Touchless Compression Using Shallow Kinetics Induced by Metronome (SKIM)

PURPOSE/OBJECTIVE(S): As an alternative to conventional compression approaches (e.g., hard plate or belt) amidst the ongoing COVID-19 pandemic, we have developed a touchless motion management strategy for stereotactic body radiation therapy (SBRT). By increasing the patient's breathing rate to induce fast shallow-breathing (FSB) with the aid of a metronome, our hypothesis was that the motion magnitude of the target would be minimized with no physical contact and compression. MATERIALS/METHODS: Ten SBRT patients who were treated under FSB were selected for this study: 4 lung and 6 liver cases. Our proposed method is called shallow kinetics induced by metronome (SKIM). We have used a metronome by setting the beats-per-minute (BPM) in the range of 50–60 to induce the SB. This corresponded to a patient breathing rate of 25–30 (breathing) cycles-per-minute. Two 4DCT scans, free-breathing (FB) and SKIM, were acquired and exported to commercially available software. Subsequently, the motion magnitude of the target in a superior-to-inferior direction was measured in each data set and compared. RESULTS: The respiratory motion was greatly reduced when using SKIM. The mean ± standard deviation (SD) values of motion magnitude of the target in FB and SKIM across patients were 1.65 ± 0.93 cm and 0.76 ± 0.20 cm, respectively. Among these cases, the mean BPM setting of the metronome was 55.2. CONCLUSION: Compared with FB, the SKIM technique could significantly reduce the respiratory motion magnitude of thoracic and abdominal targets. Our proposed method can be an excellent practical alternative to the conventional compression methods due to its flexibility and ease of implementation, especially during a global pandemic when minimal physical contact is crucial for the safety of both patients and care providers. Table 1. The comparison of motion magnitude of the target between free-breathing (FB) and shallow kinetics induced by metronome (SKIM). The mean ± standard deviation values across patients were 1.65 ± 0.93 cm and 0.76 ± 0.20 cm, respectively.