A group of researchers from Kindai University has developed a millimeter-wave sensor (MWS) that can non-invasively visualize respiratory movement during diagnostic X-ray and CT exams of the patient.
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Monitoring respiratory motion during diagnostic imaging and radiation therapy is essential for accurate diagnosis and effective treatment. However, respiratory motion is often overlooked due to a lack of practical, non-invasive monitoring tools, which can lead to compromised image quality.
In radiation therapy, precise respiratory motion tracking ensures accurate dose delivery while minimizing exposure to surrounding organs. In diagnostic imaging, monitoring respiratory motion is crucial for confirming a patient’s breath-holding and for sorting computed tomography (CT) projections to generate four-dimensional CT images.
To address this challenge, a research team in Japan, led by Dr. Hiroyuki Kosaka, alongside Dr. Kenji Matsumoto and Dr. Hajime Monzen from the Department of Medical Physics at Kindai University, has developed a millimeter-wave sensor (MWS) capable of non-invasively visualizing respiratory movement during diagnostic X-ray and CT examinations.
The MWS is a non-contact device that detects motion using electromagnetic radiation, eliminating the need for reflective markers required by traditional infrared systems. This innovation enhances patient comfort and privacy. The team's findings were published in Medical Physics on January 27, 2025.
To validate the effectiveness of the MWS, researchers tested a 24 GHz microMWS system using a controlled respiratory motion phantom (QUASAR).
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.
Dr. Hiroyuki Kosaka, Graduate School of Medical Sciences, Kindai University
The results demonstrated that the MWS could reliably track respiratory cycles, even in controlled test scenarios.
Further testing involved trials with 20 healthy volunteers ranging from six months to 64 years of age. The system exhibited several key advantages:
- Non-contact monitoring that preserves patient privacy and comfort
- Accurate motion detection through clothing
- Reliable performance in both supine and standing positions
- Cost-effective implementation compared to existing technologies
- Seamless integration with current X-ray and CT equipment
This technology has the potential to standardize respiratory monitoring across diagnostic imaging. By providing objective, real-time feedback, we can significantly reduce the need for repeat imaging and improve diagnostic accuracy.
Dr. Hajime Monzen, Professor, Graduate School of Medical Sciences, Kindai University
To further assess the sensor’s capabilities, the researchers used a radio-wave dark-box system to evaluate its directional accuracy. They also applied a fast Fourier transform technique to isolate and analyze relevant breathing signals, optimizing the sensor for precise motion detection. Comparisons between the MWS data and the QUASAR phantom’s programmed breathing patterns confirmed the sensor’s reliability in tracking respiratory motion.
Looking ahead, the MWS system could become a standard tool in hospitals and clinics worldwide, enhancing the accuracy and efficiency of diagnostic imaging and radiation therapy. With its affordability, ease of use, and precision, the MWS could significantly reduce repeat imaging caused by poor image quality or failed breath-holding. Additionally, this technology could benefit a wide range of patients, including children, the elderly, and individuals unable to follow breath-holding instructions.
The development of the MWS system marks a significant advancement in respiratory motion management for medical 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.
Dr. Hiroyuki Kosaka, Graduate School of Medical Sciences, Kindai University
Journal Reference:
Kosaka, H., et al. (2025) Exploring the feasibility of millimeter‐wave sensors for non‐invasive respiratory motion visualization in diagnostic imaging and therapy. Medical Physics. doi.org/10.1002/mp.17616.