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PubMed1981

Technetium coordination state as a factor of stability in 99mTc-complexes used in hepatobiliary system: comparative studies on 99mTc-complexes of pyridoxal with glutamate (Tc-PG) and isoleucine (Tc-PI).

Studies on 99mTc-Penicillamine (Tc-Pen) have given us some insight into the significance of the technetium coordination state in hepatobiliary clearance behavior. A 99mTc-complex of pyridoxal and glutamate (Tc-PG) prepared by Baker et al. (1975) using an autoclaving process or by a Sn-Resin kit method (Horiuchi 1981) was compared with a 99mTc-complex of pyridoxal and isoleucine (Tc-PI) prepared by the method of Kato and Hazue (1978) through an intermediate compound of stannous ion, at room temperature. Tc-PG and TcPI complexes analyzed by thin layer chromatography, sephadex column chromatography (G-15), octanol extraction, and ligand exchange reaction showed different chemical properties. Their biological evaluation also demonstrated great differences in biodistribution in mice, metabolic studies, protein binding, and rat bile excretion. Tc-PG was estimated as an hepatobiliary agent with strong metal-ligand binding, inert to ligand exchange reaction with Pen at physiological pH; the likely occurrence of technetium in a mononuclear or dinuclear state providing the great stability observed in its biological and in vivo behavior was compared with the relatively weaker binding observed in Tc-PI, a highly lipophilic complex of high liver partition but of low stability, denoting its different chemical characteristics. The technetium coordination state in radiopharmaceuticals is responsible for the integrity of the molecule while in the blood pool and its relevance in impaired liver uptake is discussed.

Animals↗
PubMed1996

Technetium, the missing element.

The history of the discovery of technetium is reviewed within the framework of the discovery and production of artificial radioactivity in the twentieth century. Important elements of this history are the accidental production of this element in a cyclotron in Berkeley, California, USA, a machine devised by Ernest Orlando Lawrence, and its subsequent discovery in 1937 by Carlo Perrier and Emilio Segrè in scrap metal parts sent by Lawrence to Palermo, Italy by mail. A detailed account is given of the steps taken; the history of the later discovery of the technetium-99m isotope in 1938 is likewise examined. Sources of natural and artificial technetium are briefly discussed.

Cyclotrons↗
PubMed1997

Site-specific conjugation and labelling of prostate antibody 7E11C5.3 (CYT-351) with technetium-99m.

Attachment of chelating agents to the sugar residues of antibodies for subsequent radiolabelling is an attractive approach since it may have less effect on the immunoreactivity than attachment through lysine residues, which are distributed throughout the antibody and may be present near the antigen binding site. We have attached a new hydrazide-linked chelator CYT-395 (Cytogen Corp., Princeton, N.J.) to the sugar residues of the anti-prostate monoclonal antibody 7E11C5.3 and optimised the conditions for labelling the conjugate with technetium-99m in order to compare the conjugate to 7E11C5.3 antibody labelled directly with technetium using a mercaptoethanol reduction technique. Labelling yields of 70%-90% were obtained at specific activities up to 2000 MBq/mg antibody. The stability of the technetium-labelled conjugate in plasma or to a challenge with 0.1 or 1.0 mM cysteine was similar to that of direct-labelled antibody. In nine patients with prostate cancer, the plasma clearance of the labelled conjugate followed a two-compartment model, with an average beta-phase half-life of 31.4+/-3.9 h. The average urinary clearance at 24 h was 15.3+/-5.0% of the injected dose. In this group of patients there was no significant difference between the blood and urine clearance of the labelled conjugate, and the clearances of the direct-labelled antibody.

Animals↗
PubMedDate not supplied

Technetium bone scanning in the diagnosis of osteomyelitis: a meta-analysis of test performance. Diagnostic Technology Assessment Consortium.

