Preclinical hyperpolarized <sup>129</sup>Xe MRI: ventilation and <i>T</i><sub>2</sub>* mapping in mouse lungs at 7 T using multi‐echo flyback UTE
Bibliographic record
Abstract
Fast apparent transverse relaxation (short T 2 *) is a common obstacle when attempting to perform quantitative 1 H MRI of the lungs. While T 2 * times are longer for pulmonary hyperpolarized (HP) gas functional imaging (in particular for gaseous 129 Xe), T 2 * can still lead to quantitative inaccuracies for sequences requiring longer echo times (such as diffusion weighted images) or longer readout duration (such as spiral sequences). This is especially true in preclinical studies, where high magnetic fields lead to shorter relaxation times than are typically seen in human studies. However, the T 2 * of HP 129 Xe in the most common animal model of human disease (mice) has not been reported. Herein, we present a multi‐echo radial flyback imaging sequence and use it to measure HP 129 Xe T 2 * at 7 T under a variety of respiratory conditions. This sequence mitigates the impact of T 1 relaxation outside the animal by using multiple gradient‐refocused echoes to acquire images at a number of effective echo times for each RF excitation. After validating the sequence using a phantom containing water doped with superparamagnetic iron oxide nanoparticles, we measured the 129 Xe T 2 * in vivo for 10 healthy C57Bl/6 J mice and found T 2 * ~ 5 ms in the lung airspaces. Interestingly, T 2 * was relatively constant over all experimental conditions, and varied significantly with sex, but not age, mass, or the O 2 content of the inhaled gas mixture. These results are discussed in the context of T 2 * relaxation within porous media.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".