Monitoring respiratory motion during diagnostic imaging and radiation therapy is crucial for accurate diagnosis and treatment. However, respiratory motion is rarely monitored during these procedures due to the lack of practical, non-invasive tools, leading to potential image quality issues. Management of respiratory motion in radiation therapy ensures accurate dose delivery while minimizing exposure to organs at risk. Whereas, in diagnostic imaging, respiratory motion is required for the confirmation of the patient's breath-holding and sorting of the computed tomography (CT) projections to obtain four-dimensional CT images.
To address this gap, researchers from Japan, led by Dr. Hiroyuki Kosaka, along with Dr. Kenji Matsumoto and Dr. Hajime Monzen from the Department of Medical Physics, Graduate School of Medical Sciences, Kindai University, have developed a millimeter-wave sensor (MWS) capable of non-invasively visualizing respiratory movement during diagnostic X-ray and CT examinations. The MWS sensor is a non-contact device that uses electromagnetic radiation to detect motion in various scenarios. Unlike traditional systems, such as infrared sensors that require the use of reflective markers on the patient's body, the MWS works without any physical contact, preserving the patient's privacy and comfort. Their findings are published online in Medical Physics on January 27, 2025.
To validate the effectiveness of the MWS, the researchers utilized a 24 GHz microMWS, detecting the respiratory motion. "We tested the system using a controlled respiratory motion phantom (QUASAR). This phantom allowed us to simulate respiratory motion under controlled conditions, comparing the MWS's ability to detect subtle changes in motion with the phantom's known motion patterns," says Dr. Kosaka. The MWS successfully detected the motion patterns, ensuring it could reliably capture respiratory cycles even in controlled test scenarios.
Furthermore, the research team validated the system through extensive testing, including trials with 20 healthy volunteers ranging from 6 months to 64 years of age.
Key advantages of the new system include:
- Non-contact monitoring that maintains patient privacy and comfort
- Accurate detection through clothing
- Stable measurements in both supine and standing positions
- Cost-effective implementation compared to existing technologies
- Easy integration with current X-ray and CT equipment
"This technology has the potential to standardize respiratory monitoring across diagnostic imaging," explains Professor Monzen. "By providing objective, real-time feedback, we can significantly reduce the need for repeat imaging and improve diagnostic accuracy."
Additionally, to test how well the MWS could detect movement, the team used a radio-wave dark-box system, which helped determine the sensor's directionality. This test measured how accurately the MWS could detect motion from different angles. The researchers also optimized the sensor to pick up specific frequencies of movement using a technique called the fast Fourier transform, which helps identify and separate the relevant breathing signals.
To ensure the accuracy of the MWS, the team compared the detected breathing patterns with those of QUASAR. This phantom allowed the researchers to simulate breathing with different levels of motion. By comparing the waveforms from the MWS and the phantom, findings confirmed the MWS's ability to reliably track respiratory motion.
Looking ahead, the MWS system could become a standard tool in hospitals and clinics worldwide, improving the accuracy and efficiency of diagnostic imaging and treatment. With its low cost, ease of use, and accuracy, the MWS system is positioned to significantly enhance the quality of healthcare by reducing the need for repeat imaging due to poor image quality or breath-holding failure. Additionally, this technology could benefit a wide range of patient populations, including the elderly, children, and those with conditions that prevent them from following breath-holding instructions.
Overall, the development of the MWS system marks a significant leap forward in the management of respiratory motion in both diagnostic imaging and radiation therapy. "By offering a precise, non-invasive, and cost-effective way to monitor respiratory movements, the MWS can enhance diagnostic accuracy, improve treatment outcomes, and contribute to more efficient healthcare. This breakthrough represents a major advancement in medical technology, with the potential to revolutionize how healthcare providers approach respiratory motion monitoring, improving both patient experiences and outcomes," concludes Dr. Kosaka.
