Evaluation of the accuracy of the CyberKnife Synchrony™ Respiratory Tracking System using a plastic scintillator

Akino, Yuichi; Sumida, Iori; Shiomi, Hiroya; Higashinaka, Naokazu; Murashima, Yoshiichi; Hayashida, Miori; Mabuchi, Nobuhisa; Ogawa, Kazuhiko

doi:10.1002/mp.13028

Cited by 24 publications

(30 citation statements)

References 25 publications

(48 reference statements)

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“…To correct for this effect, the data were collected with the phantom stationary and the offset values were calculated. The details of the corrections were described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…The offset of the virtual target position from the center of the fluorescent tapes was also considered when the effects of the plastic scintillator thickness were corrected. The details of the procedures are described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Many previous studies have investigated the motion‐tracking accuracy of the SRTS . Inoue et al investigated the tracking accuracy using a video camera mounted on the CyberKnife head .…”

Section: Introductionmentioning

confidence: 99%

“…Many previous studies have investigated the motion-tracking accuracy of the SRTS. 8,9,[13][14][15][16] Inoue et al investigated the tracking accuracy using a video camera mounted on the CyberKnife head. 13 Sumida et al evaluated the tracking accuracy by observing the laser mounted on the linac head.…”

Section: Introductionmentioning

confidence: 99%

“…We previously reported a technique to evaluate the motion tracking accuracy by measuring the treatment x-ray beam with a plastic scintillator plate. 16 The American Association of Physicists in Medicine (AAPM) Task Group 135 (TG-135) 17 recommends the Synchrony E2E test with a phase shift of ≥ 20°(approximately 6%) as an annual quality assessment tool. However, few studies have focused on the impacts of respiratory phase shifts on tracking accuracy.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of respiratory phase shifts on motion‐tracking accuracy of the CyberKnife Synchrony™ Respiratory Tracking System

et al. 2019

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Purpose The SynchronyTM Respiratory Tracking System (SRTS) component of the CyberKnife® Robotic Radiosurgery System (Accuray, Inc., Sunnyvale CA) enables real‐time tracking of moving targets by modeling the correlation between the targets and external surrogate light‐emitting diode (LED) markers placed on the patient’s chest. Previous studies reported some cases with respiratory phase shifts between lung tumor and chest wall motions. In this study, the impacts of respiratory phase shifts on the motion‐tracking accuracy of the SRTS were investigated. Methods A plastic scintillator was used to detect the position of the x‐ray beams. The scintillation light was recorded using a camera in a dark room. A moving phantom moved a U‐shaped frame on the scintillator with a 4th power of sinusoidal functions. Three metallic markers for motion tracking and four fluorescent tapes were attached to the frame. The fluorescent tapes were used to identify phantom position and respiratory phase for each video frame. The beam positions collected, when considered relative to the phantom motion, represent the degree of tracking error. Beam position was calculated by adding error value to phantom position. Motions with respiratory phase shifts between the target and an extra stage mimicking chest wall motion were also tested for LED markers. Log files of the SRTS were analyzed to evaluate correlation errors. Results When target and LED marker motions were synchronized with a respiratory cycle of 4 s, the maximum tracking errors for 90% and 95% of beam‐on time were 1.0 mm and 1.2 mm, respectively. The frequency of tracking errors increased when LED marker motion phase preceded target motion. Tracking errors that corresponded to 90% beam‐on time were within 2.4 mm for 5–15% of phase shifts. In contrast, the tracking errors were very large when the LED marker delayed to the target motions; the maximum errors of 90% beam‐on time were 3.0, 3.8, and 7.5 mm for 5%, 10%, and 15% of phase shifts, respectively. The patterns of the tracking errors derived from the scintillation light were very similar to those of the correlation data of the SRTS derived from the log files, indicating that the tracking errors caused mainly due to the errors in modeling the correlation data. With long respiratory cycle of 6 s, the tracking errors were significantly decreased; the maximum tracking errors for 95% beam‐on time were 1.6 mm and 2.2 mm for early and delayed LED motion. Conclusion We have investigated the motion‐tracking accuracy of the CyberKnife SRTS for cases with the respiratory phase shift between the target and the LED marker. The maximum tracking errors for 90% probability were within 2.4 mm when the target delays to the LED markers. When LED marker delays, however, very large tracking errors were observed. With a long respiratory cycle, the tracking errors were greatly improved to less than 2.2 mm. Coaching slow breathing will be useful for accurate motion tracking radiotherapy.

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“…To correct for this effect, the data were collected with the phantom stationary and the offset values were calculated. The details of the corrections were described elsewhere …”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…Many previous studies have investigated the motion‐tracking accuracy of the SRTS . Inoue et al investigated the tracking accuracy using a video camera mounted on the CyberKnife head .…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impacts of respiratory phase shifts on motion‐tracking accuracy of the CyberKnife Synchrony™ Respiratory Tracking System

et al. 2019

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Radiotherapy Beam Production

Flinton

2019

Practical Radiotherapy

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An effective method to reduce the interplay effects between respiratory motion and a uniform scanning proton beam irradiation for liver tumors: A case study

Akino

et al. 2018

J Applied Clin Med Phys

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PurposeFor scanning particle beam therapy, interference between scanning patterns and interfield organ motion may result in suboptimal dose within target volume. In this study, we developed a simple offline correction technique for uniform scanning proton beam (USPB) delivery to compensate for the interplay between scanning patterns and respiratory motion and demonstrate the effectiveness of our technique in treating liver cancer.MethodsThe computed tomography (CT) and respiration data of two patients who had received stereotactic body radiotherapy for hepatocellular carcinoma were used. In the simulation, the relative beam weight delivered to each respiratory phase is calculated for each beam layer after treatment of each fraction. Respiratory phases with beam weights higher than 50% of the largest weight are considered “skipped phases” for the next fraction. For the following fraction, the beam trigger is regulated to prevent beam layers from starting irradiation in skipped phases by extending the interval between each layer. To calculate dose‐volume histogram (DVH), the dose of the target volume at end‐exhale (50% phase) was calculated as the sum of each energy layer, with consideration of displacement due to respiratory motion and relative beam weight delivered per respiratory phase.ResultsFor a single fraction, D1%, D99%, and V100% were 114%, 88%, and 32%, respectively, when 8 Gy/min of dose rate was simulated. Although these parameters were improved with multiple fractions, dosimetric inhomogeneity without motion management remained even at 30 fractions, with V100% 86.9% at 30 fractions. In contrast, the V100% values with adaptation were 96% and 98% at 20 and 30 fractions, respectively. We developed an offline correction technique for USPB therapy to compensate for the interplay effects between respiratory organ motion and USPB beam delivery.ConclusionsFor liver tumor, this adaptive therapy technique showed significant improvement in dose uniformity even with fewer treatment fractions than normal USPB therapy.

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Evaluation of the accuracy of the CyberKnife Synchrony™ Respiratory Tracking System using a plastic scintillator

Abstract: This technique allows evaluation of the motion tracking accuracy of the Synchrony™ system over time by measurement of the photon beam. The velocity of the target and phase shift have significant effects on accuracy.

Cited by 24 publications

References 25 publications

Impacts of respiratory phase shifts on motion‐tracking accuracy of the CyberKnife Synchrony™ Respiratory Tracking System

Impacts of respiratory phase shifts on motion‐tracking accuracy of the CyberKnife Synchrony™ Respiratory Tracking System

Radiotherapy Beam Production

An effective method to reduce the interplay effects between respiratory motion and a uniform scanning proton beam irradiation for liver tumors: A case study

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