PURPOSE: To determine the diagnostic performance of technetium bone scanning in the setting of possible osteomyelitis in the foot of a patient who has diabetes or other vasculopathy. DESIGN: Meta-analysis. Data identification and study selection: To be eligible for inclusion, a report must have used intravenous technetium-99m methylene diphosphonate or a similar agent in humans over the age of 16 years, must have addressed possible osteomyelitis of the lower extremity with ulcer or soft-tissue inflammation in the setting of diabetes, neuropathy, or vasculopathy, and must have allowed the generation of a two-by-two table. A structured search of the MEDLARS database found 296 possibly eligible reports; ten met all the inclusion criteria. DATA EXTRACTION AND SYNTHESIS: The reported sensitivity and specificity of each report were converted to their logistic transforms and a straight line was fitted by weighted least-squares regression. The line was then back-transformed to yield a summary receiver operating characteristic curve. The false-positive rate of the bone scan is at best in the range of 10 to 20%. This occurs at sensitivities between 70 and 80%. The studies with increased sensitivity also reported sizable increases in the false-positive rate ranging from 20 to over 90%. Even small increases in sensitivity have necessitated large sacrifices in specificity. Seven of the ten studies reported specificities under 70%. CONCLUSIONS: Published data defining the effectiveness of technetium bone scanning for the diagnosis of osteomyelitis in the impaired foot indicate relatively poor performance. In many clinical situations, the specificity of the bone scan will not be high enough to confirm the diagnosis of osteomyelitis.

False Positive Reactions↗
PubMed1995

Rest technetium 99m-sestamibi tomoscintigraphy in hibernating myocardium.

The myocardial uptake of rest-injected technetium 99m sestamibi on single-photon-emission computed tomographic images was assessed in 25 patients. All had an area of myocardial dysfunction that could be related to a coronary artery stenosis. None of the patients had clinical evidence of a myocardial infarction. Three months after revascularization, viability was demonstrated by contrast angiography and center-line analysis in 21 (78%) of the 27 formerly hibernating territories. Among these, none had a transmural defect, and 38% had a normal technetium 99m-sestamibi uptake. The four transmural preoperative defects were located in territories without viability. Eight of the 9 territories that were normal at scintigraphy proved to be viable postoperatively. It is concluded that as long as some residual technetium 99m-sestamibi uptake is present, viable myocardium is also present.

Aged↗
PubMed1979

Abnormal technetium-99m pyrophosphate images in unstable angina: ischemia versus infarction?

There is controversy concerning the specificity of myocardial infarct imaging with technetium-99m pyrophosphate due to the high frequency of false positive images, especially in patients with unstable angina. In this study technetium-99m pyrophosphate images were compared with frequent determinations of plasma creatine kinase, MB isoenzyme (MB CK) activity in 116 patients admitted with the diagnosis of unstable angina. It was hypothesized that frequent measurement of MB CK activity, a sensitive and specific marker for myocardial necrosis, using sensitive assay techniques would detect small amounts of myocardial necrosis which might have been unrecognized by conventional clinical methods. The scintigraphic results and isoenzyme determinations agreed in 88 percent of patients; both tests were normal in 69 percent and both were abnormal, indicating acute myocardial infarcation, in 19 percent of patients. In the remaining 14 patients (12 percent), the scans were abnormal, but MB CK activity was normal. In five of these patients (4 percent), abnormal scintigrams presumably reflected persistent scan positivity after previous myocardial infarction. Only the remaining nine patients (8 percent) could be classified as having unexplained false positive scans, a frequency substantially less than that reported by other investigators who based the diagnosis of myocardial infarction on conventional clinical criteria. These results suggest that abnormal technetium-99m pyrophosphate images in patients with unstable angina generally indicate myocardial necrosis.

Adult↗
PubMed1993

Assessment of left ventricular wall motion in angina pectoris by two-dimensional echocardiography and myocardial perfusion by technetium-99m sestamibi tomography during adenosine-induced coronary vasodilation and comparison with coronary angiography.

Myocardial perfusion and regional wall motion during adenosine-induced coronary vasodilation were assessed in 40 patients with angina pectoris by technetium-99m sestamibi single-photon emission computed tomography (SPECT) and simultaneous 2-dimensional echocardiography. Adenosine was infused intravenously at a dose of 140 micrograms/kg body weight per minute for 6 minutes, and technetium-99m sestamibi was injected at 3 minutes. Adenosine caused a significant decrease in systolic and diastolic blood pressure and a significant increase in heart rate and the heart rate-blood pressure product. Adverse effects were mild and transient and no patient required aminophylline. Completely or partially reversible defects on SPECT were present in 28 patients, a fixed defect was seen in 4 patients, and no defect was seen in 8 patients. Two-dimensional echocardiography revealed a new or worsening wall motion abnormality in 21 patients, a fixed abnormality in 4 patients and no abnormality in 15. Transient perfusion defects were associated with transient wall motion abnormalities in 71% of cases. The overall sensitivity, specificity and predictive accuracy of adenosine echocardiography in detecting significant coronary artery disease (> 50% diameter stenosis) were 74, 100 and 78%, respectively, whereas those of adenosine SPECT were 94, 100 and 95%, respectively (p < 0.05, NS, and < 0.05, respectively). Thus adenosine technetium-99m sestamibi SPECT has a higher sensitivity and predictive accuracy than adenosine echocardiography, suggesting that adenosine-induced perfusion defects are not always associated with wall motion abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1991

Technetium-99m sestamibi tomography in patients with spontaneous chest pain: correlations with clinical, electrocardiographic and angiographic findings.

