  An increase in radiotherapy-induced secondary malignancies has led to recent
developments in analytical modelling of out-of-field dose. These models must be
validated against measurements, but currently available datasets are outdated
or limited in scope. This study aimed to address these shortcomings by
producing a large dataset of out-of-field dose profiles measured with modern
equipment. A novel method was developed with the intention of allowing
physicists in all clinics to perform these measurements themselves using
commonly available dosimetry equipment. A standard 3D scanning water tank was
used to collect 36 extended profiles. Each profile was measured in two
sections, with the inner section measured with the beam directly incident on
the tank, and the outer section with the beam incident on a water-equivalent
phantom abutted next to the tank. The two sections were then stitched using a
novel feature-matching approach. The profiles were compared against linac
commissioning data and manually inspected for discontinuities in the overlap
region. The dataset is presented as a publicly accessible comma separated
variable file containing off-axis ratios at a range of off-axis distances. This
dataset may be applied to the development and validation of analytical models
of out-of-field dose. Additionally, it may be used to inform dose estimates to
radiosensitive implants and anatomy. Physicists are encouraged to perform these
out-of-field measurements in their own clinics and share their results with the
community.
