Evaluation of the feasibility of cardiac gating for SBRT of ventricular tachycardia based on real‐time ECG signal acquisition

Abstract

Purpose To investigate the feasibility of cardiac synchronized gating in stereotactic body radiation therapy (SBRT) of ventricular tachycardia (VT) using a real‐time electrocardiogram (ECG) signal acquisition. Methods and materials Stability of beam characteristics during simulated ECG gating was examined by developing a microcontroller interface to a Varian Clinac iX linear accelerator allowing gating at frequencies and duty cycles relevant to cardiac rhythm. Delivery accuracy was evaluated by measuring dose linearity with an ionization chamber, and flatness and symmetry with a two‐dimensional detector array, for different gating windows within typical human cardiac cycle periods. To establish a practical method of gating based on actual ECG signals, an AD8232 Heart Monitor board was used to acquire the ECG signal and synchronize the beam delivery. Real‐time cardiac gated delivery measurements were performed for a single 10 × 10 cm 2 field and for a VT‐SBRT plan using intensity‐modulated radiation therapy (IMRT). Results and discussion Dose per monitor unit (MU) values were found to be linear within most gating windows investigated with maximum differences relative to non‐gated delivery of <2% for gating windows ≥200 ms and for >10 MUs. Beam profiles for both gated and non‐gated modes were also found to agree with maximum differences of 0.5% relative to central axis dose for all sets of beam‐on/beam‐off combinations. Comparison of dose distributions for intensity‐modulated SBRT plans between non‐gating and cardiac gating modes provided a gamma passing rate of 97.2% for a 2% 2 mm tolerance. Conclusions Beam output is stable with respect to linearity, flatness, and symmetry for gating windows within cardiac cycle periods. Agreement between dose distributions for VT‐SBRT using IMRT in non‐gated and cardiac cycle gated delivery modes shows that the proposed methodology is feasible. Technically, gating for delivery of SBRT for VT is possible with regard to beam stability.

Left ventricle segment-specific motion assessment for cardiac-gated radiosurgery

“…Beam timing was controlled using multi-leaf collimator (MLC) leaf motion, and the synchronized plan was created pre-delivery due to the requirements of the clinical system. In a study by Reis and Robar, simulated cardiac gating using real-time ECG signal acquisition was demonstrated using a microcontroller interface to directly control the beam delivery of a Varian Clinac iX linear accelerator [29]. Dose linearity, beam flatness, and symmetry were not strongly affected by cardiac gating, and acceptable agreement between gated and non-gated dose distributions was shown.…”

“…However, for some scenarios with treatment targets that have significant cardiacinduced motion or are proximal to critical organs at risk (OARs), the motion-encompassing ITV method may be inadequate without the use of cardiac-specific motion margins. Other motion management techniques such as breath holding [24], gating [25,26], and direct tracking [27] have been used to account for respiratory motion, but there are limited investigations of techniques to address cardiac-induced motion [28][29][30].…”

“…Cardiac gating of a radiosurgery treatment, where the radiation beam is only turned on during the quiescent interval (diastole) of the cardiac cycle when heart motion is minimal, would help improve dose conformity and minimize the dose delivered to surrounding normal tissue [28,29,32]. The higher complexity, higher frequency, and lower amplitude of cardiac motion compared to respiratory motion makes cardiac-gated radiosurgery a more challenging task, but one that would be worth pursuing if the target area has a large cardiac motion component or is close to an OAR.…”

Experimental demonstration of real‐time cardiac physiology‐based radiotherapy gating for improved cardiac radioablation on an MR‐linac

“…The dosimetric results were improved with respect to an ungated dose delivery and the radiation beam characteristics remained stable. 33,34 Cardiacsynchronized MRI was recently enabled in research mode on the 1.5 T Unity MR-linac (Elekta AB, Stockholm, Sweden) after installing the clinical Philips MRI ECG equipment (Philips Healthcare, Best, The Netherlands). 35 In this study, our aim was to investigate the feasibility of cardiac motion mitigation during dose delivery based on an ECG-signal as a cardiac motion surrogate.…”

Implementation of an Artificial Intelligence-Based Ecg Acquisition System for the Detection of Cardiac Abnormalities

“…Many publications, such as [14,15,18], and [10], deal with the acquisition and categorization of cardiac anomalies utilizing ECG signals. They created and deployed a smart health care monitoring equipment that visualizes the ECG signal and counts the number of heartbeats at a reasonable cost.…”