Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Ehrbar, Stefanie; Schmid, Sofie; Jöhl, Alexander; Klöck, Stephan; Gückenberger, Matthias; Tanadini‐Lang, Stephanie

doi:10.1016/j.radonc.2017.08.035

Cited by 16 publications

(17 citation statements)

References 23 publications

(34 reference statements)

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“…Compared to previous studies at other institutions using the same tracking system, 54,55 the dosimetric performance of MLC tracking presented in this paper is inferior. The difference could be attributed mainly to two reasons, differences in motion characteristics and treatment plans.…”

Section: Discussioncontrasting

confidence: 73%

“…A similar comparison study for prostate SBRT using the same system was reported by Ehrbar et al where couch tracking showed generally better performance compared to MLC tracking. 55 The vast majority of publications of MLC and couch tracking focus on lung and prostate cases, but limited studies have been reported for abdominal cancers, 56 which are also significantly affected by respiratory motion and other physiological motion in the gastrointestinal track. In this study, we evaluated the accuracy of both MLC and couch tracking for pancreas and liver diseases using Varian iTools Tracking.…”

Section: Introductionmentioning

confidence: 99%

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Couch and multileaf collimator tracking: A clinical feasibility study for pancreas and liver treatment

et al. 2020

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Real-time tumor tracking through active correction by the multileaf collimator or treatment couch offers a promising strategy to mitigate delivery uncertainty due to intrafractional tumor motion. This study evaluated the performance of MLC and couch tracking using the prototype iTools Tracking system in TrueBeam Developer Mode and the application for abdominal cancer treatments. Methods: Experiments were carried out using a phantom with embedded Calypso transponders and a motion simulation platform. Geometric evaluations were performed using a circular conformal field with sinusoidal traces and pancreatic tumor motion traces. Geometric tracking accuracy was retrospectively calculated by comparing the compensational MLC or couch motion extracted from machine log files to the target motion reconstructed from real-time MV and kV images. Dosimetric tracking accuracy was measured with radiochromic films using clinical abdominal VMAT plans and pancreatic tumor traces. Results: Geometrically, the root-mean-square errors for MLC tracking were 0.5 and 1.8 mm parallel and perpendicular to leaf travel direction, respectively. Couch tracking, in contrast, showed an average of 0.8 mm or less geometric error in all directions. Dosimetrically, both MLC and couch tracking reduced motion-induced local dose errors compared to no tracking. Evaluated with five pancreatic tumor motion traces, the average 2%/2 mm global gamma pass rate of eight clinical abdominal VMAT plans was 67.4% (range: 26.4%-92.7%) without tracking, which was improved to 86.0% (range: 67.9%-95.6%) with MLC tracking, and 98.1% (range: 94.9%-100.0%) with couch tracking. In 16 out of 40 deliveries with different plans and motion traces, MLC tracking did not achieve clinically acceptable dosimetric accuracy with 3%/3mm gamma pass rate below 95%. Conclusions: This study demonstrated the capability of MLC and couch tracking to reduce motioninduced dose errors in abdominal cases using a prototype tracking system. Clinically significant dose errors were observed with MLC tracking for certain plans which could be attributed to the inferior MLC tracking accuracy in the direction perpendicular to leaf travel, as well as the interplay between motion tracking and plan delivery for highly modulated plans. Couch tracking outperformed MLC tracking with consistently high dosimetric accuracy in all plans evaluated, indicating its clinical potential in the treatment of abdominal cancers.

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Section: Discussioncontrasting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Couch and multileaf collimator tracking: A clinical feasibility study for pancreas and liver treatment

et al. 2020

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“…Motion mitigation is an obvious application of motion monitoring and several mitigation methods have been compared in different treatment sites (Menten et al 2012 , Ehrbar et al 2016 , 2017a , Colvill et al 2016 , Toftegaard et al 2017 , Nankali et al 2018 ). Another application of motion monitoring is real-time dose reconstruction which can provide real-time QA for treatments delivered with or without mitigation (Ravkilde et al 2014 , 2018 , Kamerling et al 2016a , 2017 ).…”

Section: Discussionmentioning

confidence: 99%

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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“…With those dosimetry systems, the performance of couch tracking was evaluated. This has been done before, but so far only in rigid phantoms 12,42 or phantoms with rigidly moving tumors. 43 As can be seen from Fig.…”

Section: Discussionmentioning

confidence: 99%

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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Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Abstract: MLC and couch tracking at a conventional linear accelerator significantly improved the accuracy of prostate SBRT in the presence of motion, whereby couch tracking showed slightly better performance than MLC tracking.

Cited by 16 publications

References 23 publications

Couch and multileaf collimator tracking: A clinical feasibility study for pancreas and liver treatment

Couch and multileaf collimator tracking: A clinical feasibility study for pancreas and liver treatment

Real-time intrafraction motion monitoring in external beam radiotherapy

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

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