*2.3. Cyclodextrin-Based Contrast Agents for Hyperpolarized MRI*

Although molecular imaging using MRI is challenging due to the lack of sensitivity of this imaging modality [78,79], progress has been made with the development of hyperpolarized (HP) MRI [79,80]. HP MRI utilizes the advantage of a metastable state with spin population excess significantly larger compared to the thermal equilibrium state [81]. Hyperpolarization of noble gases (such as <sup>3</sup>He and <sup>129</sup>Xe) is conducted via spin exchange optical pumping (SEOP), whereas polarization of <sup>13</sup>C or <sup>1</sup>H containing molecules is created through dynamic nuclear polarization (DNP) [82–85].
