Let the patient see their own breath-hold on a screen or in video glasses

The owner's example, and the one this file was written around. Breath-hold radiotherapy depends on the patient holding a breath of the same depth, in the same place, every time, often for 20 to 40 seconds and many times a session. The machine already measures this, by tracking the chest or abdomen with a camera, an infrared block or a surface scanner. The upgrade is to close the loop: give the patient the same trace, with a band marking the target, so they can see when they are in it and correct themselves.

What the comparisons found. In 2009, five women with left breast cancer and fifteen volunteers performed breath-holds with and without visual coaching through video goggles fed by a three-dimensional surface camera: reproducibility improved from 2.1 to 0.5 millimetres and stability from 1.5 to 0.7 millimetres (p below 0.001 and below 0.01), with the largest gains in the people whose holds were worst. In a series of 43 women, chest-wall displacement on daily portal images was 0.59 millimetres on average with visual feedback against 2.09 with audio coaching alone (p below 0.001). In nine lung cancer patients scanned twice by MRI, audiovisual biofeedback improved the reproducibility of tumour position between sessions by 46 per cent, from 8.8 to 4.8 millimetres. Sixteen lung patients having stereotactic treatment through a monocular head-mounted display all tolerated it, with breath-hold variability of 1.5 and 1.2 millimetres within and between holds. Not every result points one way: in the earlier test of that head-mounted display in five healthy volunteers, feedback improved the reproducibility of breath-holds at the end of breathing out (0.63 against 0.96 millimetres, p equals 0.025) but not of deep breaths in (1.74 against 0.84 millimetres, not significant). In BRAVEHeart, 26 women analysed after randomisation between two feedback devices found both easy to follow, with no difference in accuracy or appointment length.