, when this experiment was performed. The developed pattern-recognition software could extract the target motion signal in real-time from the acquired fluoroscopic images. The range of mean deviations between the real and acquired target positions was measured for some sample structures in an anatomical model phantom. The mean and max deviation between the real and acquired positions were less than 1mm and 2mm respectively with the standardized movement using a moving stage and an anatomical model phantom. Under the real human body, the mean and maximum distance of the peak to trough was measured 23.5mm and 55.1mm respectively for 13 patients' diaphragm motion. The acquired respiration profile showed that human expiration period was longer than the inspiration period. The above results could be applied to respiratory-gated radiotherapy.

Determination of Target Motion by Using a Respiration Monitoring Mask for 4-D Radiotherapy

정태식,임상욱,박성호,안승도,이병용,이상훈,조광환,장지선,권수일,조삼주,허현도,신동호,서태석,김철용,이석 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

The normal tissue toxicity encountered in lung cancer radiotherapy is frequently due to large treatment margins. The organ motion due to respiration necessitates that large margins be added to the planning target volume (PTV) to ensure adequate dose coverage in the chest and abdomen. Many techniques have been developed to minimize the irradiated volume of normal tissue, including gated radiotherapy, breath-holding techniques, and motion adaptive radiotherapy. If these techniques are to be utilized effectively, the precise four-dimensional (4-D) localization of a moving tumor must be available in real time. The aim of this study is to develop a simple, useful respiration-monitoring mask (ReMM) that identifies respiration-induced organ motion during the clinical application of 4-D radiotherapy. A thermocouple was embedded in a dust-proof mask and connected to a thermocouple module, which amplified the signal from the thermocouple. The dust-proof mask and the thermocouple were used to measure the respiratory movements of the patient during radiation therapy. Three patients and three healthy volunteers were enrolled to investigate the utility of the ReMM. The thermocouple measured the temperature of the mask during respiration. The diaphragmatic motion along a craniocaudal direction was simultaneously monitored using a uoroscope. The relationship between the respiratory pattern and the targeted motion along the craniocaudal direction was evaluated using a correlation coefficient. Respiration-induced target motion along a ventrodorsal direction was less than 5 mm for each patient. However, target motion along the craniocaudal direction was up to 3 cm in this study. The temperature in the mask does not drift more than 5 % of its maximum amplitude, even for a "held- time" of more than 10 seconds. The average correlation coefficients between the target motions during respiration along the craniocaudal direction and the ReMM signals were 0.91 for the eight cases. The ReMM signal showed strong correlation with the target motion, compared to the target motion in uoroscopy, despite irregular breathing. ReMM is a noninvasive breathing surrogate apparatus. Our study shows that the target motion correlates with the ReMM signal. However, no baseline-drifting problem exists in this system. The spirometer, the skin motion, and the strain gauge have been reported to have gradual drifting problems. The thermocouple is accurate and can be practically applied for monitoring respiration for the determination of target organ motion. The authors hope that the ReMM can be used in 4-D radiotherapy, such as gated radiation therapy, motion-adaptive radiation therapy, retrospective CT, and prospective CT.

The Effects of Breathing Motion on DCE-MRI Images: Phantom Studies Simulating Respiratory Motion to Compare CAIPIRINHA-VIBE, Radial-VIBE, and Conventional VIBE

이창경,서니은,김보현,허지미,김정곤,이승수,김인성,Dominik Nickel,김경원 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.2

Objective: To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment. Materials and Methods: We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability. Results: With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction. Conclusion: CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.

