Analysis of Four Dopaminergic Tracers Kinetics Using Two Different Tissue Input Function Methods
Bibliographic record
Abstract
The integrity of the dopaminergic system can be studied using positron emission tomography. The presynaptic tracers [11C]-methylphenidate and [11C]dihydrotetrabenazine (DTBZ) are used to investigate the dopamine transporter availability, the dopamine vesicular transporter integrity; the postsynaptic tracers [11C]-raclopride and [11C]-Schering 23990 (SCH) are used to probe the D2 and D1 receptors. These are reversible tracers, where the binding potential (BP) = Bmax/Kd often is used to quantify the amount of their specific binding to the sites of interest. The simplified tissue input methods to calculate BP are attractive, since they do not require a blood input function. The suitability and performance of two such methods were evaluated: the Logan graphical tissue method, and the Lammertsma reference tissue method (RTM). The BP estimates obtained with the two methods were nearly identical in most cases, with similar reliability and reproducibility indicating that all four tracers satisfy the assumptions required by each method. The correlations among the fitted parameters obtained from the RTM were estimated and were found not to introduce noticeable bias in the RTM BP and R1 estimates. R1 showed low intersubject and intrasubject variability. The k2 estimate showed good reliability for SCH with cerebellar input function and DTBZ with occipital input function.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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 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".