R₁ and R₂* changes in the human placenta in response to maternal oxygen challenge

Abstract

The results demonstrate the feasibility of non-invasive investigation of placental oxygenation using MRI and the sensitivity of R1 oxygen-enhanced MRI to gestational age. The techniques have the potential to provide unique noninvasive biomarkers in compromised pregnancies.

Absence of Po2 change in fetal brain despite Po2 increase in placenta in response to maternal oxygen challenge

“…The DR 1 data were then acquired using a protocol previously described for placental imaging. 13 A baseline T 1 map was acquired under air-breathing to calibrate the sequence monitoring T 1 changes against time. Data for this were acquired using an Inversion Recovery-Turbo Spin-Echo (IR-TSE) sequence with four inversion times (TIs) (60, 300, 1100, 2000 ms) and an acquisition without an inversion pulse to provide a measurement of fully relaxed signal.…”

“…13 R 1 values were then generated for each time point on a voxel-by-voxel basis inside the ROI. Median R 1 over the ROI was calculated for each time point.…”

“…Measurements of DR 1 have been used to observe PO 2 changes in many tissues including placenta, 13 kidneys, 14 liver, spleen, fat 15,16 and blood. 8,17 Given the scarcity of such data in fetal brain and the potential of OE-MRI to investigate oxygenation, we measured DR 1 in placenta and fetal brain following a switch from maternal normoxia to hyperoxia over a range of gestational ages in normal pregnancy.…”

Non-invasive pre-clinical MR imaging of prostate tumor hypoxia for radiation therapy prognosis

“…Investigations have shown that molecular oxygen when inhaled and dissolved in tissue fluid or blood plasma, can alter T 1 values in the tissue due to its paramagnetic characteristics 3,5 . Similarly, alterations of T 2 * values can be observed in the blood due to the magnetic susceptibility differences between oxy-and deoxyhemoglobin 3 . Tumor hypoxia is associated with radiation resistance.…”

“…Innovation/Impact: Oxygenation in tissue has been shown to influence MR physical parameters such as the intrinsic longitudinal relaxation time (T 1 ) and the apparent transverse relaxation time (T 2 *) [1][2][3][4][5] . Investigations have shown that molecular oxygen when inhaled and dissolved in tissue fluid or blood plasma, can alter T 1 values in the tissue due to its paramagnetic characteristics 3,5 .…”