New Guidelines for PE VQ Scanning
Bibliographic record
Abstract
Figure: PE, pulmonary embolism, VQ, scanning, Canadian Association of Nuclear Medicine, D-dimer, SPECT, CTPA, ventilationBy EMedHome.com The Canadian Association of Nuclear Medicine recently released best practice guidelines for VQ scanning in pulmonary embolism. (J Med Imaging Radiat Sci. 2024;55[1]:158; https://tinyurl.com/mwja5hwb.) These recommendations provide a concise, updated summary of key aspects of diagnosing acute PE. D-dimer has high sensitivity but low specificity for PE, and it is not needed if the pretest probability for PE is other than low. A negative D-dimer has a high negative predictive value. A ventilation/perfusion SPECT nuclear medicine scan has at least the same or better accuracy for PE as CTPA, but it has a much lower radiation dose, especially for breast exposure. A fetal dose is roughly equivalent for V/P SPECT and MD-CTPA. A breast dose is much higher with MD-CTPA than V/P SPECT. Consider V/P SPECT for children and pregnant women as the first investigation for suspected PE due to better sensitivity, lower radiation, and no adverse reactions. A perfusion-only study might suffice, with an optional ventilation study the next day if needed, because ventilation co-morbidities are unlikely. V/P SPECT should be used in pregnant women with comorbidities or a history of smoking. Interpretation in probabilistic terms is not appropriate and must be avoided. All exams should be interpreted as either PE present or PE absent or using clear terms. PE is diagnosed when at least one lobar or segmental vascular type mismatched defect (perfusion defect with preserved ventilation) or two subsegmental vascular mismatches is present, regardless of other findings. PE is excluded when perfusion is normal or if there are only matched defects (regardless of morphology), nonvascular mismatches, or reverse mismatches (perfusion preserved but ventilation absent). This clinical pearl first appeared on www.EMedHome.com. Subscribers receive a new clinical pearl by email every Wednesday. Visit our website for videos from emergency medicine experts (http://tinyurl.com/EMedHomeVideos) and podcasts from Amal Mattu, MD, and other noted emergency physicians from EMedHome.com (http://tinyurl.com/MattuEMCast). EMedHome.com on EM-News.com This Month's Video W. Gannon Sungar, DO: Strangulation Injuries: http://tinyurl.com/EMedHomeVideos. Dr. Sungar is an associate program director at the Denver Health Residency in Emergency Medicine and an assistant professor of emergency medicine at the University of Colorado School of Medicine in Aurora, CO. This Month's Podcast Amal Mattu, MD, and colleagues: AHA Updates on Adult ACLS and Pulmonary Embolism: http://tinyurl.com/MattuEMCast. Dr. Mattu is one of the premier speakers in emergency medicine and a professor of emergency medicine and the vice chair of emergency medicine at the University of Maryland School of Medicine in Baltimore.
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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 | 0.003 | 0.022 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.005 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.006 | 0.008 |
| Insufficient payload (model declined to judge) | 0.058 | 0.038 |
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".