Reproducibility of 18F-FAZA PET-CT mouse imaging
Bibliographic record
Abstract
2534 Objectives Imaging of tumour hypoxia in mouse models of human cancer using small animal PET-CT with 18F-FAZA has been reported in several papers, however there is little data about the reproducibility of this imaging. The purpose of this study was to evaluate reproducibility of PET uptake of 18F-FAZA in mice with tumours after 2 scans within 24 hours. Methods Human ME180 cancer cells were implanted subcutaneously in mice to generate tumour xenografts. Mice (n=8) were injected awake via tail vein with 18F-FAZA (14-20 MBq), kept awake for the uptake period then anesthetized (1.5% isoflurane in medical air) for a 20 min PET scan. CT scans were acquired immediately after PET. After CT mice were allowed to recover and all imaging was repeated between 23-24 h later. Acquisition parameters of net injected 18F-FAZA, awake uptake time, and scan start time post-injection were recorded for each. Images were quantitatively assessed by 2 different operators manually drawing 2D regions-of-interest over the tumour and muscle on fused PET-CT scans. Mean and maximum standardized uptake values (SUV) of 18F-FAZA were determined for each operator. Coefficient of variation (CV) was also calculated as the SD of the first and second scans SUV divided by their mean. Results Acquisition parameters of net injected 18F-FAZA, awake uptake time, and scan start time post-injection from day 1-2 had average absolute differences of 3 MBq, and 0.3, and 0.4 min respectively. All SUV and CV data are listed in the table. Overall there was higher variation in FAZA uptake in muscle than tumour for both operators and as expected the maximum uptake in tumours was identical for both operators. Conclusions This study demonstrated that the changes in acquisition parameters from day 1-2 were small and this did not seem to affect the uptake of 18F-FAZA in tumour. The variation in tumour uptake of 18F-FAZA from day 1-2 is 15% CV or less, indicating that our method is reproducible and comparable with previously reported FDG and FLT-PET reproducibility in mice.
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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 | 0.005 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".