Amyloid plaque imaging agent [C-11]-6-OH-BTA-1: biodistribution and radiation dosimetry in baboon
Bibliographic record
Abstract
BACKGROUND: The amyloid neuritic plaque is considered to be a toxic collection of amyloid-ss protein found in brain tissue in Alzheimer's disease. A neutral analogue of the amyloid-binding thioflavin-T (BTA), has been radiolabeled as [C-11]-6-OH-BTA-1. It crosses the blood brain barrier, and is a promising tracer for imaging plaques in vivo using positron emission tomography. We now report the biodistribution and dosimetry of [C-11]-6-OH-BTA-1 in baboons. METHODS: Four 2-hour whole body studies were acquired in an ECAT ACCEL camera in two baboons after the bolus injection of [C-11]-6-OH-BTA-1. After 3.5 minute transmission scans performed per bed position prior to injection, emission scans were collected in 2-D mode over five bed positions. Regions of interest (ROI) were drawn around the brain, left and right lungs, heart, liver, gall bladder, left and right kidneys, spleen and urinary bladder. Since no fluid was removed from the baboons, total body radioactivity was calculated using the injected dose and a calibration factor determined from a cylinder phantom. The area under the curve (AUC) for each ROI was determined by trapezoidal integration of the first few points with subsequent points fit by a decreasing monoexponential. The AUC was then divided by counts in the total body, and resulting residence times were entered into the MIRDOSE3 program. RESULTS: The animals tolerated the procedure well. The ligand was eliminated via the hepatobiliary and renal systems. In the adult male and female reference the gallbladder received the highest estimated radiation dose and was the critical organ (3.9E-02 mGy/MBq and 4.3E-02 mGy/MBq respectively). CONCLUSION: In the United States, the absorbed dose to the gallbladder would limit [C-11]-6-OH-BTA-1 administered with the approval of a Radioactive Drug Research Committee (RDRC) to a single injection of 1295 MBq (35 mCi) in the adult male, and 1314 MBq (35 mCi) in the adult female.
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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) | 0.000 | 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".