Ga-68-labelled hyperbranched polyglycerol for cardiac blood pool imaging
Bibliographic record
Abstract
1100 Objectives Red blood cells tagged with Tc-99m are commonly used as cardiac blood pool agents for imaging with gamma cameras. More than 400,000 such procedures are performed yearly in North America. Replacing Tc-99m-RBC with a non-toxic biocompatible polymer that behaves similarly in vivo, can be radiolabelled in a kit format without the necessity of handling blood, and can be imaged with a PET scanner would be advantageous. Our objective was to radiolabel a long-circulating hyperbranched polyglycerol (HPG) with Ga-68 as a Tc-99m RBC substitute for blood pool imaging with PET. Methods The dendrimer-like HPG with a molecular weight of 500 kDa was derivatized with 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and radiolabelled with Ga-68 in a kit format. After injection of 200 µCi into the tail vein of rats, dynamic gated microPET/CT imaging was performed in 200 g Sprague Dawley rats on an Inveon microPET/CT scanner (Siemens). Results HPG was radiolabelled at room temperature within 2 minutes at >99% radiolabelling efficiency. No adverse effects were detected in cell toxicity studies (MTT assay) and several blood toxicity assays. The biological half life in the circulation was 50.7 h, as determined by a pharmacokinetic study with Ga-67. Dynamic imaging showed that the biodistribution was consistent with an intravascular blood pool agent, with minimal urinary excretion of Ga-68. Gated imaging showed that wall motion and cardiac contractility could be easily assessed, confirming the suitability of this agent for cardiac blood pool imaging. Conclusions Ga-68-HPG is an excellent cardiac blood pool agent for PET imaging. Its advantages are the rapid preparation without additional purification steps using a simple kit format and the good availability of the radioisotope Ga-68 from a Ge-68/Ga-68 generator which can be used up to a year. Research Support This research was supported by a Collaborative Health Research Projects (CHRP) program grant from CIHR/NSERC
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".