Respiratory phase alignment improves blood-flow quantification in Rb82 PET myocardial perfusion imaging
Bibliographic record
Abstract
PURPOSE: Positron emission tomography (PET) is considered the gold standard for measuring myocardial blood flow in vivo but it is known that respiratory motion can lead to misalignment of the PET and computed tomography (CT) data sets and introduce artifacts in the CT-based attenuation correction (AC) of images. In addition, respiratory motion blurs the PET image and degrades spatial resolution. The purpose of this study is to evaluate the combined effect of respiratory motion compensation (MC) and accurate attenuation correction on relative and absolute blood flow imaging of the heart. METHODS: Dynamic (82)Rb-PET acquisitions were generated for a homogeneous tracer distribution in the heart using an anthropomorphic computer phantom and a Monte Carlo simulator. Attenuation correction was done using three different approaches in which the PET data were corrected by: (1) a respiratory-gated CT map with each respiratory phase of the PET scan corrected by its corresponding CT phase (matched); (2) a time-averaged attenuation map (avg); or (3) an attenuation map generated from the maximum CT-number of every voxel over the respiratory cycle (max). Motion compensated was done using an automated rigid-body registration algorithm that aligned all of the phases of the respiratory-gated PET data after AC. The corrected dynamic PET data were then processed by inhouse kinetic analysis software to generate 3D maps of blood flow. Polar maps of the blood-flow for each CT-AC method with and without MC were compared to the truth using a 17-segment model. The same comparison was performed on data from a pig study. RESULTS: Motion compensation significantly reduced the segmental mean percentage error (sMPE) in all cases (p < 0.01 for matched CTAC and avg CTAC and p = 0.03 for max CTAC). MC significantly increased image uniformity in the case of matched and avg CTAC (p < 0.01, p = 0.04, respectively) with the best improvement coming for matched CTAC. Without MC, there were no significant differences between the three CTAC approaches. With MC, matched CTAC had significantly smaller mean absolute sMPE (p < 0.01 vs avg CTAC; p < 0.01 vs max CTAC) and improved uniformity (p = 0.05 vs avg CTAC; p < 0.01 vs max CTAC). The results were supported with a pig study. CONCLUSIONS: Without MC, there was no significant difference between the three CTAC methods for measuring blood flow. With MC, the matched CTAC approach was significantly better, reducing the mean difference from truth by 6% in the simulated data and improving uniformity by 5%.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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".