Audiovisual biofeedback

AV biofeedback is a simple, personalised and interactive respiratory guide designed to facilitate regular patient breathing. The AV biofeedback system is shown below in Figure 1.

Audiovisual Biofeedback

Figure 1. AV biofeedback system. Display screen and marker block on the abdomen shown. The visual display (centre) as seen by the subject (sans arrows) of the AV biofeedback system shows the guiding wave (white curve) and a marker position (marker block) in real time. The AV biofeedback system is compatible for both imaging (left) and treatment (right) environments.


The problem that AV biofeedback is addressing is that should a patient’s breathing be irregular (see Figure 2a), it can result in incorrect information presented in medical imaging (see Figure 2b). Such irregularities and image artefacts can lead to incorrect tumour targeting in radiotherapy (see Figure 2c) or an increase in the radiation target volume resulting in an increase in radiation dose delivered to healthy tissue which damages the healthy surrounding organs which can lead to loss of function and even cancer reoccurrence. This problem affects the 44% of the 10,200 lung cancer patients treated with radiotherapy in Australia, and up to 71% of the 1.2 million lung cancer patients treated with radiotherapy in the world each year.

Audiovisual Biofeedback

Figure 2.a) An example of irregular respiratory-related liver tumour motion. Adapted from Worm, et al. b) Examples of image artefacts that such irregular breathing can cause. From Yamamoto et al. c) The impact of the irregular respiratory signal shown in a) on the deviation in dose (colour painted region) from planning to treatment, resulting in underdose to the tumour (red outline) and overdose to the surrounding healthy tissue, which increases the risk of serious side effects.

A number of studies have already been performed demonstrating the effectiveness of AV biofeedback in reducing breathing irregularities in addition to improving image quality, demonstrated in Figure 3.

Audiovisual Biofeedback

Figure 3. Comparison of free breathing and AV biofeedback breathing signals (top) and image quality for 4D-CT (middle) and gated-MRI (bottom). Arrows point out image artefacts due to irregular breathing.

AV biofeedback is now at a crucial stage towards commercialisation. This will be achieved through comprehensive clinical evaluations and technology assessments of the AV biofeedback device in prospective, randomised multi-institutional clinical trials, involving both lung and liver cancer patients across a range of imaging modalities; these will be the most thorough and significant studies of their kind to date.
Such audiovisual biofeedback studies include: