$Purpose:$ Dynamic magnetic resonance spectroscopic imaging of hyperpolarized $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C-labeled cell substrates has enabled the investigation of tissue metabolism in vivo. Currently observation of these hyperpolarized substrates is limited mainly to $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C detection. We describe here an imaging pulse sequence that enables proton observation by using polarization transfer from the hyperpolarized $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C nucleus to spin-coupled protons.

$Methods:$ The pulse sequence transfers $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C hyperpolarization to $1$H using a modified reverse insensitive nuclei enhanced by polarization transfer (INEPT) sequence that acquires a fully refocused echo. The resulting hyperpolarized $1$H signal is acquired using a 2D echo-planar trajectory. The efficiency of polarization transfer was investigated using simulations with and without T$1$ and T$2$ relaxation of both the $1$H and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C nuclei.

$Results:$ Simulations showed that $1$H detection of the hyperpolarized $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C nucleus in lactate should increase significantly the signal-to-noise ratio when compared with direct $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C detection at 3T. However the advantage of $1$H detection is expected to disappear at higher fields. Dynamic $1$H images of hyperpolarized [1-$\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C]lactate, with a spatial resolution of 1.25 × 1.25 mm$2$, were acquired from a phantom injected with hyperpolarized [1-$\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C]lactate and from tumors in vivo following injection of hyperpolarized [1-$\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C]pyruvate.

$Conclusions:$ The sequence allows $1$H imaging of hyperpolarized $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C-labeled substrates in vivo.