Simultaneous acquisition of 4D ultrasound and wireless electromagnetic tracking for <i>in-vivo</i> accuracy validation

Ipsen, Svenja; Bruder, Ralf; Worm, E.; Hansen, Rune; Poulsen, Per Rugaard; Høyer, Morten; Schweikard, Achim

doi:10.1515/cdbme-2017-0016

Cited by 5 publications

(10 citation statements)

References 8 publications

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“…The motion we extracted from the ultrasound images was in high agreement with the EM signal with an in‐plane RMSE below 1 mm. The study presented by Ipsen et al . reported an even lower RMSE of 0.55 mm for their in vivo acquisition of simultaneous ultrasound and EM motion tracking.…”

Section: Discussionmentioning

confidence: 99%

“…Five motion traces (Sine10, Sine20, Chirp10, Chirp20, and Pat) were applied twice to ELPHA while either ultrasound or EM measurements were taken. The measurements were taken consecutively, since the operation of the EM detection system introduces image artifacts in the ultrasound images . The setup was kept the same for both measurements.…”

Section: Methodsmentioning

confidence: 99%

“…The measurements were taken consecutively, since the operation of the EM detection system introduces image artifacts in the ultrasound images. 23 The setup was kept the same for both measurements. While the EM transponders only give the motion of one point, three structures were chosen to be tracked in the US image: the central vessel with the implanted EM transponders, a second vessel more lateral to the central vessel, and the liver boundary.…”

Section: F Comparison Of Ultrasound Tracking and Electromagnetic Tmentioning

confidence: 99%

“…Ultrasound imaging being a low‐cost, real‐time, and nonionizing method, has the benefit of no additional imaging radiation to the patient and no need for marker implantation, while maintaining good soft tissue contrast in abdominal organs. The feasibility of ultrasound‐guided MLC tracking has been shown previously and in vivo ultrasound imaging of respiratory liver motion during a radiotherapy treatment has shown good agreement with the motion of implanted electromagnetic markers …”

Section: Introductionmentioning

confidence: 99%

“…The feasibility of ultrasoundguided MLC tracking has been shown previously 22 and in vivo ultrasound imaging of respiratory liver motion during a radiotherapy treatment has shown good agreement with the motion of implanted electromagnetic markers. 23 Motion-adaptive treatments are highly complex. All involved systems, that is, the radiation generation and beam shaping, the motion quantification, the information processing and the motion adaptation, have to work simultaneously and synergistically.…”

Section: Introductionmentioning

confidence: 99%

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ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

et al. 2019

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Purpose Real‐time motion‐adaptive radiotherapy of intrahepatic tumors needs to account for motion and deformations of the liver and the target location within. Phantoms representative of anatomical deformations are required to investigate and improve dynamic treatments. A deformable phantom capable of testing motion detection and motion mitigation techniques is presented here. Methods The dynamically dEformable Liver PHAntom (ELPHA) was designed to fulfill three main constraints: First, a reproducibly deformable anatomy is required. Second, the phantom should provide multimodality imaging contrast for motion detection. Third, a time‐resolved dosimetry system to measure temporal effects should be provided. An artificial liver with vasculature was casted from soft silicone mixtures. The silicones allow for deformation and radiographic image contrast, while added cellulose provides ultrasonic contrast. An actuator was used for compressing the liver in the inferior direction according to a prescribed respiratory motion trace. Electromagnetic (EM) transponders integrated in ELPHA help provide ground truth motion traces. They were used to quantify the motion reproducibility of the phantom and to validate motion detection based on ultrasound imaging. A two‐dimensional ultrasound probe was used to follow the position of the vessels with a template‐matching algorithm. This detected vessel motion was compared to the EM transponder signal by calculating the root‐mean‐square error (RMSE). ELPHA was then used to investigate the dose deposition of dynamic treatment deliveries. Two dosimetry systems, radio‐chromic film and plastic scintillation dosimeters (PSD), were integrated in ELPHA. The PSD allow for time‐resolved measurement of the delivered dose, which was compared to a time‐resolved dose of the treatment planning system. Film and PSD were used to investigate dose delivery to the deforming phantom without motion compensation and with treatment‐couch tracking for motion compensation. Results ELPHA showed densities of 66 and 45 HU in the liver and the surrounding tissues. A high motion reproducibility with a submillimeter RMSE (<0.32 mm) was measured. The motion of the vasculature detected with ultrasound agreed well with the EM transponder position (RMSE < 1 mm). A time‐resolved dosimetry system with a 1 Hz time resolution was achieved with the PSD. The agreement of the planned and measured dose to the PSD decreased with increasing motion amplitude: A dosimetric RMSE of 1.2, 2.1, and 2.7 cGy/s was measured for motion amplitudes of 8, 16, and 24 mm, respectively. With couch tracking as motion compensation, these values decreased to 1.1, 1.4, and 1.4 cGy/s. This is closer to the static situation with 0.7 cGy/s. Film measurements showed that couch tracking was able to compensate for motion with a mean target dose within 5% of the static situation (−5% to +1%), which was higher than in the uncompensated cases (−41% to −1%). Conclusions ELPHA is a deformable liver phantom with high motion reproducibility. It was demonstrated t...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: F Comparison Of Ultrasound Tracking and Electromagnetic Tmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

