The feasibility of<i>in vivo</i>quantification of bone-fluorine in humans by delayed neutron activation analysis: a pilot study
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Bibliographic record
Abstract
Fluorine (F) plays an important role in dental health and bone formation. Many studies have shown that excess fluoride (F(-)) can result in dental or skeletal fluorosis, while other studies have indicated that a proper dosage of fluoride may have a protective effect on bone fracture incidence. Fluorine is stored almost completely in the skeleton making bone an ideal site for measurement to assess long-term exposure. This paper outlines a feasibility study of a technique to measure bone-fluorine non-invasively in the human hand using in vivo neutron activation analysis (IVNAA) via the (19)F(n,γ)(20)F reaction. Irradiations were performed using the Tandetron accelerator at McMaster University. Eight NaI(Tl) detectors arranged in a 4π geometry were employed for delayed counting of the emitted 1.63 MeV gamma ray. The short 11 s half-life of (20)F presents a difficult and unique practical challenge in terms of patient irradiation and subsequent detection. We have employed two simultaneous timing methods to determine the fluorine sensitivity by eliminating the interference of the 1.64 MeV gamma ray from the (37)Cl(n,γ)(38)Cl reaction. The timing method consisted of three counting periods: an initial 30 s (sum of three 10 s periods) count period for F, followed by a 120 s decay period, and a subsequent 300 s count period to obtain information pertaining to Ca and Cl. The phantom minimum detectable limit (M(DL)) determined by this method was 0.96 mg F/g Ca. The M(DL) was improved by dividing the initial timing period into three equal segments (10 s each) and combining the results using inverse variance weighting. This resulted in a phantom M(DL) of 0.66 mg F/g Ca. These detection limits are comparable to ex vivo results for various bones in the adult skeleton reported in the literature. Dosimetry was performed for these irradiation conditions. The equivalent dose for each phantom measurement was determined to be 30 mSv. The effective dose was however low, 35 µSv, which is comparable to other clinical diagnostic tools. The M(DL), relatively low radiation dose and non-invasiveness indicate the suitability of this method for routine in vivo analysis of bone-fluorine content. This prompted us to perform a trial study in human subjects. A preliminary human study on 34 participants was completed, with 33 of the 34 measurements proving to be successful. The in vivo M(DL) based on the improved timing method was determined to be 0.69 mg F/g Ca for the 33 successful human measurements. In our opinion, this technique has been demonstrated to be a suitable method for in vivo assessment of fluorine bone-burden.
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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) | 0.000 | 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 | 0.000 |
| 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 it