Technical Note: Cardiac synchronized volumetric modulated arc therapy for stereotactic arrhythmia radioablation — Proof of principle

Abstract

Purpose: Ventricular tachycardia (VT) is a rapid, abnormal heart rhythm that can lead to sudden cardiac death. Current treatment options include antiarrhythmic drug therapy and catheter ablation, both of which have only modest efficacy and have potential complications. Cardiac radiosurgery has the potential to be a noninvasive and efficient treatment option for VT. Cardiac motion, however, must be accounted for to ensure accurate dose delivery to the target region. Cardiac synchronized volumetric modulated arc therapy (CSVMAT) aims to minimize the dose delivered to normal tissues by synchronizing beam delivery with a cardiac signal, irradiating only during the quiescent intervals of the cardiac cycle (when heart motion is minimal) and adjusting the beam delivery speed in response to heart rate changes. Methods: A CSVMAT plan was adapted from a conventional VMAT plan and delivered on a Varian TrueBeam linear accelerator. The original VMAT plan was divided into three interleaved CSVMAT phases, each consisting of alternating beam-on and beam-off segments synchronized to a sample heart rate. Trajectory log files were collected for the original VMAT and CSVMAT deliveries and the dose distributions were measured with Gafchromic EBT-XD film. Results: Analysis of the trajectory log files showed successful synchronization with the sample cardiac signal. Film analysis comparing the original VMAT and CSVMAT dose distributions returned a gamma passing rate of 99.14% (2%/2 mm tolerance). Conclusions: The film results indicated excellent agreement between the dose distributions of the original and cardiac synchronized beam deliveries. This study demonstrates a proof of principle cardiac synchronization strategy for precise radiation treatment plan delivery and adjustment to a variable heart rate. The cardiac synchronized technique may be advantageous in radioablation for VT.

Stereotactic body radioablation therapy as an immediate and early term antiarrhythmic palliative therapeutic choice in patients with refractory ventricular tachycardia

“…The target is referred to as the gross target volume (GTV). Respiratory and cardiac motions have to be incorporated into treatment planning to ensure accurate dose delivery to the target region [ 15 ], either through adequate range-considering internal margins or through more conformal strategies such as ECG-based gating or even 4D optimization [ 16 ]. Depending on the location (central or peripheral) of the treatment target and treatment purposes, the treatment planning margins for targets and risk volumes should be adjusted accordingly [ 17 ].…”

Cardiac radioablation for atrial fibrillation: Target motion characterization and treatment delivery considerations

“…MRI‐guided real‐time motion management for the LA has been illustrated, 4,14 however the differential LA and target displacement reported in this study requires further investigation for this technique. The concept of an ECG‐gated and/or respiratory‐gated treatment delivery appears feasible, 29 however the suitability of this technique for arrhythmia patients with irregular ECG traces needs further investigation. The suitability and accuracy of respiratory‐gating using an external surrogate placed on the sternum however requires further investigation due to only weak correlation between the sternum and target displacement.…”

Cardiac radiation dose predicts survival in esophageal cancer treated by definitive concurrent chemoradiotherapy

“…Errors of estimation would exist under such circumstance. Although cardiac synchronized radiotherapy has been developed [18], it is not routinely used in CCRT for esophageal cancer. Better protection of the heart and more precise estimation of cardiac radiation dose would be possible with cardiac synchronized radiotherapy in the future.…”