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Prototype development of an electrical impedance based simultaneous respiratory and cardiac monitoring system for gated radiotherapy.

Kohli K, Liu J, Schellenberg D, Karvat A, Parameswaran A, Grewal P, Thomas S - Biomed Eng Online (2014)

Bottom Line: The resulting signal of the system developed was also compared with the output of the commercially available Real-time Position Management™ (RPM) system in both time and frequency domains.The tracking of cardiac motion was more susceptible to interference from other sources than respiratory motion but also provided synchronous output compared with the ECG signal extracted.No significant effect on the functionality of the system was observed when it was tested in a radiation environment with the electrode lead wires directly exposed to high-energy X-Rays.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Fraser Valley Center, BC Cancer Agency, 13750 96th Avenue, Surrey V3V 1Z2, BC, Canada. kkohli@bccancer.bc.ca.

ABSTRACT

Background: In radiotherapy, temporary translocations of the internal organs and tumor induced by respiratory and cardiac activities can undesirably lead to significantly lower radiation dose on the targeted tumor but more harmful radiation on surrounding healthy tissues. Respiratory and cardiac gated radiotherapy offers a potential solution for the treatment of tumors located in the upper thorax. The present study focuses on the design and development of simultaneous acquisition of respiratory and cardiac signal using electrical impedance technology for use in dual gated radiotherapy.

Methods: An electronic circuitry was developed for monitoring the bio-impedance change due to respiratory and cardiac motions and extracting the cardiogenic ECG signal. The system was analyzed in terms of reliability of signal acquisition, time delay, and functionality in a high energy radiation environment. The resulting signal of the system developed was also compared with the output of the commercially available Real-time Position Management™ (RPM) system in both time and frequency domains.

Results: The results demonstrate that the bioimpedance-based method can potentially provide reliable tracking of respiratory and cardiac motion in humans, alternative to currently available methods. When compared with the RPM system, the impedance-based system developed in the present study shows similar output pattern but different sensitivities in monitoring different respiratory rates. The tracking of cardiac motion was more susceptible to interference from other sources than respiratory motion but also provided synchronous output compared with the ECG signal extracted. The proposed hardware-based implementation was observed to have a worst-case time delay of approximately 33 ms for respiratory monitoring and 45 ms for cardiac monitoring. No significant effect on the functionality of the system was observed when it was tested in a radiation environment with the electrode lead wires directly exposed to high-energy X-Rays.

Conclusion: The developed system capable of rendering quality signals for tracking both respiratory and cardiac motions can potentially provide a solution for simultaneous dual-gated radiotherapy.

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Related in: MedlinePlus

Block diagrams of (a) the respiratory motion monitoring circuit and (b) the cardiac motion monitoring circuit developed. This cardiac monitoring circuit has to be operated in conjunction with the respiratory monitoring unit, because the cardiac monitoring circuit does not include a carrier signal source.
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Fig1: Block diagrams of (a) the respiratory motion monitoring circuit and (b) the cardiac motion monitoring circuit developed. This cardiac monitoring circuit has to be operated in conjunction with the respiratory monitoring unit, because the cardiac monitoring circuit does not include a carrier signal source.

Mentions: The impedance based respiratory monitoring system mainly consists of two modules, the current-injecting module and the voltage measuring module. Figure 1a shows the block diagram of the system built on a single circuit board. The current-injecting module is capable of sourcing and sinking current based on the waveform of the input signal to the module, irrespective of the magnitude of the impedance. The source signal generated has a pre-defined amplitude and frequency that can be identified and isolated by the voltage-measuring module of the detection circuit. The voltage-measuring module specifically calibrated for the carrier signal also provides the required amplification so the output of the detection circuit can be properly sampled and analyzed.Figure 1


Prototype development of an electrical impedance based simultaneous respiratory and cardiac monitoring system for gated radiotherapy.

Kohli K, Liu J, Schellenberg D, Karvat A, Parameswaran A, Grewal P, Thomas S - Biomed Eng Online (2014)

Block diagrams of (a) the respiratory motion monitoring circuit and (b) the cardiac motion monitoring circuit developed. This cardiac monitoring circuit has to be operated in conjunction with the respiratory monitoring unit, because the cardiac monitoring circuit does not include a carrier signal source.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4209026&req=5

Fig1: Block diagrams of (a) the respiratory motion monitoring circuit and (b) the cardiac motion monitoring circuit developed. This cardiac monitoring circuit has to be operated in conjunction with the respiratory monitoring unit, because the cardiac monitoring circuit does not include a carrier signal source.
Mentions: The impedance based respiratory monitoring system mainly consists of two modules, the current-injecting module and the voltage measuring module. Figure 1a shows the block diagram of the system built on a single circuit board. The current-injecting module is capable of sourcing and sinking current based on the waveform of the input signal to the module, irrespective of the magnitude of the impedance. The source signal generated has a pre-defined amplitude and frequency that can be identified and isolated by the voltage-measuring module of the detection circuit. The voltage-measuring module specifically calibrated for the carrier signal also provides the required amplification so the output of the detection circuit can be properly sampled and analyzed.Figure 1

Bottom Line: The resulting signal of the system developed was also compared with the output of the commercially available Real-time Position Management™ (RPM) system in both time and frequency domains.The tracking of cardiac motion was more susceptible to interference from other sources than respiratory motion but also provided synchronous output compared with the ECG signal extracted.No significant effect on the functionality of the system was observed when it was tested in a radiation environment with the electrode lead wires directly exposed to high-energy X-Rays.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Fraser Valley Center, BC Cancer Agency, 13750 96th Avenue, Surrey V3V 1Z2, BC, Canada. kkohli@bccancer.bc.ca.

ABSTRACT

Background: In radiotherapy, temporary translocations of the internal organs and tumor induced by respiratory and cardiac activities can undesirably lead to significantly lower radiation dose on the targeted tumor but more harmful radiation on surrounding healthy tissues. Respiratory and cardiac gated radiotherapy offers a potential solution for the treatment of tumors located in the upper thorax. The present study focuses on the design and development of simultaneous acquisition of respiratory and cardiac signal using electrical impedance technology for use in dual gated radiotherapy.

Methods: An electronic circuitry was developed for monitoring the bio-impedance change due to respiratory and cardiac motions and extracting the cardiogenic ECG signal. The system was analyzed in terms of reliability of signal acquisition, time delay, and functionality in a high energy radiation environment. The resulting signal of the system developed was also compared with the output of the commercially available Real-time Position Management™ (RPM) system in both time and frequency domains.

Results: The results demonstrate that the bioimpedance-based method can potentially provide reliable tracking of respiratory and cardiac motion in humans, alternative to currently available methods. When compared with the RPM system, the impedance-based system developed in the present study shows similar output pattern but different sensitivities in monitoring different respiratory rates. The tracking of cardiac motion was more susceptible to interference from other sources than respiratory motion but also provided synchronous output compared with the ECG signal extracted. The proposed hardware-based implementation was observed to have a worst-case time delay of approximately 33 ms for respiratory monitoring and 45 ms for cardiac monitoring. No significant effect on the functionality of the system was observed when it was tested in a radiation environment with the electrode lead wires directly exposed to high-energy X-Rays.

Conclusion: The developed system capable of rendering quality signals for tracking both respiratory and cardiac motions can potentially provide a solution for simultaneous dual-gated radiotherapy.

Show MeSH
Related in: MedlinePlus