88: The use of Respiratory Gating for Delivery of Stereotactic Ablative Radiotherapy (SABR): Is there an Impact on Oncologic Outcomes?

Abstract Background Stereotactic ablative radiotherapy (SABR) aims to deliver high doses of radiation to kill cancer cells and shrink tumors in less than or equal to 6 fractions. However, organ motion during treatment is a challenging issue for this kind of technique. We develop a control system via Bluetooth technology to simulate and correct body motion during SABR. Methods Radiation doses were analyzed, and the radiation damage protection capability was checked by external beam therapy 3 (EBT3) films irradiated by a linear accelerator. A wireless signal test was also performed. A validation was performed with 8 previously treated patient respiratory pattern records and 8 healthy volunteers. Results The homemade simulation system consisted of 2 linear actuators, one movable stage with a maximal moving distance of 6.5 cm x 12.5 cm x 5 cm to simulate the respiratory pattern of 8 patients precisely with a median error of 0.36 mm and a maximal motion difference of 1.17 mm, and 3.17 and chipset transited signals to display them as a waveform. From the test with 8 volunteers, the chip could detect deep respiratory movement up to 3 cm. The effect of the chip on a radiation dose of 400 monitor units (MUs) by 6 MV photons and 200 MUs by 10 MV photons showed high penetration rates of 98.8% and 98.6%, respectively. Conclusions We invented a tubeless and wireless respiratory gating detection chip. The chip has minimal interference with the treatment angles, good noise immunity and the capability to easily penetrate a variety of materials. The simulation system consisting of linear actuators also successfully simulates the respiratory pattern of real patients.

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Computational ECG mapping and respiratory gating to optimize stereotactic ablative radiotherapy workflow for refractory ventricular tachycardia

Heart Rhythm O2 ◽

10.1016/j.hroo.2021.09.001 ◽

2021 ◽

Author(s):

Gordon Ho ◽

Todd F. Atwood ◽

Andrew R. Bruggeman ◽

Kevin L. Moore ◽

Elliot McVeigh ◽

...

Keyword(s):

Ventricular Tachycardia ◽

Respiratory Gating ◽

Stereotactic Ablative Radiotherapy

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Abstract 16347: Simplified Workflow to Improve the Precision of Non-invasive Radio-ablation of Ventricular Tachycardia Storm

Circulation ◽

10.1161/circ.142.suppl_3.16347 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Gordon Ho ◽

Todd Atwood ◽

Andrew Bruggeman ◽

Kevin Moore ◽

Elliot R McVeigh ◽

...

Keyword(s):

Ventricular Tachycardia ◽

Critically Ill ◽

Respiratory Gating ◽

Free Breathing ◽

3D Models ◽

Target Volume ◽

Stereotactic Ablative Radiotherapy ◽

Gated Radiotherapy ◽

Non Invasive

Background: Stereotactic ablative radiotherapy (SAbR) is an emerging therapy for ventricular tachycardia (VT) storm, but the feasibility and outcomes guided by computational 12-lead ECG mapping and respiratory-gated radiation delivery have not been reported. Hypothesis: We hypothesized that a novel 12-lead ECG-based mapping system and respiratory-gated radiotherapy delivery may simplify the workflow and improve precision of SAbR in critically ill patients with VT storm. Methods: We enrolled patients with VT storm who were not candidates for catheter ablation. VT was induced using non-invasive stimulation and recorded on 12-lead ECGs. Computational ECG mapping was performed to localize VT exit sites. Target volumes were contoured onto an averaged free-breathing CT. Ionizing radiation (25 Gy) was delivered using a linear accelerator (Varian, Palo Alto). In patients with significant respiratory motion, radiotherapy was delivered at end-expiration, guided by ICD lead fiducials. Results: In 5 patients (age 74±6.1 years, EF 29±14%) refractory to 2±1 ablation procedures, 1.5±0.6 VT morphologies were localized on 3D models (Fig 1A) using ECG-based mapping (mapping time 1.2±0.3 min). In patients whom respiratory gating (Fig 1B) was used prospectively due to respiratory variation, the planned target volume (PTV) was smaller compared to patients who were not gated (71 ± 7 vs 153 ± 35 cc, p<0.01). These patients also had VT targets (crux or inferior LV) close to the stomach, and did not experience adverse events. ICD shocks were decreased after SAbR compared to before (0.25±0.5 vs 26±19 shocks, p<0.001) at 4.4±3.4 months follow-up. Conclusion: Non-invasive computational mapping based upon the 12-lead ECG alone simplifies radioablation workflow in critically ill VT storm patients and reduces the burden of ICD shocks. Respiratory gated radiotherapy ablation appears feasible and may help reduce target volume of therapy. Studies with longer follow-up are ongoing.

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