The sensitivity and specificity of technetium-99m hexakis-2-methoxy-2-isobutyl-isonitrile (sestamibi) single-photon emission computed tomographic (SPECT) imaging for the diagnosis of coronary artery disease were studied in 45 patients admitted to the hospital for clinical suspicion of unstable angina. Only patients without prior myocardial infarction were included and all patients had technetium-99m sestamibi injection and a 12-lead electrocardiogram (ECG) during and less than or equal to 4 h after an episode of chest pain. Coronary angiography performed in all patients during hospitalization showed significant coronary artery disease (greater than or equal to 50% luminal diameter reduction) in 26 of the 45 patients. The SPECT studies obtained after injection of technetium-99m sestamibi during an episode of spontaneous chest pain showed a sensitivity of 96% for the detection of coronary artery disease; the 12-lead ECG obtained at the time of the injection had a sensitivity of 35%. With the patient in the pain-free state, respective sensitivity values were 65% and 38%. Specificity for the radionuclide study was 79% during pain and 84% in the pain-free state; for the ECG, it was 74% both during and between episodes of pain. The site of the perfusion defect corresponded to the most severe coronary artery lesion in 88% of patients. The severity of the perfusion defect correlated with the extent of coronary artery disease: the defect score was 5.3 +/- 3.3 with one-vessel disease, 4.9 +/- 2.8 with two-vessel disease and 10.5 +/- 5.0 with three-vessel disease (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Emergency room technetium-99m sestamibi imaging to rule out acute myocardial ischemic events in patients with nondiagnostic electrocardiograms.

OBJECTIVES: The goal of this study was to determine the role of nuclear imaging in patients with chest pain. BACKGROUND: The diagnosis of myocardial ischemic events in patients with chest pain and a nondiagnostic electrocardiogram (ECG) is problematic. METHODS: Rest tomographic technetium-99m sestamibi imaging (740 MBq intravenously) was performed in 64 patients presenting to the emergency room with chest pain of suspected cardiac origin and a nondiagnostic ECG. Patients were admitted to the coronary care unit on the basis of clinical criteria only and were strictly monitored. RESULTS: Thirty patients showed a perfusion defect on admission. Of these, 13 developed myocardial infarction within 12 h. Coronary artery disease was diagnosed in 14 patients and the remaining 3 patients were classified as having false positive findings. Normal perfusion scans were seen in 34 patients, none of whom were ultimately diagnosed as having coronary artery disease. A 100% sensitivity was demonstrated versus the final diagnosis of acute cardiac ischemia (kappa 0.91, 95% confidence interval 0.8 to 1.0). A follow-up period of up to 18 months (mean 11 +/- 3) was also carried out for major cardiac events (death, myocardial infarction, coronary angioplasty and coronary artery bypass grafting). Six events (two coronary bypass procedures, three angioplasty procedures and one death) were observed at follow-up in the group of patients with a technetium-99m sestamibi perfusion defect. Patients with normal perfusion scans on admission had no major cardiac events at follow-up study. CONCLUSIONS: Technetium-99m sestamibi perfusion imaging is a promising technique for ruling out acute myocardial ischemia in the emergency room. More efficient utilization of intensive therapy beds may be expected with this approach.

Chest Pain↗
PubMed1994

Gated technetium-99m sestamibi for simultaneous assessment of stress myocardial perfusion, postexercise regional ventricular function and myocardial viability. Correlation with echocardiography and rest thallium-201 scintigraphy.

