Normal human and sheep fetal vessel oxygen saturations by T2 magnetic resonance imaging
Bibliographic record
Abstract
Key points Human fetal Doppler ultrasound and invasive blood gas measurements obtained by cordocentesis or at the time of delivery reveal similarities with sheep (an extensively used model for human fetal cardiovascular physiology). Oxygen saturation (SO 2 ) measurements in human fetuses have been limited to the umbilical and scalp vessels, providing little information about normal regional SO 2 differences in the fetus. Blood T2 MRI relaxometry presents a non‐invasive measure of SO 2 in the major fetal vessels. This study presents the first in vivo validation of fetal vessel T2 oximetry against the in vitro T2–SO 2 relationship using catheterized sheep fetuses and compares the normal SO 2 in the major vessels between the human and sheep fetal circulations. Human fetal vessel SO 2 by T2 MRI confirms many similarities with the sheep fetal circulation and is able to demonstrate regional differences in SO 2 ; in particular the significantly higher SO 2 in the left versus right heart. Abstract Blood T2 magnetic resonance imaging (MRI) relaxometry non‐invasively measures oxygen saturation (SO 2 ) in major vessels but has not been validated in fetuses in vivo . We compared the blood T2–SO 2 relationship in vitro (tubes) and in vivo (vessels) in sheep, and measured SO 2 across the normal human and sheep fetal circulations by T2. Singleton pregnant ewes underwent surgery to implant vascular catheters. In vitro and in vivo sheep blood T2 measurements were related to corresponding SO 2 measured using a blood gas analyser, as well as relating T2 and SO 2 of human fetal blood in vitro . MRI oximetry was performed in the major vessels of 30 human fetuses at 36 weeks (term, 40 weeks) and 10 fetal sheep (125 days; term, 150 days). The fidelity of in vivo fetal T2 oximetry was confirmed through comparison of in vitro and in vivo sheep blood T2–SO 2 relationships ( P = 0.1). SO 2 was similar between human and sheep fetuses, as was the fetal oxygen extraction fraction (human, 33 ± 11%; sheep, 34 ± 7%; P = 0.798). The presence of streaming in the human fetal circulation was demonstrated by the SO 2 gradient between the ascending aorta (68 ± 10%) and the main pulmonary artery (49 ± 9%; P < 0.001). Human and sheep fetal vessel MRI oximetry based on T2 is a validated approach that confirms the presence of streaming of umbilical venous blood towards the heart and brain. Streaming is important in ensuring oxygen delivery to these organs and its disruption may have important implications for organ development, especially in conditions such as congenital heart disease and fetal growth restriction.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".