  We report the results of the deepest Galactic Plane (|b| < 17.5 deg) survey
in the 67.9 and 78.4 keV nuclear de-excitation lines of titanium-44 (44Ti)
performed using the data acquired with the IBIS/ISGRI instrument onboard the
INTEGRAL satellite during 12 years of operation. The peak sensitivity of our
survey reached an unprecedented level of $4.8\times10^{-6}$ erg s$^{-1}$
cm$^{-2}$ (3 sigma) that improves the sensitivity of the survey done by
CGRO/COMPTEL by a factor of ~5. As a result, constraining upper limits for all
sources from the catalog of Galactic supernova remnants (SNRs; Green 2014) are
derived. These upper limits can be used to estimate the exposure needed to
detect 44Ti emission from any known SNR using existing and prospective X- and
gamma-ray telescopes. Among the youngest Galactic SNRs, only Cas A shows
significant 44Ti emission flux in good agreement with the NuSTAR measurements.
We did not detect any other sources of titanium emission in the Galactic Plane
at significance level higher than 5 sigma confirming previous claims of the
rarity of such 44Ti-producing SNRs.
