  We present 10" to 18" images of four massive clusters of galaxies through the
Sunyaev-Zel'dovich Effect (SZE). These measurements, made at 90~GHz with the
MUSTANG receiver on the Green Bank Telescope (GBT), reveal pressure
sub-structure to the intra-cluster medium (ICM) in three of the four systems.
We identify the likely presence of a previously unknown weak shock-front in
MACS0744+3927. By fitting the Rankine-Hugoniot density jump conditions in a
complementary SZE/X-ray analysis, we infer a Mach number of M =
1.2^{+0.2}_{-0.2} and a shock-velocity of 1827^{+267}_{-195}~km/s. In
RXJ1347-1145, we present a new reduction of previously reported data and
confirm the presence of a south-east SZE enhancement with a significance of
13.9 sigma when smoothed to 18" resolution. This too is likely caused by
shock-heated gas produced in a recent merger. In our highest redshift system,
CL1226+3332, we detect sub-structure at a peak significance of 4.6 sigma in the
form of a ridge oriented orthogonally to the vector connecting the main mass
peak and a sub-clump revealed by weak lensing. We also conclude that the gas
distribution is elongated in a south-west direction, consistent with a
previously proposed merger scenario. The SZE image of the cool core cluster
Abell 1835 is, in contrast, consistent with azimuthally symmetric signal only.
This pilot study demonstrates the potential of high-resolution SZE images to
complement X-ray data and probe the dynamics of galaxy clusters