Combined Electrocardiography- and RespiratoryTriggered CT of the Lung to Reduce Respiratory Misregistration Artifacts between Imaging Slabs in Free-Breathing Children: Initial Experience

구현우,Thomas Allmendinger 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.5

Objective: Cardiac and respiratory motion artifacts degrade the image quality of lung CT in free-breathing children. The aim of this study was to evaluate the effect of combined electrocardiography (ECG) and respiratory triggering on respiratory misregistration artifacts on lung CT in free-breathing children. Materials and Methods: In total, 15 children (median age 19 months, range 6 months–8 years; 7 boys), who underwent freebreathing ECG-triggered lung CT with and without respiratory-triggering were included. A pressure-sensing belt of a respiratory gating system was used to obtain the respiratory signal. The degree of respiratory misregistration artifacts between imaging slabs was graded on a 4-point scale (1, excellent image quality) on coronal and sagittal images and compared between ECGtriggered lung CT studies with and without respiratory triggering. A p value < 0.05 was considered significant. Results: Lung CT with combined ECG and respiratory triggering showed significantly less respiratory misregistration artifacts than lung CT with ECG triggering only (1.1 ± 0.4 vs. 2.2 ± 1.0, p = 0.003). Conclusion: Additional respiratory-triggering reduces respiratory misregistration artifacts on ECG-triggered lung CT in freebreathing children.

The Effects of Breathing Motion on DCE-MRI Images: Phantom Studies Simulating Respiratory Motion to Compare CAIPIRINHA-VIBE, Radial-VIBE, and Conventional VIBE

Lee, Chang Kyung,Seo, Nieun,Kim, Bohyun,Huh, Jimi,Kim, Jeong Kon,Lee, Seung Soo,Kim, In Seong,Nickel, Dominik,Kim, Kyung Won The Korean Society of Radiology 2017 KOREAN JOURNAL OF RADIOLOGY Vol.18 No.2

<P><B>Objective</B></P><P>To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment.</P><P><B>Materials and Methods</B></P><P>We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability.</P><P><B>Results</B></P><P>With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (<I>p</I> < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, <I>p</I> < 0.001) and radial-VIBE (from 4.3 to 4.96, <I>p</I> < 0.001) after motion correction.</P><P><B>Conclusion</B></P><P>CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.</P>

Development of an Advanced Deformable Phantom to Analyze Dose Differences due to Respiratory Motion

Shin, Dong-Seok,Kang, Seong-Hee,Kim, Dong-Su,Kim, Tae-Ho,Kim, Kyeong-Hyeon,Koo, Hyun-Jae,Cho, Min-Seok,Ha, Jin-Suk,Yoon, Do-Kun,Suh, Tae Suk Korean Society of Medical Physics 2017 의학물리 Vol.28 No.1

The difference between three-dimensional (3D) and four-dimensional (4D) dose could be affected by factors such as tumor size and motion. To quantitatively analyze the effects of these factors, a phantom that can independently control each factor is required. The purpose of this study is to develop a deformable lung phantom with the above attributes and evaluate the characteristics. A phantom was designed to simulate diaphragm motion with amplitude in the range 1~7 cm and period up to ${\geq}2s$ of regular breathing. To simulate different tumors sizes, custom molds were created using a 3D printer and filled with liquid silicone. The accuracy of the phantom diaphragm motion was assessed by comparing measured motion with predicted motion. Because the phantom diaphragm motion is not identical to the tumor motion, the correlation between the diaphragm and tumor motions was calculated by a curve fitting method to emulate user-intended tumor motion. Tumors of different sizes were located at same position, and tumor set-up positions were evaluated. The accuracy of phantom diaphragm motion was better than 1 mm. The diaphragm-tumor correlation showed that the tumor motion in the superior-inferior direction increased with increasing diaphragm motion. The tumor motion was larger in the $10cm^3$ tumor than in the $90cm^3$ tumor. The range of difference between the tumor set-up positions was 0 to 0.45 cm. This phantom showed independently adjusting factors such as tumor size and motion to facilitate quantitative analysis of the dosimetric impact of respiratory motion according to these factors.

