  Fast coronal mass ejections (CMEs) can drive shock waves capable of
accelerating electrons to high energies. These shock-accelerated electrons act
as sources of electromagnetic radiation, often in the form of solar radio
bursts. Recent findings suggest that radio imaging of solar radio bursts can
provide a means to estimate the lateral expansion of CMEs and associated shocks
in the low corona. Our aim is to estimate the expansion speed of a CME-driven
shock at the locations of radio emission using 3D reconstructions of the shock
wave from multiple viewpoints. We estimated the 3D location of radio emission
using radio imaging from the Nan\c{c}ay Radioheliograph and the 3D location of
the shock. The 3D shock was reconstructed using white-light and extreme
ultraviolet images of the CME from the Solar Terrestrial Relations Observatory,
Solar Dynamics Observatory, and the Solar and Heliospheric Observatory. The
lateral expansion speed of the CME-driven shock at the electron acceleration
locations was then estimated using the approximate 3D locations of the radio
emission on the surface of the shock. The radio bursts associated with the CME
were found to reside at the flank of the expanding CME-driven shock. We
identified two prominent radio sources at two different locations and found
that the lateral speed of the shock was in the range of
$800-1000\,\mathrm{km\,s^{-1}}$ at these locations. Such a high speed during
the early stages of the eruption already indicates the presence of a fast shock
in the low corona. We also found a larger ratio between the radial and lateral
expansion speed compared to values obtained higher up in the corona. The high
shock speed obtained is indicative of a fast acceleration during the initial
stage of the eruption. This acceleration is most likely one of the key
parameters contributing to the presence of metric radio emissions, such as type
II radio bursts.
