Proton-resonance frequency shift MR thermometry is affected by changes in the electrical conductivity of tissue
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Bibliographic record
Abstract
The proton-resonance frequency (PRF) shift method of MR thermometry provides an easy and practical means of quantitatively monitoring in vivo temperatures for MR image-guided thermal-coagulation therapy. However, reported discrepancies in the numerical value of the PRF-thermal coefficient persist, when measured in a variety of experimental conditions and in different tissue types, both ex vivo and in vivo. In this report, a potential source of variation in the PRF-shift method of thermometry is identified that manifests as a constant incremental phase shift per unit change in temperature that is independent of the echo-time setting, when constructing temperature-sensitive phase images from a gradient-echo pulse sequence. It is proposed that this confounding phase-shift offset arises from thermally induced changes in the electrical conductivity of the material. To this end, it is demonstrated that the MR-derived temperature changes could be in error by as much as 28%, as measured from a simple calibration experiment on freshly excised cow liver. A simple method of overcoming this phase-shift offset is described.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| 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) | 0.002 | 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 it