Assessment of Human Biodistribution and Dosimetry of 4-Fluoro-11β-Methoxy-16α-<sup>18</sup>F-Fluoroestradiol Using Serial Whole-Body PET/CT
Bibliographic record
Abstract
UNLABELLED: 4-Fluoro-11beta-methoxy-16alpha-18F-fluoroestradiol (4FMFES) is a newly developed radiolabeled estradiol analog for PET imaging of estrogen receptors (ERs) that shows improved target-to-background ratios, compared with 16alpha-18F-fluoroestradiol (FES), in small-animal models. The aim of this study was to assess the biodistribution, dosimetry, and safety of 4FMFES in healthy women. METHODS: Ten healthy subjects (6 pre- and 4 postmenopausal women) who had fasted were injected with 66-201 MBq of 4FMFES at a high effective specific activity (median, 251 GBq/micromol). During a 2-h period, each subject underwent 4 serial rapid PET acquisitions and 2 low-dose CT acquisitions on a PET/CT camera. Volumes of interest were drawn over source organs for each PET acquisition, allowing the calculation of time-activity curves, residence times, and radiation dosimetry estimates. Serial blood samples were obtained to measure blood and plasma activity clearance. 4FMFES safety was assessed by blood and urine analyses and vital-sign monitoring. RESULTS: A 4FMFES injection was well tolerated in all subjects. The liver showed high uptake, and the hepatobiliary excretion was massive. Little urinary excretion occurred. Uterus uptake was visualized in all subjects and remained relatively constant over time (maximum and mean standardized uptake values at 60 min were 5.34+/-3.32 and 2.68+/-1.89, respectively). Background activity was low and decreased over time, resulting in an increasing uterus-to-background ratio (12.1+/-2.2 at 60 min). The critical organ was the gallbladder (0.80+/-0.51 mGy/MBq), followed by the upper large intestine (0.13+/-0.04 mGy/MBq), small intestine (0.12+/-0.04 mGy/MBq), and liver (0095+/-0.019 mGy/MBq). For a typical 4FMFES dose of 185 MBq, the effective dose was calculated at 4.82+/-0.70 mSv. CONCLUSION: 4FMFES is considered safe for use in humans, and its effective dose remains well within acceptable limits. The absorbed dose to the gallbladder was relatively high and could potentially be reduced by injecting 4FMFES in patients who had not fasted. 4FMFES showed a significant, potentially estrogen receptor-mediated uterus uptake in both pre- and postmenopausal subjects.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 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".