OBJECTIVES: This study compares technetium-99m sestamibi (sestamibi) electrocardiographic (ECG) gated single-photon emission computed tomography (gated SPECT) and echocardiography for the evaluation of myocardial function and assesses the feasibility of single-injection, single-acquisition stress perfusion/rest function technetium-99m sestamibi-gated SPECT as an alternative to conventional stress/rest imaging for assessment of myocardial perfusion and viability. BACKGROUND: Simultaneous assessment of stress perfusion and rest function is possible with gated SPECT acquisition of stress-injected technetium-99m sestamibi. METHODS: Rest thallium-201 SPECT followed by stress sestamibi-gated SPECT (acquired 0.5 to 1 h after sestamibi injection) was performed in 58 patients. Echocardiography was performed immediately after or before gated SPECT in 43 of the patients. All studies were analyzed by semiquantitative visual scoring. Sestamibi-gated SPECT studies were read for stress perfusion and rest wall motion and thickening. Reversibility on sestamibi-gated SPECT was defined as the presence of a definite stress defect with normal or mildly impaired wall motion or thickening on gated SPECT: RESULTS: There was high segmental score agreement between gated SPECT and echocardiography for wall motion (91%, kappa = 0.68, p < 0.001) and thickening (90%, kappa = 0.62, p < 0.001). Correlation for global wall motion (r = 0.98, p < 0.001) and thickening (r = 0.96, p < 0.001) scores between the two modalities was excellent. In 32 patients without previous myocardial infarction, there was excellent agreement for reversibility between stress sestamibi-gated SPECT and rest thallium-201/stress sestamibi (98%, kappa = 0.93, p < 0.01). However, in 26 patients with previous infarction, discordance between the two approaches was frequent, with 26% (20 of 78) of nonreversible defects by stress sestamibi-gated SPECT being reversible by rest thallium-201/stress sestamibi and 21% (23 of 112) of reversible defects by stress sestamibi-gated SPECT being nonreversible by rest thallium-201/stress sestamibi. CONCLUSIONS: Gated SPECT of stress-injected sestamibi correlates well with echocardiographic assessment of regional function and thus adds information to perfusion SPECT: In patients without previous myocardial infarction, a single-injection stress perfusion/rest function approach using sestamibi-gated SPECT can substitute for conventional stress/rest myocardial perfusion imaging, adding a rest perfusion study only if there are nonreversible defects or consideration of attenuation artifacts. In patients with previous myocardial infarction, the gated SPECT approach does not replace the need for a rest perfusion study.

Aged↗
PubMed1996

Comparison of rest thallium-201 imaging and rest technetium-99m sestamibi imaging for assessment of myocardial viability in patients with coronary artery disease and severe left ventricular dysfunction.

OBJECTIVES: We prospectively compared myocardial uptake of thallium-201 (201Tl) at rest with rest technetium-99m (99mTc) sestamibi uptake in the same patients, using quantitative singlephoton emission computed tomography (SPECT). BACKGROUND: Because of only slightly delayed redistribution, 99mTc-sestamibi uptake at rest may be less than 201Tl uptake, thereby underestimating the extent of viability. METHODS: Twenty patients (2.25 stenoses per patient) with a mean left ventricular ejection fraction of 33 +/- 2% underwent early and 3-h delayed rest 201Tl SPECT, rest 99mTc-sestamibi SPECT and two-dimensional echocardiography. RESULTS: The 280 scan segments were classified as either a normal, mild reduction in viability, defined as delayed 201Tl uptake < or = 75% and > or = 5%, or a severe reduction in viability, defined as delayed 201Tl uptake < 50%. Mild and severe defects were further classified as fixed or having rest 201Tl redistribution. Comparisons by patients were made using repeated measures analysis of variance and Dunnett's multiple comparisons test to compare 99mTc-sestamibi with initial rest 201Tl and delayed 201Tl uptake. Twenty patients had at least one mild fixed defect (95 total segments). The average percent uptake in these defects for initial 201Tl, delayed 201Tl and 99mTc-sestamibi was 62.5 +/- 2.7%, 63.1 +/- 7.1% and 67.3 +/- 9.7%, respectively (p = NS). Twelve patients (27 segments) had mild redistribution defects on serial rest 201Tl imaging. The average percent uptake was 61.6 +/- 5.2% for initial 201Tl, 67.0 +/- 9.1% for delayed 201Tl and 67.7 +/- 12.4% for 99mTc-sestamibi defects. Technetium-99m sestamibi uptake was not significantly different than that for delayed 201Tl but was significantly greater than initial 201Tl uptake. Seventeen patients (52 segments) had severe fixed 201Tl defects. The average percent uptake was 38.9 +/- 7.3% for initial 201Tl, 38.3 +/- 12.2% for delayed 201Tl and 42.7 +/- 14.2% for 99mTc-sestamibi defects in these patients (p = NS). Ten patients (19 segments) had severe redistribution defects on rest 201Tl imaging. The average percent uptake was 37.0 +/- 8.5% for initial 201Tl, 42.9 +/- 8.6% for delayed 201Tl and 44.5 +/- 11.3% for 99mTc-sestamibi defects. As was seen for mild 201Tl redistribution defects, 99mTc-sestamibi uptake was significantly higher than initial 201Tl uptake, but not significantly different than delayed 201Tl uptake in these severe defects. CONCLUSIONS: Technetium-99m sestamibi uptake after injection at rest is comparable to 201Tl uptake after injection at rest in patients with severe coronary artery disease and left ventricular dysfunction, suggesting comparable worth for viability assessment.

