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High-speed bioimpedance-based gating system for radiotherapy: Prototype and proof of principle
Mikhail A Belikhin1, Alexander P Chernyaev2, Alexander A Pryanichnikov3
1JSC Protom, Protvino, Russian Federation.
Purpose:
To investigate a novel bioimpedance-based respiratory gating system (BRGS) designed for external beam radiotherapy and to evaluate its technical characteristics in comparison with existing similar systems.
Materials And Methods:
The BRGS was tested on three healthy volunteers in free breathing and breath-hold patterns under laboratory conditions. Its parameters, including the time delay (TD) between the actual impedance change and the gating signal, temperature drift, root mean square (RMS) noise, and signal-to-noise ratio (SNR), were measured and analyzed.
Results:
The gate-on TD and the gate-off TD were found to be 9.0 ± 2.0 ms [mean ± standard deviation (M ± SD)] and 7.2 ± 1.3 ms, respectively. The temperature drift of the BRGS output signal was 0.02 Ω after 30 min of operation. RMS noise averaged 0.14 ± 0.05 Ω (M ± SD) for all subjects and varied from 0.08 to 0.20 Ω with repeated measurements. A significant difference in SNR (p < 0.001) was observed between subjects, ranging from 4 to 15.
Conclusion:
The evaluated bioimpedance-based gating system showed a high performance in real-time respiratory monitoring and may potentially be used as an external surrogate guidance for respiratory-gated external beam radiotherapy. Direct comparison with commercially available systems, 4D correlation studies, and expansion of the patient sample are goals for future preclinical studies.
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