Comparing Large Vessel Uptake of 68Ga-HA-DOTATATE to 18F-FDG Using PET/CT Imaging in Patients with Active Giant Cell Arteritis
Bibliographic record
Abstract
Objectives 18F-fluoro-deoxyglucose (FDG) is currently widely used for PET/CT imaging of large vessel vasculitis (LVV) in giant cell arteritis (GCA), but its performance is influenced by glucocorticoid therapy. We aimed to compare 68Ga-HA-DOTATATE (DOTA), a somatostatin-analog tracer specific for macrophages, to FDG for detection of LVV using PET/CT in a small number of patients with active GCA. Methods In this pilot study, 8 active GCA patients (with disease confirmation by either temporal artery biopsy or positive large vessel imaging) who had initiated glucocorticoids within 2 weeks of enrollment were prospectively consented and sequentially scanned with both FDG PET/CT and 68Ga-HA-DOTATATE PET/CT. Images were reviewed by 2 experienced Nuclear Medicine physicians. Tracer uptake was assessed semi-quantitatively in 8 vascular territories (thoracic and abdominal aorta, bilateral subclavian, vertebral, carotid, femoral/iliac, temporal arteries and coronary arteries) using SUVmax. Target-background ratios (TBR) were calculated using both right atrium (RA) mean (TBRRA) and liver mean (TBRliver) as comparator. Index vessel was defined as the vessel with the greatest tracer uptake in each participant. SUVmax and TBR’s of individual vascular territories and index vessels were compared using students’ t tests. P<0.05 was considered statistically significant. Results The median patient age was 71.5 years (range 64-82), and 4 (50%) were women. See Table 1 for baseline characteristics (Table 1). Five of 8 (62.5%) FDG scans had grade 2 visual uptake in the large vessels, consistent with active LVV. Tracer uptake could be detected semi-quantitatively in the medium-large arteries in both FDG and DOTA scans. FDG scans demonstrated a significantly higher RA activity than DOTA (RA SUVmean 1.88 vs 0.36, p<0.001), while DOTA had a significantly higher liver uptake (liver SUVmean 7.54 vs 2.39, p<0.001). Vascular uptake (as measured by both SUVmax and TBRliver) was significantly higher in FDG than DOTA scans in every vascular territory (p<=0.05 for all comparisons), including index vessels (SUVmax 4.04 vs 1.91, p=0.01, TBRliver 1.73 vs 0.27, p=0.0009). Table 1. Baseline demographics and clinical characteristics of GCA patients. Conclusion 68Ga-HA-DOTATATE uptake can be detected in the aorta and medium branch vessels, including temporal and coronary arteries, of patients with active GCA receiving glucocorticoids. The distribution of DOTA uptake differs from that of FDG, with significantly lower blood pool uptake and higher liver uptake. In this pilot study, the arterial uptake of DOTA was overall lower than that of FDG, suggesting this may not be an optimal substitute for the more established tracer.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".