Cell Survival↗
PubMed1987

Molecular weights of technetium hydroxyethylidene diphosphonate complexes.

The results of recycle size-exclusion and anion-exchange chromatography are combined to determine molecular weights and radii of gyration for selected components of a carrier-added technetium hydroxyethylidene diphosphonate radiopharmaceutical bone-imaging preparation. Samples evaluated by size-exclusion are selected from fractions collected as the preparation elutes from the anion-exchange column. Polyethylene glycol and polyphosphate molecular weight standards are used, in conjunction with the universal calibration method, to determine Mark-Houwink constants and to estimate molecular weights for the complexes. The results of this study support a spherical shape model for the collection of technetium complexes. Given the combined knowledge of molecular weights, charges, technetium concentration dependencies, and mass spectral data, several formula assignments are proposed, including TcO(OH)L-1, Tc2O(OH)6L-3, Tc2O(OH)2L3(-6), Tc3O2(OH)3L2(-5), Tc3O2(OH)3L3(-7), Tc2O2(OH)4(HL)3(-7) and Tc2O2(OH)4(H2L)4(-8).

Chemical Phenomena↗
PubMed1988

Technetium carboxylate complexes--II. Structural and chemical studies.

Formate, acetate, and pivalate based complexes of technetium have been prepared by the electrochemical reduction of pertechnetate in the appropriate carboxylate buffer. Also, chemical synthetic routes to these complexes have been explored using technetium chloro compounds of known oxidation states as starting materials. The technetium carboxylate complexes were selectively examined by subtractively normalized interfacial Fourier transform infrared, electron spin resonance, and electronic spectroscopy, electrochemistry, electrophoresis, and anion exchange chromatography. These complexes have been proposed to be metal-metal bonded dioxo bridged ditechnetium(IV) species with axial and bridged carboxylate ligands.

Carboxylic Acids↗
PubMed1992

Importance of precise determination of technetium-labeled DISIDA concentrations for in vitro hepatocellular transport studies.

Technetium 99m-labeled diisopropyliminodiacetic (acid [99mTc]DISIDA) has been used extensively in the evaluation of hepatobiliary diseases. As a result of investigation into transport mechanisms of [99mTc]DISIDA, we undertook to determine precise concentrations of this compound in the standard clinical formulation. Calculations based on published formulas were used. These take into account column efficiency, the time since the previous elution of 99mTc from the 99Mo column, and the total quantity of 99mTc eluted. Primary cultures of rat hepatocytes were used to evaluate the transport of Na99mTcO4 and the 99mTc-labeled DISIDA monomer. Pertechnetate was not taken up by the hepatocytes, the amount of [99mTc]DISIDa taken up was not dependent on the concentration of DISIDA but rather on the concentration of technetium, when the DISIDA/99mTc ratio was varied in the culture medium. We conclude that calculation of the total technetium concentration is necessary to determine the amount of compound taken up by the liver, and to interpret kinetic studies of hepatocellular transport mechanisms.

Animals↗
PubMed2002

Prevalence and prognostic value of perfusion defects detected by stress technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography in asymptomatic patients with diabetes mellitus and no known coronary artery disease.

