Clinical Accuracy of the Respiratory Tumor Tracking System of the CyberKnife: Assessment by Analysis of Log Files

Hoogeman, M.; Prévost, Jean-Briac; Nuyttens, J.; Pöll, Johan J.; Levendag, Peter C.; Heijmen, B.

doi:10.1016/j.ijrobp.2008.12.041

Cited by 305 publications

(333 citation statements)

References 18 publications

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“…The accuracy of the correlation model has been evaluated in a previous publication 14. The mean correlation model errors were less than 0.3 mm in their study, indicating that use of the correlation model to predict the tumor position is reliable.…”

Section: Methodsmentioning

confidence: 90%

Evaluation of the intra‐ and interfractional tumor motion and variability by fiducial‐based real‐time tracking in liver stereotactic body radiation therapy

Liang

Liu

Xue

et al. 2018

J Applied Clin Med Phys

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PurposeTumor motion amplitude varies during treatment. The purpose of the study was to evaluate the intra‐ and interfraction tumor motion and variability in patients with liver cancer treated with fiducial‐based real‐time tracking stereotactic body radiotherapy (SBRT).MethodsFourteen liver patients were treated with SBRT using a CyberKnife. Two to four fiducial markers implanted near the tumor were used for real‐time monitoring using the Synchrony system. The tumor motion information during treatment was extracted from the log files recorded by the Synchrony system. Logfile‐based amplitudes in the superior–posterior (SI), left–right (LR) and anterior–posterior (AP) directions were compared to the 4DCT‐based amplitudes. The intra‐ and interfraction amplitude variations and the incidence of baseline shifts were analyzed for 66 fractions administered to 14 patients.ResultsThe median (range) logfile‐based liver motion amplitudes for all patients were 11.9 (5.1–17.3) mm, 1.3 (0.4–4) mm and 3.8 (0.9–7.7) mm in the SI, LR and AP directions, respectively. Compared with the logfile‐based amplitude, the 4DCT‐based amplitude was underestimated (P < 0.05). The median (range) intra‐ and interfraction liver motion amplitude variations were 4.3 (1.6–6.0) mm (SI), 0.5 (0.2–2.2) mm(LR) and 1.5 (0.3–3.3) mm (AP) and 1.7 (0.5–4.6) mm (SI), 0.3 (0.1–3.0) mm (LR) and 0.7 (0.3–2.7) mm (AP), respectively. Baseline shifts exceeding 2 mm, 3 mm and 5 mm were observed in 27.3%, 7.6% and 3% of the measurements, respectively, within 10 min, and in 66.7%, 38.1% and 19%, respectively, within 30 min for the square root of the sum of the squares of the distances in the SI, LR and AP directions (3D). The tumor motion amplitude was found to be correlated with the baseline shift.ConclusionsMost patients showed significant intra‐ and interfraction liver motion amplitude variations over the entire course of radiation. More caution is needed for patients with large tumor motion amplitudes.

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Section: Methodsmentioning

confidence: 90%

Evaluation of the intra‐ and interfractional tumor motion and variability by fiducial‐based real‐time tracking in liver stereotactic body radiation therapy

Liang

Liu

Xue

et al. 2018

J Applied Clin Med Phys

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“…We assumed that the motion of a lung tumor occurs in this direction, and the infrared marker on the abdomen was used to estimate tumor motion. Because the major axis of tumor motion inside the patient is in the SI direction rather than in AP or LR directions, the synchrony system reduces tracking errors (16) . However, directions and amplitudes of the motion of normal tumors in the lung or liver differ in absolute terms from those of the chest and abdomen.…”

Section: Discussionmentioning

confidence: 99%

“…The system includes the Synchrony Respiratory Tracking System v.9.6, which makes real‐time adjustments to the robotic arm position to follow the moving target 15 , 16 , 17 . The target locating system (TLS) is composed of two ceiling‐mounted diagnostic X‐ray sources paired with amorphous silicon detectors, and acquires live digital radiographic images of the target, bony anatomy, and fiducial markers.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of tracking accuracy of the CyberKnife system using a webcam and printed calibrated grid

