Development and preliminary evaluation of a prototype audiovisual biofeedback device incorporating a patient-specific guiding waveform

Abstract

The aim of this research was to investigate the effectiveness of a novel audio-visual biofeedback respiratory training tool to reduce respiratory irregularity. The audiovisual biofeedback system acquires sample respiratory waveforms of a particular patient and computes a patient-specific waveform to guide the patient's subsequent breathing. Two visual feedback models with different displays and cognitive loads were investigated: a bar model and a wave model. The audio instructions were ascending/descending musical tones played at inhale and exhale respectively to assist in maintaining the breathing period. Free-breathing, bar model and wave model training was performed on ten volunteers for 5 min for three repeat sessions. A total of 90 respiratory waveforms were acquired. It was found that the bar model was superior to free breathing with overall rms displacement variations of 0.10 and 0.16 cm, respectively, and rms period variations of 0.77 and 0.33 s, respectively. The wave model was superior to the bar model and free breathing for all volunteers, with an overall rms displacement of 0.08 cm and rms periods of 0.2 s. The reduction in the displacement and period variations for the bar model compared with free breathing was statistically significant (p = 0.005 and 0.002, respectively); the wave model was significantly better than the bar model (p = 0.006 and 0.005, respectively). Audiovisual biofeedback with a patient-specific guiding waveform significantly reduces variations in breathing. The wave model approach reduces cycle-to-cycle variations in displacement by greater than 50% and variations in period by over 70% compared with free breathing. The planned application of this device is anatomic and functional imaging procedures and radiation therapy delivery.

Impact of incorporating visual biofeedback in 4D MRI

“…Therefore, faster scan times were observed with VBF while also reducing breathing irregularities. Our results were consistent with the literature, where 40%–55% reductions in irregularity were observed when using visual and audiovisual biofeedback systems, 18 , 19 respectively.…”

“…However, 17 out of 40 paired evaluations had better image quality scores when VBF was used. The incorporation of a respiratory guiding system has shown similar improvements in image quality for 4D CT, 3D MR, and 4D PET 27 , 28 , 29 . VBF tended to improve image quality for intermediate phases (i.e., mid‐exhale [i.e., 25%] and EI).…”

“…However, because this 4D MRI algorithm is prospectively triggered based on amplitude, long acquisition times were reported due to recurring pauses arising from highly irregular breathing patterns 14 , 15 , 16 . It has been shown that incorporating audio coaching and visual biofeedback (VBF) into 4D CT acquisition and radiation therapy delivery improves breathing regularity, increases anatomic reproducibility, and reduces the overall time burden of these procedures 17 , 18 , 19 . Given long 4D MRI exam times, efforts to reduce breathing irregularities are advantageous.…”

The impact of audiovisual biofeedback on 4D functional and anatomic imaging: Results of a lung cancer pilot study

“…The patients were scanned in pre-treatment, except patients 4 (post-treatment) and 5 (mid-treatment), with arms raised above their head on a Discovery ST PET/CT scanner (GE Healthcare, Waukesha, WI) along with a real-time position management (RPM) system (Varian Medical Systems, Palo Alto, CA). In each scan, 4D-PET and 4D-CT data with AV biofeedback (AV) and free breathing (FB) were acquired consecutively in the same session [4].…”

“…For this reason, respiratory training or coaching is a commonly used technique to reduce irregularity in breathing cycles. Among the techniques, audiovisual (AV) biofeedback is a real-time, interactive and personalized system designed to help a patient self-regulate their breathing, demonstrating a reduction in the average cycle-to-cycle variations in respiratory amplitude and period by up to 50% and 70%, respectively [4]. To date, only two studies have investigated the impact of breathing training on anatomic imaging such as MRI and CT [5], [6]; however, no investigation has been performed for the impact of AV biofeedback on functional imaging.…”