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in diabetics. Early diagnosis of CAD and identification of high-risk subgroups, followed by appropriate therapy, may therefore enhance survival. This study sought to determine the value of stress myocardial perfusion single-photon emission computed tomography (SPECT) with technetium-99m sestamibi to detect perfusion defects and predict cardiac events in asymptomatic diabetics. One hundred eighty asymptomatic diabetics without known CAD who underwent 2-day stress technetium-99m sestamibi SPECT were followed up for 36 +/- 18 months. End points were defined as hard (myocardial infarction or cardiac death) or total events (myocardial infarction, cardiac death, or late revascularization). Logistic regression analysis evaluated clinical variables, type of stress, exercise treadmill test (ETT), and SPECT as predictors of end points. Perfusion defects were found in 26% of patients (15% reversible, 6% mixed, and 5% fixed). Clinical or ETT variables were not associated with perfusion defect type or with hard events. However, male gender predicted total events (chi-square 3.3; p = 0.01). An abnormal SPECT significantly increased the risk of hard events (chi-square 5.4; p = 0.001) and total events (chi-square 7.4; p = 0.0001). Extensive defects determined the highest risk of total events (chi-square 18.8; p = 0.0001). Event rates increased according to SPECT: 2% of hard events per year and 5% of total events per year in patients with normal SPECT versus 9% per year and 38% per year, respectively, in those with abnormal SPECT. Importantly, a normal SPECT identified a relatively low-risk subgroup of patients. Thus, stress technetium-99m sestamibi SPECT was useful in evaluating asymptomatic diabetics for the presence of CAD, and effectively risk-stratified this population.

Aged↗
PubMed1977

New approach to interpretation of technetium-99m pyrophosphate scintigraphy in detection of acute myocardial infarction: clinical assessment of diagnostic accuracy.

A modified classification for interpreting technetium-99m pyrophosphate scintigrams defines the 2+ diffuse pattern of tracer uptake as equlvocal rather than positive for acute myocardial infarction. Results of scintigraphy using this classification were compared with results of standard diagnostic tests for myocardial infarction in 235 patients admitted to a coronary care unit with acute chest pain. Of 81 patients with acute transmural infarction by standard clinical, electrocardiographic and serum enzyme criteria, 76 had a positive, 5 an equivocal and none a negative scintigram. Of 18 with acute nontransmural infarction by standard criteria, 7 had a positive, 9 an equivocal and 2 a negative scintigram. This it was uncommon for a patient with acute myocardial infarction, transmural or nontransmural, to have a definitely negative technetium-99m pyrophosphate study. Ten patients had equivocal evidence of infarction by standard criteria. Of the remaining 126 patients with no evidence of acute myocardial infarction by standard criteria, 87 had a negative, 35 an equivocal and 4 a definitely positive scintigram. Thus the definitely positive scintigraphic pattern was relatively highly specific for acute myocardial infarction. If the 2+ pattern had been considered positive, the specificity of the technique would have been greatly decreased. Computer processing strengthened observer certainty of the visual impression but changed the scintigraphic evaluation in only eight cases. Thus, use of an equivocal pattern renders technetium-99m pyrophosphate imaging both an extremely sensitive and specific method for detecting acute myocardial infarction.

Acute Disease↗
PubMed1988

Quantification of myocardial infarction during coronary occlusion and myocardial salvage after reperfusion using cardiac imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile.

Myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a means to assess myocardial infarct size during coronary occlusion and to quantify the extent of salvaged myocardium after coronary occlusion followed by reperfusion. Open chest dogs underwent either a permanent coronary artery occlusion (Group 1, n = 16) or a 2 h occlusion followed by reperfusion (Group 2, n = 15). Animals in both groups were killed 48 h after occlusion. During coronary occlusion, 23 of the 25 dogs that survived the coronary occlusions had abnormal myocardial scintigrams. The scintigraphic perfusion defect size correlated well with the pathologic infarct size (r = 0.85 and 0.95 by planar and tomographic imaging, respectively). The planar scintigraphic defect size, but not the tomographic defect size, overestimated the pathologic size. The planar scintigraphic defect size observed during coronary occlusion was markedly reduced 48 h after reperfusion (24.8 +/- 12.8% to 10.6 +/- 9.7% of the left ventricle, p less than 0.003). The uptake of technetium-99m hexakis 2-methoxyisobutyl isonitrile in the ischemic myocardium increased significantly 48 h after reperfusion (p less than 0.003) and correlated with the increase in regional myocardial blood flow, as assessed by radioactive microspheres (r = 0.83, p less than 0.01). Thus, myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile allows reliable demonstration of the presence of acute infarction, estimation of infarct size and quantification of the extent of salvaged myocardium after coronary reperfusion.

Animals↗