Clinical Implementation and Initial Experience of Real-Time Motion Tracking With Jaws and Multileaf Collimator During Helical Tomotherapy Delivery

Abstract

This work reports the clinical implementation of a real-time motion tracking and correction system using dynamic multileaf collimator and jaws during helical tomotherapy delivery (Synchrony on Radixact; Accuray, Inc). Methods and Materials: The first clinical Synchrony on Radixact system was recently installed and tested at our institution. Various clinical workflows, including fiducial implantation, computed tomography simulation, treatment planning, delivery quality assurance, treatment simulation, and delivery, for both fiducial-free and fiducial-based motion tracking methods were developed. Treatment planning and delivery data from initial patients, including dosimetric benefits, real-time target detection, model building, motion tracking accuracy, delivery smoothness, and extra dose from real-time radiographic imaging, were analyzed. Results: The Synchrony on Radixact system was tested to be within its performance specifications and has been used to treat 10 lung (fiducial-free) and 5 prostate (fiducial-based) patients with cancer so far in our clinic. The success of these treatments, especially for fiducial-free tracking, depends on multiple factors, including careful selection of the patient, appropriate setting of system parameters, appropriate positioning of the patient and skin markers, and use of treatment simulation. For the lung tumor cases, difficulties in model building, due primarily to the changes of target detectability or respiration patterns, were observed, which led to important system upgrades, including the addition of a treatment delivery simulation capability. Motion tracking metrics for all treated patients were within specifications, for example, (1) delivery quality assurance passing rates >95%; (2) extra dose from radiograph <0.5% of the prescription dose; and (3) average Potential Diff, measured D, and Rigid Body were within 6.5, 2.9, and 3.9 mm, respectively. Conclusions: Practical workflows for the use of the first clinical motion tracking and correction system in helical tomotherapy delivery have been developed, and the system has now been successfully implemented in our clinic for treating patients with lung and prostate cancer.

Effects of variable‐width jaw motion on beam characteristics for Radixact Synchrony®

“…This hypo-fractionated treatment schedule was chosen since hypofractionated stereotactic body radiotherapy (SBRT) deliveries require more precise localization and this fractionation scheme has been used for Synchrony treatments for lung cancer published in the literature. 4,7 Dose calculation used a convolution/superposition algorithm.…”

“…A description of the Synchrony system has been provided by others in previous publications. [1][2][3][4][5][6] The Radixact uses an un-flattened 6-MV beam for helical tomotherapy treatment delivery. The un-flattened beam profile is not an issue during standard intensity-modulated radiation therapy (IMRT) treatments because the change in fluence off-axis is accounted for in the treatment planning system.…”

A first report of tumour-tracking radiotherapy with helical tomotherapy for lung and liver tumours: A double case report

“… 5 – 7 However, there have only been a limited number of reports on clinical cases using such tumour tracking. 8 In addition, to the best of our knowledge, TTT for liver tumours has never been documented in patients. Herein, we present two cases of tumour tracking with helical tomotherapy for lung stereotactic body radiotherapy (SBRT) and liver radiotherapy, capturing an early clinical experience of this approach.…”

Using 4D dose accumulation to calculate organ‐at‐risk dose deviations from motion‐synchronized liver and lung tomotherapy treatments

“…There have been several studies demonstrating Synchrony's ability to accurately correct the treatment for target motion. [1][2][3][4][5][6][7] However, there have not been any publications to date investigating the effect of the motion compensation on doses to OARs, which is a critical component of successful tracking since the planned treatment is changed in real time. 8 In fact, to our knowledge there are no works in the literature investigating the effect of any real-time tracking system on dose deviations to OARs.…”