조영증강 초음파 진단에서 호흡에 의한 움직임 보정 기법

박소정(SoJeong Park),이승강(Seung-Kang Lee),김호준(Ho-Joon Kim) 한국정보과학회 2013 정보과학회논문지 : 소프트웨어 및 응용 Vol.40 No.3

본 연구에서는 의료 진단 초음파 진단과정에서 호흡으로 인한 흔들림 현상을 보정하는 ROI 추적 기법을 제안한다. 조영증강 초음파 진단에서 조영효과의 전이시간(transit time)은 간 섬유화 정도를 판별하는 중요한 파라미터로 사용된다. 조영증강 초음파 데이터에서 나타나는 마이크로 버블 형태의 노이즈와 호흡에 의한 흔들림 현상은 픽셀단위의 영상처리 과정을 어렵게 할 뿐만 아니라 유사도(similarity) 평가를 기반으로 하는 ROI 추적 과정에서 성능저하의 원인이 된다. 이를 위하여 초음파 진단 데이터에서 조영제 확산효과의 측정 곡선을 4개의 단계로 구분하고, 단계의 특성과 호흡주기에 따른 움직임에 대한 모멘텀 요소를 고려하여 동적 가중치를 정의하였다. 제안된 방법이 초음파 진단에서 호흡에 의한 흔들림을 보정함으로써 간 섬유화 진단과정에서 신뢰도를 향상시킬 수 있음을 실험을 통하여 고찰하였다. In this paper, we propose a ROI tracking method for correcting the respiratory motion in ultrasonography. The transit time of contrast-enhanced ultrasound is an important parameter to assess the stages of liver fibrosis in patients with liver disease. Respiratory motion and micro-bubble noise in the ultrasound data may bring some difficulties in pixel-based image processing and may be the cause of performance degradation in similarity-based ROI tracking processes. We have classified the time-intensity curve into four stages and defined the dynamic weights which reflect the momentum of the respiratory motion. Through the experiments, we have shown that the proposed method improves the reliability of the liver-fibrosis assessment process by compensating the respiratory motion in ultrasonography.

Feasibility Study of Robotics-based Patient Immobilization Device for Real-time Motion Compensation

Chung, Hyekyun,Cho, Seungryong,Cho, Byungchul Korean Society of Medical Physics 2016 의학물리 Vol.27 No.3

Intrafractional motion of patients, such as respiratory motion during radiation treatment, is an important issue in image-guided radiotherapy. The accuracy of the radiation treatment decreases as the motion range increases. We developed a control system for a robotic patient immobilization system that enables to reduce the range of tumor motion by compensating the tumor motion. Fusion technology, combining robotics and mechatronics, was developed and applied in this study. First, a small-sized prototype was established for use with an industrial miniature robot. The patient immobilization system consisted of an optical tracking system, a robotic couch, a robot controller, and a control program for managing the system components. A multi speed and position control mechanism with three degrees of freedom was designed. The parameters for operating the control system, such as the coordinate transformation parameters and calibration parameters, were measured and evaluated for a prototype device. After developing the control system using the prototype device, a feasibility test on a full-scale patient immobilization system was performed, using a large industrial robot and couch. The performances of both the prototype device and the realistic device were evaluated using a respiratory motion phantom, for several patterns of respiratory motion. For all patterns of motion, the root mean squared error of the corresponding detected motion trajectories were reduced by more than 40%. The proposed system improves the accuracy of the radiation dose delivered to the target and reduces the unwanted irradiation of normal tissue.

간암의 방사선치료 시 호흡운동 감소장치(respiratory motion reduction device, RRD)의 유용성에 관한 연구

이석(Suk Lee),성진실(Jinsil Seong),김용배(Yong Bae Kim),조광환(Kwang Hwan Cho),김주호(Joo Ho Kim),장세경(Sae Kyung Jang),권수일(Soo Il Kwon),추성실(Sung Sil Chu),서창옥(Chang Ok Suh) 대한방사선종양학회 2001 Radiation Oncology Journal Vol.19 No.4

