  We describe an image-based method that uses two radio criteria, compactness
and spectral index, to identify promising pulsar candidates among Fermi Large
Area Telescope (LAT) unassociated sources. These criteria are applied to those
radio sources from the Giant Metrewave Radio Telescope all-sky survey at 150
MHz (TGSS ADR1) found within the error ellipses of unassociated sources from
the 3FGL catalog and a preliminary source list based on 7 years of LAT data.
After follow-up interferometric observations to identify extended or variable
sources, a list of 16 compact, steep-spectrum candidates is generated. An
ongoing search for pulsations in these candidates, in gamma rays and radio, has
found six millisecond pulsars and one normal pulsar. A comparison of this
method with existing selection criteria based on gamma-ray spectral and
variability properties suggests that the pulsar discovery space using Fermi may
be larger than previously thought. Radio imaging is a hitherto underutilized
source selection method that can be used, as with other multi-wavelength
techniques, in the search for Fermi pulsars.