Sumida

Shiomi

Higashinaka³

et al. 2016

J Applied Clin Med Phys

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Tracking accuracy for the CyberKnife's Synchrony system is commonly evaluated using a film‐based verification method. We have evaluated a verification system that uses a webcam and a printed calibrated grid to verify tracking accuracy over three different motion patterns. A box with an attached printed calibrated grid and four fiducial markers was attached to the motion phantom. A target marker was positioned at the grid's center. The box was set up using the other three markers. Target tracking accuracy was evaluated under three conditions: 1) stationary; 2) sinusoidal motion with different amplitudes of 5, 10, 15, and 20 mm for the same cycle of 4 s and different cycles of 2, 4, 6, and 8 s with the same amplitude of 15 mm; and 3) irregular breathing patterns in six human volunteers breathing normally. Infrared markers were placed on the volunteers’ abdomens, and their trajectories were used to simulate the target motion. All tests were performed with one‐dimensional motion in craniocaudal direction. The webcam captured the grid's motion and a laser beam was used to simulate the CyberKnife's beam. Tracking error was defined as the difference between the grid's center and the laser beam. With a stationary target, mean tracking error was measured at 0.4 mm. For sinusoidal motion, tracking error was less than 2 mm for any amplitude and breathing cycle. For the volunteers’ breathing patterns, the mean tracking error range was 0.78‐1.67 mm. Therefore, accurate lesion targeting requires individual quality assurance for each patient.PACS number(s): 87.55.D‐, 87.55.km, 87.55.Qr, 87.56.Fc

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“…Patient respiration is a particular challenge for treatment sites such as the lung and liver 2 . Imaging‐based respiratory motion compensation strategies generally use kilo‐voltage x‐rays and often assume correlation between external surrogates and internal motion 3 , 4 . Ultrasound has been explored for use in both inter‐ and intra‐fraction motion compensation strategies and its use in RT has recently been reviewed 5 .…”

Section: Introductionmentioning

confidence: 99%

Temporal regularization of ultrasound-based liver motion estimation for image-guided radiation therapy

2015

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Purpose:Ultrasound‐based motion estimation is an expanding subfield of image‐guided radiation therapy. Although ultrasound can detect tissue motion that is a fraction of a millimeter, its accuracy is variable. For controlling linear accelerator tracking and gating, ultrasound motion estimates must remain highly accurate throughout the imaging sequence. This study presents a temporal regularization method for correlation‐based template matching which aims to improve the accuracy of motion estimates.Methods:Liver ultrasound sequences (15–23 Hz imaging rate, 2.5–5.5 min length) from ten healthy volunteers under free breathing were used. Anatomical features (blood vessels) in each sequence were manually annotated for comparison with normalized cross‐correlation based template matching. Five sequences from a Siemens Acuson™ scanner were used for algorithm development (training set). Results from incremental tracking (IT) were compared with a temporal regularization method, which included a highly specific similarity metric and state observer, known as the α–β filter/similarity threshold (ABST). A further five sequences from an Elekta Clarity™ system were used for validation, without alteration of the tracking algorithm (validation set).Results:Overall, the ABST method produced marked improvements in vessel tracking accuracy. For the training set, the mean and 95th percentile (95%) errors (defined as the difference from manual annotations) were 1.6 and 1.4 mm, respectively (compared to 6.2 and 9.1 mm, respectively, for IT). For each sequence, the use of the state observer leads to improvement in the 95% error. For the validation set, the mean and 95% errors for the ABST method were 0.8 and 1.5 mm, respectively.Conclusions:Ultrasound‐based motion estimation has potential to monitor liver translation over long time periods with high accuracy. Nonrigid motion (strain) and the quality of the ultrasound data are likely to have an impact on tracking performance. A future study will investigate spatial uniformity of motion and its effect on the motion estimation errors.

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Clinical Accuracy of the Respiratory Tumor Tracking System of the CyberKnife: Assessment by Analysis of Log Files

Cited by 305 publications

References 18 publications

Evaluation of the intra‐ and interfractional tumor motion and variability by fiducial‐based real‐time tracking in liver stereotactic body radiation therapy

Evaluation of the intra‐ and interfractional tumor motion and variability by fiducial‐based real‐time tracking in liver stereotactic body radiation therapy

Evaluation of tracking accuracy of the CyberKnife system using a webcam and printed calibrated grid

Temporal regularization of ultrasound-based liver motion estimation for image-guided radiation therapy

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