Purpose: Planning target volume (PTV) for tumors in abdomen or thorax includes enough margin for breathing-related movement of tumor volumes during treatment. Depending on the location of the tumor, the magnitude of PTV margin extends from 10mm to 30mm, which increases substantial volume of the irradiated normal tissue hence, resulting in increase of normal tissue complication probability (NTCP). We developed a simple and handy method which can reduce PTV margins in patients with liver tumors, respiratory motion reduction device (RRD). Materials and methods: For 10 liver cancer patients, the data of internal organ motion were obtained by examining the diaphragm motion under fluoroscope. It was tested for both supine and prone position. A RRD was made using MeV-Green and Styrofoam panels and then applied to the patients. By analyzing the diaphragm movement from patients with RRD, the magnitude of PTV, the magnitude of PTV margin was determined and dose volume histogram (DVH) was computed using AcQ-Plan, a treatment planning software. Dose to normal tissue between patients with RRD and without RRD was analyzed by comparing the fraction of the normal liver receiving to 50% of the isocenter dose. DVH and NTCP for normal liver and adjacent organs were also evaluated. Results: When patients breathed freely, average movement of disphragm was 12±1.9 m m in prone position in contrast to 16±1.9 mm in supine position. In prone position, difference in diaphragm movement with and without RRD was 3±0.9 mm and 12 mm, respectively, showing that PTV margins could be reduced to as much as 9 mm. With RRD, volume of the irradiated normal liver reduced up to 22.7% in DVH analysis. Conclusion: Internal organ motion due to breathing can be reduced using RRD, which is simple and easy to use in clinical setting. It can reduce the organ motion-related PTV margin, thereby decrease volume of the irradiated normal tissue. 목적: 폐, 간 등의 상 복부에 위치한 종양의 방사선 조사 체적은 호흡에 의한 종양의 이동을 포함하는 영격으로 조사 체적이 증가된다. 이로 인하여 방사선 독성 및 정상조직 선량이 증가되며, 호흡으로 인한 환자자세의 변화로 인해 종양의 정확한 위치파악이 어렵게 된다. 본 연구에서는 호흡에 따른 장기 움직임 유형을 분석하여 호흡에 의한 장기의 움직임을 최소화 할 수 있는 호흡운동 감소장치를 고안하고 방사선치료 시 호흡운동 감소장치의 유용성을 평가해 보고자 하였다. 대상 및 방법: 간암환자 10명을 대상으로 하여 MeV-Green과 벨트, 스티로폼판 등을 사용하여 호흡운동감소장치(respiratory motion reduction device, RRD)를 제작하였다. 내부장기의 이동정도는 모의치료 시에 관찰된 횡경막의 이동 정도로 평가하였으며 앙와위와 복와위 및 RRD의 사용 시 이동정도를 알아보았고, 각각의 경우에서 이동정도를 고려하여 방사선치료계획을 수립하였다. 선량체적 히스토그램(dose-volume histogram, DVH)을 통해서 전체 간 용적중 처방선량의 50%가 조사되는 정상간 용적을 구하였다. 결과: 호흡에 EKfms 횡경막의 평균이동거리는 앙와위 자세에서 16±1.9mm이었고, 복와위 자세에서는 12±1.9mm임을 알 수 있었다. 복와위 자세에서 본원에서 자체 제작한 RRD를 사용한 경우에는 5±1.4mm으로 감소되었고, 벨트 고정장치의 추가 사용 시에는 3±0.9mm으로 감소하여 총 9mm 감소함을 알 수 있었다. 방사선치료계획에 따른 DVH에서 처방선량의 50%가 조사되는 정상간의 용적은 호흡운동감소장치를 사용하지 않은 경우에 앙와위 자세에서 43,7%, 복와위 자세에서 40%이었고, 호흡운동 감소장치를 사용한 경우에 복와위 자세에서 30.7%, 여기에 벨트 고장장치를 추가 사용하였을 경우에는 21%로서 전체 간 용적 중 방사선에 조사되는 정상 간 용적은 최대 22.7% 감소됨을 알 수 있었다. 결론: 호흡에 따른 내부장기의 움직임을 최소화 할 수 있는 RRD를 사용하여 정상조직에 불필요하게 조사되는 방사선을 감소시킬 수 있었다.