Bibliographic record
Abstract
ABSTRACT Thallium-201 ( 201 T1) has been the most commonly used agent for myocardial perfusion imaging. Its uptake is proportional to myocardial blood flow. Its ability to redistribute with time is useful in differentiating between ischemia and necrosis. However, its gamma energy is suboptimal for imaging and its three day half-life presents a heavy radiation burden to the patient. Thus, new myocardial perfusion imaging agents have been developed. Two classes of perfusion imaging agents, the isonitrile complexes and BATO compounds are reviewed in this article. Of the isonitriles, Technetium 99m( 99m Tc)-sestamibi is the most promising. It exhibits a very good myocardium to background ratio which is reached at 1-1.5 hours post-injection. The radioisotope 99m Tc has an optimum gamma energy for imaging and a short half-life. 99m Tc-sestamibi does not redistribute and as such, two injections are required to distinguish between ischemia and necrosis. A same day rest-stress study can be carried out by having the two required doses in a 1:5 radioactivity ratio. The smaller dose is used for the rest study and the larger dose for the stress study. The BATO compound currently under study is 99m Tcteboroxime. It exhibits a very high and rapid myocardial uptake allowing images of the heart to be obtained at 1-2 minutes post-injection. Due to a very rapid clearance, a second dose of equal radioactivity can be given 1-2 hours later for the rest study. 99m Tc-teboroxime is currently not yet licensed for use in Canada. RESUME Le thallium 201 ( 201 Tl) est la substance la plus couramment utilisee en scintigraphie myocardique. La captation de cet element est proportionnelle au debit sanguin du myocarde. De plus, la redistribution du thallium avec le temps permet de distinguer l'ischemie de la necrose. Toutefois, le rayonnement gamma est inferieur au rayonnement optimal pour la scintigraphie et la demi-vie de trois jours de l'isotope exerce un lourd tribut sur le malade. On a donc mis au point de nouveaux produits pour la scintigraphie myocardique. Le present article en examine deux, les complexes isonitriles et les composes BATO. Parmi les isonitriles, le technetium 99m ( 99m Tc)-sestamibi parait le plus prometteur. Ce compose donne un excellent rapport entre le myocarde et le rayonnement de fond 1 a 1,5 heure apres l'injection. L'isotope 99m Tc a un rayonnement gamma optimal pour la scintigraphie et une breve demi-vie. Cependant, il n'y a pas redistribution, ce qui necessite deux injections si on veut faire la distinction entre l'ischemie et la necrose. On peut neanmoins effectuer un examen au repos et un autre sous contrainte la meme journee en injectant les deux doses requises selon un rapport de radioactivite de 1:5. La plus petite dose servira a l'examen au repos tandis que la seconde ira a la scintigraphie d'effort. Le compose BATO a l’etude est le 99m Tc-teboroxim. Ce produit est capte rapidement par le myocarde et en tres grande quantite, ce qui permet d'obtenir une image du coeur 1 ou 2 minutes apres l'injection. Une clairance tres rapide autorise l’administration d'une deuxieme dose de meme puissance radioactive 1 ou 2 heures plus tard, pour la scintigraphie au repos. A l’heure actuelle, le 99m Tc-teboroxime n'est pas commercialise au Canada.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".