Possibilities of the T2* relaxometry method in the diagnosis of hypoxia of the fetal brain

The currently existing methods for assessing fetal brain oxygenation are indirect and lead either to underestimation of the clinical situation or, conversely, to excessive obstetric interventions. During hypoxia, the amount of paramagnetic deoxyhemoglobin in tissues increases, so it reduces the T2* relaxation time. This phenomenon opens up the possibility of using T2* as a specific diagnostic marker of brain hypoxia during fetal MRI. This review is devoted to the study of the capabilities of the T2* magnetic resonance relaxometry method in the diagnosis of hypoxic conditions of the fetal brain. The currently available data on T2* of various fetal brain structures and their changes in various pathological conditions are presented. According to the data from the studies presented in this review, T2* relaxation time of fetal brain tissue decreases with gestational age, which is associated with both a physiological decrease in brain oxygenation, especially in the third trimester, and with the natural maturation of tissue during fetal development. Also, a number of studies have observed a noticeable decrease in T2* relaxation time of the fetal brain under various hypoxic conditions. Fetal MRI is technically challenging due to the small size of the brain, unpredictable fetal movements, and also a number of maternal factors. All researchers indicate a decrease of T2* in the presence of hypoxia. In the review various methods for quickly obtaining and processing T2*-weighted images that are resistant to chaotic fetal movements are considered. The presented material can be used for further development of quantitative T2* relaxometry in prenatal diagnostics.