et al. 2019

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Real‐time motion monitoring using orthogonal cine MRI during MR‐guided adaptive radiation therapy for abdominal tumors on 1.5T MR‐Linac

et al. 2023

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Background Real‐time motion monitoring (RTMM) is necessary for accurate motion management of intrafraction motions during radiation therapy (RT). Purpose Building upon a previous study, this work develops and tests an improved RTMM technique based on real‐time orthogonal cine magnetic resonance imaging (MRI) acquired during magnetic resonance‐guided adaptive RT (MRgART) for abdominal tumors on MR‐Linac. Methods A motion monitoring research package (MMRP) was developed and tested for RTMM based on template rigid registration between beam‐on real‐time orthogonal cine MRI and pre‐beam daily reference 3D‐MRI (baseline). The MRI data acquired under free‐breathing during the routine MRgART on a 1.5T MR‐Linac for 18 patients with abdominal malignancies of 8 liver, 4 adrenal glands (renal fossa), and 6 pancreas cases were used to evaluate the MMRP package. For each patient, a 3D mid‐position image derived from an in‐house daily 4D‐MRI was used to define a target mask or a surrogate sub‐region encompassing the target. Additionally, an exploratory case reviewed for an MRI dataset of a healthy volunteer acquired under both free‐breathing and deep inspiration breath‐hold (DIBH) was used to test how effectively the RTMM using the MMRP can address through‐plane motion (TPM). For all cases, the 2D T2/T1‐weighted cine MRIs were captured with a temporal resolution of 200 ms interleaved between coronal and sagittal orientations. Manually delineated contours on the cine frames were used as the ground‐truth motion. Common visible vessels and segments of target boundaries in proximity to the target were used as anatomical landmarks for reproducible delineations on both the 3D and the cine MRI images. Standard deviation of the error (SDE) between the ground‐truth and the measured target motion from the MMRP package were analyzed to evaluate the RTMM accuracy. The maximum target motion (MTM) was measured on the 4D‐MRI for all cases during free‐breathing. Results The mean (range) centroid motions for the 13 abdominal tumor cases were 7.69 (4.71–11.15), 1.73 (0.81–3.05), and 2.71 (1.45–3.93) mm with an overall accuracy of <2 mm in the superior–inferior (SI), the left‐right (LR), and the anterior‐posterior (AP) directions, respectively. The mean (range) of the MTM from the 4D‐MRI was 7.38 (2–11) mm in the SI direction, smaller than the monitored motion of centroid, demonstrating the importance of the real‐time motion capture. For the remaining patient cases, the ground‐truth delineation was challenging under free‐breathing due to the target deformation and the large TPM in the AP direction, the implant‐induced image artifacts, and/or the suboptimal image plane selection. These cases were evaluated based on visual assessment. For the healthy volunteer, the TPM of the target was significant under free‐breathing which degraded the RTMM accuracy. RTMM accuracy of <2 mm was achieved under DIBH, indicating DIBH is an effective method to address large TPM. Conclusions We have successfully developed and tested the use of a template‐based...

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Real-time intrafraction motion monitoring in external beam radiotherapy

et al. 2019

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Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to ‘see what we treat, as we treat’ and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT.

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Simultaneous acquisition of 4D ultrasound and wireless electromagnetic tracking for in-vivo accuracy validation

Cited by 5 publications

References 8 publications

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

Real‐time motion monitoring using orthogonal cine MRI during MR‐guided adaptive radiation therapy for abdominal tumors on 1.5T MR‐Linac

Real-time intrafraction motion monitoring in external beam radiotherapy

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